Shielded metal arc welding (SMAW), Also known as Manual Metal Arc (MMA) welding Informally as stick welding

1. Dr. N. RAMACHANDRAN, NITC 1
ARC WELDING

3. Dr. N. RAMACHANDRAN, NITC 3
LIQUID STATE PROCESS
PARTIAL MELTING
BY STRIKING AN ARC
AFTER THE INVENTION OF ELECTRICITY
HOW ARC STRUCK?
ARC COLUMN THEORY

4. Dr. N. RAMACHANDRAN, NITC 4
• ARC WELDING
ELECTRIC ARC
WITHOUT ADDITIONAL EXTERNAL SOURCE
AUTOGENEOUS NONCONSUMABLE- CONSUMABLE
CARBON ARC WELDING (CAW) - OLDEST
METALLIC ARC WELDING (MAW)
COATING MATERIALS
ARC TO BE CREATED BY ELECTRICITY
WHEN? WITH THE INVENTION OF AC DYNAMO IN 1877

5. Dr. N. RAMACHANDRAN, NITC 5
BEGINNING IN 1881- TO CONNECT PLATES OF STORAGE BATTERY
1886- BUTT WELDING TECHNIQUE WAS DEVELOPED
BUTTED, CLAMPED HIGH CURRENT PASSED
AT THE JOINT, RESISTANCE OF METAL TO ELECTRIC CURRENT
PRODUCES HIGH HEAT- PIECES FUSED

6. Dr. N. RAMACHANDRAN, NITC 6
ARC WELDING- MELTING AND FUSING OF METAL BY ELECTRODES
1ST BY N.V. BERNADO USING CARBON ELECTRODES
CONSISTANTLY IMPROVED
1895 N.G. SLAVIANOFF USED METALLIC ELECTRODES
1905 BARE ELECTRODES COATED—SHIELDING--- (SAW)
PORTABLE AND AUTOMATIC WELDING MACHINES

7. Dr. N. RAMACHANDRAN, NITC 7
ARC WELDING PROCESSES
USE OF CONSUMABLE ELECTRODES
SHIELDED METAL ARC WELDING
(SMAW)
• SIMPLEST AND MOST VERSATILE
• ABOUT 50% OF INDUSTRIAL WELDING
BY THIS PROCESS
• CURRENT- 50 TO 300 A, < 10 KW
• AC/DC USED
• FOR THICKNESSES UPTO 19 –20 MM

8. SHIELDED METAL ARC WELDING
(SMAW)

9. Dr. N. RAMACHANDRAN, NITC 9
•Shielded metal arc welding (SMAW),
•Also known as Manual Metal Arc (MMA) welding
• Informally as stick welding
is a manual arc welding process that uses a
consumable electrode coated in flux to lay the weld.
•An electric current, in the form of either alternating
current or direct current from a welding power supply, is
used to form an electric arc between the electrode and
the metals to be joined.

10. ANODE +
CATHODE -
ELECTRICAL / IONIC THEORY
IONS FROM ANODE TO CATHODE,
AS METAL IONS ARE +VE CHARGED
DC
ARC COLUMN THEORY
•TOUCH AND THEN ESTABLISH A GAP
TO BALANCE THE ATOMIC STRUCTURE
•IONS COLLIDE WITH GAS MOLECULES
•PRODUCES A THERMAL IONISATION LAYER
•IONISED GAS COLUMN – AS HIGH
RESISTANCE CONDUCTOR
•ON STRIKING CATHODE, HEAT GENERATED
•TERMED AS IONIC THEORY
•NOT COMPLETE IN EXPLAINING ARC
COLUMN THEORY
•THUS, ELECTRON THEORY

