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WELDING
Metal Joining processes
Joining processes and equipments
Welding

Fusion

Brazing & soldering

chemical
Electrical

Oxyfue...
Examples of joints
Fusion welding processes
Types of flames

For neutral flame ratio
of Oxygen and
acetylene is 1:1.

Neutral flame
For Oxidi...
Gas welding – Oxy-acetylene
welding

(a) General view and (b) cross section of a torch used in oxy-acetylene
welding. The ...
Oxy-acetylene welding - Equipments

Basic equipment used in oxyfuel gas welding. Other equipments include
safety shields, ...
Arc – welding processes
Consumable Electrodes
Arc – welding processes
Consumable Electrodes
•
•
•
•
•

Shielded metal - arc welding
Sub merged arc welding
Gas Metal Arc...
Shielded metal - arc welding
• Definition:
– Consumable electrode coated with chemicals
that provide flux and shielding
– ...
Shielded metal - arc welding
a
b

Fig (a). Schematic illustration of
shielded metal-arc welding
operation, also known as s...
Shielded Metal Arc Welding
• Benefits
• Simple, portable,& inexpensive
• Self flux provided by electrode
• Provides all po...
Shielded Metal Arc Welding Cont.:
• Applications
• Construction, pipelines, shipbuilding,
fabrication job shops.
• Used fo...
Specifications of an Electrode

E6010

Stands for electrode
Designates the tensile strength in ksi*
Position the electrode...
Volt – Ampere characteristic in Arc
welding
a

b

Fig.a
Produces only small amount
of ampere change when
the arc voltage i...
Comparison of weld penetration

weld penetration obtained by dc straight polarity

weld penetration obtained by dc reverse...
Wave form of high frequency, low-power
current

A super imposed high – frequency current along with capacitors
stabilizes ...
Sub merged arc welding
Process features
Similar to MIG welding, SAW involves formation of an arc between a continuously-fe...
Sub merged arc welding
Applications
SAW is ideally suited for longitudinal and circumferential butt and
fillet welds. Howe...
Sub merged arc welding – Equipment
layout

Schematic illustration of sub merged arc welding process
Gas Metal Arc Welding (MIG)
• Definition:
– The heat source is formed by creating an electric arc
between the work piece a...
Gas Metal Arc Welding (MIG) Cont.
• Shielding Gases:
• Inert
– Argon, Helium
» Used for aluminum alloys and stainless stee...
Gas metal arc welding - Equipment

Schematic illustration of gas metal arc welding process
Flux cored arc welding

Schematic illustration of Flux cored arc welding process
Electro gas welding

Schematic illustration of Electro gas welding process
Electro slag welding
Unlike other high current fusion processes, electro slag welding is not an
arc process. Heat required...
Electro slag welding

A view of Electro slag welding process in component
Electro slag welding

Layout of equipment used for electro slag welding operations.
Electro slag welding
Benefits
The principal benefits of the process are:
 speed of joint completion; typically 1 hour per...
Electro slag welding
Limitations
Electro slag welding is not one of the major welding processes
because the high heat inpu...
Arc welding processes
Non consumable Electrodes
Arc welding processes
(non consumable Electrodes) are
•
•
•
•
•

Gas tungsten arc welding process
Plasma arc welding proce...
Gas tungsten arc welding process
• Definition:

– TIG welding is an arc that is formed
between a non-consumable tungsten
e...
Tungsten Inert Gas Welding (TIG)
• Applications
• Most commonly used for aluminum and
stainless steel
• For steel
– Slower...
Gas tungsten arc welding process
Equipment
Plasma arc welding processes
Plasma welding is very similar to TIG
as the arc is formed between a pointed
tungsten electro...
Thermit welding
Thermit welding (TW) is a welding process which produces
coalescence of metals by heating them with superh...
Thermit welding
Few images of rails, joined by thermit welding
Thermit welding
Few images of rails joined by thermit welding
Electron beam welding
Laser beam welding
Cutting
• Definition:

Oxy fuel gas cutting

– A stream of oxygen is directed against a piece of
heated metal, causing the metal t...
Oxy fuel gas cutting
Process fundamentals
The cutting process is illustrated in Fig.
Basically, a mixture of oxygen and th...
Oxy fuel gas cutting
There are four basic requirements for oxy-fuel cutting:
• the ignition temperature of the material mu...
SOLID STATE WELDING
PROCESSES
SOLID STATE WELDING
PROCESSES ARE

