The document discusses key terminology and concepts related to welding inspection. Some key points: - It defines different types of welds (e.g. butt weld, fillet weld), joints (e.g. butt, tee, lap), and weld zones (e.g. weld metal, heat affected zone). - It discusses joint preparation details like bevel angles, root faces, gaps for different joint types (e.g. single V, single J). - It covers features of fillet welds like leg length, throat thickness, and how they relate. Leg length and throat thickness determine weld strength. - It also discusses duties of a welding inspector like observing welding, recording

1. Welding Inspector
Duties and Responsibilities
Section 1
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2. Main Responsibilities 1.1
• Code compliance
• Workmanship control
• Documentation control
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3. Personal Attributes 1.1
Important qualities that good Inspectors are expected to have
are:
• Honesty
Integrity
•
•Knowledge
•Good communicator
Physical fitness
•
• Good eyesight
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4. Standard for Visual Inspection 1.1
Basic Requirements
BS EN 970 - Non-destructive examination of fusion
welds - Visual examination
Welding Inspection Personnel should:
• be familiar with relevant standards, rules and specifications
applicable to the fabrication work to be undertaken
• be informed about the welding procedures to be used
• have good vision (which should be checked every 12
months)
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5. Welding Inspection 1.2
Conditions for Visual Inspection (to BS EN 970)
Illumination:
• 350 lux minimum required
• (recommends 500 lux - normal shop or office lighting)
Vision Access:
• eye should be within 600mm of the surface
• viewing angle (line from eye to surface) to be not less than
30°
600mm
30°
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6. Welding Inspection 1.3
Aids to Visual Inspection (to BS EN 970)
When access is restricted may use:
• a mirrored boroscope
• a fibre optic viewing system
} usually by
agreement
Other aids:
• welding gauges (for checking bevel angles, weld profile, fillet
sizing, undercut depth)
• dedicated weld-gap gauges and linear misalignment (high-low)
gauges
• straight edges and measuring tapes
• magnifying lens (if magnification lens used it should have
magnification between X2 to X5)
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7. Welding Inspectors Equipment 1.3
Measuring devices:
• flexible tape, steel rule
• Temperature indicating crayons
• Welding gauges
• Voltmeter
• Ammeter
• Magnifying glass
• Torch / flash light
• Gas flow-meter
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8. Welding Inspectors Gauges 1.3
10mm 10mm 1
2
G.A.L. G.A.L. 3
4
S.T.D. L S.T.D.
16mm 5
16mm
6
Fillet Weld Gauges
HI-LO Single Purpose Welding Gauge
IN
0 1/4 1/2 3/4
TWI Multi-purpose Welding Gauge Misalignment Gauges
Hi-Lo Gauge
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9. Welding Inspectors Equipment 1.3
Voltmeter Ammeter
Tong Tester
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10. Welding Inspection 1.3
Stages of Visual Inspection (to BS EN 970)
Extent of examination and when required should be defined in
the application standard or by agreement between the
contracting parties
For high integrity fabrications inspection required throughout
the fabrication process:
Before welding
(Before assemble & After assembly)
During welding
After welding
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11. Typical Duties of a Welding Inspector 1.5
Before Welding
Preparation:
Familiarisation with relevant „documents‟…
• Application Standard/Code - for visual acceptance
requirements
• Drawings - item details and positions/tolerances etc
• Quality Control Procedures - for activities such as material
handling, documentation control, storage & issue of
welding consumables
• Quality Plan/Inspection & Test Plan/Inspection Checklist -
details of inspection requirements, inspection procedures
& records required
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12. Typical Duties of a Welding Inspector 1.5
Before Welding
Welding Procedures:
• are applicable to joints to be welded & approved
• are available to welders & inspectors
Welder Qualifications:
• list of available qualified welders related to WPS‟s
• certificates are valid and ‘in-date’
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13. Typical Duties of a Welding Inspector 1.5
Before Welding
Equipment:
• all inspection equipment is in good condition & calibrated as
necessary
• all safety requirements are understood & necessary equipment
available
Materials:
• can be identified & related to test certificates, traceability !
• are of correct dimensions
• are in suitable condition (no damage/contamination)
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14. Typical Duties of a Welding Inspector 1.5
Before Welding
Consumables:
• in accordance with WPS’s
• are being controlled in accordance with Procedure
Weld Preparations:
• comply with WPS/drawing
• free from defects & contamination
Welding Equipment:
• in good order & calibrated as required by Procedure
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15. Typical Duties of a Welding Inspector 1.5
Before Welding
Fit-up
• complies with WPS
• Number / size of tack welds to Code / good
workmanship
Pre-heat
• if specified
• minimum temperature complies with WPS
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16. Typical Duties of a Welding Inspector 1.5
During Welding
Weather conditions
• suitable if site / field welding
Welding Process(es)
• in accordance with WPS
Welder
• is approved to weld the joint
Pre-heat (if required)
• minimum temperature as specified by WPS
• maximum interpass temperature as WPS
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17. Typical Duties of a Welding Inspector 1.6
During Welding
Welding consumables
• in accordance with WPS
• in suitable condition
• controlled issue and handling
Welding Parameters
• current, voltage & travel speed – as WPS
Root runs
• if possible, visually inspect root before single-sided welds are
filled up
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18. Typical Duties of a Welding Inspector 1.6
During Welding
Inter-run cleaning
in accordance with an approved method (& back gouging) to
good workmanship standard
Distortion control
• welding is balanced & over-welding is avoided
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19. Typical Duties of a Welding Inspector 1.6
After Welding
Weld Identification
• identified/numbered as required
• is marked with welder‟s identity
Visual Inspection
• ensure weld is suitable for all NDT
• visually inspect & „sentence‟ to Code requirements
Dimensional Survey
• ensure dimensions comply with Code/drawing
Other NDT
• ensure all NDT is completed & reports available
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20. Typical Duties of a Welding Inspector 1.6
After Welding
Repairs
• monitor repairs to ensure compliance with Procedure, ensure
NDT after repairs is completed
• PWHT
• monitor for compliance with Procedure
• check chart records confirm Procedure compliance
Pressure / Load Test
• ensure test equipment is suitably calibrated
• monitor to ensure compliance with Procedure
• ensure all records are available
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21. Typical Duties of a Welding Inspector 1.6
After Welding
Documentation
• ensure any modifications are on ‘as-built’ drawings
• ensure all required documents are available
• Collate / file documents for manufacturing records
• Sign all documentation and forward it to QC department.
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22. Summary of Duties
It is the duty of a Welding Inspector to ensure all the welding and
associated actions are carried out in accordance with the
specification and any applicable procedures.
A Welding Inspector must:
• Observe
To observe all relevant actions related to weld quality throughout
production.
• Record
To record, or log all production inspection points relevant to quality,
including a final report showing all identified imperfections
• Compare
To compare all recorded information with the acceptance criteria
and any other relevant clauses in the applied application standard
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23. Welding Inspector
Terms & Definitions
Section 2
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24. Welding Terminology & Definitions 2.1
What is a Weld?
• A localised coalescence of metals or non-metals produced
either by heating the materials to the welding temperature,
with or without the application of pressure, or by the
application of pressure alone (AWS)
• A permanent union between materials caused by heat, and
or pressure (BS499)
• An Autogenous weld:
A weld made with out the use of a filler material and can
only be made by TIG or Oxy-Gas Welding
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25. Welding Terminology & Definitions 2.1
What is a Joint?
• The junction of members or the edges of members that are
to be joined or have been joined (AWS)
• A configuration of members (BS499)
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26. Joint Terminology 2.2
Edge Open & Closed Corner Lap
Tee Butt
Cruciform
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27. Welded Butt Joints 2.2
Butt
A_________Welded butt joint
Fillet
A_________Welded butt joint
Compound
A____________Welded butt joint
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28. Welded Tee Joints 2.2
Fillet
A_________Welded T joint
Butt
A_________Welded T joint
Compound
A____________Welded T joint
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29. Weld Terminology 2.3
Butt weld Spot weld
Fillet weld
Edge weld Plug weld
Compound weld
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30. Butt Preparations – Sizes 2.4
Partial Penetration Butt Weld
Actual Throat
Design Throat
Thickness
Thickness
Full Penetration Butt Weld
Design Throat Actual Throat
Thickness Thickness
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31. Weld Zone Terminology 2.5
Face
A B
Weld
metal
Heat Weld
Affected Boundary
Zone
C D
Root
A, B, C & D = Weld Toes
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32. Weld Zone Terminology 2.5
Weld cap width
Excess
Cap height Actual Throat Design
or Weld Thickness Throat
Reinforcement Thickness
Excess Root
Penetration
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33. Heat Affected Zone (HAZ) 2.5
Maximum solid solid-liquid Boundary
Temperature weld
grain growth zone
metal
recrystallised zone
partially transformed zone
tempered zone
unaffected base
material
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34. Joint Preparation Terminology 2.7
Included angle Included angle
Angle of
bevel
Root
Radius
Root Face Root Face
Root Gap Root Gap
Single-V Butt Single-U Butt
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35. Joint Preparation Terminology 2.8 & 2.9
Angle of bevel Angle of bevel
Root
Radius
Root Face Root Gap Root Face
Root Gap Land
Single Bevel Butt Single-J Butt
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36. Single Sided Butt Preparations 2.10
Single sided preparations are normally made on thinner materials, or
when access form both sides is restricted
Single Bevel Single Vee
Single-J Single-U
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37. Double Sided Butt Preparations 2.11
Double sided preparations are normally made on thicker materials, or
when access form both sides is unrestricted
Double -Bevel Double -Vee
Double - J Double - U
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38. Weld Preparation
Terminology & Typical Dimensions: V-Joints
bevel angle
included angle
root face
root gap
Typical Dimensions
bevel angle 30 to 35°
root face ~1.5 to ~2.5mm
root gap ~2 to ~4mm
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39. Butt Weld - Toe Blend
6 mm •Most codes quote the weld
toes shall blend smoothly
80 •This statement is not
quantitative and therefore
open to individual
Poor Weld Toe Blend Angle interpretation
3 mm •The higher the toe blend
angle the greater the
20 amount of stress
concentration
•The toe blend angle ideally
Improved Weld Toe Blend
Angle should be between 20o-30o
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40. Fillet Weld Features 2.13
Excess
Weld
Metal
Vertical
Leg
Length Design
Throat
Horizontal leg
Length
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41. Fillet Weld Throat Thickness 2.13
a
b
a = Design Throat Thickness
b = Actual Throat Thickness
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42. Deep Penetration Fillet Weld Features 2.13
a
a = Design Throat Thickness b
b = Actual Throat Thickness
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43. Fillet Weld Sizes 2.14
Calculating Throat Thickness from a known Leg Length:
Design Throat Thickness = Leg Length x 0.7
Question: The Leg length is 14mm.
What is the Design Throat?
Answer: 14mm x 0.7 = 10mm Throat Thickness
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44. Fillet Weld Sizes 2.14
Calculating Leg Length from a known Design Throat
Thickness:
Leg Length = Design Throat Thickness x 1.4
Question: The Design Throat is 10mm.
What is the Leg length?
Answer: 10mm x 1.4 = 14mm Leg Length
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45. Features to Consider 2 2.14
Importance of Fillet Weld Leg Length Size
(a) (b)
8mm
4mm
4mm 2mm
Approximately the same weld volume in both Fillet
Welds, but the effective throat thickness has been
altered, reducing considerably the strength of weld B
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46. Fillet Weld Sizes 2.14
Importance of Fillet weld leg length Size
(a) (b) Excess
Excess
4mm 6mm
(a) (b)
4mm 6mm
Area = 4 x 4 = Area = 6 x 6 =
8mm2 18mm2
2 2
The c.s.a. of (b) is over double the area of (a) without the extra
excess weld metal being added
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47. Fillet Weld Profiles 2.15
Fillet welds - Shape
Mitre Fillet Convex Fillet
A concave profile
is preferred for
joints subjected to
Concave Fillet fatigue loading
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48. Fillet Features to Consider 2.15
EFFECTIVE THROAT THICKNESS
“a” = Nominal throat thickness “s” = Effective throat thickness
a s
Deep penetration fillet welds from high heat
input welding process MAG, FCAW & SAW etc
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49. Welding Positions 2.17
PA 1G / 1F Flat / Downhand
PB 2F Horizontal-Vertical
PC 2G Horizontal
PD 4F Horizontal-Vertical (Overhead)
PE 4G Overhead
PF 3G / 5G Vertical-Up
PG 3G / 5G Vertical-Down
H-L045 6G Inclined Pipe (Upwards)
J-L045 6G Inclined Pipe (Downwards)
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50. Welding Positions 2.17
ISO
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51. Welding position designation 2.17
Butt welds in plate (see ISO 6947)
Flat - PA Overhead - PE
Vertical
up - PF
Vertical Horizontal - PC
down - PG
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52. Welding position designation 2.17
Butt welds in pipe (see ISO 6947)
Vertical up - PF Vertical down - PG
Flat - PA axis: horizontal axis: horizontal
axis: horizontal pipe: fixed pipe: fixed
pipe: rotated
H-L045 J-L045 Horizontal - PC
axis: inclined at 45° axis: inclined at 45° axis: vertical
pipe: fixed pipe: fixed pipe: fixed
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53. Welding position designation 2.17
Fillet welds on plate (see ISO 6947)
Flat - PA Horizontal - PB Overhead - PD
Vertical up - PF Vertical down - PG
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54. Welding position designation 2.17
Fillet welds on pipe (see ISO 6947)
Flat - PA Horizontal - PB Overhead - PD
axis: inclined at 45° axis: vertical axis: vertical
pipe: rotated pipe: fixed pipe: fixed
Horizontal - PB Vertical up - PF Vertical down - PG
axis: horizontal axis: horizontal axis: horizontal
pipe: rotated pipe: fixed pipe: fixed
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55. Plate/Fillet Weld Positions 2.17
PA / 1G
PA / 1F
PF / 3G
PB / 2F
PC / 2G
PE / 4G PG / 3G
PD / 4F
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56. Pipe Welding Positions 2.17
PF / 5G PG / 5G
PA / 1G
Weld: Flat Weld: Vertical upwards Weld: Vertical Downwards
Pipe: rotated Pipe: Fixed Pipe: Fixed
Axis: Horizontal Axis: Horizontal Axis: Horizontal
45o 45o
PC / 2G
H-LO 45 / 6G J-LO 45 / 6G
Weld: Horizontal Weld: Upwards Weld: Downwards
Pipe: Fixed Pipe: Fixed Pipe: Fixed
Axis: Vertical Axis: Inclined Axis: Inclined
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57. Travel Speed Measurement 2.18
Definition: the rate of weld progression
measured in case of mechanised and automatic
welding processes
in case of MMA can be determined using ROL and arc
time
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58. Welding Inspector
Welding Imperfections
Section 3
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59. Welding Imperfections 3.1
All welds have imperfections
• Imperfections are classed as defects when they are of a
type, or size, not allowed by the Acceptance Standard
A defect is an unacceptable imperfection
• A weld imperfection may be allowed by one Acceptance
Standard but be classed as a defect by another Standard
and require removal/rectification
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60. Welding Imperfections 3.1
Standards for Welding Imperfections
BS EN ISO 6520-1(1998) Welding and allied processes –
Classification of geometric
imperfections in metallic materials -
Part 1: Fusion welding
Imperfections are classified into 6 groups, namely:
1 Cracks
2 Cavities
3 Solid inclusions
4 Lack of fusion and penetration
5 Imperfect shape and dimensions
6 Miscellaneous imperfections
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61. Welding Imperfections 3.1
Standards for Welding Imperfections
EN ISO 5817 (2003) Welding - Fusion-welded joints in steel,
nickel, titanium and their alloys (beam
welding excluded) - Quality levels for
imperfections
This main imperfections given in EN ISO 6520-1 are listed in
EN ISO 5817 with acceptance criteria at 3 levels, namely
Level B (highest)
Level C (intermediate)
Level D (general)
This Standard is „directly applicable to visual testing of welds‟
...(weld surfaces & macro examination)
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62. Welding imperfections 3.1
classification
Cracks
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63. Cracks 3.1
Cracks that may occur in welded materials are
caused generally by many factors and may be
classified by shape and position.
Classified by Shape Classified by Position
•Longitudinal •HAZ
•Transverse •Centerline
•Chevron •Crater
•Lamellar Tear •Fusion zone
•Parent metal
Note: Cracks are classed as Planar Defects.
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64. Cracks 3.1
Longitudinal parent metal Transverse weld metal
Longitudinal weld metal
Lamellar tearing
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65. Cracks 3.1
Transverse crack Longitudinal crack
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66. Cracks 3.2
Main Crack Types
• Solidification Cracks
• Hydrogen Induced Cracks
• Lamellar Tearing
• Reheat cracks
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67. Cracks 3.2
Solidification Cracking
• Occurs during weld solidification process
• Steels with high sulphur impurities content (low ductility
at elevated temperature)
• Requires high tensile stress
• Occur longitudinally down centre of weld
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68. Cracks 3.3
Hydrogen Induced Cold Cracking
• Requires susceptible hard grain structure, stress, low
temperature and hydrogen
• Hydrogen enters weld via welding arc mainly as result of
contaminated electrode or preparation
• Hydrogen diffuses out into parent metal on cooling
• Cracking developing most likely in HAZ
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69. Lamellar Tearing 3.5
• Location: Parent metal
• Steel Type: Any steel type possible
• Susceptible Microstructure: Poor through thickness ductility
• Lamellar tearing has a step like appearance due to the solid
inclusions in the parent material (e.g. sulphides and
silicates) linking up under the influence of welding stresses
• Low ductile materials in the short transverse direction
containing high levels of impurities are very susceptible to
lamellar tearing
• It forms when the welding stresses act in the short
transverse direction of the material (through thickness
direction)
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70. Gas Cavities 3.6
Gas pore Cluster porosity
Causes:
•Loss of gas shield
•Damp electrodes
•Contamination
Blow hole •Arc length too large
Herringbone porosity
•Damaged electrode flux
•Moisture on parent material
•Welding current too low
Gas pore <1.5mm
Root piping Blow hole.>1.6mm
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71. Gas Cavities 3.7
Porosity
Root piping
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72. Gas Cavities 3.8
Cluster porosity Herringbone porosity
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73. Crater Pipe 3.9
Weld crater
Crater pipe
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74. Crater Pipe 3.9
Crater pipe is a shrinkage defect and not a gas defect, it has
the appearance of a gas pore in the weld crater
Crater cracks Causes:
(Star cracks)
• Too fast a cooling
rate
• Deoxidization
reactions and
liquid to solid
Crater pipe volume change
• Contamination
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75. Solid Inclusions 3.10
Slag inclusions are defined as a non-metallic inclusion caused
by some welding process
Causes:
•Slag originates from
welding flux
Slag inclusions Lack of sidewall •MAG and TIG welding
fusion with process produce silica
associated slag inclusions
•Slag is caused by
inadequate cleaning
•Other inclusions include
Parallel slag lines Lack of interun tungsten and copper
fusion + slag inclusions from the TIG
and MAG welding process
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76. Solid Inclusions 3.11
Interpass slag inclusions Elongated slag lines
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77. Welding Imperfections 3.13
Typical Causes of Lack of Fusion:
• welding current too low
• bevel angle too steep
• root face too large (single-sided weld)
• root gap too small (single-sided weld)
• incorrect electrode angle
• linear misalignment
• welding speed too high
• welding process related – particularly dip-transfer GMAW
• flooding the joint with too much weld metal (blocking Out)
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78. Lack of Fusion 3.13
Causes:
•Poor welder skill
• Incorrect electrode
Incomplete filled groove +
manipulation
Lack of sidewall fusion
• Arc blow
• Incorrect welding
1 current/voltage
2 • Incorrect travel speed
1. Lack of sidewall fusion • Incorrect inter-run cleaning
2. Lack of inter-run fusion
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79. Lack of Fusion 3.13
Lack of sidewall fusion + incomplete filled groove
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80. Weld Root Imperfections 3.15
Lack of Root Fusion Lack of Root Penetration
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81. Cap Undercut 3.18
Intermittent Cap Undercut
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82. Undercut 3.18
Root undercut Cap undercut
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83. Surface and Profile 3.19
Incomplete filled groove Poor cap profile
Poor cap profiles and
excessive cap reinforcements
may lead to stress
concentration points at the
weld toes and will also
contribute to overall poor toe
blend Excessive cap height
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84. Surface and Profile 3.19
Excess cap reinforcement Incomplete filled groove
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85. Weld Root Imperfections 3.20
Excessive root
penetration
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86. Overlap 3.21
An imperfection at the toe or root of a weld caused by metal
flowing on to the surface of the parent metal without fusing to it
Causes:
•Contamination
•Slow travel speed
•Incorrect welding
technique
•Current too low
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87. Overlap 3.21
Toe Overlap
Toe Overlap
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88. Set-Up Irregularities 3.22
Linear misalignment is
measured from the lowest
plate to the highest point.
Plate/pipe Linear Misalignment
(Hi-Lo)
Angular misalignment is
measured in degrees
Angular Misalignment
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89. Set-Up Irregularities 3.22
Linear Misalignment
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90. Set-Up Irregularities 3.22
Linear Misalignment
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91. Incomplete Groove 3.23
Lack of sidewall fusion + incomplete filled groove
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92. Weld Root Imperfections 3.24
A shallow groove, which may occur in the root of a butt weld
Causes:
• Excessive back purge
pressure during TIG welding
Excessive root bead grinding
before the application of the
second pass
Concave Root
welding current too high for
2nd pass overhead welding
root gap too large - excessive
„weaving‟
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93. Weld Root Imperfections 3.24
Concave Root
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94. Weld Root Imperfections 3.24
Concave root Excess root penetration
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95. Weld Root Imperfections 3.25
A localized collapse of the weld pool due to excessive
penetration resulting in a hole in the root run
Causes:
• High Amps/volts
• Small Root face
• Large Root Gap
• Slow Travel
Burn through Speed
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96. Weld Root Imperfections 3.25
Burn Through
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97. Oxidized Root (Root Coking)
Causes:
• Loss or insufficient
back purging gas (TIG)
• Most commonly occurs
when welding stainless
steels
• Purging gases include
argon, helium and
occasionally nitrogen
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98. Miscellaneous Imperfections 3.26
Causes:
• Accidental striking of the
arc onto the parent
material
• Faulty electrode holder
• Poor cable insulation
• Poor return lead
clamping
Arc strike
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99. Miscellaneous Imperfections 3.27
Causes:
• Excessive current
• Damp electrodes
• Contamination
• Incorrect wire feed
speed when welding
with the MAG welding
process
Spatter • Arc blow
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100. Mechanical Damage 3.28
Mechanical damage can be defined as any surface material
damage cause during the manufacturing process.
• Grinding
• Hammering
• Chiselling
• Chipping
• Breaking off welded attachments
(torn surfaces)
• Using needle guns to compress
weld capping runs
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101. Mechanical Damage 3.28
Chipping Marks
Mechanical Damage/Grinding Mark
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102. Welding Inspector
Destructive Testing
Section 4
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103. Qualitative and Quantitative Tests 4.1
The following mechanical tests have units and are termed
quantitative tests to measure Mechanical Properties
• Tensile tests (Transverse Welded Joint, All Weld Metal)
• Toughness testing (Charpy, Izod, CTOD)
• Hardness tests (Brinell, Rockwell, Vickers)
The following mechanical tests have no units and are termed
qualitative tests for assessing joint quality
• Macro testing
• Bend testing
• Fillet weld fracture testing
• Butt weld nick-break testing
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104. Mechanical Test Samples 4.1
Tensile Specimens
CTOD Specimen
Bend Test
Specimen
Charpy Specimen
Fracture Fillet
Specimen
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105. Destructive Testing 4.1
WELDING PROCEDURE QUALIFICATION TESTING
top of fixed pipe
2 Typical Positions for Test
Pieces
Specimen Type Position
•Macro + Hardness 5
3
•Transverse Tensile 2, 4
•Bend Tests 2, 4
•Charpy Impact Tests 3
4 •Additional Tests 3
5
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106. Definitions
Mechanical Properties of metals are related to the amount of
deformation which metals can withstand under different
circumstances of force application.
• Malleability Ability of a material to
withstand deformation
• Ductility
under static compressive
• Toughness loading without rupture
• Hardness
• Tensile Strength
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107. Definitions
Mechanical Properties of metals are related to the amount of
deformation which metals can withstand under different
