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9/27/2015
BASICS OF MANUFACTURING
PROCESS 1
L12
 Welding: Introduction, classification of welding
processes. Gas-welding, types of flames and their
applications.
L13...
 It is process of joining two
similar or dissimilar metals
with the application of heat
and with or without the
applicati...
 Welding is a process of joining two or more
similar or dissimilar metals by melting them
locally at the place of intende...
 Pressure welding- resistance
welding
 Non pressure welding- arc
welding, gas welding
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BASICS OF MANUFACTURIN...
Gas Welding
 1. Oxy-acetylene welding
 2. Air acetylene welding
 Oxy-hydrogen welding
 4. Oxy-fuel welding
Electric Ar...
Resistance Welding
 Spot welding
 Seam welding
 Projection welding
 Flash welding
Solid Friction welding
 Ultra sonic...
Thermo-chemical Welding
 Thermit welding
 Atomic hydrogen welding
Low temperature State Welding
 Cold welding
 welding...
 Welding Source of heat
 Arc welding electric arc
 Gas welding gas
 Resistance welding electric current
 Laser weldin...
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BASICS OF MANUFACTURING
PROCESS
 In this method, metal pieces to be welded are
heated locally to the melting temperature by
creating an electric arc and ...
 Filler material is used to supply extra molten
metal to fill the gap between joints. Filler
material has similar composi...
The potential difference should be such that
the heat generated at positive terminal is 2/3
and at negative terminal is 1/...
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BASICS OF MANUFACTURING
PROCESS
 Power supply- A.C. OR D.C SUPPLY
 ELECTRODE HOLDER
 ELECTRODE- BARE ELECTRODE AND COATED
ELECTRODE
 PROTECTIVE SHIELD...
 Various equipment used in Electric arc welding:
Following equipment are needed in Electric arc
welding
 High current Lo...
 Apart from transformer following equipment are
also needed( as shown in figure of arc welding
set up)
 Well insulated e...
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BASICS OF MANUFACTURING
PROCESS
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BASICS OF MANUFACTURING
PROCESS
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PROCESS 20
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PROCESS 21
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PROCESS 22
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BASICS OF MANUFACTURING
PROCESS
 Suitable for variety of application and
positions
 High metal deposition rate
 Less training required for welders and ...
 Incorrect welding may result into low weld
toughness
 Lack of fusion of metal if weld parameters are
incorrect
 Slag i...
9/27/2015 26
BASICS OF MANUFACTURING
PROCESS
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BASICS OF MANUFACTURING
PROCESS
In this process heat for melting is supplied
by combustion of a fuel gas with oxygen. The
fuel gas can be acetylene, hydro...
9/27/2015
BASICS OF MANUFACTURING
PROCESS 29
 Gas cylinders- oxygen( black colour) and
acetylene ( red colour)gas cylinders
 Hose pipes
 Pressure regulators
 Weldi...
 Oxy Acetylene Welding : This is used for
welding almost all metals because it produces
comparatively higher temperatures...
9/27/2015 32
BASICS OF MANUFACTURING
PROCESS
Pressure Regulators: Oxygen and acetylene
cylinders are fitted with pressure regulators to
reduce pressure of gases as per...
Other equipment: Other equipment needed for gas
welding are
 Keys for cylinders and valves
 Hoses for Oxygen and Acetyle...
9/27/2015 35
BASICS OF MANUFACTURING
PROCESS
 Oxidising Flame : Oxidizing flame is obtained when the
quantity of oxygen is more than that required for perfect
combust...
9/27/2015 37
BASICS OF MANUFACTURING
PROCESS
 Mainly two types of weld joints are made by
gas welding :-
◦ Butt Welds i.e. welding two pieces of metal
without any ove...
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BASICS OF MANUFACTURING
PROCESS 39
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BASICS OF MANUFACTURING
PROCESS 40
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PROCESS 41
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BASICS OF MANUFACTURING
PROCESS
 Resistance welding processes are
pressure welding processes in which
heavy current is passed for short time
through the ...
 All resistance welding operations are
automatic and, therefore, all process
variables are preset and maintained
constant...
The heat generated during resistance welding is
given by following expression:
H = I 2 R T
 Where, H is heat generated
 ...
9/27/2015 46
BASICS OF MANUFACTURING
PROCESS
Spot welding
Seam welding
Butt welding
Projection welding
9/27/2015 47
BASICS OF MANUFACTURING
PROCESS
 In resistance spot welding, two or
more sheets of metal are held
between electrodes through which
welding current is sup...
9/27/2015 49
BASICS OF MANUFACTURING
PROCESS
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BASICS OF MANUFACTURING
PROCESS
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BASICS OF MANUFACTURING
PROCESS
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BASICS OF MANUFACTURING
PROCESS
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BASICS OF MANUFACTURING
PROCESS
 In seam welding overlapping sheets
are gripped between two wheels or
roller disc electrodes and current is
passed to obt...