• Cold Welding

• Ultrasonic Welding
• Friction welding
• Resistance welding
- Resistan...
Cold Welding

Schematic illustration of the roll bonding, or
cladding process
Ultrasonic Welding

Fig. a) Components of an ultrasonic
welding machine for lap welds

Fig. b) ultrasonic seam welding
usi...
Friction welding

Sequence of operations in the friction welding process
Fig. (a) Left part is rotated at high speed
Fig. ...
Friction welding

Shape of fusion zone in friction welding, as a
function of force applied and rotational speed
Friction welding of a bolt head
Resistance spot welding

Fig. a) Sequence in resistance spot welding process
Fig. b) cross – section of a spot weld, showi...
Spot welding machine

Schematic illustration of an air operated rocker arm spot welding
machine
Spot welding operations for
complex shape

Types of special electrodes designed for easy access in spot
welding operations...
High frequency resistance welding

Fig. b) overlapping spots in Fig. c) roll spot weld
seam weld
Fig. a) seam welding proc...
High frequency resistance welding
of tubes

Methods in high frequency butt welding of tubes
Resistance projection welding

Before welding

After welding

Schematic illustration of resistance projection welding
The ...
Resistance projection welding

Fig. a) projection welding of nuts
(or) threaded bosses

Fig. b) projection welding of
stud...
Flash welding

Fig. a) Flash welding process for
end-to-end welding of solid rods

Fig. b) Design guidelines for
Flash wel...
Stud welding

Sequence of operations in stud welding, which is used for welding
bars, threaded rods, and various fasteners...
Explosion welding

Fig. a) constant interface
clearance gap

Fig. b) angular interface
clearance gap

Schematic illustrati...
Explosion welding

Fig. a) Titanium (top) on low
carbon steel

Fig. b) Incoloy 800(iron nickel
based alloy) on low carbon ...
Explosion welding

Before welding

During welding

completed weld

Explosion welding of tube on head plate for heat exchan...
Diffusion welding

Sequence of diffusion
bonding between two
titanium-alloy sheets.
Temperature;925 C:
time: 1 hr;
Pressur...
Why Would You Weld Under Water?
• It saves time.
• It can be cheaper
How Is It Done?
There are 3 main ways:
1. Preparing an enclosure filled with gas (helium) under
pressure and have the weld...
DISADVANTAGES

Electric Shock
Dangerous Gases
Underwater Hazards
New Processes

A relatively new underwater
welding process is “Friction
Stud Welding”, which is used
for military and comm...
Thank you
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Transcript of "Welding2003ver"