circumstances of force application.
• Malleability Ability of a material
undergo plastic
• Ductility
deformation under static
• Toughness tensile loading without
• Hardness rupture. Measurable
elongation and reduction
• Tensile Strength in cross section area
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108. Definitions
Mechanical Properties of metals are related to the amount of
deformation which metals can withstand under different
circumstances of force application.
• Malleability Ability of a material to
withstand bending or the
• Ductility
application of shear
• Toughness stresses by impact loading
• Hardness without fracture.
• Tensile Strength
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109. Definitions
Mechanical Properties of metals are related to the amount of
deformation which metals can withstand under different
circumstances of force application.
• Malleability Measurement of a
materials surface
• Ductility
resistance to indentation
• Toughness from another material by
• Hardness static load
• Tensile Strength
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110. Definitions
Mechanical Properties of metals are related to the amount of
deformation which metals can withstand under different
circumstances of force application.
• Malleability Measurement of the
maximum force required to
• Ductility
fracture a materials bar of
• Toughness unit cross-sectional area in
• Hardness tension
• Tensile Strength
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111. Transverse Joint Tensile Test 4.2
Weld on plate
Multiple cross joint
Weld on pipe specimens
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112. Tensile Test 4.3
All-Weld Metal Tensile
Specimen
Transverse Tensile
Specimen
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113. STRA (Short Transverse Reduction Area)
For materials that may be subject to Lamellar Tearing
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114. UTS Tensile test 4.4
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115. Charpy V-Notch Impact Test 4.5
Objectives:
• measuring impact strength in different weld joint areas
• assessing resistance toward brittle fracture
Information to be supplied on the test report:
• Material type
• Notch type
• Specimen size
• Test temperature
• Notch location
• Impact Strength Value
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116. Ductile / Brittle Transition Curve 4.6
Ductile fracture
Temperature range
47 Joules
Transition range Ductile/Brittle
transition
point
28 Joules
Energy absorbed
Brittle fracture
- 50 - 40 - 30 - 20 - 10 0
Testing temperature - Degrees Centigrade
Three specimens are normally tested at each temperature
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117. Comparison Charpy Impact Test Results 4.6
Impact Energy Joules
Room Temperature -20oC Temperature
1. 197 Joules 1. 49 Joules
2. 191 Joules 2. 53 Joules
3. 186 Joules 3. 51 Joules
Average = 191 Joules Average = 51 Joules
The test results show the specimens carried out at room
temperature absorb more energy than the specimens carried
out at -20oC
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118. Charpy V-notch impact test specimen 4.7
Specimen dimensions according ASTM E23
ASTM: American Society of Testing Materials
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119. Charpy V-Notch Impact Test 4.8
Specime Pendulu
n m
(striker)
Anvil (support)
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120. Charpy Impact Test 4.9
22.5o
2 mm 10 mm 100% Brittle
Machined
notch
Fracture surface
8 mm
100% bright
crystalline brittle
fracture
100% Ductile
Machined
notch
Large reduction
in area, shear
lips
Randomly torn,
dull gray fracture
surface
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121. Hardness Testing 4.10
Definition
Measurement of resistance of a material against
penetration of an indenter under a constant load
There is a direct correlation between UTS and
hardness
Hardness tests:
Brinell
Vickers
Rockwell
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122. Hardness Testing 4.10
Objectives:
• measuring hardness in different areas of a welded joint
• assessing resistance toward brittle fracture, cold cracking
and corrosion sensitivity within a H2S (Hydrogen Sulphide)
environment.
Information to be supplied on the test report:
• material type
• location of indentation
• type of hardness test and load applied on the indenter
• hardness value
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123. Vickers Hardness Test 4.11
Vickers hardness tests:
indentation body is a square based diamond pyramid
(136º included angle)
the average diagonal (d) of the impression is
converted to a hardness number from a table
it is measured in HV5, HV10 or HV025
Adjustable
Diamond Indentation shutters
indentor
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124. Vickers Hardness Test Machine 4.11
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125. Brinell Hardness Test 4.11
• Hardened steel ball of given diameter is subjected for
a given time to a given load
• Load divided by area of indentation gives Brinell
hardness in kg/mm2
• More suitable for on site hardness testing
30KN
Ø=10mm
steel ball
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126. Rockwell Hardness Test
Rockwell B Rockwell C
1KN
1.5KN
Ø=1.6mm 120 Diamond
steel ball Cone
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127. Hardness Testing 4.12
usually the hardest region
1.5 to 3mm
fusion line
or
fusion HAZ
boundary
Hardness Test Methods Typical Designations
Vickers 240 HV10
Rockwell Rc 22
Brinell 200 BHN-W
Hardness specimens can also be used for CTOD samples
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128. Crack Tip Opening Displacement testing 4.12
• Test is for fracture toughness
• Square bar machined with a notch placed in
the centre.
• Tested below ambient temperature at a
specified temperature.
• Load is applied at either end of the test
specimen in an attempt to open a crack at the
bottom of the notch
• Normally 3 samples
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129. Fatigue Fracture 4.13
Location: Any stress concentration area
Steel Type: All steel types
Susceptible Microstructure: All grain structures
Test for Fracture Toughness is CTOD
(Crack Tip Opening Displacement)
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130. Fatigue Fracture 4.13
• Fatigue cracks occur under cyclic stress conditions
• Fracture normally occurs at a change in section, notch
and weld defects i.e stress concentration area
• All materials are susceptible to fatigue cracking
• Fatigue cracking starts at a specific point referred to as
a initiation point
• The fracture surface is smooth in appearance
sometimes displaying beach markings
• The final mode of failure may be brittle or ductile or a
combination of both
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131. Fatigue Fracture
Precautions against Fatigue Cracks
• Toe grinding, profile grinding.
• The elimination of poor profiles
• The elimination of partial penetration welds and weld
defects
• Operating conditions under the materials endurance limits
• The elimination of notch effects e.g. mechanical damage
cap/root undercut
• The selection of the correct material for the service
conditions of the component
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132. Fatigue Fracture
Fatigue fracture occurs in structures subject to repeated
application of tensile stress.
Crack growth is slow (in same cases, crack may grow into an
area of low stress and stop without failure).
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133. Fatigue Fracture
Secondary mode of failure Fatigue fracture surface
ductile fracture rough fibrous
appearance smooth in appearance
Initiation points / weld defects
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134. Fatigue Fracture
Fatigue fracture distinguish features:
• Crack growth is slow
• It initiate from stress concentration points
• load is considerably below the design or yield stress level
• The surface is smooth
• The surface is bounded by a curve
• Bands may sometimes be seen on the smooth surface –”beachmarks”.
They show the progress of the crack front from the point of origin
• The surface is 90° to the load
• Final fracture will usually take the form of gross yielding (as the
maximum stress in the remaining ligament increase!)
• Fatigue crack need initiation + propagation periods
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135. Bend Tests 4.15
Object of test:
• To determine the soundness of the weld zone. Bend
testing can also be used to give an assessment of
weld zone ductility.
• There are three ways to perform a bend test:
Face bend
Root bend Side bend
Side bend tests are normally carried out on welds over 12mm in thickness
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136. Bending test 4.16
Types of bend test for welds (acc. BS EN 910):
“t” up to 12 mm Root / face
bend
Thickness of material - “t”
“t” over 12 mm Side bend
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137. Fillet Weld Fracture Tests 4.17
Object of test:
• To break open the joint through the weld to permit
examination of the fracture surfaces
• Specimens are cut to the required length
• A saw cut approximately 2mm in depth is applied along
the fillet welds length
• Fracture is usually made by striking the specimen with a
single hammer blow
• Visual inspection for defects
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138. Fillet Weld Fracture Tests 4.17
Hammer
2mm
Notch
Fracture should break weld saw cut to root
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139. Fillet Weld Fracture Tests 4.17
This fracture indicates This fracture has
lack of fusion occurred saw cut to root
Lack of Penetration
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140. Nick-Break Test 4.18
Object of test:
• To permit evaluation of any weld defects across the
fracture surface of a butt weld.
• Specimens are cut transverse to the weld
• A saw cut approximately 2mm in depth is applied along the
welds root and cap
• Fracture is usually made by striking the specimen with a
single hammer blow
• Visual inspection for defects
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141. Nick-Break Test 4.18
Notch cut by hacksaw
2 mm
19 mm
2 mm
Approximately 230 mm
Weld reinforcement
may or may not be
removed
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142. Nick Break Test 4.18
Alternative nick-break test
specimen, notch applied all
way around the specimen
Lack of root penetration Inclusions on fracture
or fusion line
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143. Summary of Mechanical Testing 4.19
We test welds to establish minimum levels of mechanical
properties, and soundness of the welded joint
We divide tests into Qualitative & Quantitative methods:
Quantitative: (Have units/numbers) Qualitative: (Have no units/numbers)
To measure mechanical properties For assessing joint quality
Hardness (VPN & BHN) Macro tests
Toughness (Joules & ft.lbs) Bend tests
Strength (N/mm2 & PSI, MPa) Fillet weld fracture tests
Ductility / Elongation (E%) Butt Nick break tests
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144. Welding Inspector
WPS – Welder Qualifications
Section 5
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145. Welding Procedure Qualification 5.1
Question:
What is the main reason for carrying out a Welding Procedure
Qualification Test ?
(What is the test trying to show ?)
Answer:
To show that the welded joint has the properties* that satisfy
the design requirements (fit for purpose)
* properties
•mechanical properties are the main interest - always strength but
toughness & hardness may be important for some applications
•test also demonstrates that the weld can be made without defects
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146. Welding Procedures 5.1
Producing a welding procedure involves:
• Planning the tasks
• Collecting the data
• Writing a procedure for use of for trial
• Making a test welds
• Evaluating the results
• Approving the procedure
• Preparing the documentation
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147. Welding Procedures 5.2
In most codes reference is made to how the procedure are to
be devised and whether approval of these procedures is
required.
The approach used for procedure approval depends on the
code:
Example codes:
• AWS D.1.1: Structural Steel Welding Code
• BS 2633: Class 1 welding of Steel Pipe Work
• API 1104: Welding of Pipelines
• BS 4515: Welding of Pipelines over 7 Bar
Other codes may not specifically deal with the requirement of
a procedure but may contain information that may be used in
writing a weld procedure
• EN 1011Process of Arc Welding Steels
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148. Welding Procedure Qualification 5.3
(according to EN ISO 15614)
The welding engineer writes qualified Welding Procedure
Specifications (WPS) for production welding
Production welding conditions must remain within the range of
qualification allowed by the WPQR
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149. Welding Procedure Qualification 5.3
(according to EN Standards)
welding conditions are called welding variables
welding variables are classified by the EN ISO Standard as:
•Essential variables
•Non-essential variables
•Additional variables
Note: additional variables = ASME supplementary essential
The range of qualification for production welding is based on
the limits that the EN ISO Standard specifies for essential
variables*
(* and when applicable - the additional variables)
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150. Welding Procedure Qualification 5.3
(according to EN Standards)
WELDING ESSENTIAL VARIABLES
Question:
Why are some welding variables classified as essential ?
Answer:
A variable, that if changed beyond certain limits (specified by
the Welding Standard) may have a significant effect on the
properties* of the joint
* particularly joint strength and ductility
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151. Welding Procedure Qualification 5.3
(according to EN Standards)
SOME TYPICAL ESSENTIAL VARIABLES
• Welding Process
• Post Weld Heat Treatment (PWHT)
• Material Type
• Electrode Type, Filler Wire Type (Classification)
• Material Thickness
• Polarity (AC, DC+ve / DC-ve)
• Pre-Heat Temperature
• Heat Input
• Welding Position
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152. Welding Procedures 5.3
Components of a welding procedure
Parent material
• Type (Grouping)
• Thickness
• Diameter (Pipes)
• Surface condition)
Welding process
• Type of process (MMA, MAG, TIG, SAW etc)
• Equipment parameters
• Amps, Volts, Travel speed
Welding Consumables
• Type of consumable/diameter of consumable
• Brand/classification
• Heat treatments/ storage
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153. Welding Procedures 5.3
Components of a welding procedure
Joint design
•Edge preparation
•Root gap, root face
•Jigging and tacking
•Type of baking
Welding Position
•Location, shop or site
•Welding position e.g. 1G, 2G, 3G etc
•Any weather precaution
Thermal heat treatments
•Preheat, temps
•Post weld heat treatments e.g. stress relieving
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154. Welding Procedures 5.3
Object of a welding procedure test
To give maximum confidence that the welds mechanical
and metallurgical properties meet the requirements of the
applicable code/specification.
Each welding procedure will show a range to which the
procedure is approved (extent of approval)
If a customer queries the approval evidence can be
supplied to prove its validity
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155. Welding Procedures
Summary of designations:
pWPS: Preliminary Welding Procedure Specification
(Before procedure approval)
WPAR (WPQR): Welding Procedure Approval Record
(Welding procedure Qualification record)
WPS: Welding Procedure Specification
(After procedure approval)
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156. Example:
Welding
Procedure
Specification
(WPS)
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157. Welder Qualification 5.4
Numerous codes and standards deal with welder qualification,
e.g. BS EN 287.
• Once the content of the procedure is approved the next
stage is to approve the welders to the approved procedure.
• A welders test know as a Welders Qualification Test (WQT).
Object of a welding qualification test:
• To give maximum confidence that the welder meets the
quality requirements of the approved procedure (WPS).
• The test weld should be carried out on the same material and
same conditions as for the production welds.
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158. Welder Qualification 5.4 & 5.5
(according to EN Standards)
Question:
What is the main reason for qualifying a welder ?
Answer:
To show that he has the skill to be able to make production
welds that are free from defects
Note: when welding in accordance with a Qualified WPS
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159. Welder Qualification
(according to EN 287 )
5.5
The welder is allowed to make production welds within the
range of qualification shown on the Certificate
The range of qualification allowed for production welding is
based on the limits that the EN Standard specifies for the
welder qualification essential variables
A Certificate may be withdrawn by the Employer if there is
reason to doubt the ability of the welder, for example
• a high repair rate
• not working in accordance with a qualified WPS
The qualification shall remain valid for 2 years provided there is certified
confirmation of welding to the WPS in that time.
A Welder‟s Qualification Certificate automatically expires if the welder has not
used the welding process for 6 months or longer.
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160. Welding Procedure Qualification 5.7
(according to EN ISO 15614)
Welding Engineer writes a preliminary Welding Procedure
Specification (pWPS) for each test weld to be made
• A welder makes a test weld in accordance with the pWPS
• A welding inspector records all the welding conditions used
for the test weld (referred to as the „as-run‟ conditions)
An Independent Examiner/ Examining Body/ Third Party
inspector may be requested to monitor the qualification
process
The finished test weld is subjected to NDT in accordance with
the methods specified by the EN ISO Standard - Visual, MT or
PT & RT or UT
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161. Welding Procedure Qualification 5.7
(according to EN ISO 15614)
Test weld is subjected to destructive testing (tensile, bend,
macro)
The Application Standard, or Client, may require additional
tests such as impact tests, hardness tests (and for some
materials - corrosion tests)
A Welding Procedure Qualification Record (WPQR) is prepared
giving details of: -
• The welding conditions used for the test weld
• Results of the NDT
• Results of the destructive tests
• The welding conditions that the test weld allows for
production welding
The Third Party may be requested to sign the WPQR as a true
record
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162. Welder Qualification 5.9
(according to EN 287 )
An approved WPS should be available covering the range of
qualification required for the welder approval.
• The welder qualifies in accordance with an approved WPS
• A welding inspector monitors the welding to make sure that the
welder uses the conditions specified by the WPS
EN Welding Standard states that an Independent Examiner,
Examining Body or Third Party Inspector may be required to
monitor the qualification process
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163. Welder Qualification 5.9
(according to EN 287 )
The finished test weld is subjected to NDT by the methods
specified by the EN Standard - Visual, MT or PT & RT or UT
The test weld may need to be destructively tested - for certain
materials and/or welding processes specified by the EN
Standard or the Client Specification
• A Welder‟s Qualification Certificate is prepared showing the
conditions used for the test weld and the range of qualification
allowed by the EN Standard for production welding
• The Qualification Certificate is usually endorsed by a Third
Party Inspector as a true record of the test
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164. Welder Qualification 5.10
Information that should be included on a welders test certificate are,
which the welder should have or have access to a copy of !
• Welders name and identification number
• Date of test and expiry date of certificate
• Standard/code e.g. BS EN 287
• Test piece details
• Welding process.
• Welding parameters, amps, volts
• Consumables, flux type and filler classification details
• Sketch of run sequence
• Welding positions
• Joint configuration details
• Material type qualified, pipe diameter etc
• Test results, remarks
• Test location and witnessed by
• Extent (range) of approval
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165. Welding Inspector
Materials Inspection
Section 6
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166. Material Inspection
One of the most important items to consider is Traceability.
The materials are of little use if we can not, by use of an effective QA
system trace them from specification and purchase order to final
documentation package handed over to the Client.
All materials arriving on site should be inspected for:
• Size / dimensions
• Condition
• Type / specification
In addition other elements may need to be considered depending on
the materials form or shape
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167. Pipe Inspection
We inspect the condition
(Corrosion, Damage, Wall thickness Ovality, Laminations & Seam)
Specification LP5
Welded Size
seam
Other checks may need to be made such as: distortion tolerance,
number of plates and storage.
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168. Plate Inspection
We inspect the condition
(Corrosion, Mechanical damage, Laps, Bands &
Laminations)
Specification
5L
Size
Other checks may need to be made such as: distortion
tolerance, number of plates and storage.
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169. Parent Material Imperfections
Mechanical damage Lap
Lamination
Segregation line
Laminations are caused in the parent plate by the steel making
process, originating from ingot casting defects.
Segregation bands occur in the centre of the plate and are low
melting point impurities such as sulphur and phosphorous.
Laps are caused during rolling when overlapping metal does not
fuse to the base material.
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170. Lapping
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171. Lamination
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172. Laminations
Plate Lamination
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173. Welding Inspector
Codes & Standards
Section 7
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174. Codes & Standards
The 3 agencies generally identified in a code or standard:
The customer, or client
The manufacturer, or contractor
The 3rd party inspection, or clients representative
Codes often do not contain all relevant data, but may
refer to other standards
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175. Standard/Codes/Specifications
STANDARDS
SPECIFICATIONS CODES
Examples Examples
plate, pipe pressure vessels
forgings, castings bridges
valves pipelines
electrodes tanks
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176. Welding Inspector
Welding Symbols
Section 8
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177. Weld symbols on drawings
Advantages of symbolic representation:
• simple and quick plotting on the drawing
• does not over-burden the drawing
• no need for additional view
• gives all necessary indications regarding the specific joint to
be obtained
Disadvantages of symbolic representation:
• used only for usual joints
• requires training for properly understanding of symbols
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178. Weld symbols on drawings
The symbolic representation includes:
• an arrow line
• a reference line
• an elementary symbol
The elementary symbol may be completed by:
• a supplementary symbol
• a means of showing dimensions
• some complementary indications
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179. Dimensions
Convention of dimensions
In most standards the cross sectional dimensions are given to
the left side of the symbol, and all linear dimensions are give on
the right side
BS EN ISO 22553
a = Design throat thickness
s = Depth of Penetration, Throat thickness
z = Leg length (min material thickness)
AWS A2.4
•In a fillet weld, the size of the weld is the leg length
•In a butt weld, the size of the weld is based on the depth of the
joint preparation
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180. Weld symbols on drawings
A method of transferring information from the
design office to the workshop is:
Please weld
here
The above information does not tell us much about the wishes
of the designer. We obviously need some sort of code which
would be understood by everyone.
Most countries have their own standards for symbols.
Some of them are AWS A2.4 & BS EN 22553 (ISO 2553)
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181. Weld symbols on drawings
Joints in drawings may be indicated:
•by detailed sketches, showing every dimension
•by symbolic representation
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182. Elementary Welding Symbols
(BS EN ISO 22553 & AWS A2.4)
Convention of the elementary symbols:
Various categories of joints are characterised by an elementary symbol.
The vertical line in the symbols for a fillet weld, single/double bevel butts
and a J-butt welds must always be on the left side.
Weld type Sketch Symbol
Square edge
butt weld
Single-v
butt weld
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183. Elementary Welding Symbols
Weld type Sketch Symbol
Single-V butt
weld with broad
root face
Single
bevel butt
weld
Single bevel
butt weld with
broad root
face
Backing run
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184. Elementary Welding Symbols
Weld type Sketch Symbol
Single-U
butt weld
Single-J
butt weld
Surfacing
Fillet weld
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185. ISO 2553 / BS EN 22553
Plug weld Square Butt weld
Resistance spot weld Steep flanked
Single-V Butt
Resistance seam weld Surfacing
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186. Arrow Line
(BS EN ISO 22553 & AWS A2.4):
Convention of the arrow line:
• Shall touch the joint intersection
• Shall not be parallel to the drawing
• Shall point towards a single plate preparation (when only
one plate has preparation)
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187. Reference Line
(AWS A2.4)
Convention of the reference line:
Shall touch the arrow line
Shall be parallel to the bottom of the drawing
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188. Reference Line
(BS EN ISO 22553)
Convention of the reference line:
• Shall touch the arrow line
• Shall be parallel to the bottom of the drawing
• There shall be a further broken identification line above or
beneath the reference line (Not necessary where the weld
is symmetrical!)
or
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189. Double side weld symbols
(BS EN ISO 22553 & AWS A2.4)
Convention of the double side weld symbols:
Representation of welds done from both sides of the joint
intersection, touched by the arrow head
Fillet weld Double bevel Double J
Double V Double U
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190. ISO 2553 / BS EN 22553
Reference lines
Arrow line
Other side Arrow side
Arrow side Other side
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191. ISO 2553 / BS EN 22553
MR
M
Single-V Butt with Single-U Butt with
permanent backing strip removable backing strip
Single-V Butt flush cap Single-U Butt with sealing run
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192. ISO 2553 / BS EN 22553
Single-bevel butt Double-bevel butt
Single-bevel butt Single-J butt
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193. ISO 2553 / BS EN 22553
s10
10
15
Partial penetration single-V butt
„S‟ indicates the depth of penetration
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194. ISO 2553 / BS EN 22553
a = Design throat thickness
s = Depth of Penetration, Throat
thickness
z = Leg length(min material thickness)
a = (0.7 x z)
a4
a
z s 4mm Design throat
z6
s6
6mm leg 6mm Actual throat
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195. ISO 2553 / BS EN 22553
Arrow side
Arrow side
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196. ISO 2553 / BS EN 22553
s6
6mm fillet weld
Other side
s6
Other side
4/23/2007 198 of 691