9/27/2015 55
BASICS OF MANUFACTURING
PROCESS
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BASICS OF MANUFACTURING
PROCESS
9/27/2015 57
BASICS OF MANUFACTURING
PROCESS
 In this process projections are provided in
one of the work piece at the place of intended
welding. Thus surface of the ...
9/27/2015 59
BASICS OF MANUFACTURING
PROCESS
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PROCESS 60
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PROCESS
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PROCESS 62
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PROCESS 63
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BASICS OF MANUFACTURING
PROCESS
 Very little skill is required to operate the
resistance welding machine
 Process is suitable for high production rate
...
9/27/2015 66
BASICS OF MANUFACTURING
PROCESS
 Soldering is a process in which two or more
metal items are joined together by melting and
flowing a filler metal into t...
 This method is used for joining metals
particularly when they are in the form of
sheets or wires, by using another metal...
9/27/2015 69
BASICS OF MANUFACTURING
PROCESS
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BASICS OF MANUFACTURING
PROCESS
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BASICS OF MANUFACTURING
PROCESS
 It is a process of joining metals with the help
of hard solder. Brass is generally the main
constituent of this solder. ...
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BASICS OF MANUFACTURING
PROCESS
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BASICS OF MANUFACTURING
PROCESS
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PROCESS 75
 Cracks may be of micro or macro size and
may appear in the weld metal or base metal
or base metal and weld metal boundar...
9/27/2015
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PROCESS 77
 Porosity results when the gases are entrapped in the
solidifying weld metal.
 These gases are generated from the flux o...
9/27/2015
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PROCESS 79
 Slag inclusions may be in the form of slag or any other
nonmetallic material entrapped in the weld metal as these
may no...
9/27/2015
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PROCESS 81
 Lack of fusion is the failure to fuse together
either the base metal and weld metal or
subsequent beads in multipass wel...
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PROCESS 83
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PROCESS 84
 Imperfect shape means the variation from the
desired shape and size of the weld bead.
 During undercutting a notch is f...
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PROCESS 86
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PROCESS 87
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PROCESS 88
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Welding ppt bmp unit 3

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Welding ppt bmp unit 3

  1. 1. 9/27/2015 BASICS OF MANUFACTURING PROCESS 1
  2. 2. L12  Welding: Introduction, classification of welding processes. Gas-welding, types of flames and their applications. L13  Electric -Arc welding and its applications, Resistance welding and its types L14  Soldering and brazing processes and their uses 9/27/2015 BASICS OF MANUFACTURING PROCESS 2
  3. 3.  It is process of joining two similar or dissimilar metals with the application of heat and with or without the application of pressure. 9/27/2015 3 BASICS OF MANUFACTURING PROCESS
  4. 4.  Welding is a process of joining two or more similar or dissimilar metals by melting them locally at the place of intended joint. Filler material may be added and a pool of molten metal is made.  This pool of metal becomes a strong joint after solidification. Sometimes help of pressure along with heating is taken to produce a weld.  Flux is added to remove impurities and protect the weld from oxidation. 9/27/2015 4 BASICS OF MANUFACTURING PROCESS
  5. 5.  Pressure welding- resistance welding  Non pressure welding- arc welding, gas welding 9/27/2015 5 BASICS OF MANUFACTURING PROCESS
  6. 6. Gas Welding  1. Oxy-acetylene welding  2. Air acetylene welding  Oxy-hydrogen welding  4. Oxy-fuel welding Electric Arc Welding  Metal Arc welding  Carbon arc welding  Tungsten inert gas welding  Metal inert gas welding  Submerged arc welding  Plasma arc welding  Fluxed cored arc welding  Electro slag welding 9/27/2015 6 BASICS OF MANUFACTURING PROCESS
  7. 7. Resistance Welding  Spot welding  Seam welding  Projection welding  Flash welding Solid Friction welding  Ultra sonic welding  Diffusion welding  Explosive welding 9/27/2015 7 BASICS OF MANUFACTURING PROCESS
  8. 8. Thermo-chemical Welding  Thermit welding  Atomic hydrogen welding Low temperature State Welding  Cold welding  welding process  Soldering  Brazing  Bronze Welding 9/27/2015 8 BASICS OF MANUFACTURING PROCESS
  9. 9.  Welding Source of heat  Arc welding electric arc  Gas welding gas  Resistance welding electric current  Laser welding laser  Friction welding friction  Thermit welding chemical reaction ( exothermic reaction) 9/27/2015 9 BASICS OF MANUFACTURING PROCESS
  10. 10. 9/27/2015 10 BASICS OF MANUFACTURING PROCESS
  11. 11.  In this method, metal pieces to be welded are heated locally to the melting temperature by creating an electric arc and then allowed to solidify to form welded joint. Additional metal for filling the weld is provided by core wire of electrode (As in metal arc welding) or by filler rod (As in case of carbon arc welding).  For creating an arc low voltage high amperage AC or DC current is used. 9/27/2015 11 BASICS OF MANUFACTURING PROCESS