  1. 1. WELDING
  2. 2. Metal Joining processes Joining processes and equipments Welding Fusion Brazing & soldering chemical Electrical Oxyfuel gas Thermit Adhesive bonding Solid state Electrical Resistance Chemical Diffusion Explosion Mechanical Arc Resistance Electron beam Laser beam Mechanical fastening Cold Friction Ultrasonic Fastening Seaming Crimping stitching
  3. 3. Examples of joints
  4. 4. Fusion welding processes Types of flames For neutral flame ratio of Oxygen and acetylene is 1:1. Neutral flame For Oxidising flame Oxygen is more and acetylene is less. Oxidising flame Carburising flame For carburising flame Oxygen is less and acetylene is more.
  5. 5. Gas welding – Oxy-acetylene welding (a) General view and (b) cross section of a torch used in oxy-acetylene welding. The acetylene valve is opened first, the gas is lit with a spark lighter or a pilot light, and then the oxygen valve is opened and the flame adjusted.
  6. 6. Oxy-acetylene welding - Equipments Basic equipment used in oxyfuel gas welding. Other equipments include safety shields, goggles, gloves, and protective clothing. To ensure correct connections, all threads in the acetylene fittings are left handed, and those for oxygen are right handed. Oxygen regulators are usually painted green, and acetylene regulators red.
  7. 7. Arc – welding processes Consumable Electrodes
  8. 8. Arc – welding processes Consumable Electrodes • • • • • Shielded metal - arc welding Sub merged arc welding Gas Metal Arc Welding (MIG) Flux cored arc welding Electro gas welding
  9. 9. Shielded metal - arc welding • Definition: – Consumable electrode coated with chemicals that provide flux and shielding – The filler metal (here the consumable electrode) is usually very close in composition to the metal being welded.
  10. 10. Shielded metal - arc welding a b Fig (a). Schematic illustration of shielded metal-arc welding operation, also known as stick welding because the electrode is in the shape of a stick Fig. (b) weld zone showing the built up sequence of individual weld beads in deep welds
  11. 11. Shielded Metal Arc Welding • Benefits • Simple, portable,& inexpensive • Self flux provided by electrode • Provides all position flexibility • Shielding Gases • No shield gases added • Lower sensitivity to Wind
  12. 12. Shielded Metal Arc Welding Cont.: • Applications • Construction, pipelines, shipbuilding, fabrication job shops. • Used for: Steels, stainless steels, cast irons. • Not used for aluminum and its alloys, or copper and its alloys (energy density is too high).
  13. 13. Specifications of an Electrode E6010 Stands for electrode Designates the tensile strength in ksi* Position the electrode can be used 1- all positions 2- horizontal and flat Electrode coating type *1ksi = 7 Mpa
  14. 14. Volt – Ampere characteristic in Arc welding a b Fig.a Produces only small amount of ampere change when the arc voltage is changed c Fig. a & b Flat and rising volt-ampere curves as used on automatic machines are designed to provide a relatively constant current by balancing the effect of volt X amps.
  15. 15. Comparison of weld penetration weld penetration obtained by dc straight polarity weld penetration obtained by dc reversed polarity Reverse polarity: Electrode connected to positive terminal and work connected to negative terminal straight polarity: Electrode connected to negative terminal and work connected to positive terminal An alternating – current welder is, in case, a combination reverse – and straight – polarity machine.
  16. 16. Wave form of high frequency, low-power current A super imposed high – frequency current along with capacitors stabilizes the welding current and produces a balanced wave form.
  17. 17. Sub merged arc welding Process features Similar to MIG welding, SAW involves formation of an arc between a continuously-fed bare wire electrode and the work piece. The process uses a flux to generate protective gases and slag, and to add alloying elements to the weld pool. A shielding gas is not required. Prior to welding, a thin layer of flux powder is placed on the work piece surface. The arc moves along the joint line and as it does so, excess flux is recycled via a hopper. Remaining fused slag layers can be easily removed after welding. As the arc is completely covered by the flux layer, heat loss is extremely low. This produces a thermal efficiency as high as 60% (compared with 25% for manual metal arc). There is no visible arc light, welding is spatter-free and there is no need for fume extraction Operating characteristics
  18. 18. Sub merged arc welding Applications SAW is ideally suited for longitudinal and circumferential butt and fillet welds. However, because of high fluidity of the weld pool, molten slag and loose flux layer, welding is generally carried out on butt joints in the flat position and fillet joints in both the flat and horizontal-vertical positions. For circumferential joints, the work piece is rotated under a fixed welding head with welding taking place in the flat position. Depending on material thickness, either singlepass, two-pass or multipass weld procedures can be carried out. There is virtually no restriction on the material thickness, provided a suitable joint preparation is adopted. Most commonly welded materials are carbon-manganese steels, low alloy steels and stainless steels, although the process is capable of welding some non-ferrous materials with judicious choice of electrode filler wire and flux combinations