197. ISO 2553 / BS EN 22553
n = number of weld elements
l = length of each weld element
(e) = distance between each weld element
n x l (e)
Welds to be
staggered
2 x 40 (50)
111
3 x 40 (50)
Process
4/23/2007 199 of 691

198. ISO 2553 / BS EN 22553
All dimensions in mm
z5 3 x 80 (90)
z6 3 x 80 (90)
5
80 80 80
5
6 90 90 90
6
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199. ISO 2553 / BS EN 22553
All dimensions in mm
z8 3 x 80 (90)
z6 3 x 80 (90)
6
80 80 80
6
8 90 90
90
8
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200. Supplementary symbols
(BS EN ISO 22553 & AWS A2.4)
Convention of supplementary symbols
Supplementary information such as welding process, weld
profile, NDT and any special instructions
Toes to be ground smoothly
(BS EN only)
Site Weld
Concave or Convex
Weld all round
4/23/2007 202 of 691

201. Supplementary symbols
(BS EN ISO 22553 & AWS A2.4)
Convention of supplementary symbols
Supplementary information such as welding process, weld profile,
NDT and any special instructions
Ground flush
111
MR M
Removable Permanent Welding process
backing strip backing strip numerical BS EN
Further supplementary information, such as WPS number, or
NDT may be placed in the fish tail
4/23/2007 203 of 691

202. ISO 2553 / BS EN 22553
a b
c d
4/23/2007 204 of 691

203. ISO 2553 / BS EN 22553
Mitre Convex
Toes
Concave
shall be
blended
4/23/2007 205 of 691

204. ISO 2553 / BS EN 22553
a = Design throat thickness
s = Depth of Penetration, Throat
thickness
z = Leg length(min material thickness)
a = (0.7 x z)
a4
a
z s 4mm Design throat
z6
s6
6mm leg 6mm Actual throat
4/23/2007 206 of 691

205. ISO 2553 / BS EN 22553
Complimentary Symbols
Field weld (site weld) Welding to be carried out
all round component
(peripheral weld)
NDT WPS
The component requires Additional information,
NDT inspection the reference document
is included in the box
4/23/2007 207 of 691

206. ISO 2553 / BS EN 22553
Numerical Values for Welding Processes:
111: MMA welding with covered electrode
121: Sub-arc welding with wire electrode
131: MIG welding with inert gas shield
135: MAG welding with non-inert gas shield
136: Flux core arc welding
141: TIG welding
311: Oxy-acetylene welding
72: Electro-slag welding
15: Plasma arc welding
4/23/2007 208 of 691

207. AWS A2.4 Welding Symbols
4/23/2007 209 of 691

208. AWS Welding Symbols
Depth of Root Opening
Bevel
1(1-1/8)
1/8
60o
Effective Groove Angle
Throat
4/23/2007 210 of 691

209. AWS Welding Symbols
Welding Process
GSFCAW
1(1-1/8)
1/8
60o
GMAW
GTAW
SAW
4/23/2007 211 of 691

210. AWS Welding Symbols
Welds to be
staggered
3 – 10
SMAW
3 – 10
Process
3 3
10
4/23/2007 212 of 691

211. AWS Welding Symbols
3rd Operation
Sequence of
Operations 2nd Operation
1st Operation
FCAW
1(1-1/8)
1/8
60o
4/23/2007 213 of 691

212. AWS Welding Symbols
RT
Sequence of
Operations MT
MT
FCAW
1(1-1/8)
1/8
60o
4/23/2007 214 of 691

213. AWS Welding Symbols
Dimensions- Leg Length
6 leg on member A
6/8
Member A 6
8
Member B
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214. Welding Inspector
Intro To Welding Processes
Section 9
4/23/2007 221 of 691

215. Welding Processes
Welding is regarded as a joining process in which the work
pieces are in atomic contact
Pressure welding Fusion welding
• Forge welding • Oxy-acetylene
• Friction welding • MMA (SMAW)
• Resistance Welding • MIG/MAG (GMAW)
• TIG (GTAW)
• Sub-arc (SAW)
• Electro-slag (ESW)
• Laser Beam (LBW)
• Electron-Beam (EBW)
4/23/2007 222 of 691

216. Constant Current Power Source
(Drooping Characteristic)
100
O.C.V. Striking voltage (typical) for
90
arc initiation
80
Required for: MMA, TIG, Plasma
70
arc and SAW > 1000 AMPS
60
Voltage
50
40 Large voltage variation, e.g. +
Normal Operating 10v (due to changes in arc
30 Voltage Range length)
Small amperage change
20
resulting in virtually constant
current e.g. + 5A.
10
20 40 60 80 100 120 130 140 160 180 200
Amperage
4/23/2007 225 of 691

217. Monitoring Heat Input
• Heat Input:
The amount of heat generated in the
welding arc per unit length of weld.
Expressed in kilo Joules per millimetre
length of weld (kJ/mm).
Heat Input (kJ/mm)= Volts x Amps
Travel speed(mm/s) x 1000
4/23/2007 227 of 691

218. Monitoring Heat Input
Weld and weld pool temperatures
4/23/2007 228 of 691

219. Monitoring Heat Input
4/23/2007 229 of 691

220. Monitoring Heat Input
• Monitoring Heat Input As Required by
• BS EN ISO 15614-1:2004
• In accordance with EN 1011-1:1998
When impact requirements and/or hardness requirements are
specified, impact test shall be taken from the weld in the highest
heat input position and hardness tests shall be taken from the
weld in the lowest heat input position in order to qualify for all
positions
4/23/2007 230 of 691

221. Welding Inspector
MMA Welding
Section 10
4/23/2007 231 of 691

222. MMA - Principle of operation
4/23/2007 233 of 691

223. MMA welding
Main features:
• Shielding provided by decomposition of flux covering
• Electrode consumable
• Manual process
Welder controls:
• Arc length
• Angle of electrode
• Speed of travel
• Amperage settings
4/23/2007 234 of 691

224. Manual Metal Arc Basic Equipment
Control panel Power source
(amps, volts)
Electrode Holding oven
oven
Electrodes Inverter power
source
Return lead
Electrode holder
Welding visor
filter glass Power cables
4/23/2007 235 of 691

225. MMA Welding Plant
Transformer:
• Changes mains supply voltage to a voltage suitable for welding.
Has no moving parts and is often termed static plant.
Rectifier:
• Changes a.c. to d.c., can be mechanically or statically achieved.
Generator:
• Produces welding current. The generator consists of an armature
rotating in a magnetic field, the armature must be rotated at a
constant speed either by a motor unit or, in the absence of
electrical power, by an internal combustion engine.
Inverter:
• An inverter changes d.c. to a.c. at a higher frequency.
4/23/2007 236 of 691

226. MMA Welding Variables
Voltage
• The arc voltage in the MMA process is measured as close to
the arc as possible. It is variable with a change in arc length
O.C.V.
• The open circuit voltage is the voltage required to initiate, or
re-ignite the electrical arc and will change with the type of
electrode being used e.g 70-90 volts
Current
• The current used will be determined by the choice of
electrode, electrode diameter and material type and
thickness. Current has the most effect on penetration.
Polarity
• Polarity is generally determined by operation and electrode
type e.g DC +ve, DC –ve or AC
4/23/2007 237 of 691

227. Constant Current Power Source
(Drooping Characteristic)
100
O.C.V. Striking voltage (typical) for arc
90
initiation
80
70
60
Voltage
50
40 Large voltage variation, e.g. +
Normal Operating 10v (due to changes in arc
30 Voltage Range length)
Small amperage change
20
resulting in virtually constant
current e.g. + 5A.
10
20 40 60 80 100 120 130 140 160 180 200
Amperage
4/23/2007 239 of 691

228. MMA welding parameters
Travel speed
Travel
Too low speed Too high
•wide weld bead contour •lack of root fusion
•lack of penetration •incomplete root
•burn-through penetration
•undercut
•poor bead profile,
difficult slag removal
4/23/2007 240 of 691

229. MMA welding parameters
Type of current:
• voltage drop in welding cables is lower with AC
• inductive looses can appear with AC if cables are coiled
• cheaper power source for AC
• no problems with arc blow with AC
• DC provides a more stable and easy to strike arc, especially
with low current, better positional weld, thin sheet applications
• welding with a short arc length (low arc voltage) is easier with
DC, better mechanical properties
• DC provides a smoother metal transfer, less spatter
4/23/2007 241 of 691

230. MMA welding parameters
Welding current
– approx. 35 A/mm of diameter
– governed by thickness, type of joint and welding
position
Welding
Too low current Too high
•poor starting •spatter
•slag inclusions •excess
•weld bead contour too penetration
high •undercut
•lack of •burn-through
fusion/penetration
4/23/2007 242 of 691

231. MMA welding parameters
Arc length = arc voltage
Arc
Too low voltage Too high
•arc can be extinguished •spatter
•“stubbing” •porosity
•excess
penetration
•undercut
•burn-through
Polarity: DCEP generally gives deeper penetration
4/23/2007 243 of 691

232. MMA - Troubleshooting
MMA quality (left to right)
current, arc length and travel speed normal;
current too low;
current too high;
arc length too short;
arc length too long;
travel speed too slow;
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233. MMA electrode holder
“Tongs” type with
Collet or twist type
spring-loaded jaws
4/23/2007 245 of 691

234. MMA Welding Consumables
MMA Covered Electrodes
The three main electrode covering types used in MMA welding
• Cellulosic - deep penetration/fusion
• Rutile - general purpose
• Basic - low hydrogen
(Covered in more detail in Section 14)
4/23/2007 246 of 691

235. MMA welding typical defects
Most welding defects in MMA are caused by a lack of welder
skill (not an easily controlled process), the incorrect settings
of the equipment, or the incorrect use, and treatment of
electrodes
Typical Welding Defects:
•Slag inclusions
•Arc strikes
•Porosity
•Undercut
•Shape defects (overlap, excessive root penetration, etc.)
4/23/2007 247 of 691

236. Manual Metal Arc Welding (MMA)
Advantages:
• Field or shop use
• Range of consumables
• All positions
• Portable
• Simple equipment
Disadvantages:
• High welder skill required
• High levels of fume
• Hydrogen control (flux)
• Stop/start problems
• Comparatively uneconomic when compared with some
other processes i.e MAG, SAW and FCAW
4/23/2007 248 of 691

237. Welding Inspector
TIG Welding
Section 11
4/23/2007 249 of 691

238. Tungsten Inert Gas Welding
The TIG welding process was first developed in the USA
during the 2nd world war for the welding of aluminum alloys
• The process uses a non-consumable tungsten electrode
• The process requires a high level of welder skill
• The process produces very high quality welds.
• The TIG process is considered as a slow process compared
to other arc welding processes
• The arc may be initiated by a high frequency to avoid scratch
starting, which could cause contamination of the tungsten
and weld
4/23/2007 250 of 691

239. TIG - Principle of operation
4/23/2007 251 of 691

240. TIG Welding Variables
Voltage
The voltage of the TIG welding process is variable only by the
type of gas being used, and changes in the arc length
Current
The current is adjusted proportionally to the tungsten
electrodes diameter being used. The higher the current the
deeper the penetration and fusion
Polarity
The polarity used for steels is always DC –ve as most of the
heat is concentrated at the +ve pole, this is required to keep
the tungsten electrode at the cool end of the arc. When
welding aluminium and its alloys AC current is used
4/23/2007 254 of 691

241. Types of current
DC • can be DCEN or DCEP
• DCEN gives deep penetration
AC can be sine or square wave
Type of requires a HF current (continuos
welding or periodical)
current provide cleaning action
Pulsed • requires special power source
current • low frequency - up to 20 pulses/sec
(thermal pulsing)
• better weld pool control
• weld pool partially solidifies
4/23/2007 between pulses 256 of 691

242. Choosing the proper electrode
Current type influence
+ - + - + -
+ - + - + -
+ - + - + -
Current type & polarity DCEN AC (balanced) DCEP
Heat balance 70% at work 50% at work 35% at work
30% at electrode 50% at electrode 65% at electrode
Penetration Deep, narrow Medium Shallow, wide
Oxide cleaning action No Yes - every half cycle Yes
Electrode capacity Excellent Good Poor
(e.g. 3,2 mm/400A) (e.g. 3,2 mm/225A) (e.g. 6,4 mm/120A)
4/23/2007 257 of 691

243. ARC CHARACTERISTICS
Constant Current/Amperage Characteristic
Large change in voltage =
OCV Smaller change in amperage
Volts
Large arc gap
Welding Voltage
Small arc
gap
Amps
4/23/2007 258 of 691

244. TIG - arc initiation methods
Arc initiation
method
Lift arc HF start
• simple method need a HF generator (spark-
• tungsten electrode is in contact gap oscillator) that generates a
with the workpiece!
high voltage AC output (radio
• high initial arc current due to the
short circuit frequency) costly
• impractical to set arc length in reliable method required on
advance both DC (for start) and AC (to
• electrode should tap the re-ignite the arc)
workpiece - no scratch!
can be used remotely
• ineffective in case of AC
• used when a high quality is not HF produce interference
essential requires superior insulation
4/23/2007 259 of 691

245. Pulsed current
• usually peak current is 2-10 times
Pulse Cycle Peak Background background current
Current (A)
time time current current
• useful on metals sensitive to high heat
input
• reduced distortions
• in case of dissimilar thicknesses equal
penetration can be achieved
Average current
Time
one set of variables can be used in all positions
used for bridging gaps in open root joints
require special power source
4/23/2007 260 of 691

246. Choosing the proper electrode
Polarity Influence – cathodic cleaning effect
4/23/2007 261 of 691

247. Tungsten Electrodes
Old types: (Slightly Radioactive)
• Thoriated: DC electrode -ve - steels and most metals
• 1% thoriated + tungsten for higher current values
• 2% thoriated for lower current values
• Zirconiated: AC - aluminum alloys and magnesium
New types: (Not Radioactive)
• Cerium: DC electrode -ve - steels and most metals
• Lanthanum: AC - Aluminum alloys and magnesium
4/23/2007 262 of 691

248. TIG torch set-up
• Electrode extension
Stickout 2-3 times
electrode
Electrode diameter
extension
Low electron Overheating
Too Electrode Too
emission Tungsten
small extension large
Unstable arc inclusions
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249. Choosing the correct electrode
Polarity Influence – cathodic cleaning effect
4/23/2007 264 of 691

250. Tungsten Electrodes
Old types: (Slightly Radioactive)
• Thoriated: DC electrode -ve - steels and most metals
• 1% thoriated + tungsten for higher current values
• 2% thoriated for lower current values
• Zirconiated: AC - aluminum alloys and magnesium
New types: (Not Radioactive)
• Cerium: DC electrode -ve - steels and most metals
• Lanthanum: AC - Aluminum alloys and magnesium
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251. Tungsten electrode types
Pure tungsten electrodes:
colour code - green
no alloy additions
low current carrying capacity
maintains a clean balled end
can be used for AC welding of Al and Mg alloys
poor arc initiation and arc stability with AC compared
with other electrode types
used on less critical applications
low cost
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252. Tungsten electrode types
Thoriated tungsten electrodes:
colour code - yellow/red/violet
20% higher current carrying capacity compared to
pure tungsten electrodes
longer life - greater resistance to contamination
thermionic - easy arc initiation, more stable arc
maintain a sharpened tip
recommended for DCEN, seldom used on AC
(difficult to maintain a balled tip)
This slightly radioactive
4/23/2007 267 of 691

253. Tungsten electrode types
Ceriated tungsten electrodes:
colour code - grey (orange acc. AWS A-5.12)
operate successfully with AC or DC
Ce not radioactive - replacement for thoriated types
Lanthaniated tungsten electrodes:
colour code - black/gold/blue
operating characteristics similar with ceriated
electrode
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254. Tungsten electrode types
Zirconiated tungsten electrodes:
colour code - brown/white
operating characteristics fall between those of pure
and thoriated electrodes
retains a balled end during welding - good for AC
welding
high resistance to contamination
preferred for radiographic quality welds
4/23/2007 269 of 691