11. Dr. N. RAMACHANDRAN, NITC 11
ANODE +
CATHODE -
ELECTRON THEORY
IONS FROM ANODE TO CATHODE
AS METAL IONS ARE +VE
CHARGED
-VELY CHARGED ELECTRONS
DISSOCIATED FROM CATHODE
MOVE OPPOSITE WITH HIGH
VELOCITY
DC
(MASS- 9.1x 10-28 gm)
CAUSES HEAT IN ARC COLUMN
RELEASES HEAT ENERGY IN
STRIKING THE ANODE
CALLED
ELECTRON IMPINGEMENT
AND
IONIC BOMBARDMENT
ARC COLUMN THEORY

12. Dr. N. RAMACHANDRAN, NITC 12
HIGH HEAT
MEDIUM HEAT
LOW HEAT
ANODE+
CATHODE -
ELECTRON IMPINGEMENT
IONIC BOMBARDMENT

13. Dr. N. RAMACHANDRAN, NITC 13
MAGNETIC FLUX THEORY
• THE COLUMN NOT FLAIRING
DUE TO THE FLUX LINES AROUND
THE ARC COLUMN.
(Right hand Thumb Rule)
THIS COMPLETES THE ARC COLUMN THEORY

14. Dr. N. RAMACHANDRAN, NITC 14
POLARITY
AC
1. Currents higher than
those of DCRP can be
employed (400 A to 500
Afor 6 mm electrode)
2. Arc cleaning of the base
metal
3. Normal penetration
4. Equal heat distribution
at electrode and job
5. Electrode tip is colder
as compared to that in
DCRP
6. Average arc voltage in
argon atmosphere is
16V

15. Dr. N. RAMACHANDRAN, NITC 15
DCRP 1. Currents generally less
than 125 amps (upto 6
mm dia electrodes) to
avoid overheating
2. 2/3rd heat at electrode
and 1/3rd at the job
3. Least penetration
4. Average arc voltage on
argon atmosphere is
19V
5. Chances of electrode
overheating, melting and
losses
6. Better arc cleaning
action

16. Dr. N. RAMACHANDRAN, NITC 16
DCSP
1. Welding currents upto
1000 amps can be
employed for 6 mm
electrodes
2. 33.33% heat is generated
at the electrode and
66.66% at the job.
3. Deep penetration
4. Average arc voltage in an
argon atmsphere is 12 V
5. Electrode runs colder as
compared to AC or DCRP
6. No arc cleaning of base
metal

17. Dr. N. RAMACHANDRAN, NITC 17

18. METALLURGY OF WELDING
During joining, localized heating occurs.
This leads to metallurgical and physical changes in materials welded.
Hence, study of:
1. Nature of welded joint
2. Quality and property of welded joint
3. Weldability of metals
4. Methods of testing welds
5. Welding design
6. Process selection- important
.

19. Dr. N. RAMACHANDRAN, NITC 19
(2) Fusion Zone
(1) Base Metal
Structures: (1) SMALL (2) MEDIUM (3) LARGE
Properties of (2) and (3) important
(3) Heat Affected Zone (HAZ)

20. Dr. N. RAMACHANDRAN, NITC 20
• Cooling of Bead-
similar to a casting in mould, which is metallic here.
Cooling is slow Hence the structure is coarse and
Strength toughness and ductility low.
But use of proper electrodes improves these.
• The purpose of coating the electrode is to
achieve the improved properties. If without,
nitrides and oxides of base metal form and
these result in weak and brittle nature.
• With coating, properties comparable with base metal
achieved.

21. Dr. N. RAMACHANDRAN, NITC 21
Arc column makes CRATER on
striking the surface- Temperature
above 1500 C
Gas shield
Flux + impurities- less dense. Floats as SLAG
Slag prevents heat loss- makes an evenly distribution
of heat radiation.
Preheating to receive the molten metal at an elevated temperature and
modify the structure. Not for M.S.
Locked in stresses due to heating and cooling- to be relieved by
PEENING, or other heat treatment processes.

22. Dr. N. RAMACHANDRAN, NITC 22
MAGNETIC ARC BLOW -- FOR AC SUPPLY.
Current through conductor- magnetic Flux lines perpendicular to
current flow- apply Right hand Thumb Rule.
Three areas of magnetic field
1. Arc; 2. Electrode; 3. Work piece, when ground.
Forward pull of Arc column results, called as Magnetic Arc Blow.