  19. 19. Sub merged arc welding – Equipment layout Schematic illustration of sub merged arc welding process
  20. 20. Gas Metal Arc Welding (MIG) • Definition: – The heat source is formed by creating an electric arc between the work piece and a wire, which is fed continuously into the weld pool. • Benefits: – Long welds can be made without starts and stops – Minimal skill required – Minimal cleaning of surface before weld – Allows welding in all positions
  21. 21. Gas Metal Arc Welding (MIG) Cont. • Shielding Gases: • Inert – Argon, Helium » Used for aluminum alloys and stainless steels. • Active – 1 to 5% Oxygen, 3 to 25% CO 2 » Used for low and medium carbon steels • Applications • Gas Metal Arc Welding (MIG) is used to weld all commercially important metals, including steel, aluminum, copper, and stainless steel.
  22. 22. Gas metal arc welding - Equipment Schematic illustration of gas metal arc welding process
  23. 23. Flux cored arc welding Schematic illustration of Flux cored arc welding process
  24. 24. Electro gas welding Schematic illustration of Electro gas welding process
  25. 25. Electro slag welding Unlike other high current fusion processes, electro slag welding is not an arc process. Heat required for melting both the welding wire and the plate edges is generated through a molten slag's resistance to the passage of an electric current. Schematic illustration of Electro slag welding process
  26. 26. Electro slag welding A view of Electro slag welding process in component
  27. 27. Electro slag welding Layout of equipment used for electro slag welding operations.
  28. 28. Electro slag welding Benefits The principal benefits of the process are:  speed of joint completion; typically 1 hour per meter of seam, irrespective of thickness  lack of angular distortion  lateral angular distortion limited to 3mm per meter of weld  high quality welds produced  simple joint preparation, i.e. flame-cut square edge  major repairs can be made simply by cutting out total weld and rewelding
  29. 29. Electro slag welding Limitations Electro slag welding is not one of the major welding processes because the high heat input generates large, coarse grained weld metal and HAZs which lead to poor fracture toughness properties in these areas. Toughness improvements can only be achieved by post-weld normalising treatment. Additionally, the near parallel-sided geometry of the weld, combined with the coarse grains, can make it difficult to identify defects at the fusion boundary by standard ultrasonic NDT techniques.
  30. 30. Arc welding processes Non consumable Electrodes
  31. 31. Arc welding processes (non consumable Electrodes) are • • • • • Gas tungsten arc welding process Plasma arc welding processes Thermit welding Electron beam welding Laser beam welding
  32. 32. Gas tungsten arc welding process • Definition: – TIG welding is an arc that is formed between a non-consumable tungsten electrode and the metal being welded. – Gas is fed through the torch to shield the electrode and molten weld pool. • Benefits: – Welds with or without filler metal – Precise control of welding variables (heat) – Low distortion • Shielding Gases: – Argon – 2 to 5% Hydrogen – w/Helium
  33. 33. Tungsten Inert Gas Welding (TIG) • Applications • Most commonly used for aluminum and stainless steel • For steel – Slower and more costly than consumable welding – Except for thin sections or where very high quality is needed
  34. 34. Gas tungsten arc welding process Equipment
  35. 35. Plasma arc welding processes Plasma welding is very similar to TIG as the arc is formed between a pointed tungsten electrode and the work piece. However, by positioning the electrode within the body of the torch, the plasma arc can be separated from the shielding gas envelope. Plasma is then forced through a fine-bore copper nozzle which constricts the arc. Three operating modes can be produced by varying bore diameter and plasma gas flow rate:
  36. 36. Thermit welding Thermit welding (TW) is a welding process which produces coalescence of metals by heating them with superheated liquid metal from a chemical reaction between a metal oxide and aluminum with or without the application of pressure. Filler metal is obtained from an exothermic reaction between iron oxide and aluminum. The temperature resulting from this reaction is approximately 2500°C. The superheated steel is contained in a crucible located immediately above the weld joint. The superheated steel runs into a mold which is built around the parts to be welded. Since it is almost twice as hot as the melting temperature of the base metal melting occurs at the edges of the joint and alloys with the molten steel from the crucible. Normal heat losses cause the mass of molten metal to solidify, coalescence occurs, and the weld is Completed.
  37. 37. Thermit welding Few images of rails, joined by thermit welding
  38. 38. Thermit welding Few images of rails joined by thermit welding
  39. 39. Electron beam welding
  40. 40. Laser beam welding
  41. 41. Cutting
  42. 42. • Definition: Oxy fuel gas cutting – A stream of oxygen is directed against a piece of heated metal, causing the metal to oxidize or burn away. • Making a Cut – Mark a line as a guide. – Turn on acetylene as for welding and light. – Turn on oxygen adjusting flame to neutral. – Make sure the oxygen lever flame remains neutral. – Place metal on the cutting table so metal will fall clear.