255. Electrode tip for DCEN
Penetration
increase
electrode diameter
Increase
2-2,5 times
Vertex
angle
Decrease
Bead width
increase
Electrode tip prepared for low Electrode tip prepared for high
current welding current welding
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256. Electrode tip for AC
DC -ve AC
Electrode tip ground and
Electrode tip ground
then conditioned
4/23/2007 271 of 691

257. TIG Welding Variables
Tungsten electrodes
The electrode diameter, type and vertex angle are all critical
factors considered as essential variables. The vertex angle is
as shown
DC -ve AC
Vetex angle
Note: when welding
Note: too fine an angle will aluminium with AC
promote melting of the current, the tungsten end
electrodes tip is chamfered and forms a
ball end when welding
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258. Choosing the proper electrode
Factors to be considered:
Electrode tip Excessive
Too Welding Too
not properly melting or
low current high
heated volatilisation
Unstable Tungsten
arc Penetration inclusions
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259. Shielding gas requirements
• Preflow and Shielding gas flow
postflow Welding current
Preflow Postflow
Flow rate Flow rate
too low too high
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260. Special shielding methods
Pipe root run shielding – Back Purging to prevent
excessive oxidation during welding, normally argon.
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261. TIG torch set-up
Electrode extension
Stickout 2-3 times
electrode
Electrode diameter
extension
Low electron Overheating
Too Electrode Too
emission Tungsten
small extension large
Unstable arc inclusions
4/23/2007 277 of 691

262. TIG Welding Consumables
Welding consumables for TIG:
•Filler wires, Shielding gases, tungsten electrodes (non-
consumable).
•Filler wires of different materials composition and variable
diameters available in standard lengths, with applicable
code stamped for identification
•Steel Filler wires of very high quality, with copper coating to
resist corrosion.
•shielding gases mainly Argon and Helium, usually of highest
purity (99.9%).
4/23/2007 278 of 691

263. Tungsten Inclusion
May be caused by Thermal Shock of
heating to fast and small fragments
break off and enter the weld pool, so a
“slope up” device is normally fitted to
prevent this could be caused by touch
down also.
Most TIG sets these days have slope-
up devices that brings the current to
the set level over a short period of
time so the tungsten is heated more
slowly and gently
A Tungsten Inclusion always shows up as
bright white on a radiograph
4/23/2007 279 of 691

264. TIG typical defects
Most welding defects with TIG are caused by a lack of welder
skill, or incorrect setting of the equipment. i.e. current, torch
manipulation, welding speed, gas flow rate, etc.
• Tungsten inclusions (low skill or wrong vertex angle)
• Surface porosity (loss of gas shield mainly on site)
• Crater pipes (bad weld finish technique i.e. slope out)
• Oxidation of S/S weld bead, or root by poor gas cover
• Root concavity (excess purge pressure in pipe)
• Lack of penetration/fusion (widely on root runs)
4/23/2007 280 of 691

265. Tungsten Inert Gas Welding
Advantages Disadvantages
• High quality • High skill factor required
• Good control • Low deposition rate
• All positions • Small consumable range
• Lowest H2 process • High protection required
• Minimal cleaning • Complex equipment
• Autogenous welding • Low productivity
(No filler material) • High ozone levels +HF
• Can be automated
4/23/2007 281 of 691

266. Welding Inspector
MIG/MAG Welding
Section 12
4/23/2007 282 of 691

267. Gas Metal Arc Welding
The MIG/MAG welding process was initially developed in the
USA in the late 1940s for the welding of aluminum alloys.
The latest EN Welding Standards now refer the process by the
American term GMAW (Gas Metal Arc Welding)
• The process uses a continuously fed wire electrode
• The weld pool is protected by a separately supplied
shielding gas
• The process is classified as a semi-automatic welding
process but may be fully automated
• The wire electrode can be either bare/solid wire or flux
cored hollow wire
4/23/2007 283 of 691

268. MIG/MAG - Principle of operation
4/23/2007 284 of 691

269. MIG/MAG process variables
• Welding current
•Increasing welding current
•Increase in depth and width
•Increase in deposition rate
• Polarity
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270. MIG/MAG process variables
• Arc voltage
•Increasing arc voltage
•Reduced penetration, increased width
•Excessive voltage can cause porosity,
spatter and undercut
• Travel speed
•Increasing travel speed
•Reduced penetration and width, undercut
4/23/2007 287 of 691

271. Gas Metal Arc Welding
Types of Shielding Gas
MIG (Metal Inert Gas)
• Inert Gas is required for all non-ferrous alloys (Al, Cu, Ni)
• Most common inert gas is Argon
• Argon + Helium used to give a „hotter‟ arc - better for thicker
joints and alloys with higher thermal conductivity
4/23/2007 289 of 691

272. MIG/MAG – shielding gases
Type of material Shielding gas
Carbon steel CO2 , Ar+(5-20)%CO2
Stainless steel Ar+2%O2
Aluminium Ar
4/23/2007 290 of 691

273. MIG/MAG shielding gases
Ar Ar-He He CO2
Argon (Ar):
higher density than air; low thermal conductivity the arc
has a high energy inner cone; good wetting at the toes; low
ionisation potential
Helium (He):
lower density than air; high thermal conductivity uniformly
distributed arc energy; parabolic profile; high ionisation
potential
Carbon Dioxide (CO2):
cheap; deep penetration profile; cannot support spray
transfer; poor wetting; high spatter
4/23/2007 291 of 691

274. MIG/MAG shielding gases
Gases for dip transfer:
• CO2: carbon steels only: deep penetration; fast welding
speed; high spatter levels
• Ar + up to 25% CO2: carbon and low alloy steels: minimum
spatter; good wetting and bead contour
• 90% He + 7.5% Ar + 2.5% CO2:stainless steels: minimises
undercut; small HAZ
• Ar: Al, Mg, Cu, Ni and their alloys on thin sections
• Ar + He mixtures: Al, Mg, Cu, Ni and their alloys on thicker
sections (over 3 mm)
4/23/2007 292 of 691

275. MIG/MAG shielding gases
Gases for spray transfer
• Ar + (5-18)% CO2: carbon steels: minimum spatter; good
wetting and bead contour
• Ar + 2% O2: low alloy steels: minimise undercut; provides
good toughness
• Ar + 2% O2 or CO2: stainless steels: improved arc stability;
provides good fusion
• Ar: Al, Mg, Cu, Ni, Ti and their alloys
• Ar + He mixtures: Al, Cu, Ni and their alloys: hotter arc than
pure Ar to offset heat dissipation
• Ar + (25-30)% N2: Cu alloys: greater heat input
4/23/2007 293 of 691

276. Gas Metal Arc Welding
Types of Shielding Gas
MAG (Metal Active Gas)
• Active gases used are Oxygen and Carbon Dioxide
• Argon with a small % of active gas is required for all steels
(including stainless steels) to ensure a stable arc & good
droplet wetting into the weld pool
• Typical active gases are
Ar + 20% CO2 for C-Mn & low alloy steels
Ar + 2% O2 for stainless steels
100% CO2 can be used for C - steels
4/23/2007 294 of 691

277. MIG/MAG Gas Metal Arc Welding
Electrode
orientation
Penetration Deep Moderate Shallow
Excess weld metal Maximum Moderate Minimum
Undercut Severe Moderate Minimum
Electrode extension
•Increased extension
4/23/2007 295 of 691

278. MIG / MAG - self-regulating arc
Stable condition Sudden change in gun position
Arc length L = 6,4 mm Arc length L‟ = 12,7 mm
Arc voltage = 24V Arc voltage = 29V
Welding current = 250A Welding current = 220A
WFS = 6,4 m/min WFS = 6,4 m/min
Melt off rate = 6,4 m/min Melt off rate = 5,6
m/min
L‟ 25 mm
L 19 mm
Voltage (V)
Current (A)
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279. MIG/MAG - self-regulating arc
Sudden change in gun position Re-established stable condition
Arc length L‟ = 12,7 mm Arc length L = 6,4 mm
Arc voltage = 29V Arc voltage = 24V
Welding current = 220A Welding current = 250A
WFS = 6,4 m/min WFS = 6,4 m/min
Melt off rate = 5,6 m/min Melt off rate = 6,4 m/min
L‟ 25 mm 25 mm
L
Voltage (V)
Current (A)
4/23/2007 297 of 691

280. Terminating the arc
Crater fill
• Burnback time
– delayed current cut-off to prevent wire freeze
in the weld end crater
– depends on WFS (set as short as possible!)
Contact tip
3 mm
8 mm Current - 250A
14 mm
Insulatin Voltage - 27V
g slag WFS - 7,8 m/min
Wire diam. - 1,2 mm
Burnback time 0.05 sec 0.10 sec 0.15 sec
Shielding gas -
Workpiec
Ar+18%CO2
e
4/23/2007 298 of 691

281. MIG/MAG - metal transfer modes
Contact tip Electrode
Contact tip recessed extension
extension Electrode
(3-5 mm) 19-25 mm
(0-3,2 mm) extension
6-13 mm
Set-up for dip transfer Set-up for spray transfer
4/23/2007 299 of 691

282. MIG/MAG - metal transfer modes
Electrode diameter = 1,2 mm
Voltage
WFS = 8,3 m/min
Current = 295 A
Voltage = 28V
Globular Spray
transfer transfer
Electrode diameter = 1,2 mm
WFS = 3,2 m/min
Current = 145 A
Dip transfer Voltage = 18-20V
Current
4/23/2007
Current/voltage conditions 301 of 691

283. MIG/MAG-methods of metal transfer
Dip transfer
Transfer occur due to short circuits
between wire and weld pool, high
level of spatter, need inductance
control to limit current raise
Can use pure CO2 or Ar- CO2
mixtures as shielding gas
Metal transfer occur when arc is
extinguished
Requires low welding current/arc
voltage, a low heat input process.
Resulting in low residual stress
and distortion
Used for thin materials and all
position welds
4/23/2007 303 of 691

284. MIG/MAG-methods of metal transfer
Spray transfer
Transfer occur due to pinch
effect NO contact between wire
and weld pool!
Requires argon-rich shielding
gas
Metal transfer occur in small
droplets, a large volume weld
pool
Requires high welding
current/arc voltage, a high heat
input process. Resulting in high
residual stress and distortion
Used for thick materials and
flat/horizontal position welds
4/23/2007 306 of 691

285. MIG/MAG-methods of metal transfer
Pulsed transfer
Controlled metal transfer, one droplet per pulse,
No transfer between droplet and weld pool!
Requires special power sources
Metal transfer occur in small droplets (diameter equal
to that of electrode)
Requires moderate welding current/arc voltage, a
reduced heat input . Resulting in smaller residual
stress and distortion compared to spray transfer
Pulse frequency controls the volume of weld pool,
used for root runs and out of position welds
4/23/2007 307 of 691

286. MIG/MAG - metal transfer modes
Pulsed transfer
Controlled metal transfer. one droplet
per pulse. NO transfer during
background current!
Requires special power sources
Metal transfer occur in small droplets
(diameter equal to that of electrode)
Requires moderate welding current/arc voltage, reduced
heat input‟ smaller residual stress and distortions
compared to spray transfer
Pulse frequency controls the volume of weld pool, used
for root runs and out of position welds
4/23/2007 308 of 691

287. MIG/MAG-methods of metal transfer
Globular transfer
Transfer occur due to gravity or
short circuits between drops and
weld pool
Requires CO2 shielding gas
Metal transfer occur in large drops
(diameter larger than that of
electrode) hence severe spatter
Requires high welding current/arc
voltage, a high heat input process.
Resulting in high residual stress
and distortion
Non desired mode of transfer!
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288. Flat or Constant Voltage Characteristic
Flat or Constant Voltage Characteristic Used With
MIG/MAG, ESW & SAW < 1000 amps
O.C.V. Arc Voltage
Virtually no Change.
33
32
31
Small Voltage
Change.
Voltage
Large Current Change
100 200 300
Amperage
4/23/2007 315 of 691

289. MIG/MAG welding gun assembly
Gas The Push-Pull gun
Contact diffuser
tip
Union nut
Trigger WFS remote
Gas
control
nozzle
potentiometer
Handle
4/23/2007 316 of 691

290. Gas Metal Arc Welding
PROCESS CHARACTERISTICS
• Requires a constant voltage power source, gas supply, wire
feeder, welding torch/gun and „hose package‟
• Wire is fed continuously through the conduit and is burnt-off
at a rate that maintains a constant arc length/arc voltage
• Wire feed speed is directly related to burn-off rate
• Wire burn-off rate is directly related to current
• When the welder holds the welding gun the process is said
to be a semi-automatic process
• The process can be mechanised and also automated
• In Europe the process is usually called MIG or MAG
4/23/2007 318 of 691

291. MIG/MAG typical defects
Most welding imperfections in MIG/MAG are caused by lack of
welder skill, or incorrect settings of the equipment
•Worn contact tips will cause poor power pick up, or transfer
•Bad power connections will cause a loss of voltage in the arc
•Silica inclusions (in Fe steels) due to poor inter-run cleaning
•Lack of fusion (primarily with dip transfer)
•Porosity (from loss of gas shield on site etc)
•Solidification problems (cracking, centerline pipes, crater
pipes) especially on deep narrow welds
4/23/2007 322 of 691

292. WELDING PROCESS
Flux Core Arc Welding
(Not In The Training Manual)
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293. Flux cored arc welding
FCAW
methods
With gas Without gas With metal
shielding - shielding - powder -
“Outershield” “Innershield” “Metal core”
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294. “Outershield” - principle of operation
4/23/2007 325 of 691

295. “Innershield” - principle of operation
4/23/2007 326 of 691

296. ARC CHARACTERISTICS
Constant Voltage Characteristic
OCV Small change in voltage =
large change in amperage
Large arc gap
Small arc gap
The self
Volts adjusting arc.
Amps
4/23/2007 327 of 691

297. Flux Core Arc Welding (FCAW)
Flux core Insulated extension nozzle
Current carrying guild tube
Wire joint
Flux cored hollow wire
Flux powder
Arc shield composed of
vaporized and slag forming
Flux core compounds
wires
Molten
weld Metal droplets covered
Solidified weld pool
with thin slag coating
metal and slag
4/23/2007 328 of 691

298. Flux cored arc welding
FCAW
methods
With gas Without gas With metal
shielding - shielding - powder -
“Outershield” “Innershield” “Metal core”
(114)
With active With inert gas
gas shielding shielding (137)
(136)
4/23/2007 329 of 691

299. FCAW - differences from MIG/MAG
• usually operates in DCEP
but some “Innershield”
wires operates in DCEN
• power sources need to be
more powerful due to the
higher currents
• doesn't work in deep
transfer mode
• require knurled feed rolls
“Innershield” wires use
a different type of
welding gun
4/23/2007 330 of 691

300. Backhand (“drag”) technique
Advantages
preferred method for flat or horizontal position
slower progression of the weld
deeper penetration
weld stays hot longer, easy to remove dissolved
gasses
Disadvantages
produce a higher weld profile
difficult to follow the weld joint
can lead to burn-through on thin sheet plates
4/23/2007 331 of 691

301. Forehand (“push”) technique
Advantages
preferred method for vertical up or overhead
position
arc is directed towards the unwelded joint , preheat
effect
easy to follow the weld joint and control the
penetration
Disadvantages
produce a low weld profile, with coarser ripples
fast weld progression, shallower depth of penetration
the amount of spatter can increase
4/23/2007 332 of 691

302. FCAW advantages
• less sensitive to lack of fusion
• requires smaller included angle compared to MMA
• high productivity
• all positional
• smooth bead surface, less danger of undercut
• basic types produce excellent toughness properties
• good control of the weld pool in positional welding especially
with rutile wires
• seamless wires have no torsional strain, twist free
• ease of varying the alloying constituents
• no need for shielding gas
4/23/2007 333 of 691

303. FCAW disadvantages
• limited to steels and Ni-base alloys
• slag covering must be removed
• FCAW wire is more expensive on a weight basis than solid
wires (exception: some high alloy steels)
• for gas shielded process, the gaseous shield may be
affected by winds and drafts
• more smoke and fumes are generated compared with
MIG/MAG
• in case of Innershield wires, it might be necessary to
break the wire for restart (due to the high amount of
insulating slag formed at the tip of the wire)
4/23/2007 334 of 691

304. FCAW advantages/disadvantages
Advantages: Disadvantages:
1) Field or shop use 1) High skill factor
2) High productivity 2) Slag inclusions
3) All positional 3) Cored wire is
Expensive
4) Slag supports and
shapes the weld Bead 4) High level of fume
(Inner-shield)
5) No need for shielding
gas 5) Limited to steels and
nickel alloys
4/23/2007 335 of 691

305. Welding Inspector
Submerged Arc Welding
Section 13
4/23/2007 336 of 691

306. Submerged Arc Welding Introduction
• Submerged arc welding was developed in the Soviet Union
during the 2nd world war for the welding of thick section steel.
• The process is normally mechanized.
• The process uses amps in the range of 100 to over 2000, which
gives a very high current density in the wire producing deep
penetration and high dilution welds.
• A flux is supplied separately via a flux hopper in the form of either
fused or agglomerated.
• The arc is not visible as it is submerged beneath the flux layer
and no eye protection is required.
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307. SAW Principle of operation
4/23/2007 338 of 691

308. Principles of operation
Factors that determine whether to use SAW chemical
composition and mechanical properties required for the weld
deposit
• thickness of base metal to be welded
• joint accessibility
• position in which the weld is to be made
• frequency or volume of welding to be performed
SAW methods
Semiautomatic Mechanised Automatic
4/23/2007 339 of 691

309. Submerged Arc Welding
Filler wire spool
Flux hopper
Power
supply
- +
Slide rail
Wire electrode
Flux
4/23/2007 340 of 691

310. SAW process variables
• welding current
• current type and polarity
• welding voltage
• travel speed
• electrode size
• electrode extension
• width and depth of the layer of flux
4/23/2007 341 of 691

311. SAW process variables
Welding current
•controls depth of penetration and the amount of
base metal melted & dilution
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312. SAW operating variables
Current type and polarity
•Usually DCEP, deep
penetration, better
resistance to
porosity
•DCEN increase
deposition rate but
reduce penetration
(surfacing)
•AC used to avoid
arc blow; can give
unstable arc
4/23/2007 343 of 691

313. SAW Consumables
(Covered in detail in Section 14)
Fused fluxes advantages:
•good chemical homogeneity
•easy removal of fines without affecting flux
composition
•normally not hygroscopic & easy storage and handling
•readily recycled without significant change in particle
size or composition
Fused fluxes disadvantages:
•difficult to add deoxidizers and ferro-alloys (due to
segregation or extremely high loss)
•high temperatures needed to melt ingredients limit the
range of flux compositions
4/23/2007 344 of 691

314. SAW Consumables
Agglomerated fluxes advantages:
• easy addition of deoxidizers and alloying elements
• usable with thicker layer of flux when welding
• colour identification
Agglomerated fluxes disadvantages:
• tendency to absorb moisture
• possible gas evolution from the molten slag leading to
porosity
• possible change in flux composition due to segregation or
removal of fine mesh particles
4/23/2007 345 of 691

315. SAW equipment
Power sources can be:
• transformers for AC
• transformer-rectifiers for DC
Static characteristic can be:
• Constant Voltage (flat) - most of the power sources
• Constant Current (drooping)
4/23/2007 346 of 691

316. SAW equipment
Constant Voltage (Flat Characteristic) power sources:
• most commonly used supplies for SAW
• can be used for both semiautomatic and automatic welding
• self-regulating arc
• simple wire feed speed control
• wire feed speed controls the current and power supply
controls the voltage
• applications for DC are limited to 1000A due to severe arc
blow (also thin wires!)
4/23/2007 347 of 691

317. ARC CHARACTERISTICS
Constant Voltage Characteristic
OCV Small change in voltage =
large change in amperage
Large arc gap
Small arc gap
The self
Volts adjusting arc.
Amps
4/23/2007 348 of 691

318. SAW equipment
Constant Current (Drooping Characteristic) power sources:
• Over 1000A - very fast speed required - control of burn off
rate and stick out length
• can be used for both semiautomatic and automatic welding
• not self-regulating arc
• must be used with a voltage-sensing variable wire feed
speed control
• more expensive due to more complex wire feed speed
control
• arc voltage depends upon wire feed speed whilst the power
source controls the current
• cannot be used for high-speed welding of thin steel
4/23/2007 349 of 691

319. SAW equipment
Welding heads can be mounted on a:
Tractor type carriage
• provides travel along straight or
gently curved joints
• can ride on tracks set up along the
joint (with grooved wheels) or on
the workpiece itself Courtesy of ESAB AB
• can use guide wheels as tracking
device
• due to their portability, are used in
field welding or where the piece
cannot be moved
4/23/2007
Courtesy of ESAB AB 350 of 691