23. Dr. N. RAMACHANDRAN, NITC 23
EQUIPMENT

24. Dr. N. RAMACHANDRAN, NITC 24

25. Dr. N. RAMACHANDRAN, NITC 25
PURPOSE OF COATING
• Gives out inert or protective gas- shields
• Stabilizes the arc- by chemicals
• Low rate consumption of electrode- directs arc and
molten metal
• Removes impurities and oxides as slag
• Coatings act as insulators- so narrow grooves welded
• Provide means to introduce alloying elements
Bare electrodes - carbon- more conductive- slow
consumption in welding

26. Dr. N. RAMACHANDRAN, NITC 26
ELECTRODE COATING INGREDIENTS
• Slag forming ingredients- silicates of sodium, potassium, Mg,
Al, iron oxide, China clay, mica etc.
• Gas shielding- cellulose, wood, starch, calcium carbonate
• De-oxidising elements- ferro manganese, ferro silicon- to
refine molten metal
• Arc stabilizing – calcium carbonate, potassium silicate,
titanates, Mg silicate etc.
• Alloying elements- ferro alloys, Mn, Mo., to impart special
properties
• Iron powder- to improve arc behaviour, bead appearance
• Other elements - to improve penetration, limit spatter,
improve metal deposition rates,

27. Dr. N. RAMACHANDRAN, NITC 27
• As the weld is laid, the flux coating of
the electrode disintegrates, giving off
vapors that serve as a shielding gas
and providing a layer of slag, both of
which protect the weld area from
atmospheric contamination.
• Because of the versatility of the
process and the simplicity of its
equipment and operation, shielded
metal arc welding is one of the world's
most popular welding processes.

28. Dr. N. RAMACHANDRAN, NITC 28
• It dominates other welding processes in the
maintenance and repair industry, used
extensively in the construction of steel
structures and in industrial fabrication.
• The process is used primarily to weld iron
and steels (including stainless steel) but
aluminum, nickel and copper alloys can also
be welded with this method.
• Flux-Cored Arc Welding (FCAW) , a
modification to SMAW is growing in
popularity

29. (A).BARE ELECTRODE MOLTEN METAL TRANSFER
(B). LIGHT COATED ELECTRODE ARCACTION

30. Dr. N. RAMACHANDRAN, NITC 30
Various welding electrodes and an electrode holder

31. Dr. N. RAMACHANDRAN, NITC 31
SAFETY PRECAUTIONS
• Uses an open electric arc, so
risk of burns – to be prevented
by protective clothing in the
form of heavy leather gloves
and long sleeve jackets.
•The brightness of the weld area
can lead arc eye, in which
ultraviolet light causes the
inflammation of the cornea and
can burn the retinas of the eyes.
•Welding helmets with dark face
plates to be worn to prevent this
exposure

32. Dr. N. RAMACHANDRAN, NITC 32
• New helmet models have been
produced that feature a face plate
that self-darkens upon exposure
to high amounts of UV light
• To protect bystanders, especially
in industrial environments,
transparent welding curtains
often surround the welding area.
• These are made of a polyvinyl
chloride plastic film, shield
nearby workers from exposure to
the UV light from the electric arc,
but should not be used to replace
the filter glass used in helmets.

33. Dr. N. RAMACHANDRAN, NITC 33
Arc eye, also known as arc flash or welder's flash or
corneal flash burns, is a painful condition sometimes
experienced by welders who have failed to use adequate
eye protection.
It can also occur due to light from sunbeds, light
reflected from snow (known as snow blindness), water
or sand. The intense ultraviolet light emitted by the arc
causes a superficial and painful keratitis.
Symptoms tend to occur a number of hours
after exposure and typically resolve
spontaneously within 36 hours.
It has been described as having sand poured
into the eyes.
ARC EYE