  43. 43. Oxy fuel gas cutting Process fundamentals The cutting process is illustrated in Fig. Basically, a mixture of oxygen and the fuel gas is used to preheat the metal to its 'ignition' temperature which, for steel, is 700°C - 900°C (bright red heat) but well below its melting point. A jet of pure oxygen is then directed into the preheated area instigating a vigorous exothermic chemical reaction between the oxygen and the metal to form iron oxide or slag. The oxygen jet blows away the slag enabling the jet to pierce through the material and continue to cut through the material.
  44. 44. Oxy fuel gas cutting There are four basic requirements for oxy-fuel cutting: • the ignition temperature of the material must be lower than its melting point otherwise the material would melt and flow away before cutting could take place • the oxide melting point must be lower than that of the surrounding material so that it can be mechanically blown away by the oxygen jet • the oxidation reaction between the oxygen jet and the metal must be sufficient to maintain the ignition temperature •a minimum of gaseous reaction products should be produced so as not to dilute the cutting oxygen As stainless steel, cast iron and non-ferrous metals form refractory oxides ie the oxide melting point is higher than the material, powder must be injected into the flame to form a low melting point, fluid slag
  45. 45. SOLID STATE WELDING PROCESSES
  46. 46. SOLID STATE WELDING PROCESSES ARE • Cold Welding • Ultrasonic Welding • Friction welding • Resistance welding - Resistance spot welding - High frequency resistance welding - Resistance projection welding • Flash welding • Stud welding • Explosion welding • Diffusion welding
  47. 47. Cold Welding Schematic illustration of the roll bonding, or cladding process
  48. 48. Ultrasonic Welding Fig. a) Components of an ultrasonic welding machine for lap welds Fig. b) ultrasonic seam welding using roller
  49. 49. Friction welding Sequence of operations in the friction welding process Fig. (a) Left part is rotated at high speed Fig. (b) Right part is brought into contact under an axial force Fig. (c) Axial force increased; flash begins to form Fig. (d) Left part stops rotation. Weld is completed. Flash can be removed by machining or grinding.
  50. 50. Friction welding Shape of fusion zone in friction welding, as a function of force applied and rotational speed
  51. 51. Friction welding of a bolt head
  52. 52. Resistance spot welding Fig. a) Sequence in resistance spot welding process Fig. b) cross – section of a spot weld, showing weld nugget and light indentation by the electrode on sheet surfaces. This is one of the most common processes used in sheet – metal fabrication and automotive body assembly.
  53. 53. Spot welding machine Schematic illustration of an air operated rocker arm spot welding machine
  54. 54. Spot welding operations for complex shape Types of special electrodes designed for easy access in spot welding operations for complex shapes
  55. 55. High frequency resistance welding Fig. b) overlapping spots in Fig. c) roll spot weld seam weld Fig. a) seam welding process
  56. 56. High frequency resistance welding of tubes Methods in high frequency butt welding of tubes
  57. 57. Resistance projection welding Before welding After welding Schematic illustration of resistance projection welding The projections are produced by embossing operations
  58. 58. Resistance projection welding Fig. a) projection welding of nuts (or) threaded bosses Fig. b) projection welding of studs The projections are produced by forging or machining operations
  59. 59. Flash welding Fig. a) Flash welding process for end-to-end welding of solid rods Fig. b) Design guidelines for Flash welding
  60. 60. Stud welding Sequence of operations in stud welding, which is used for welding bars, threaded rods, and various fasteners on metal plates.
  61. 61. Explosion welding Fig. a) constant interface clearance gap Fig. b) angular interface clearance gap Schematic illustration of the explosion welding process
  62. 62. Explosion welding Fig. a) Titanium (top) on low carbon steel Fig. b) Incoloy 800(iron nickel based alloy) on low carbon steel Cross – sections of explosion – welded joints
  63. 63. Explosion welding Before welding During welding completed weld Explosion welding of tube on head plate for heat exchangers and boilers Note: The tube ends are expanded by placing and detonating the explosives inside the tube
  64. 64. Diffusion welding Sequence of diffusion bonding between two titanium-alloy sheets. Temperature;925 C: time: 1 hr; Pressure: 700-3500kpa magnification; 500X
  65. 65. Why Would You Weld Under Water? • It saves time. • It can be cheaper
  66. 66. How Is It Done? There are 3 main ways: 1. Preparing an enclosure filled with gas (helium) under pressure and have the welder fitted with protective equipment. 2. Wet underwater method, where the power of the arc generates a bubble of mixture of gases and the welding is done, more or less, normally, with special electrodes. 3. Build a pit, near where the welding will occur and take the water out.
  67. 67. DISADVANTAGES Electric Shock Dangerous Gases Underwater Hazards
  68. 68. New Processes A relatively new underwater welding process is “Friction Stud Welding”, which is used for military and commercial use.
  69. 69. Thank you
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