320. SAW operating variables
Welding current
•too high current: excessive excess weld metal
(waste of electrode), increase weld shrinkage and
causes greater distortions
•excessively high current: digging arc, undercut,
burn through; also a high and narrow bead &
solidification cracking
•too low current: incomplete
fusion or inadequate penetration
•excessively low current:
unstable arc
4/23/2007 351 of 691

321. SAW operating variables
Welding voltage
•welding voltage controls arc
length
•increase in voltage produce a
flatter and wider bead
•increase in voltage increase
flux consumption
•increase in voltage tend to
reduce porosity
•an increased voltage may
help bridging an excessive
root gap
•an increased voltage can increase pick-up of alloying elements
from an alloy flux
4/23/2007 352 of 691

322. SAW operating variables
Welding voltage
•low voltage produce a
“stiffer” arc & improves
penetration in a deep
weld groove and resists
arc blow
•excessive low voltage
produce a high narrow
bead & difficult slag
removal
4/23/2007 353 of 691

323. SAW operating variables
Welding voltage
•excessively high voltage
produce a “hat-shaped” bead
& tendency to crack
•excessively high voltage
increase undercut & make slag
removal difficult in groove
welds
•excessively high voltage
produce a concave fillet weld
that is subject to cracking
4/23/2007 354 of 691

324. SAW operating variables
Travel speed
•increase in travel speed: decrease heat input & less
filler metal applied per unit of length, less excess
weld metal & weld bead becomes smaller
4/23/2007 355 of 691

325. SAW operating variables
Travel speed
•excessively high speed
lead to undercut, arc
blow and porosity
•excessively low speed
produce “hat-shaped” beads
danger of cracking
•excessively low speed produce rough beads and
lead to slag inclusions
4/23/2007 356 of 691

326. SAW operating variables
Electrode size
•at the same current, small electrodes have higher
current density & higher deposition rates
4/23/2007 357 of 691

327. SAW operating variables
Electrode extension
•increased electrode extension adds resistance in the
welding circuit I increase in deposition rate, decrease in
penetration and bead width
•to keep a proper weld shape, when electrode extension is
increased, voltage must also be increased
•when burn-through is a problem (e.g. thin gauge), increase
electrode extension
•excessive electrode extension: it is more difficult to
maintain the electrode tip in the correct position
4/23/2007 358 of 691

328. SAW operating variables
Depth of flux
•depth of flux layer influence the appearance of weld
•usually, depth of flux is 25-30 mm
•if flux layer is to deep the arc is too confined, result is
a rough ropelike appearing weld
•if flux layer is to deep the gases cannot escape & the
surface of molten weld metal becomes irregularly
distorted
•if flux layer is too shallow, flashing and spattering will
occur, give a poor appearance and porous weld
4/23/2007 359 of 691

329. SAW technological variables
Travel angle effect - Butt weld on plates
Penetration Deep Moderate Shallow
Excess weld metal Maximum Moderate Minimum
Tendency to undercut Severe Moderate Minimum
4/23/2007 363 of 691

330. SAW technological variables
Earth position +
Direction of
travel
-
•welding towards earth produces backward arc blow
•deep penetration
•convex weld profile
4/23/2007 364 of 691

331. SAW technological variables
Earth position
+
Direction of
travel
-
•welding away earth produces forward arc blow
•normal penetration depth
•smooth, even weld profile
4/23/2007 365 of 691

332. Weld backing
Backing strip
Backing weld
Copper backing
4/23/2007 366 of 691

333. Starting/finishing the weld
4/23/2007 367 of 691

334. SAW variants
Twin wire SAW welding •two electrodes are feed
into the same weld pool
•wire diameter usually 1,6 to
3,2 mm
•electrodes are connected
to a single power source & a
single arc is established
•normally operate with
DCEP
•offers increased deposition
rate by up to 80% compared
to single wire SAW
4/23/2007 368 of 691

335. SAW variants
Wires can be oriented
for maximum or
minimum penetration
4/23/2007 369 of 691

336. SAW variants
Tandem arc SAW process •usually DCEP on lead
and AC on trail to reduce
arc blow
•requires two separate
power sources
•the electrodes are active
in the same puddle BUT
there are 2 separate arcs
•increased deposition
rate by up to 100%
compared with single
wire SAW
4/23/2007 370 of 691

337. SAW variants
SAW tandem arc
with two wires
Courtesy of ESAB AB
4/23/2007 371 of 691

338. SAW variants
Single pool - highest deposition rate
Twin pool - travel speed limited by undercut;
4/23/2007
very resistant to porosity and cracks 372 of 691

339. SAW variants
Tandem arc SAW process - multiple wires
•only for welding thick
sections (>30 mm)
•not suitable for use in
narrow weld
preparations (root
passes)
•one 4 mm wire at 600 A,
6.8 kg/hr
•tandem two 4 mm wires
Courtesy of ESAB AB at 600 A, 13.6 kg/hr
4/23/2007 373 of 691

340. SAW variants
Strip cladding needs a
special welding head
4/23/2007 374 of 691

341. SAW variants
Narrow gap welding
•for welding thick
materials
•less filler metal required
•requires special groove
preparation and special
welding head
•requires special fluxes,
otherwise problems with
slag removal
•defect removal is very
difficult
4/23/2007 375 of 691

342. SAW variants
Hot wire welding
•the hot wire is connected to power source & much
more efficient than cold wire (current is used entirely
to heat the wire!)
•increase deposition rates
up to 100%
•requires additional
welding equipment,
additional control of
variables, considerable
set-up time and closer
operator attention
4/23/2007 377 of 691

343. SAW variants
SAW with metal powder addition
•increased deposition rates up to
70%; increased welding speed
•gives smooth fusion, improved
bead appearance, reduced
penetration and dilution from parent
metal & higher impact strength
•metal powders can modify
chemical composition of final weld
deposit
•does not increase risk of cracking
•do not require additional arc energy
•metal powder can be added ahead
or directly into the weld pool
4/23/2007 378 of 691

344. SAW variants
SAW with metal powder addition
•magnetic attachment of powder
•SAW with metal cored wires
4/23/2007 379 of 691

345. SAW variants
Storage tank
SAW of circular
welds
Courtesy of ESAB AB
4/23/2007 380 of 691

346. Advantages of SAW
• high current density, high deposition rates (up to 10 times
those for MMA), high productivity
• deep penetration allowing the use of small welding grooves
• fast travel speed, less distortion
• deslagging is easier
• uniform bead appearance with good surface finish and good
fatigue properties
• can be easily performed mechanised, giving a higher duty
cycle and low skill level required
• provide consistent quality when performed automatic or
mechanised
• Virtually assured radiographically sound welds
• arc is not visible
• little smoke/fumes are developed
4/23/2007 382 of 691

347. Submerged Arc Welding
Advantages Disadvantages
• Low weld-metal cost • Restricted welding
positions
• Easily automated
• Arc blow on DC
• Low levels of ozone current
• High productivity • Shrinkage defects
• No visible arc light • Difficult penetration
control
• Minimum cleaning
• Limited joints
4/23/2007 384 of 691

348. Welding Inspector
Welding Consumables
Section 14
4/23/2007 385 of 691

349. BS EN 499 MMA Covered Electrodes
E 50 3 2Ni B 7 2 H10
Covered Electrode
Yield Strength N/mm2
Toughness
Chemical composition
Flux Covering
Weld Metal Recovery
and Current Type
Welding Position
Hydrogen Content
4/23/2007 386 of 691

350. Welding consumables
Welding consumables are any products that are used up in
the production of a weld
Welding consumables may be:
• Covered electrodes, filler wires and electrode wires.
• Shielding or oxy-fuel gases.
• Separately supplied fluxes.
• Fusible inserts.
4/23/2007 387 of 691

351. Welding Consumable Standards
MIG/MAG (GMAW) TIG (GTAW)
MMA (SMAW) • BS 2901: Filler wires
• BS EN 499: Steel electrodes • BS EN 440: Wire electrodes
• AWS A5.1 Non-alloyed steel • AWS A5.9: Filler wires
electrodes • BS EN 439: Shielding gases
• AWS A5.4 Chromium SAW
electrodes • BS 4165: Wire and fluxes
• AWS A5.5 Alloyed steel • BS EN 756: Wire electrodes
electrodes • BS EN 760: Fluxes
• AWS A5.17: Wires and fluxes
4/23/2007 388 of 691

352. Welding Consumable Gases
welding gases
• GMAW, FCAW, TIG, Oxy- Fuel
• Supplied in cylinders or storage
tanks for large quantities
• Colour coded cylinders to minimise
wrong use
• Subject to regulations concerned
handling, quantities and positioning
of storage areas
• Moisture content is limited to avoid
cold cracking
• Dew point (the temperature at which
the vapour begins to condense)
must be checked
4/23/2007 389 of 691

353. Welding Consumables
Each consumable is critical in respect to:
• Size, (diameter and length)
• Classification / Supplier
• Condition
• Treatments e.g. baking / drying
• Handling and storage is critical for consumable control
• Handling and storage of gases is critical for safety
4/23/2007 390 of 691

354. MMA Welding Consumables
MMA Covered Electrodes
The three main electrode covering types used in MMA welding
• Cellulosic - deep penetration/fusion
• Rutile - general purpose
• Basic - low hydrogen
4/23/2007 392 of 691

355. MMA Welding Consumables
Welding consumables for MMA:
• Consist of a core wire typically between 350-450mm in length
and from 2.5mm - 6mm in diameter
• The wire is covered with an extruded flux coating
• The core wire is generally of a low quality rimming steel
• The weld quality is refined by the addition of alloying and
refining agents in the flux coating
• The flux coating contains many elements and compounds
that all have a variety of functions during welding
4/23/2007 393 of 691

356. MMA Welding Consumables
Function of the Electrode Covering:
• To facilitate arc ignition and give arc stability
• To generate gas for shielding the arc & molten metal from air
contamination
• To de-oxidise the weld metal and flux impurities into the slag
• To form a protective slag blanket over the solidifying and
cooling weld metal
• To provide alloying elements to give the required weld metal
properties
• To aid positional welding (slag design to have suitable
freezing temperature to support the molten weld metal)
• To control hydrogen contents in the weld (basic type)
4/23/2007 394 of 691

357. Covered electrode inspection
1: Electrode size (diameter and length)
2: Covering condition: adherence, cracks, chips and concentricity
3: Electrode designation
EN 499-E 51 3 B
Arc ignition enhancing materials (optional!)
See BS EN ISO 544 for further information
4/23/2007 395 of 691

358. MMA Welding Consumables
Plastic foil sealed cardboard box
•rutile electrodes
•general purpose basic electrodes
Courtesy of Lincoln Electric
Courtesy of Lincoln Electric
Tin can
•cellulosic electrodes
Vacuum sealed pack
•extra low hydrogen electrodes
4/23/2007 396 of 691

359. MMA Welding Consumables
Cellulosic electrodes:
• covering contains cellulose (organic material).
• produce a gas shield high in hydrogen raising the arc
voltage.
• Deep penetration / fusion characteristics enables welding
at high speed without risk of lack of fusion.
• generates high level of fumes and H2 cold cracking.
• Forms a thin slag layer with coarse weld profile.
• not require baking or drying (excessive heat will damage
electrode covering!).
• Mainly used for stove pipe welding
• hydrogen content is 80-90 ml/100 g of weld metal.
4/23/2007 397 of 691

360. MMA Welding Consumables
Cellulosic Electrodes
Disadvantages:
• weld beads have high hydrogen
• risk of cracking (need to keep joint hot during welding to allow
H to escape)
• not suitable for higher strength steels - cracking risk too
high (may not be allowed for Grades stronger than X70)
• not suitable for very thick sections (may not be used on
thicknesses > ~ 35mm)
• not suitable when low temperature toughness is required
(impact toughness satisfactory down to ~ -20°C)
4/23/2007 398 of 691

361. MMA Welding Consumables
Cellulosic Electrodes
Advantages: Disadvantages:
• Deep penetration/fusion • High in hydrogen
• Suitable for welding in all • High crack tendency
positions • Rough weld appearance
• Fast travel speeds • High spatter contents
• Large volumes of shielding gas • Low deposition rates
• Low control
4/23/2007 399 of 691

362. MMA Welding Consumables
Rutile electrodes:
• covering contains TiO2 slag former and arc stabiliser.
• easy to strike arc, less spatter, excellent for positional
welding.
• stable, easy-to-use arc can operate in both DC and AC.
• slag easy to detach, smooth profile.
• Reasonably good strength weld metal.
• Used mainly on general purpose work.
• Low pressure pipework, support brackets.
• electrodes can be dried to lower H2 content but cannot be
baked as it will destroy the coating.
• hydrogen content is 25-30 ml/100 g of weld metal.
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363. MMA Welding Consumables
Rutile electrodes
Disadvantages:
• they cannot be made with a low hydrogen content
• cannot be used on high strength steels or thick joints -
cracking risk too high
• they do not give good toughness at low temperatures
• these limitations mean that they are only suitable for general
engineering - low strength, thin steel
4/23/2007 401 of 691

364. MMA Welding Consumables
Rutile Electrodes
Advantages: Disadvantages:
• Easy to use • High in hydrogen
• Low cost / control • High crack tendency
• Smooth weld profiles • Low strength
• Slag easily detachable • Low toughness values
• High deposition possible
with the addition of iron
powder
4/23/2007 402 of 691

365. MMA Welding Consumables
Rutile Variants
High Recovery Rutile Electrodes
Characteristics:
• coating is „bulked out‟ with iron powder
• iron powder gives the electrode „high recovery‟
• extra weld metal from the iron powder can mean that weld
deposit from a single electrode can be as high as 180% of
the core wire weight
• give good productivity
• large weld beads with smooth profile can look very similar to
SAW welds
4/23/2007 403 of 691

366. MMA Welding Consumables
High Recovery Rutile Electrodes
Disadvantages:
• Same as standard rutile electrodes with respect to hydrogen
control
• large weld beads produced cannot be used for all-positional
welding
• the very high recovery types usually limited to PA & PB
positions
• more moderate recovery may allow PC use
4/23/2007 404 of 691