34. Dr. N. RAMACHANDRAN, NITC 34
Signs
Intense lacrimation
Blepharospasm
Photophobia
Fluorescein dye staining will reveal corneal ulcers
under blue light
Management
• Instill topical anaesthesia
• Inspect the cornea for any foreign body
• Patch the worse of the two eyes and prescribe analgesia
• Topical antibiotics in the form of eye drops or eye
ointment or both should be prescribed for prophylaxis
against infection

35. Shielded Metal Arc Welding

36. What Is Welding ?
Process of joining metals / alloys
The process performed by Heat with or
without Pressure
Filler metal may or may not be used
The joint will be homogeneous

37. Classification Of Welding
1 Pressure Welding – With Heat &
Pressure
2 Fusion Welding – With Heat &
mostly with Filler

38. Pressure Welding Process
Metal parts heated to forging temperature
Heating by Oven, Oxy fuel flame or Electric
Resistance
Pressure applied on heated parts – by
Hammer, Hydraulic Press or Mechanical lever
The Parts remain permanent homogeneous
joint

39. Types Of Pressure Welding
Forge Welding
Resistance Butt / Flash Butt / Stud
Welding
Resistance Spot Welding
Resistance Seam welding

40. Fusion Welding Process
Metal parts locally heated to melt along the joint.
Heating by oxy fuel flame or electric Arc.
Invariably filler metal added to molten pool.
On cooling, molten puddle solidifies to permanent
homogeneous joint.

41. Types Of Fusion Welding
Shielded Metal Arc Welding- SMAW
Gas Tungsten Arc Welding - GTAW
Gas Metal Arc Welding - MIG / MAG
Submerged Arc Welding – SAW
Gas welding – Oxy Fuel Gas
Electron Beam Welding - EBW
Thermit Welding

42. An electric Arc struck between
electrode and base metal joint
Base metal melts under arc
Electrode tip melts in drops
and transfers to molten pool of
BM
Electrode with Arc moves along
the joint keeping constant arc
length
On cooling pool solidifies
Arc
Base Metal
Flux Coating
Core Wire
Pool
SMAW Process

43. Equipment, Accessories &
tools
Power Source
Welding Cables, Holder & Earthing
Clamp
Head Screen, Hand gloves, Chipping
Hammer & Wire Brush

44. Types Of Power Source
Inverter- DC
Thyrester – DC
Motor Generator / Diesel Generator Set -DC
Rectifier – DC
Transformer - AC

45. Characteristic Of Power
Source
Manual welding Machine welding
Drooping – Cons. A Linear – Cons. V
V V
A A
Vertical
Curve
Horizontal
Curve
V1
V2
A1 A2
V1
V2
A1 A2

46. Electrode
Consumable
Metallic Wire Coated with Flux
Conducts Current and generates Arc
Wire melts & deposited as filler in joint

47. Flux Coating On Electrode
Sodium Chloride
Potassium Chloride
Titanium Dioxide
Sodium Silicate
Ferrosilicon
Iron Powder
Alloying Elements
Binding Material

48. Function Of Flux In welding
Stabilizes Arc
Prevents contamination of weld metal
Cleans the weld from unwanted impurities
Increases fluidity of molten metal
Generates inert gas shielding while metal
transfers

49. Function Of Flux In welding
Forms slag after melting & covers weld
Allows deposited metal to cool slowly
Introduces alloying elements in the weld
Increases deposition efficiency
Minimizes the spatter generation
Helps in even & uniform bead finish

50. CS & LAS Electrode Sizes &
Recommended Currents
No
Core Wire in mm
Gage Current
Time
required for
burning in
seconds
Average
electrodes
consumed in
8 Hrs shift
Dia Length
1 2 300 14 40 – 60 A 50-55 ---
2 2.5 350 12 60 – 85 A 60-65 ---
3 3.15 450 10
100 – 130
A
80 -85 120 - 140
4 4 450 8
130 – 180
A
85-90 110 - 120
5 5 450 6
150 – 210
A
90-95 80 - 90
6 6.3 450 4
240 – 250
A
95-100 60 -70