367. MMA Welding Consumables
Basic covering:
• Produce convex weld profile and difficult to detach slag.
• Very suitable for for high pressure work, thick section steel
and for high strength steels.
• Prior to use electrodes should be baked, typically 350°C for 2
hour plus to reduce moisture to very low levels and achieve
low hydrogen potential status.
• Contain calcium fluoride and calcium carbonate compounds.
• cannot be re-baked indefinitely!
• low hydrogen potential gives weld metal very good
toughness and YS.
• have the lowest level of hydrogen (less than 5 ml/100 g of
weld metal).
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368. MMA Welding Consumables
Basic Electrodes
Disadvantages:
• Careful control of baking and/or issuing of electrodes is
essential to maintain low hydrogen status and avoid risk of
cracking
• Typical baking temperature 350°C for 1 to 2hours.
• Holding temperature 120 to 150°C.
• Issue in heated quivers typically 70°C.
• Welders need to take more care / require greater skill.
• Weld profile usually more convex.
• Deslagging requires more effort than for other types.
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369. MMA Welding Consumables
Basic Electrodes
Advantages Disadvantages
• High toughness values • High cost
• Low hydrogen contents • High control
• Low crack tendency • High welder skill
required
• Convex weld profiles
• Poor stop / start
properties
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370. BS EN 499 MMA Covered Electrodes
E 50 3 2Ni B 7 2 H10
Covered Electrode
Yield Strength N/mm2
Toughness
Chemical composition
Flux Covering
Weld Metal Recovery
and Current Type
Welding Position
Hydrogen Content
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371. BS EN 499 MMA Covered Electrodes
Electrodes classified as follows:
• E 35 - Minimum yield strength 350 N/mm2
Tensile strength 440 - 570 N/mm2
• E 38 - Minimum yield strength 380 N/mm2
Tensile strength 470 - 600 N/mm2
• E 42 - Minimum yield strength 420 N/mm2
Tensile strength 500 - 640 N/mm2
• E 46 - Minimum yield strength 460 N/mm2
Tensile strength 530 - 680 N/mm2
• E 50 - Minimum yield strength 500 N/mm2
Tensile strength 560 - 720 N/mm2
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372. AWS A5.1 Alloyed Electrodes
E 60 1 3
Covered Electrode
Tensile Strength (p.s.i)
Welding Position
Flux Covering
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373. AWS A5.5 Alloyed Electrodes
E 70 1 8 M G
Covered Electrode
Tensile Strength (p.s.i)
Welding Position
Flux Covering
Moisture Control
Alloy Content
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374. MMA Welding Consumables
TYPES OF ELECTRODES
(for C, C-Mn Steels)
BS EN 499 AWS A5.1
• Cellulosic E XX X C EXX10
EXX11
• Rutile E XX X R EXX12
EXX13
• Rutile Heavy Coated E XX X RR EXX24
• Basic E XX X B EXX15
EXX16
EXX18
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375. Electrode efficiency
up to 180% for iron powder electrodes
Mass of weld metal deposited
Electrode Eficiency =
Mass of core wire melted
75-90% for usual electrodes
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376. Covered electrode treatment
Cellulosic Use straight from the
box - No baking/drying!
electrodes
If necessary, dry up to
Rutile 120°C- No baking!
electrodes
Vacuum Use straight from the pack
within 4 hours - No
packed basic rebaking!
electrodes
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377. Covered electrode treatment
Baking in oven 2 hours
Basic electrodes
at 350°C!
Limited number of After baking, maintain in
rebakes! oven at 150°C
If not used within 4
Use from quivers at
hours, return to oven Weld
75°C
and rebake!
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378. Welding Consumables
TIG Consumables
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379. TIG Welding Consumables
Welding consumables for TIG:
•Filler wires, Shielding gases, tungsten electrodes (non-
consumable).
•Filler wires of different materials composition and variable
diameters available in standard lengths, with applicable
code stamped for identification
•Steel Filler wires of very high quality, with copper coating to
resist corrosion.
•shielding gases mainly Argon and Helium, usually of highest
purity (99.9%).
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380. TIG Welding Consumables
Welding rods:
•supplied in cardboard/plastic tubes
Courtesy of Lincoln Electric
•must be kept clean and free from oil and dust
•might require degreasing
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381. Fusible Inserts
Pre-placed filler material
Before Welding After Welding
Other terms used include:
 EB inserts (Electric Boat Company)
 Consumable socket rings (CSR)
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382. Fusible Inserts
Consumable inserts:
• used for root runs on pipes
• used in conjunction with TIG welding
• available for carbon steel, Cr-Mo steel, austenitic stainless
steel, nickel and copper-nickel alloys
• different shapes to suit application
Radius
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383. Fusible Inserts
Application of consumable inserts
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384. Shielding gases for TIG welding
Argon
• low cost and greater availability
• heavier than air - lower flow rates than Helium
• low thermal conductivity - wide top bead profile
• low ionisation potential - easier arc starting, better arc
stability with AC, cleaning effect
• for the same arc current produce less heat than helium -
reduced penetration, wider HAZ
• to obtain the same arc arc power, argon requires a higher
current - increased undercut
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385. Shielding gases for TIG welding
Helium
• costly and lower availability than Argon
• lighter than air - requires a higher flow rate compared with
argon (2-3 times)
• higher ionisation potential - poor arc stability with AC, less
forgiving for manual welding
• for the same arc current produce more heat than argon -
increased penetration, welding of metals with high melting
point or thermal conductivity
• to obtain the same arc arc power, helium requires a lower
current - no undercut
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386. Shielding gases for TIG welding
Hydrogen
• not an inert gas - not used as a primary shielding gas
• increase the heat input - faster travel speed and increased
penetration
• better wetting action - improved bead profile
• produce a cleaner weld bead surface
• added to argon (up to 5%) - only for austenitic stainless
steels and nickel alloys
• flammable and explosive
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387. Shielding gases for TIG welding
Nitrogen
• not an inert gas
• high availability - cheap
• added to argon (up to 5%) - only for back purge for duplex
stainless, austenitic stainless steels and copper alloys
• not used for mild steels (age embritlement)
• strictly prohibited in case of Ni and Ni alloys (porosity)
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388. Welding Consumables
MIG / MAG Consumables
(Gases Covered previously)
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389. MIG/MAG Welding Consumables
Welding consumables for MIG/MAG
• Spools of Continuous electrode wires and shielding gases
• variable spool size (1-15Kg) and Wire diameter (0.6-
1.6mm) supplied in random or orderly layers
• Basic Selection of different materials and their alloys as
electrode wires.
• Some Steel Electrode wires copper coating purpose is
corrosion resistance and electrical pick-up
• Gases can be pure CO2, CO2+Argon mixes and Argon+2%O2
mixes (stainless steels).
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390. MIG/MAG Welding Consumables
Welding wires:
•carbon and low alloy wires may be copper coated
• stainless steel wires are not coated
Courtesy of Lincoln Electric Courtesy of ESAB AB
•wires must be kept clean and free from oil and dust
•flux cored wires does not require baking or drying
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391. Welding Consumables
Flux Core Wire Consumables
(Not in training manual)
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392. Flux Core Wire Consumables
Functions of metallic sheath: Function of the filling powder:
provide form stability stabilise the arc
to the wire add alloy elements
serves as current produce gaseous
transfer during shield
welding produce slag
add iron powder
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393. Types of cored wire
Seamless Butt joint Overlapping
cored wire cored wire cored wire
• not sensitive to moisture • good resistance to sensitive to
pick-up moisture pick-up moisture pick-
• can be copper coated, better • can be copper coated up
current transfer cannot be
• thick sheath
• thick sheath, good form copper coated
stability, 2 roll drive feeding • difficult to seal the
possible sheath thin sheath
• difficult to manufacture easy to
manufacture
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394. Core elements and their function
Aluminium - deoxidize & denitrify
Calcium - provide shielding & form slag
Carbon - increase hardness & strength
Manganese - deoxidize & increase strength and toughness
Molybdenum - increase hardness & strength
Nickel - improve hardness, strength, toughness & corrosion
resistance
Potassium - stabilize the arc & form slag
Silicon - deoxidize & form slag
Sodium - stabilize arc & form slag
Titanium - deoxidize, denitrify & form slag
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395. Welding Consumables
SAW Consumables
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396. SAW Consumables
Welding fluxes:
• are granular mineral compounds mixed according to various
formulations
• shield the molten weld pool from the atmosphere
• clean the molten weld pool
• can modify the chemical composition of the weld metal
• prevents rapid escape of heat from welding zone
• influence the shape of the weld bead (wetting action)
• can be fused, agglomerated or mixed
• must be kept warm and dry to avoid porosity
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397. SAW Consumables
Welding flux:
• might be fused or agglomerated
• supplied in bags
• must be kept warm and dry
• handling and stacking requires care Courtesy of Lincoln Electric
• Fused fluxes are normally not hygroscopic but particles can
hold surface moisture so only drying
• Agglomerated fluxes contain chemically bonded water. Similar
treatment as basic electrodes
• If flux is too fine it will pack and not feed properly. It cannot be
recycled indefinitely
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398. SAW Consumables
Fused Flux
• Flaky appearance
• Lower weld quality
• Low moisture intake
• Low dust tendency
• Good re-cycling
• Very smooth weld
profile
Fused Flux:
Baked at high temperature, glossy, hard and black in colour,
cannot add ferro-manganese, non moisture absorbent and
tends to be of the acidic type
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399. SAW Consumables
TYPES OF FLUX
FUSED (ACID TYPE)
• name indicates method of manufacture
• minerals are fused (melted) and granules produced by
allowing to cool to a solid mass and then crushing or by
spraying the molten flux into water
• flux tends to be „glass-like‟ (high in Silica)
• granules are hard and may appear shiny
• granules do not absorb moisture
• granules do not tend break down into powder when being
re-circulated
• are effectively a low hydrogen flux
• welds do not tend to give good toughness at low
temperatures
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400. SAW Consumables
Fused fluxes advantages:
•good chemical homogeneity
•easy removal of fines without affecting flux
composition
•normally not hygroscopic easy storage and
handling
•readily recycled without significant change in
particle size or composition
Fused fluxes disadvantages:
•difficult to add deoxidizers and ferro-alloys (due to
segregation or extremely high loss)
•high temperatures needed to melt ingredients limit
the range of flux compositions
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401. SAW Consumables
Agglomerated Flux
• Granulated appearance
• High weld quality
• Addition of alloys
• Lower consumption
• Easy slag removal
• Smooth weld profile
Agglomerated Flux:
Baked at a lower temperature, dull, irregularly shaped, friable,
(easily crushed) can easily add alloying elements, moisture
absorbent and tend to be of the basic type
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402. SAW Consumables
Agglomerated fluxes advantages:
• easy addition of deoxidizers and alloying elements
• usable with thicker layer of flux when welding
• colour identification
Agglomerated fluxes disadvantages:
• tendency to absorb moisture
• possible gas evolution from the molten slag leading to
porosity
• possible change in flux composition due to segregation or
removal of fine mesh particles
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403. SAW Consumables
TYPES OF FLUX
AGGLOMERATED (BASIC TYPE)
• name indicates method of manufacture
• basic minerals are used in powder form and are mixed with a
binder to form individual granules
• granules are soft and easily crushed to powder
• granules will absorb moisture and it is necessary to protect
the flux from moisture pick-up - usually by holding in a
heated silo
• granules tend to break down into powder when being re-
circulated
• are a low hydrogen flux - if correctly controlled
• welds give good toughness at low temperatures
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404. SAW Consumables
Mixed fluxes - two or more fused or bonded fluxes are
mixed in any ratio necessary to yield the desired
results
Mixed fluxes advantages:
•several commercial fluxes may be mixed for highly
critical or proprietary welding operations
Mixed fluxes disadvantages:
•segregation of the combined fluxes during
shipment, storage and handling
•segregation occurring in the feeding and recovery
systems during welding
•inconsistency in the combined flux from mix to mix
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405. SAW filler material
Welding wires can be used to weld:
•carbon steels
•low alloy steels
•creep resisting steels
•stainless steels
•nickel-base alloys
•special alloys for surfacing applications
Welding wires can be:
•solid wires
•metal-cored wires
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406. SAW filler material
Welding wires:
•carbon and low alloy wires are copper coated
•stainless steel wires are not coated
Courtesy of Lincoln Electric Courtesy of Lincoln Electric
•wires must be kept clean and free from oil and dust
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407. SAW filler material
Copper coating functions:
•to assure a good electric contact between wire
and contact tip
•to assure a smooth feed of the wire through the
guide tube, feed rolls and contact tip (decrease
contact tube wear)
•to provide protection against corrosion
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408. Welding Inspector
Non Destructive Testing
Section 15
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409. Non-Destructive Testing
A welding inspector should have a working knowledge of NDT
methods and their applications, advantages and
disadvantages.
Four basic NDT methods
• Radiographic inspection (RT)
• Ultrasonic inspection (UT)
• Magnetic particle inspection (MT)
• Dye penetrant inspection (PT)
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410. Non-Destructive Testing
Surface Crack Detection
• Liquid Penetrant (PT or Dye-Penetrant)
• Magnetic Particle Inspection (MT or MPI)
Volumetric & Planar Inspection
• Ultrasonics (UT)
• Radiography (RT)
Each technique has advantages & disadvantages with respect
to:
• Technical Capability and Cost
Note: The choice of NDT techniques is based on consideration
of these advantages and disadvantages
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411. Radiographic Testing (RT)
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412. Radiographic Testing
The principles of radiography
• X or Gamma radiation is imposed upon a test object
• Radiation is transmitted to varying degrees
dependant upon the density of the material through
which it is travelling
• Thinner areas and materials of a less density show as
darker areas on the radiograph
• Thicker areas and materials of a greater density show
as lighter areas on a radiograph
• Applicable to metals,non-metals and composites
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413. Radiographic Testing
X – Rays Gamma Rays
Electrically generated Generated by the decay
of unstable atoms
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414. Radiographic Testing
Source
Radiation beam Image quality indicator
Test specimen
Radiographic film with latent image after exposure
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415. Radiographic Testing
Density - relates to the degree of darkness
Densitometer
Contrast - relates to the degree of difference
Definition - relates to the degree of sharpness
Sensitivity - relates to the overall quality of the radiograph
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416. Radiographic Sensitivity
7FE12
Step / Hole type IQI Wire type IQI
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417. Radiographic Sensitivity
Step/Hole Type IQI
Wire Type IQI
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418. Radiographic Techniques
Single Wall Single Image (SWSI)
• film inside, source outside
Single Wall Single Image (SWSI) panoramic
• film outside, source inside (internal exposure)
Double Wall Single Image (DWSI)
• film outside, source outside (external exposure)
Double Wall Double Image (DWDI)
• film outside, source outside (elliptical exposure)
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419. Single Wall Single Image (SWSI)
Film
Film
IQI‟s should be placed source side
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420. Single Wall Single Image Panoramic
Film
• IQI‟s are placed on the film side
• Source inside film outside (single exposure)
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421. Double Wall Single Image (DWSI)
Film
• IQI‟s are placed on the film side
• Source outside film outside (multiple exposure)
• This technique is intended for pipe diameters
over 100mm
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422. Double Wall Single Image (DWSI)
• Identification
• Unique identification
EN W10
• IQI placing
• Pitch marks indicating A B
readable film length
ID MR11
Radiograph
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423. Double Wall Single Image (DWSI)
Radiograph
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424. Double Wall Double Image (DWDI)
Film
• IQI‟s are placed on the source or film side
• Source outside film outside (multiple exposure)
• A minimum of two exposures
• This technique is intended for pipe diameters less than 100mm
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425. Double Wall Double Image (DWDI)
• Identification 4 3
• Unique identification EN W10
• IQI placing
• Pitch marks indicating 1 2
readable film length
ID MR12
Shot A Radiograph
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426. Double Wall Double Image (DWDI)
4 3
1 2
Elliptical Radiograph
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427. Radiography
PENETRATING POWER
Question:
What determines the penetrating power of an X-ray ?
•the kilo-voltage applied (between anode & cathode)
Question:
What determines the penetrating power of a gamma ray ?
•the type of isotope (the wavelength of the gamma rays)
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428. Radiography
GAMMA SOURCES
Isotope Typical Thickness Range
• Iridium 192 10 to 50 mm (mostly used)
• Cobalt 60 > 50 mm
• Ytterbium < 10 mm
• Thulium < 10 mm
• Cesium < 10 mm
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429. Radiographic Testing
Disadvantages
Advantages
• Expensive consumables
• Permanent record
• Bulky equipment
• Little surface preparation
• Harmful radiation
• Defect identification
• Defect require significant
• No material type limitation
depth in relation to the
• Not so reliant upon operator radiation beam (not good
skill for planar defects)
• Thin materials • Slow results
• Very little indication of
depths
• Access to both sides
required
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430. Radiographic Testing
Comparison with Ultrasonic Examination
ADVANTAGES
good for non-planar defects
good for thin sections
gives permanent record
easier for 2nd party interpretation
can use on all material types
high productivity
direct image of imperfections
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431. Radiographic Testing
Comparison with Ultrasonic Examination
DISADVANTAGES
• health & safety hazard
• not good for thick sections
• high capital and relatively high running costs
• not good for planar defects
• X-ray sets not very portable
• requires access to both sides of weld
• frequent replacement of gamma source needed (half life)
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432. Ultrasonic Testing (UT)
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433. Ultrasonic Testing
Main Features:
• Surface and sub-surface detection
• This detection method uses high frequency sound waves,
typically above 2MHz to pass through a material
• A probe is used which contains a piezo electric crystal to
transmit and receive ultrasonic pulses and display the
signals on a cathode ray tube or digital display
• The actual display relates to the time taken for the
ultrasonic pulses to travel the distance to the interface and
back
• An interface could be the back of a plate material or a defect
• For ultrasound to enter a material a couplant must be
introduced between the probe and specimen
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434. Ultrasonic Testing
Pulse echo Digital
signals UT Set,
A scan
Display
Compression probe checking the material Thickness
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435. Ultrasonic Testing
defect Back wall
initial pulse echo echo
Material Thk
defect
0 10 20 30 40 50
Compression Probe CRT Display
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436. Ultrasonic Testing
UT Set
A Scan
Display
Angle Probe
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437. Ultrasonic Testing
initial pulse
defect echo
defect 0 10 20 30 40 50
½ Skip CRT Display
initial pulse
defect echo
defect 0 10 20 30 40 50
Full Skip CRT Display
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438. Ultrasonic Testing
Disadvantages
Advantages
 Trained and skilled operator
 Rapid results
required
 Both surface and
 Requires high operator skill
sub-surface detection
 Good surface finish required
 Safe
 Defect identification
 Capable of measuring the
 Couplant may contaminate
depth of defects
 No permanent record
 May be battery powered
 Calibration Required
 Portable
 Ferritic Material (Mostly)
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439. Ultrasonic Testing
Comparison with Radiography
ADVANTAGES
•good for planar defects
•good for thick sections
•instant results
•can use on complex joints
•can automate
•very portable
•no safety problems (‘parallel’ working is possible)
•low capital & running costs
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440. Ultrasonic Testing
Comparison with Radiography
DISADVANTAGES
• no permanent record (with standard equipment)
• not suitable for very thin joints <8mm
• reliant on operator interpretation
• not good for sizing Porosity
• good/smooth surface profile needed
• not suitable for coarse grain materials (e.g., castings)
• Ferritic Materials (with standard equipment)
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441. Magnetic Particle testing (MT)
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442. Magnetic Particle Testing
Main features:
• Surface and slight sub-surface detection
• Relies on magnetization of component being tested
• Only Ferro-magnetic materials can be tested
• A magnetic field is introduced into a specimen being tested
• Methods of applying a magnetic field, yoke, permanent
magnet, prods and flexible cables.
• Fine particles of iron powder are applied to the test area
• Any defect which interrupts the magnetic field, will create a
leakage field, which attracts the particles
• Any defect will show up as either a dark indication or in the
case of fluorescent particles under UV-A light a green/yellow
indication
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443. Magnetic Particle Testing
Collection of ink
particles due to
leakage field
Electro-magnet (yoke) DC or AC
Prods DC or AC
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444. Magnetic Particle Testing
A crack like
indication
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445. Magnetic Particle Testing
Alternatively to contrast inks, fluorescent inks may be used
for greater sensitivity. These inks require a UV-A light source
and a darkened viewing area to inspect the component
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446. Magnetic Particle Testing
Typical sequence of operations to inspect a weld
• Clean area to be tested
• Apply contrast paint
• Apply magnetisism to the component
• Apply ferro-magnetic ink to the component during
magnatising
• Iterpret the test area
• Post clean and de-magnatise if required
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447. Magnetic Particle Testing
Advantages Disadvantages
• Simple to use • Surface or slight sub-surface
detection only
• Inexpensive
• Magnetic materials only
• Rapid results
• No indication of defects
• Little surface preparation depths
required
• Only suitable for linear
• Possible to inspect through defects
thin coatings
• Detection is required in two
directions
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448. Magnetic Particle Testing
Comparison with Penetrant Testing
ADVANTAGES
• much quicker than PT
• instant results
• can detect near-surface imperfections (by current flow
technique)
• less surface preparation needed
DISADVANTAGES
• only suitable for ferromagnetic materials
• electrical power for most techniques
• may need to de-magnetise (machine components)
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449. Penetrant Testing (PT)
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450. Penetrant Testing
Main features:
• Detection of surface breaking defects only.
• This test method uses the forces of capillary action
• Applicable on any material type, as long they are non porous.
• Penetrants are available in many different types:
• Water washable contrast
• Solvent removable contrast
• Water washable fluorescent
• Solvent removable fluorescent
• Post-emulsifiable fluorescent
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451. Penetrant Testing
Step 1. Pre-Cleaning
Ensure surface is very Clean normally with the use of a solvent
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452. Penetrant Testing
Step 2. Apply penetrant
After the application, the penetrant is normally left on the
components surface for approximately 15-20 minutes (dwell
time).
The penetrant enters any defects that may be present by
capillary action.
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453. Penetrant Testing
Step 3. Clean off penetrant
the penetrant is removed after sufficient penetration time (dwell
time).
Care must be taken not to wash any penetrant out off any
defects present
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454. Penetrant Testing
Step 3. Apply developer
After the penetrant has be cleaned sufficiently, a thin layer of
developer is applied.
The developer acts as a contrast against the penetrant and
allows for reverse capillary action to take place.
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455. Penetrant Testing
Step 4. Inspection / development time
Inspection should take place immediately after the developer
has been applied.
any defects present will show as a bleed out during
development time.
After full inspection has been carried out post cleaning is
generally required.
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456. Penetrant Testing
Fluorescent Penetrant Bleed out viewed
under a UV-A light
source
Bleed out viewed
under white light
Colour contrast Penetrant
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457. Penetrant Testing
Advantages Disadvantages
• Simple to use • Surface breaking defect only
• Inexpensive • little indication of depths
• Quick results • Penetrant may contaminate
component
• Can be used on any non- • Surface preparation critical
porous material
• Post cleaning required
• Portability • Potentially hazardous
• Low operator skill required chemicals
• Can not test unlimited times
• Temperature dependant
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458. Penetrant Testing
Comparison with Magnetic Particle Inspection
ADVANTAGES
•easy to interpret results
•no power requirements
•relatively little training required
•can use on all materials
DISADVANTAGES
•good surface finish needed
•relatively slow
•chemicals - health & safety issue
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459. Welding Inspector
Weld Repairs
Section 16
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460. Weld Repairs
Weld repairs can be divided into 2 specific areas:
• Production repairs
• In service repairs
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461. Weld Repairs
A weld repair can be a relatively straight forward activity, but
in many instances it is quite complex, and various
engineering disciplines may need to be involved to ensure a
successful outcome.
• Analysis of the defect types may be carried out by the
Q/C department to discover the likely reason for their
occurrence, (Material/Process or Skill related).
In general terms, a welding repair involves What!
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462. Weld Repairs
A weld repair may be used to improve weld profiles or
extensive metal removal:
•Repairs to fabrication defects are generally easier than
repairs to service failures because the repair procedure
may be followed
•The main problem with repairing a weld is the
maintenance of mechanical properties
•During the inspection of the removed area prior to
welding the inspector must ensure that the defects have
been totally removed and the original joint profile has
been maintained as close as possible
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463. Weld Repairs
In the event of repair, it is required:
• Authorization and procedure for repair
• Removal of material and preparation for repair
• Monitoring of repair Weld
• Testing of repair - visual and NDT
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464. Weld Repairs
There are a number of key factors that need to be considered
before undertaking any repair:
• The most important - is it financially worthwhile?
• Can structural integrity be achieved if the item is repaired?
• Are there any alternatives to welding?
• What caused the defect and is it likely to happen again?
• How is the defect to be removed and what welding process is to
be used?
• What NDE is required to ensure complete removal of the defect?
• Will the welding procedures require approval/re-approval?
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465. Weld Repairs
• Cleaning the repair area, (removal of paint, grease, etc)
• A detailed assessment to find out the extremity of the defect.
This may involve the use of a surface or sub surface NDE method.
• Once established the excavation site must be clearly identified
and marked out.
• An excavation procedure may be required (method used i.e.
grinding, arc-air gouging, preheat requirements etc).
• NDE should be used to locate the defect and confirm its removal.
• A welding repair procedure/method statement with the
appropriate welding process, consumable, technique, controlled
heat input and interpass temperatures etc will need to be
approved.
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466. Weld Repairs
• Use of approved welders.
• Dressing the weld and final visual.
• A NDT procedure/technique prepared and carried out to ensure
that the defect has been successfully removed and repaired.
• Any post repair heat treatment requirements.
• Final NDT procedure/technique prepared and carried out after
heat treatment requirements.
• Applying protective treatments (painting etc as required).
• (*Appropriate’ means suitable for the alloys being repaired and
may not apply in specific situations)
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467. Weld Repairs
• What will be the effect of welding distortion and residual
stress?
• Will heat treatment be required?
• What NDE is required and how can acceptability of the
repair be demonstrated?
• Will approval of the repair be required – if yes, how and by
whom?
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468. Production Weld Repairs
Before the repair can commence, a number of elements need
to be fulfilled:
If the defect is surface breaking and has occurred at the fusion
face the problem could be cracking or lack of sidewall fusion.
If the defect is found to be cracking the cause may be
associated with the material or the welding procedure
If the defect is lack of sidewall fusion this can be apportioned
to the lack of skill of the welder.
In this particular case as the defect is open to the surface, MPI
or DYE-PEN may be used to gauge the length of the defect and
U/T inspection used to gauge the depth.
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469. Weld Repairs
The specification or procedure will govern how the defective
areas are to be removed. The method of removal may be:
• Grinding
• Chipping
• Machining
• Filing
• Oxy-Gas gouging
• Arc air gouging
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470. Defect Excavation
Arc-air gouging
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471. Arc-air gouging features
• Operate ONLY on DCEP
• Special gouging copper
coated carbon electrode
• Can be used on carbon
and low alloy steels,
austenitic stainless steels
and non-ferrous materials
• Requires CLEAN/DRY
compressed air supply
• Provides fast rate of metal removal
• Can remove complex shape defects
• After gouging, grinding of carbured layer is mandatory
• Gouging doesn‟t require a qualified welder!
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472. Production Weld Repairs
Production Repairs
• are usually identified during production inspection
• evaluation of the reports is usually carried out by
the Welding Inspector, or NDT operator
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473. Production Weld Repairs
Plan View of defect
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474. Production Weld Repairs
Side View of defect excavation
W
D
Side View of repair welding
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475. In Service Weld Repairs
In service repairs
• Can be of a very complex nature, as the component is very
likely to be in a different welding position and condition
than it was during production
• It may also have been in contact with toxic, or combustible
fluids hence a permit to work will need to be sought prior
to any work being carried out
• The repair welding procedure may look very different to the
original production procedure due to changes in these
elements.
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476. In Service Weld Repairs
Other factors to be taken into consideration:
Effect of heat on any surrounding areas of the component
i.e. electrical components, or materials that may become
damaged by the repair procedure.
This may also include difficulty in carrying out any required
pre or post welding heat treatments and a possible
restriction of access to the area to be repaired.
For large fabrications it is likely that the repair must also
take place on site and without a shut down of operations,
which may bring other elements that need to be
considered.
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477. Weld Repairs
• Is welding the best method of repair?
• Is the repair really like earlier repairs?
• What is the composition and weldability of the base metal?
• What strength is required from the repair?
• Can preheat be tolerated?
• Can softening or hardening of the HAZ be tolerated?
• Is PWHT necessary and practicable?
• Will the fatigue resistance of the repair be adequate?
• Will the repair resist its environment?
• Can the repair be inspected and tested?
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478. Weld repair related problems
• heat from welding may affect dimensional stability and/or
mechanical properties of repaired assembly
• due to heat from welding, YS goes down, danger of
collapse
• filler materials used on dissimilar welds may lead to
galvanic corrosion
• local preheat may induce residual stresses
• cost of weld metal deposited during a weld joint repair
can reach up to 10 times the original weld metal cost!
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479. Welding Inspector
Residual Stress & Distortion
Section 17
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480. Residual stress
Residual stresses are undesirable because:
they lead to distortion
they affect dimensional stability of the
welded assembly
they enhance the risk of brittle fracture
they can facilitate certain types of
corrosion
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481. Residual Stresses
The heating and subsequent cooling from welding produces
expansion and contractions which affect the weld metal and
adjacent material.
If this contraction is prevented or inhibited residual stress will
develop.
The tendency to develop residual stresses increases when the
heating and cooling is localised.
Residual stresses are very difficult to measure with any real
accuracy.
Residual stresses are self balancing internal forces and not
stresses induced whilst applying external load
Stresses are more concentrated at the surface of the
component.
The removal of residual stresses is termed stress relieving.
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482. Stresses
Normal Stress
Stress arising from a force perpendicular to the
cross sectional area
Compression
Tension
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483. Stresses
Shear Stress
Stress arising from forces which are parallel to, and
lie in the plane of the cross sectional area.
Shear Stress
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484. Stresses
Hoop Stress
Internal stress acting on the wall a pipe or cylinder
due to internal pressure.
Hoop Stress
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485. Residual Stresses
Residual stresses occur in welds in the following directions
 Along the weld – longitudinal residual stresses
 Across the weld – transverse residual stresses
 Through the weld – short transverse residual stresses
Longitudinal
Transverse
Short Transverse
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486. Residual stress
Heating and
cooling causes
expansion and
contraction
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487. Residual stress
In case of a heated
bar, the resistance
of the surrounding
material to the
expansion and
contraction leads
to formation of
residual stress
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488. Summary
1. Residual stresses are locked in elastic strain, which is
caused by local expansion and contraction in the weld
area.
2. Residual stresses should be removed from structures
after welding.
3. The amount of contraction is controlled by, the volume of
weld metal in the joint, the thickness, heat input, joint
design and the materials properties
4. Offsetting may be used to finalise the position of the joint.
5. If plates or pipes are prevented from moving by tacking,
clamping or jigging etc (restraint), then the amount of
residual stresses that remain will be higher.
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489. Summary
6. The movement caused by welding related stresses is
called distortion.
7. The directions of contractional stresses and distortion is
very complex, as is the amount and type of final distortion,
however we can say that there are three directions:
a. Longitudinal b. Transverse c. Short transverse
8. A high percentage of residual stresses can be removed by
heat treatments.
9. The peening of weld faces will only redistribute the
residual stress, and place the weld face in compression.
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490. Types of distortion
Angular distortion
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491. Distortion
Angular Distortion
Transverse Distortion
Bowing Distortion Longitudinal Distortion
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492. Distortion
Factors which affect distortion
• Material properties and condition
• Heat input
• The amount of restrain
• The amount of weld metal deposited
Control of distortion my be achieved in the following way:
•The used of a different joint design
•Presetting the joints to be welded – so that the metal distorts
into the required position.
•The use of a balanced welding technique
•The use of clamps, jigs and fixtures.
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493. Distortion
• Distortion will occur in all welded joints if the material are
free to move i.e. not restrained
• Restrained materials result in low distortion but high
residual stress
• More than one type of distortion may occur at one time
• Highly restrained joints also have a higher crack tendency
than joints of a low restraint
• The action of residual stress in welded joints is to cause
distortion
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494. Distortion
Factors affecting distortion:
parent material properties
amount of restrain
joint design
fit-up
welding sequence
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495. Factors affecting distortion
Parent material properties:
thermal expansion coefficient - the greater the value, the
greater the residual stress
yield strength - the greater the value, the greater the
residual stress
Young‟s modulus - the greater the value (increase in
stiffness), the greater the residual stress
thermal conductivity - the higher the value, the lower the
residual stress
transformation temperature - during phase
transformation, expansion/contraction takes place. The
lower the transformation temperature, the lower the
residual stress
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496. Factors affecting distortion
Joint design:
weld metal volume
type of joint - butt vs. fillet, single vs. double side
Amount of restrain:
thickness - as thickness increase, so do the stresses
high level of restrain lead to high stresses
preheat may increase the level of stresses (pipe
welding!)
Fit-up:
misalignment may reduce stresses in some cases
root gap - increase in root gap increases shrinkage
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497. Factors affecting distortion
Welding sequence:
number of passes - every pass adds to the total
contraction
heat input - the higher the heat input, the greater
the shrinkage
travel speed - the faster the welding speed, the
less the stress
build-up sequence
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498. Distortion prevention
Distortion prevention by pre-setting
a) pre-setting of fillet joint to
prevent angular distortion
b) pre-setting of butt joint to
prevent angular distortion
c) tapered gap to prevent
closure
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499. Distortion
Pre-set or Offsetting:
The amount of offsetting required is generally a function of
trial and error.
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500. Distortion prevention
Distortion prevention by pre-bending using
strongbacks and wedges
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501. Distortion
Clamping and jigging:
The materials to be welded are prevented from moving by the
clamp or jig the main advantage of using a jig is that the
elements in a fabrication can be precisely located in the
position to be welded. Main disadvantage of jigging is high
restraint and high levels of residual stresses.
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502. Distortion prevention
Distortion prevention by restraint techniques
a) use of welding jigs
b) use of flexible
clamps
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503. Distortion prevention
Distortion prevention by restraint techniques
c) use of strongbacks
with wedges
d) use of fully welded
strongbacks
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504. Distortion prevention
Distortion prevention by design
Consider eliminating the welding!!
a) by forming the plate
b) by use of rolled or extruded sections
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505. Distortion prevention
Distortion prevention by design
consider weld placement
reduce weld metal volume
and/or number of runs
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506. Distortion prevention
The volume of weld metal in a joint will affect the amount of
local expansion and contraction, hence the more weld
deposited the higher amount of distortion
Preparation angle 60o
Preparation angle 40o
Preparation angle 0o
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507. Distortion prevention
Distortion prevention by design
use of balanced welding
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508. Distortion prevention
Distortions prevention by design
Allowances to cover shrinkage
- Transverse Shrinkage
Fillet Welds 0.8mm per weld where the leg length
does not exceed 3/4 plate thickness
Butt weld 1.5 to 3mm per weld for 60° V joint,
depending on number of runs
- Longitudinal Shrinkage
Fillet Welds 0.8mm per 3m of weld
Butt Welds 3mm per 3m of weld
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509. Distortion prevention
Distortion prevention by fabrication techniques
tack welding
a) tack weld straight through
to end of joint
b) tack weld one end, then use
back-step technique for
tacking the rest of the joint
c) tack weld the centre, then
complete the tack welding
by the back-step technique
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510. Distortion prevention
Distortion prevention by fabrication techniques
back to back assembly
a) assemblies tacked together
before welding
b) use of wedges for
components that distort on
separation after welding
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511. Distortion prevention
Distortion prevention by fabrication techniques
use of stiffeners
control welding process by:
- deposit the weld metal as quickly as possible
- use the least number of runs to fill the joint
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512. Distortion prevention
Distortion prevention by welding procedure
reduce the number of
runs required to make a
weld (e.g. angular
distortion as a function
of number of runs for a
10 mm leg length weld)
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513. Distortion prevention
Distortion prevention by welding procedure
control welding techniques by use
balanced welding about the neutral axis
control welding techniques by keeping
the time between runs to a minimum
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514. Distortion prevention
Distortion prevention by welding procedure
control welding techniques by
a) Back-step welding
b) Skip welding
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515. Distortion prevention
Back-step welding technique
1. 2. 3. 4. 5. 6.
Back-skip welding technique
1. 4. 2. 5. 3. 6.
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516. Distortion prevention
Distortion - Best practice for fabrication corrective techniques
using tack welds to set up and maintain the joint gap
identical components welded back to back so welding can be
balanced about the neutral axis
attachment of longitudinal stiffeners to prevent longitudinal
bowing in butt welds of thin plate structures
where there is choice of welding procedure, process and
technique should aim to deposit the weld metal as quickly as
possible; MIG in preference to MMA or gas welding and
mechanised rather than manual welding
in long runs, the whole weld should not be completed in one
direction; back-step or skip welding techniques should be used
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517. Distortion corrective techniques
Distortion - mechanical corrective techniques
Use of press to correct bowing in T butt joint
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518. Distortion corrective techniques
Distortion - Best practice for mechanical corrective techniques
Use packing pieces which will over correct the distortion so
that spring-back will return the component to the correct shape
Check that the component is adequately supported during
pressing to prevent buckling
Use a former (or rolling) to achieve a straight component or
produce a curvature
As unsecured packing pieces may fly out from the press, the
following safe practice must be adopted:
- bolt the packing pieces to the platen
- place a metal plate of adequate thickness to intercept the
'missile'
- clear personnel from the hazard area
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519. Distortion corrective techniques
Distortion - thermal corrective techniques
Localised heating to
correct distortion
Spot heating for
correcting buckling
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520. Distortion corrective techniques
Distortion - thermal corrective techniques
Line heating to correct angular
distortion in a fillet weld
Use of wedge shaped heating
to straighten plate
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521. Distortion corrective techniques
Distortion - thermal corrective techniques
Wedge shaped heating to correct distortion
a) standard rolled b) buckled edge of c) box fabrication
steel section plate
General guidelines:
•Length of wedge = two-thirds of the plate width
•Width of wedge (base) = one sixth of its length (base to apex)
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522. Distortion corrective techniques
Distortion - thermal corrective techniques
•use spot heating to remove buckling in thin sheet structures
•other than in spot heating of thin panels, use a wedge-shaped
heating technique
•use line heating to correct angular distortion in plate
•restrict the area of heating to avoid over-shrinking the component
•limit the temperature to 60° to 650°C (dull red heat) in steels to
prevent metallurgical damage
•in wedge heating, heat from the base to the apex of the wedge,
penetrate evenly through the plate thickness and maintain an even
temperature
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523. Welding Inspector
Heat Treatment
Section 18
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524. Heat Treatment
Why?
Improve mechanical properties
Change microstructure
Reduce residual stress level
Change chemical composition
How?
Flame oven
Electric oven/electric heating blankets
induction/HF heating elements
Global Where? Local
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525. Heat Treatments
Many metals must be given heat treatment before and after
welding.
The inspector’s function is to ensure that the treatment is
given correctly in accordance with the specification or as per
the details supplied.
Types of heat treatment available:
•Preheat
•Annealing
•Normalising
•Quench Hardening
•Temper
•Stress Relief
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526. Heat Treatments
Pre-heat treatments
• are used to increase weldability, by reducing sudden
reduction of temperature, and control expansion and
contraction forces during welding
Post weld heat treatments
• are used to change the properties of the weld metal,
controlling the formation of crystalline structures
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527. Post Weld -Heat Treatments
Post Hydrogen Release (according to BS EN1011-2)
Temperature: Approximately 250 C hold up to 3 hours
Cooling: Slow cool in air
Result: Relieves residual hydrogen
Procedure: Maintaining pre-heat / interpass temperature after
completion of welding for 2 to 3 hours.
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528. Post Weld Heat Treatments
A B
(A) Normalised
(B) Fully Annealed
(C) Water-quenched
(D) Water-quenched & tempered
C D
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529. Post Weld Heat Treatments
The inspector, in general, should ensure that:
• Equipment is as specified
• Temperature control equipment is in good condition
• Procedures as specified, is being used e.g.
o Method of application
o Rate of heating and cooling
o Maximum temperature
o Soak time
o Temperature measurement (and calibration)
• DOCUMENTATION AND RECORDS
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530. Post Weld Heat Treatment Cycle
Variables for heat treatment process must be carefully controlled
Temperature
SoakingTemperature
and time at the
attained temperature
heating rate Cooling rate
Time
Heating Soaking Cooling
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531. Post Weld Heat Treatment
Removal of Residual Stress
Cr-Mo steel - typical • At PWHT temp. the yield
Yield 500 strength of steel reduced
Strength
so that it it is not strong
(N/mm2 )
400 enough to give restraint.
C-Mn steel - typical
300
• Residual stress reduced
to very low level by
200 straining (typically < ~
0.5% strain)
100
100 200 300 400 500 600 700
Temperature (°C)
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532. Heat Treatment
Recommendations
• Provide adequate support (low YS at high temperature!)
• Control heating rate to avoid uneven thermal expansions
• Control soak time to equalise temperatures
• Control temperature gradients - NO direct flame impingement!
• Control furnace atmosphere to reduce scaling
• Control cooling rate to avoid brittle structure formation
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533. Post Weld Heat Treatment Methods
Advantages:
Easy to set up
Good portability
repeatability and
temperature uniformity
Disadvantages:
Gas furnace heat treatment Limited to size of parts
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534. Post Weld Heat Treatment Methods
Advantages:
High heating rates
Ability to heat a
narrow band
Disadvantages:
High equipment
cost
Large equipment,
HF (Induction) local heat treatment less portable
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535. Post Weld Heat Treatment Methods
Advantages:
Ability to vary
heat
Ability to
continuously
maintain heat
Disadvantages:
Elements may
burn out or arcing
Local heat treatment using during heating
electric heating blankets
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536. Welding Inspector
Cutting Processes
Section 19
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537. Use of gas flame
Welding Brazing Cutting Gouging
Heating Straightening Blasting Spraying
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538. Regulators
Oxygen regulator Fuel gas regulator
Single stage used when slight rise in delivery
pressure from full to empty cylinder
Regulator condition can be tolerated
type
Two stage used when a constant delivery
pressure from full to empty
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cylinder condition is required of 691
583

539. Flashback arrestors
Flashback - recession of the flame into or back of the mixing chamber
SAFETY SAFETY SAFETY
Normal Reverse Flashback
flow flow
Built- Built-in
in check Flashback
check valve flame
Flame
valve stops quenched
barrie reverse at the
r flow flashback
barrier
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540. Oxyfuel gas cutting process
A jet of pure oxygen reacts with iron, that has been
preheated to its ignition point, to produce the
oxide Fe3O4 by exothermic reaction.This oxide is
then blown through the material by the velocity of
the oxygen stream
Different types of fuel gases may be used for the
pre-heating flame in oxy fuel gas cutting: i.e.
acetylene, hydrogen, propane. etc
By adding iron powder to the flame we are able
to cut most metals - “Iron Powder Injection”
The high intensity of heat and rapid cooling will
cause hardening in low alloy and medium/high C
steels they are thus pre-heated to avoid the
hardening effect
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541. Oxyfuel gas cutting equipment
The cutting torch
Neutral cutting flame
Neutral cutting flame with
oxygen cutting stream
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542. Oxyfuel gas cutting related terms
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543. Oxyfuel gas cutting quality
• Good cut - sharp top edge, fine and even drag lines, little
oxide and a sharp bottom edge
Cut too slow - top edge is Cut too fast -
melted, deep groves in the pronounced break in
lower portion, heavy scaling, the drag line,
rough bottom edge irregular cut edge
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544. Oxyfuel gas cutting quality
• Good cut - sharp top edge, fine and even drag lines, little
oxide and a sharp bottom edge
Preheat flame too low - Preheat flame too high -
deep groves in the lower top edge is melted,
part of the cut face irregular cut, excess of
4/23/2007
adherent dross 589 of 691

545. Oxyfuel gas cutting quality
• Good cut - sharp top edge, fine and even drag lines, little
oxide and a sharp bottom edge
Nozzle is too high above
the works - excessive Irregular travel speed - uneven
melting of the top edge, space between drag lines,
much oxide irregular bottom with adherent
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oxide 590 of 691