51. ASME Classification Of
Electrodes
SFA 5.1
E 7018
E = Electrode
70 = UTS in 1000 psi ( 60/70/80/90/100/ 110)
1 = Position (1= all, 2= 1G, 1F & 2F, 3= 1G &
1F)
8 = Type of coating (0,1,2,3,5,6,8)

52. Baking Of Basic Coated
Electrodes
Bake the loose electrodes in a baking Oven
Baking Temperature 250° C to 300° C
Baking Time 2Hrs to 3 Hrs
Reduce the temperature to 100° C to 150° C
Hold the electrodes at this temperature till use
Unused / left over electrodes to be re-baked

53. ELECTRODE IDENTIFICATION
Arc welding electrodes are identified using
the A.W.S, (American Welding Society)
numbering system and are made in sizes
from 1/16 to 5/16 .
An example would be a welding rod
identified as an 1/8" E6011 electrode.
The electrode is 1/8" in diameter
The "E" stands for arc welding electrode.

54. Dr. N. RAMACHANDRAN, NITC 54
• Next will be either a 4 or 5 digit number stamped
on the electrode. The first two numbers of a 4
digit number and the first 3 digits of a 5 digit
number indicate the minimum tensile strength (in
thousands of pounds per square inch) of the weld
that the rod will produce, stress relieved.
Examples would be as follows:
• E60xx would have a tensile strength of 60,000 psi
E110XX would be 110,000 psi
• The next to last digit indicates the position the
electrode can be used in.
• EXX1X is for use in all positions
• EXX2X is for use in flat and horizontal positions
• EXX3X is for flat welding

55. Dr. N. RAMACHANDRAN, NITC 55
• The last two digits together, indicate the
type of coating on the electrode and the
welding current the electrode can be used
with. Such as DC straight, (DC -) DC
reverse (DC+) or A.C.
Type of coatings of the various electrodes
are explained elsewhere.
• Examples of the type current each will work
with are as below.

56. Dr. N. RAMACHANDRAN, NITC 56
• ELECTRODES AND CURRENTS USED
• EXX10 DC+ (DC reverse or DCRP) electrode positive.
• EXX11 AC or DC- (DC straight or DCSP) electrode
negative.
• EXX12 AC or DC-
• EXX13 AC, DC- or DC+
• EXX14 AC, DC- or DC+
• EXX15 DC+
• EXX16 AC or DC+
• EXX18 AC, DC- or DC+
• EXX20 AC ,DC- or DC+
• EXX24 AC, DC- or DC+
• EXX27 AC, DC- or DC+
• EXX28 AC or DC+

57. Dr. N. RAMACHANDRAN, NITC 57
• CURRENT TYPES
• SMAW is performed using either AC or
DCcurrent. Since DC current flows in one
direction, DC current can be DC straight,
(electrode negative) or DC reversed (electrode
positive). With DC reversed,(DC+ OR DCRP)
the weld penetration will be deep. DC straight
(DC- OR DCSP) the weld will have a faster melt
off and deposit rate. The weld will have medium
penetration.
Ac current changes it's polarity 120 times a
second by it's self and can not be changed as
can DC current.

58. Dr. N. RAMACHANDRAN, NITC 58
ELECTRODE SIZE AND AMPS USED
Electrode Table
ELECTRODE
DIAMETER
AMP
RANGE
PLATE
1/16" 20 - 40 UP TO 3/16"
3/32" 40 - 125 UP TO 1/4"
1/8 75 - 185 OVER 1/8"
5/32" 105 - 250 OVER 1/4"
3/16" 140 - 305 OVER 3/8"
1/4" 210 - 430 OVER 3/8"
5/16" 275 - 450 OVER 1/2"
The table shown will serve as
a basic guide of the amp
range that can be used for
different size electrodes.
These ratings can be different
between various electrode
manufactures for the same
size rod.
The type coating on the
electrode could effect the
amperage range.
Check manufacturer’s
recommended amperage
settings.
Note! The thicker the material
to be welded, the higher the
current needed and the larger
the electrode needed