546. Mechanised oxyfuel cutting
• can use portable carriages or gantry type machines and
obtain high productivity
• accurate cutting for complicate shapes
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547. OFW/C advantages/disadvantages
Advantages: Disadvantages:
1) No need for power 1) High skill factor
supply, portable
2) Wide HAZ
2) Versatile: preheat,
brazing, surfacing, repair, 3) Safety issues
straightening 4) Slow process
3) Low equipment cost 5) Limited range of
consumables
4) Can cut carbon and low
alloy steels 6) Not suitable for reactive
& refractory metals
5) Good on thin materials
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548. Special oxyfuel operations
• Gouging Rivet cutting
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549. Special oxyfuel operations
• Thin sheet cutting Rivet washing
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550. Cutting Processes
Plasma arc cutting
• Uses high velocity jet of ionised gas through a
constricted nozzle to remove the molten
metal
• Uses a tungsten electrode and water cooled
nozzle
• High quality cutting
• High intensity and UV radiation – EYES !
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551. Cutting Processes
Air-arc for cutting or gouging
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552. Air-arc gouging features
• Operate ONLY on DCEP
• Special gouging copper
coated carbon electrode
• Can be used on carbon
and low alloy steels,
austenitic stainless steels
and non-ferrous materials
• Requires CLEAN/DRY
compressed air supply
• Provides fast rate of metal removal
• Can remove complex shape defects
• After gouging, grinding of carbured layer is mandatory
• Gouging doesn‟t require a qualified welder!
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553. Welding Inspector
Arc Welding Safety
Please discuss
Section 20
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554. Safety
• Electrical safety
• Heat & Light
– Visible light
– UV radiation - effects on skin
and eyes
• Fumes & Explosive Gasses
• Noise levels
• Fire Hazards
• Scaffolding & Staging
• Slips, trips and falls
• Protection of others from
exposure
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555. Welding Inspector
Weldability Of Steels
Section 21
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556. Weldability of Steels
Definition
It relates to the ability of the metal (or alloy) to be welded with
mechanical soundness by most of the common welding processes,
and the resulting welded joint retain the properties for which it
has been designed.
is a function of many inter-related factors but these may be
summarised as:
•Composition of parent material
•Joint design and size
•Process and technique
•Access
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557. Weldability of Steels
The weldability of steel is mainly dependant on carbon & other alloying
elements content.
If a material has limited weldability, we need to take special measures to
ensure the maintenance of the properties required
Poor weldability normally results in the occurrence of cracking
A steel is considered to have poor weldability when:
• an acceptable joint can only be made by using very narrow range of
welding conditions
• great precautions to avoid cracking are essential (e.g., high pre-heat etc)
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558. The Effect of Alloying on Steels
Elements may be added to steels to produce the properties
required to make it useful for an application.
Most elements can have many effects on the properties of
steels.
Other factors which affect material properties are:
•The temperature reached before and during welding
•Heat input
•The cooling rate after welding and or PWHT
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559. Steel Alloying Elements
Iron (Fe): Main steel constituent. On its own, is relatively soft, ductile, with low
strength.
Carbon (C): Major alloying element in steels, a strengthening element with
major influence on HAZ hardness. Decreases weldability.
•typically < ~ 0.25%
Manganese (Mn): Secondary only to carbon for strength, toughness and
ductility, secondary de-oxidiser and also reacts with sulphur to form
manganese sulphide.
< ~0.8% is residual from steel de-oxidation
•up to ~1.6% (in C-Mn steels) improves strength & toughness
Silicon (Si): Residual element from steel de-oxidation.
•typically to ~0.35%
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560. Steel Alloying Elements
Phosphorus (P): Residual element from steel-making minerals. difficult to reduce
below < ~ 0.015% brittleness
Sulphur (S): Residual element from steel-making minerals
< ~ 0.015% in modern steels
< ~ 0.003% in very clean steels
Aluminium (Al): De-oxidant and grain size control
•typically ~ 0.02 to ~ 0.05%
Chromium (Cr): For creep resistance & oxidation (scaling) resistance for elevated
temperature service. Widely used in stainless steels for corrosion resistance,
increases hardness and strength but reduces ductility.
•typically ~ 1 to 9% in low alloy steels
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561. Steel Alloying Elements
Nickel (Ni): Used in stainless steels, high resistance to corrosion from acids,
increases strength and toughness
Molybdenum (Mo): Affects hardenability. Steels containing molybdenum
are less susceptible to temper brittleness than other alloy steels.
Increases the high temperature tensile and creep strengths of steel.
typically ~ 0.5 to 1.0%
Niobium (Nb): a grain refiner, typically~ 0.05%
Vanadium (V): a grain refiner, typically ~ 0.05%
Titanium (Ti): a grain refiner, typically ~ 0.05%
Copper (Cu): present as a residual, (typically < ~ 0.30%)
added to ‘weathering steels’ (~ 0.6%) to give better resistance to
atmospheric corrosion
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562. Classification of Steels
Mild steel (CE < 0.4)
• Readily weldable, preheat generally not required if low hydrogen
processes or electrodes are used
• Preheat may be required when welding thick section material, high
restraint and with higher levels of hydrogen being generated
C-Mn, medium carbon, low alloy steels (CE 0.4 to 0.5)
• Thin sections can be welded without preheat but thicker sections will
require low preheat levels and low hydrogen processes or electrodes
should be used
Higher carbon and alloyed steels (CE > 0.5)
• Preheat, low hydrogen processes or electrodes, post weld heating and
slow cooling may be required
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563. Process Cracks
• Hydrogen Induced HAZ Cracking (C/Mn steels)
• Hydrogen Induced Weld Metal Cracking (HSLA steels).
• Solidification or Hot Cracking (All steels)
• Lamellar Tearing (All steels)
• Re-heat Cracking (All steels, very susceptible Cr/Mo/V steels)
• Inter-Crystalline Corrosion or Weld Decay (stainless steels)
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564. Cracking
When considering any type of cracking mechanism, three
elements must always be present:
• Stress
Residual stress is always present in a weldment, through
unbalanced local expansion and contraction
• Restraint
Restraint may be a local restriction, or through plates
being welded to each other
• Susceptible microstructure
The microstructure may be made susceptible to
cracking by the process of welding
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565. Cracks
Hydrogen Induced Cold Cracking
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566. Hydrogen Induced Cold Cracking
May occur: Also know as:
• up to 48 hrs after completion Cold Cracking, happens when
the welds cool down.
• In weld metal, HAZ, parent
metal. HAZ cracking, normally occurs
in the HAZ.
• At weld toes
Delayed cracking, as it takes
• Under weld beads time for the hydrogen to
migrate. 48 Hours normally but
• At stress raisers.
up to 72,
Under-bead cracking, normally
happens in the HAZ under a
weld bead
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567. Hydrogen Induced Cold Cracking
There is a risk of hydrogen cracking when all of the 4 factors
occur together:
•Hydrogen More than 15ml/100g of weld metal
•Stress More than ½ the yield stress
•Temperature Below 300oC
•Hardness Greater than 400HV Vickers
•Susceptible Microstructure (Martensite)
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568. Hydrogen Induced Cold Cracking
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569. Hydrogen Induced Cold Cracking
Precautions for controlling hydrogen cracking
• Pre heat, removes moisture from the joint preparations, and
slows down the cooling rate
• Ensure joint preparations are clean and free from
contamination
• The use of a low hydrogen welding process and correct arc
length
• Ensure all welding is carried out is carried out under controlled
environmental conditions
• Ensure good fit-up as to reduced stress
• The use of a PWHT
• Avoid poor weld profiles
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570. Hydrogen Induced Cold Cracking
• Hydrogen is the smallest atom known
• Hydrogen enters the weld via the arc
• Source of hydrogen mainly from moisture pick-up on
the electrodes coating, welding fluxes or from the
consumable gas
Water vapour Moisture on
in the air or H2 the electrode
in the H2 or grease on
shielding gas the wire
H2
Oxide or grease on H2 H2
the plate
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571. Hydrogen Induced Cold Cracking
Cellulosic electrodes Hydrogen absorbed
produce hydrogen as a in a long, or
shielding gas unstable arc
Hydrogen introduced in Hydrogen
weld from consumable,
crack
oils, or paint on plate
H2 H2
Martensite forms from γ H2 diffuses to γ in HAZ
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572. Hydrogen Induced Cold Cracking
Susceptible Microstructure:
Hard brittle structure – MARTENSITE Promoted by:
A) High Carbon Content, Carbon Equivalent (CE)
CEV = %C + Mn + Cr+Mo+V + Ni+Cu
6 5 15
B) high alloy content
C) fast cooling rate: Inadequate Pre-Heating
Cold Material
Thick Material
Low Heat Input.
Heat input (Kj/mm) = Amps x Volts x arc time
Run out length x 103 (1000)
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573. Hydrogen Induced Cold Cracking
Typical locations for Cold Cracking
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574. HICC in HSLA steels
•HSLA or Micro-Alloyed Steels are high strength steels
(800MPa/N/mm2) that derive their high strength from small
percentage alloying (over-alloyed Weld metal to match the
strength of parent metal)
•Typically the level of alloying is in the elements such as
vanadium molybdenum and titanium, nickel and chromium
Strength. are used. It would be impossible to match this micro
alloying in the electrode due to the effect of losses across an
electric arc (Ti burn in the arc)
•It is however important to match the strength of the weld to
the strength of the plate, Mn 1.6 Cr Ni Mo
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575. Hydrogen Scales
List of hydrogen scales from BS EN 1011:part 2.
Hydrogen content related to 100 grams of weld metal
deposited.
• Scale A High: >15 ml
• Scale B Medium: 10 ml - 15 ml
• Scale C Low: 5 ml - 10 ml
• Scale D Very low: 3 ml - 5 ml
• Scale E Ultra-low: < 3 ml
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576. Potential Hydrogen Level Processes
list of welding processes in order of potential lowest hydrogen
content with regards to 100g of deposited weld metal.
•TIG < 3 ml
•MIG < 5 ml
•ESW < 5 ml
•MMA (Basic Electrodes) < 5 ml
•SAW < 10ml
•FCAW < 15 ml
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577. Weldability
Solidification Cracking
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578. Solidification Cracking
Usually Occurs in Weld Centerline
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579. Solidification Cracking
Also referred as
Hot Cracking: Occurring at high temperatures while the weld is hot
Centerline cracking: cracks appear down the centre line of the bead.
Crater cracking: Small cracks in weld centers are solidification cracks
Crack type: Solidification cracking
Location: Weld centreline (longitudinal)
Steel types: High sulphur & phosphor concentration in steels.
Susceptible Microstructure: Columnar grains In direction
of solidification
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580. Solidification Cracking
Factors for solidification cracking
• Columnar grain growth with impurities in weld metal (sulphur,
phosphor and carbon)
• The amount of stress/restraint
• Joint design high depth to width ratios
Liquid iron sulphides are formed around solidifying grains.
High contractional strains are present
High dilution processes are being used.
There is a high carbon content in the weld metal
• Most commonly occurring in sub-arc welded joints
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581. Solidification Cracking
• Sulphur in the parent material may dilute in the weld
metal to form iron sulphides (low strength, low melting
point compounds)
• During weld metal solidification, columnar crystals push
still liquid iron sulphides in front to the last place of
solidification, weld centerline.
• The bonding between the grains which are themselves
under great stress and may now be very poor to maintain
cohesion and a crack will result, weld centerline.
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582. Solidification Cracking
Avoidance
Intergranular liquid film
Columnar
grains Columnar
HAZ grains HAZ
Shallow, wider weld bead Deep, narrower weld bead
On solidification the On solidification the
bonding between the bonding between the grains
grains may be adequate to may now be very poor to
maintain cohesion and a maintain cohesion and a
crack is unlikely to occur crack may result
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583. Solidification Cracking
Precautions for controlling solidification cracking
•The first steps in eliminating this problem would be to choose a low
dilution process, and change the joint design
Grind and seal in any lamination and avoid further dilution????
Add Manganese to the electrode to form spherical Mn/S which form
between the grain and maintain grain cohesion
As carbon increases the Mn/S ratio required increases
exponentially and is a major factor. Carbon content % should be a
minimised by careful control in electrode and dilution
Limit the heat input, hence low contraction, & minimise restraint
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584. Solidification Cracking
Precautions for controlling solidification cracking
• The use of high manganese and low carbon content fillers
• Minimise the amount of stress / restraint acting on the joint
during welding
• The use of high quality parent materials, low levels of
impurities (Phosphor & sulphur)
• Clean joint preparations contaminants (oil, grease, paints and
any other sulphur containing product)
• Joint design selection depth to width ratios
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585. Solidification Cracking
Solidification cracking in Austenitic Stainless Steel
• particularly prone to solidification cracking
• large grain size gives rise to a reduction in grain boundary area with
high concentration of impurities
• Austenitic structure very intolerant to contaminants (sulphur,
phosphorous and other impurities).
• High coefficient of thermal expansion /Low coefficient of thermal
conductivity, with high resultant residual stress
• same precautions against cracking as for plain carbon steels with extra
emphasis on thorough cleaning and high dilution controls.
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586. Cracks
Lamellar Tearing
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587. Lamellar Tearing
Factors for lamellar tearing to occur
Cracks only occur in the rolled plate !
Close to or just outside the HAZ !
Cracks lay parallel to the plate surface and the fusion boundary
of the weld and has a stepped aspect.
• Low quality parent materials, high levels of impurities
• Joint design, direction of stress
• The amount of stress acting across the joint during welding
• Note: very susceptible joints may form lamellar tearing under
very low levels of stress
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588. Lamellar Tearing
Susceptible joint types combined with susceptible rolled plate
used to make a joint.
High stresses act in the through thickness direction of the plate
(know as the short transverse direction).
T, K & Y joints normally end up with a tensile residual stress
component in the through thickness direction.
Tee fillet weld Tee butt weld Corner butt weld
(double-bevel) (single-bevel)
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589. Lamellar Tearing
Critical area Critical area
Critical
area
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590. Lamellar Tearing
Modifying a corner joint to avoid lamellar tearing
Susceptible Non-Susceptible
Prior welding both An open corner joint
plates may be grooved may be selected to
to avoid lamellar tearing avoid lamellar tearing
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591. Lamellar Tearing
Precautions for controlling lamellar tearing
• The use of high quality parent materials, low levels of
impurities
• The use of buttering runs
• A gap can be left between the horizontal and vertical
members enabling the contraction movement to take
place
• Joint design selection
• Minimise the amount of stress / restraint acting on the
joint during welding
• Hydrogen precautions
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592. Lamellar Tearing
Crack type: Lamellar tearing
Location: Below weld HAZ
Steel types: High sulphur & phosphorous steels
Microstructure: Lamination & Segregation
Occurs when:
High contractional strains are through the short
transverse direction. There is a high sulfur content in
the base metal.
There is low through thickness ductility in the base
metal.
There is high restraint on the work
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593. Short Tensile (Through Thickness) Test
The short tensile test or through thickness test is a
test to determine a materials susceptibility to
lamellar tearing
Friction Welded Caps
Short Tensile Specimen
Sample of Parent Material
Through
Thickness
Ductility
The results are given as a STRA value
Short Transverse Reduction in Area
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594. Lamellar Tearing
Restraint
Lamellar tear
High contractional
strains
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595. Welding Inspector
Practical Visual Inspection
Section 22
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596. Fillet Weld Gauges
10mm
G.A.L.
L S.T.D.
16mm
Leg Length Gauge
10mm
G.A.L.
S.T.D.
16mm
Throat Thickness Gauge
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597. HI-LO Welding Gauge
1
2
3
4
5
6
Root gap
dimension
HI-LO Single Purpose Welding Gauge
Internal
alignment
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598. Plate / Pipe Inspection
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599. Plate Inspection Examination
Remember in the CSWIP 3.1 Welding Inspectors
examination your are required to conduct a practical
examination of a plate test weld, complete a thumb
print sketch and a final report on your findings
 Time allowed 1 hour and 15 minutes
 The code is provided
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600. Plate Inspection Points
1) Use a pencil for the arrow lines, but make all
written comments and measurements in ink
only
2) Report everything that you can observe
3) Do not forget to compare and sentence your
report
4) Do not forget to date & sign your report
5) Make any observations, such as
recommendations for further investigation for
crack-like imperfections.
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601. Plate Thumb Print Report
After you have observed an imperfection and
determined its type, you must be able to take
measurements and complete the thumb print report
sketch
The first thumb print report sketch should be in the
form of a repair map of the weld. (i.e. All
observations are Identified Sized and Located)
The thumb print report sketch used in CSWIP exam
will look like the following example.
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602. Plate Inspection Final Report
After you have completed your thumb print report
sketch of your test plate the next step is to complete
your final report again the report must be completed in
ink (no pencil).
The report must be completed to your thumb print
sketch, do not leave any boxes empty, every box must
be completed or dashed out. You must also make any
comments you feel are necessary regarding any
defects observed.
The report form used in CSWIP will look like the
following example.
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603. Pipe Inspection
Remember in the CSWIP 3.1 Welding Inspectors
examination your are required to conduct a
practical examination of a pipe test weld, complete
a thumb print sketch and a final report on your
findings
 Time allowed 1 hour and 45 minutes
 The code is nominated e.g API 1104
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604. Welding Inspector
Application & Control of Pre heat
Section 23
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605. Welding Temperatures
Definitions
Preheat temperature
• is the temperature of the workpiece in the weld zone immediately before
any welding operation (including tack welding!)
• normally expressed as a minimum Interpass temperature
– is the temperature in a multi-run weld and adjacent parent metal
immediately prior to the application of the next run
– normally expressed as a maximum
Minimum interpass temperature = Preheat temperature
Pre heat maintenance temperature = the minimum temperature in the
weld zone which shall be maintained if welding is interrupted and shall be
monitored during the interruption.
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606. Pre-heat Application
Furnace - Heating entire component - best
Electrical elements -Controllable; Portable; Site use; Clean; Component
cannot be moved.
Gas burners - direct flame impingement; Possible local overheating; Less
controllable;Portable; Manual operation possible; Component
can be moved.
Radiant gas heaters - capable of automatic control; No flame
impingement; No contact with component; Portable.
Induction heating - controllable; Rapid heating (mins not hours); Large
power supply; Expensive equipment
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607. Measuring pre heat in Welding
The purposes
of measuring
Demonstration of Welding
conformance to process
specified requirements control
Parameters to be measured:
welding current preheat/interpass
arc voltage temperature
travel speed force/pressure
shielding gas flow rate humidity
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608. Pre-heat Application
Application Of Preheat
• Heat either side of joint
• Measure temp 2 mins after heat removal
• Always best to heat complete component rather than local if
possible to avoid distortion
• Preheat always higher for fillet than butt welds due to
different combined thicknesses and chill effect factors.
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609. Pre-Heat Application
Electrical Heated Manual Gas Operation
Elements
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610. Welding Temperatures
Point of Measurement
BS EN ISO 13916
t < 50 mm
A = 4 x t but max. 50 mm
the temperature shall be
measured on the surface
of the workpiece facing the
welder
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611. Welding Temperatures
Point of Measurement
BS EN ISO 13916
t > 50mm
A = 75mm minimum
the temperature shall be
measured on the face
opposite to that being
heated
allow 2 min per every 25
mm of parent metal
thickness for temperature
equalisation
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612. Combined Thickness
The Chilling Effect of the Joint
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613. Combined Thickness
The Chilling Effect of the Joint
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614. Combined Thickness
Combined chilling effect of joint type and
thickness.
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615. The Chill Effect of the Material
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616. Heating Temperature Control
• TEMPILSTICKS - crayons, melt at set temps. Will not measure
max temp.
• Pyrometers - contact or remote, measure actual temp.
• Thermocouples - contact or attached, very accurate, measure
actual temp.
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617. Temperature Test Equipment
Temperature sensitive
materials:
•crayons, paints and
pills
•cheap
•convenient, easy to
use
•doesn‟t measure the
actual temperature!
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618. Temperature Test Equipment
Contact thermometer
•Accurate
•Easy to use
•Gives the actual temperature
•Requires calibration
•suitable for moderate
temperatures
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619. Temperature Test Equipment
Thermocouple
• based on measuring the thermoelectric potential difference
between a hot junction (on weld) and a cold junction
• accurate method
• measures over a wide range of temperatures
• gives the actual temperature
• need calibration
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620. Temperature Test Equipment
Thermistors
• temperature-sensitive resistors
whose resistance varies inversely
with temperature
• used when high sensitivity is
required
• gives the actual temperature
• need calibration
• can be used up to 999°C
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621. Temperature test equipment
Devices for contactless measurement
• IR radiation and optical
pyrometer
• measure the radiant energy
emitted by the hot body
• contactless method, can be
used for remote measurements
• very complex
• for measuring high
temperatures
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622. Welding Inspector
Calibration
Section 24
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623. Calibration, validation and monitoring
Definitions:
Measurement = set of operations for determining a value of a
quantity
Repeatability = closeness between successive measuring
results of the same instrument carried out under the same
conditions
Accuracy class = class of measuring instruments that are
intended to keep the errors within specified limits
Calibration = checking the errors in a meter or measuring
device
Validation = checking the control knobs and switches provide
the same level of accuracy when returned to a pre-determined
point
Monitoring = checking the welding parameters (and other
items) are in accordance with the procedure or specification
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624. Calibration and validation
Frequency - When it is required?
once a year unless otherwise specified
whenever there are indications that the
instrument does not register properly
whenever the equipment has been
damaged, misused or subject to severe
stress
whenever the equipment has been rebuild
or repaired
See BS EN ISO 17662 for details!
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625. Welding parameter calibration/validation
Which parameters need calibration/validation?
How accurate?
depends on the application
welding current - ±2,5%
arc voltage - ±5%
wire feed speed - ±2,5%
gas flow rate - ±20% (±25% for backing gas flow rate)
temperature (thermocouple) - ±5%
depends on the welding process
see BS EN ISO 17662 and BS 7570 for details
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626. PAMS (Portable Arc Monitor System)
What does a PAMS measure?
Gas flow
Welding rate
current (Hall (heating
effect element
device) sensor)
Arc voltage
(connection Wire feed
leads) speed
Temperature (tachometer)
(thermocouple)
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627. PAMS (Portable Arc Monitor System)
The purposes of
a PAMS
For measuring For calibrating
and recording and validating
the welding the welding
parameters equipment
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628. Use of PAMS
Wire feed speed
monitoring
Incorporated pair of
rolls connected to a
tachogenerator
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629. Use of PAMS
Shielding gas flow
rate monitoring
Heating element
sensor
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630. Summary
• a welding power source can only be calibrated if it has
meters fitted
• the inspector should check for calibration stickers, dates
etc.
• a welding power source without meters can only be
validated that the control knobs provide repeatability
• the main role is to carryout “in process monitoring” to
ensure that the welding requirements are met during
production
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631. Welding Inspector
Macro/Micro Examination
Section 25
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632. Macro Preparation
Purpose
To examine the weld cross-section to give assurance that: -
• The weld has been made in accordance with the WPS
• The weld is free from defects
Specimen Preparation
• Full thickness slice taken from the weld (typically ~10mm thick)
• Width of slice sufficient to show all the weld and HAZ on both sides
plus some unaffected base material
• One face ground to a progressively fine finish (grit sizes 120 to ~ 400)
• Prepared face heavily etched to show all weld runs & all HAZ
• Prepared face examined at up to x10 (& usually photographed for records)
• Prepared face may also be used for a hardness survey
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633. Micro Preparation
Purpose
To examine a particular region of the weld or HAZ in order to:-
• To examine the microstructure
• Identify the nature of a crack or other imperfection
Specimen Preparation
• A small piece is cut from the region of interest
(typically up to ~ 20mm x 20mm)
• The piece is mounted in plastic mould and the surface of interest
prepared by progressive grinding (to grit size 600 or 800)
• Surface polished on diamond impregnated cloths to a mirror finish
• Prepared face may be examined in as-polished condition & then lightly
etched
• Prepared face examined under the microscope at up to ~ x 600
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634. Macro / Micro Examination
Object:
• Macro / microscopic examinations are used to give a visual
evaluation of a cross-section of a welded joint
• Carried out on full thickness specimens
• The width of the specimen should include HAZ, weld and
parent plate
• They maybe cut from a stop/start area on a welders
approval test
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635. Macro / Micro Examination
Will Reveal:
• Weld soundness
• Distribution of inclusions
• Number of weld passes
• Metallurgical structure of weld, fusion zone and HAZ
• Location and depth of penetration of weld
• Fillet weld leg and throat dimensions
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636. Macro Micro
• Visual examination for • Visual examination for
defects defects & grain structure
• Cut transverse from the • Cut transverse from a
weld weld
• Ground & polished P400 • Ground & polished P1200
grit paper grit paper, 1µm paste
• Acid etch using 5-10% • Acid etch using 1-5%
nitric acid solution nitric acid solution
• Wash and dry • Wash and dry
• Visual evaluation under 5x • Visual evaluation under
magnification 100-1000x magnification
• Report on results • Report on results
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637. Metallographic Examination
Macro examination Micro examination
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