59. Dr. N. RAMACHANDRAN, NITC 59
SOME ELECTRODE TYPES
• E6010 :
Used for all position welding using DCRP. It produces a deep
penetrating weld and works well on dirty,rusted, or painted metals
• E6011:
Same characteristics as of the E6010, but can be used with AC and
DC currents.
• E6013:
Used with AC and DC currents. It produces a medium penetrating
weld with a superior weld bead appearance.
• E7018:
Known as a low hydrogen electrode and can be used with AC or
DC. The coating on the electrode has a low moisture content that
reduces the introduction of hydrogen into the weld. The electrode
can produce welds of x-ray quality with medium penetration.
(This electrode must be kept dry. If wet, it must be dried in a rod
oven before use.)

60. Why Baking?
To remove the moisture (H2O) from coating
to avoid possible cracking of weld

61. How Does Moist Electrode
Generate Crack Within Weld?
Moist electrodes introduce atomic hydrogen at high
temperature in weld
On cooling, atomic hydrogen try to form molecules
The reaction results in stresses and fine cracks
Cracks occur within hardened metal - HAZ
Known as “Hydrogen Embrittlement” , “Under Bead
Crack”, HIC, Delayed Crack

62. Important Terminologies used in
Critical Welding Operation
Preheating
Post Heating or Dehydrogenation
Intermediate Stress leaving
Inter pass Temperature
Post Weld Heat Treatment

63. What Is Preheating?
Heating the base metal along the weld joint to a
predetermined minimum temperature
immediately before starting the weld.
Heating by Oxy fuel flame or electric resistant
coil
Heating from opposite side of welding wherever
possible
Temperature to be verified by thermo chalks
prior to starting the weld

64. Why Preheating?
Preheating eliminates possible cracking of weld
and HAZ
Applicable to
 Hardenable low alloy steels of all thickness
 Carbon steels of thickness above 25 mm.
 Restrained welds of all thickness
Preheating temperature vary from 75°C to
200°C depending on hardenability of material,
thickness & joint restraint

65. How does Preheating Eliminate
Crack?
Preheating promotes slow cooling of weld
and HAZ
Slow cooling softens or prevents
hardening of weld and HAZ
Soft material not prone to crack even in
restrained condition

66. What Is Post Heating?
Raising the pre heating temperature of the weld
joint to a predetermined temperature range (250°
C to 350° C) for a minimum period of time (3 Hrs)
before the weld cools down to room temperature.
Post heating performed when welding is
completed or terminated any time in between.
Heating by Oxy fuel flame or electric resistant coil
Heating from opposite side of welding wherever
possible
Temperature verified by thermo chalks during the
period

67. Why Post Heating?
Post heating eliminates possible delayed
cracking of weld and HAZ
Applicable to
Thicker hardenable low alloy steels
Restrained hardenable welds of all
thickness
Post heating temperature and duration
depends on hardenability of material,
thickness & joint restrain

68. How does Post Heating
Eliminate Crack?
SMAW introduces hydrogen in weld metal
Entrapped hydrogen in weld metal induces
delayed cracks unless removed before
cooling to room temperature
Retaining the weld at a higher temperature
for a longer duration allows the hydrogen to
come out of weld

69. What Is Intermediate Stress
Relieving?
Heat treating a subassembly in a furnace to a
predetermined cycle immediately on
completion of critical restrained weld joint /
joints without allowing the welds to go down
the pre heat temperature. Rate of heating,
Soaking temperature, Soaking time and rate
of cooling depends on material quality and
thickness
Applicable to
Highly restrained air hardenable material

70. Why Intermediate Stress
Relieving?
Restrained welds in air hardenable steel highly prone
to crack on cooling to room temperature.
Cracks due to entrapped hydrogen and built in stress
“Intermediate stress relieving” relieves built in stresses
and entrapped hydrogen making the joint free from
crack prone

71. What Is Inter- Pass
Temperature?
The temperature of a previously layed weld
bead immediately before depositing the next
bead over it
Temperature to be verified by thermo chalk
prior to starting next bead
Applicable to
 Stainless Steel
 Carbon Steel & LAS with minimum impact

72. Why Inter Pass Temperature?
Control on inter pass temperature avoids over
heating, there by
 Refines the weld metal with fine grains
 Improves the notch toughness properties
 Minimize the loss of alloying elements in welds
 Reduces the distortion

73. What Is Post Weld Heat
Treatment?
Heat treating an assembly on completion of
all applicable welding, in an enclosed furnace
with controlled heating/cooling rate and
soaking at a specific temperature for a
specific time.
Rate of heating, Soaking temperature,
Soaking time and rate of cooling depends on
material quality and thickness
Applicable to
 All type of CS & LAS

74. Why Post Weld Heat Treatment?
Welded joints retain internal stresses within the
structure
HAZ of welds remains invariably hardened
“Post Weld Heat Treatment” relieves internal
stresses and softens HAZ. This reduces the
cracking tendency of the equipment in service

75. Welding Terminologies used in
Qualifications
Heat In Put
Heat Effected Zone – HAZ
Dilution
Overlap In Weld Overlay
Tempering Bead

76. What Is Heat In Put In Welding?
The extent of heat energy generated in Joules per
unit length while making each weld bead.
“Heat In Put” is the Function of Welding Current,
Arc Voltage, And the Welding Speed
It is measured in Joules -
Heat In Put In Joules / mm
= (A x V x 60) ÷ Travel Speed in mm / min

77. Why Control On Heat in Put?
“Heat In put” controls the grain size of weld
metal.
 Lower the Heat in put finer the grain size.
 Finer the Grain size Better the impact properties
“Heat In Put” Also controls Dilution, HAZ &
Geometry of Bead size

78. What Is Heat Affected Zone
(HAZ)
A small volume of BM adjacent to weld
fusion line, which is totally changed in its
structure due to intense heat of each weld
bead is known HAZ
Weld Zone
HAZ
Diluted BM
Diluted BM
Weld Zone
Fusion Line

79. What Is Significant Of HAZ
It is a part and parcel of weld joint
It is inevitable
It has properties different from BM &
Weld Metal
Weld Zone
HAZ
Diluted BM
Diluted BM
Weld Zone
Fusion Line

80. What Is Dilution In Weld
In all Fusion welding, a small portion of BM
very close to the welding heat gets melted and
added to weld zone / fusion zone. Dilution is
the ratio of molten base metal volume (Area)
to the volume ( Area) of total fusion zone
HAZ
Diluted BM
Weld / Fusion Zone
Fusion Line
% Dilution = (Area of Diluted BM ÷ Total Fused Area) × 100

81. What Is Significant Of Dilution
Weld metal chemistry changes depending on
the extent of dilution
Chemical elements influence Physical
properties of the joint.
Weld chemistry influences corrosion
resistance of weld overlays
Weld Zone
HAZ
Diluted BM
Diluted BM
Weld Zone
Fusion Line

82. What Is Overlap In Weld
Overlay?
The extent of covering or over lapping of
previous weld bead by the adjacent bead.
40 to 50 % Over Lap 10 to 15 % Over Lap
Less Dilution More Dilution
More Thickness
Less Thickness

83. What Is Significant Of Overlap
In Weld Overlay?
Overlap of 40 to 50% results in Less Dilution & more weld
overlay Thickness per layer
Less dilution results weld metal chemistry more towards
filler metal chemistry
40 to 50 % Over Lap 10 to 15 % Over Lap
Less Dilution More Dilution
More Thickness
Less Thickness

84. What Is Temper Bead
Technique?
In a multi pass groove & Fillet Welds, each bead &
its HAZ are getting tempered (heat treated) by the
welding heat of the next bead.
Thus all beads & their HAZ, except those in last
layer, are tempered.
Temper beads are the specially & carefully welded
temporary beads on the top of final weld
reinforcement with out allowing to generate any
HAZ within the BM. Temper beads are to be
ground flush with the required reinforcement.

85. Temper Bead
Temper Bead T1 & T2 Not To Generate
HAZ In BM
Temper Beads To Be Ground Flush
T2
T1
2
1
3 3
4 4
5
5
T1 & T2 To be ground Flush
HAZ
Rqd. Reinforcement

86. Good Engineering Practices In
SMAW
Do Welding with properly baked electrodes
Basic coated CS electrodes to be baked to 250°C
to 300°C for two hours
Baked electrodes to be directly used on job or to
be retained in a hold over oven at 100°C to
150°C until use
Unused balance electrodes shall be returned to
baking oven

87. Do not weld with damp Electrodes
Do not try to heat electrodes by touching the job
(Short circuiting)
Do not use electrodes with damaged coating
Do not use electrodes with cracked coating
Do not bend the electrodes after holding it in the
holder
Good Engineering Practices In
SMAW

88. Do not weld on groove / surface with mill
scale or rusting
Prior to welding, clean the weld groove
with power wire wheel
Do not weld with unidentified electrodes
Do not leave balance electrodes
unattended on shop
Good Engineering Practices In
SMAW

89. All connections with earthing and welding
cables shall be tight fitted
Earthing clamp shall always be tightly
connected to the job
Burn the full length of electrode till 37
mm stub length
Good Engineering Practices In
SMAW

90. Earthing cable shall directly connect to
the job with an earthing clamp.
Tacks for set up shall be minimum 5
times the electrode diameter
Weaving shall be limited to three times
the electrode diameter.
Only trained & qualified welders shall be
employed for welding
Good Engineering Practices In
SMAW

91. Do not direct fan or blower to welding arc
Remove paint if any from the area near welding
While welding in open, area shall be covered to
protect from rain water & breeze
Weld edge preparation shall be free from
serrations
Good Engineering Practices In
SMAW

92. Use poison plates between the job
material & structural supports.
Do not damage parent metal while
removing temporary supports.
Locations where from temporary supports
are removed shall be touched up by
welding / grinding and PT checked.
Good Engineering Practices In
SMAW

93. Remove visible defects from welds before
placing the subsequent beads
Do not weld over a visible crack
Electrodes kept out side more than 2 Hrs
shall be returned to baking oven
Maximum 15 electrodes at a time shall be
taken from oven for welding
Good Engineering Practices In
SMAW

94. When preheat is required, heat from
opposite side of welding.
Use temperature indicating crayons for
checking temperature
Do not Weld more than specified weld
size- Fillet / Reinforcement.
Good Engineering Practices In
SMAW

95. Safety Precautions in
Shielded Metal Arc Welding

96. Safety Precautions In SMAW
Welders shall use safety devises – Hand
gloves, Head screen with right glass &
Safety shoes
Welders shall use full sleeve boiler suit
Use welding glass-DIN 11/12 up to 250
Amps and 13 above 250 Amps
Do not look at the arc with naked eyes

97. Do not throw Stubs on ground. They shall be
placed in stub collector.
Do not keep electrode in the holder when work
is not in progress
Do not touch the electrode held on holder and
the the job when the power source is on
Keep welding cables duly wound near power
source when no welding is done
Safety Precautions In SMAW

98. Do not breath welding fumes
When working in confined area, ensure
adequate ventilation / exhaust
Gas cutting torch / preheating burner
shall not be taken inside confined area
unless the flame is lit
When not in use, switch off the the power
source from electric supply
Safety Precautions In SMAW

99. Acetone / inflammable liquids (Chemical
for dye penetrant test) shall not be
brought near welding
Gas cutting unit / fuel gas cylinders shall
be away from welding area
Wet safety Shoes or wet hand gloves shall
not be worn while welding
……………………………………………………
Safety Precautions In SMAW