  12. 12.  Filler material is used to supply extra molten metal to fill the gap between joints. Filler material has similar composition and lower melting point then the base material.  Flux is some time used to remove the oxides formed during welding process by combining with the impurities and forming slag, which floats on the molten metal. Molten slag covers the weld and protects it from oxidation. 9/27/2015 12 BASICS OF MANUFACTURING PROCESS
  13. 13. The potential difference should be such that the heat generated at positive terminal is 2/3 and at negative terminal is 1/3. The temperature of the arc is 3700oC to 4000oC. In DC welding two types of polarities are used. In DC welding two types of polarities are used. Straight Polarity: welding electrode is kept negative and work piece is kept positive. Reverse Polarity: In this work piece is negative and electrode is positive. 9/27/2015 13 BASICS OF MANUFACTURING PROCESS
  14. 14. 9/27/2015 14 BASICS OF MANUFACTURING PROCESS
  15. 15.  Power supply- A.C. OR D.C SUPPLY  ELECTRODE HOLDER  ELECTRODE- BARE ELECTRODE AND COATED ELECTRODE  PROTECTIVE SHIELD  GLOVES  WELDING CLOTHES 9/27/2015 15 BASICS OF MANUFACTURING PROCESS
  16. 16.  Various equipment used in Electric arc welding: Following equipment are needed in Electric arc welding  High current Low Voltage AC or DC Source :  In DC arc welding current is generated by a DC generator. The generator can be driven by means of an electric motor of by means of a petrol or Diesel engine. They can be portable or standing type. The voltage required is 60-80V for striking the arc and 15-25volts for maintaining the arc.  In AC arc welding a step down transformer is used which transforms AC supply from 440 Volts AC to 80-100 Volts AC. 9/27/2015 16 BASICS OF MANUFACTURING PROCESS
  17. 17.  Apart from transformer following equipment are also needed( as shown in figure of arc welding set up)  Well insulated electrode holder  Wire cables and cable connectors  Welding helmet and hand screen or shield  Safety Goggles  Weld chipping hammer  Earthling Clamp  Hand Gloves  Apron and Sleeves  Wire brush, chipping hammer 9/27/2015 17 BASICS OF MANUFACTURING PROCESS
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  24. 24.  Suitable for variety of application and positions  High metal deposition rate  Less training required for welders and less supervision needed.  Equipment are easy to use and are less costly  Equipment are portable and can be used in confined places  Auxiliary gas shield is not required  Suitable for most commonly used metals and alloys 9/27/2015 24 BASICS OF MANUFACTURING PROCESS
  25. 25.  Incorrect welding may result into low weld toughness  Lack of fusion of metal if weld parameters are incorrect  Slag is to be removed after every pass in multipass welding 9/27/2015 25 BASICS OF MANUFACTURING PROCESS
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  28. 28. In this process heat for melting is supplied by combustion of a fuel gas with oxygen. The fuel gas can be acetylene, hydrogen, propane or butane. The molten metal from the edges of metal flows and solidifies together in the weld and a continuous joint is obtained. A filler metal may be added when the metal is flowing to fill the cavity. 9/27/2015 28 BASICS OF MANUFACTURING PROCESS
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  30. 30.  Gas cylinders- oxygen( black colour) and acetylene ( red colour)gas cylinders  Hose pipes  Pressure regulators  Welding torch or blow pipe with needles valves 9/27/2015 BASICS OF MANUFACTURING PROCESS 30
  31. 31.  Oxy Acetylene Welding : This is used for welding almost all metals because it produces comparatively higher temperatures and also an inert gas envelope consisting of CO2 and H2O is formed around the weld, which prevents liquid metal from oxidation. The temperatures obtained are of the order of 3200oC -3500oC. 9/27/2015 31 BASICS OF MANUFACTURING PROCESS
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  33. 33. Pressure Regulators: Oxygen and acetylene cylinders are fitted with pressure regulators to reduce pressure of gases as per the requirement. Blow pipes or Torches: Torch for high pressure and low pressure system differ in design. The low pressure torch has an inbuilt ejector which draws acetylene from the low pressure generator and mixes with the Oxygen. In high pressure torch there is only a mixing provision for the two gases. The torch is fitted with regulating valves for oxygen and acetylene. 9/27/2015 33 BASICS OF MANUFACTURING PROCESS
  34. 34. Other equipment: Other equipment needed for gas welding are  Keys for cylinders and valves  Hoses for Oxygen and Acetylene  Spanners for connecting hoses  Safety equipment like goggles, Screens, Lather hand glows and lather apron  Chipping hammer  goggles  Wire brush, Spark lighter etc.  Trolley to carry oxygen cylinders 9/27/2015 34 BASICS OF MANUFACTURING PROCESS
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  36. 36.  Oxidising Flame : Oxidizing flame is obtained when the quantity of oxygen is more than that required for perfect combustion. The inner cone is pointed and very short in this case. Such flame is not required except for welding brass. Maximum temperature of about 3400oC - 3500oC at the tip of inner cone is obtained. Neutral Flame : When quantity of oxygen is so adjusted that it is just sufficient for complete combustion a neural flame is obtained. The length of the inner cone becomes more. Most of the metals are welded using this flame. Maximum temperature of about 3200oC - 3300oC at the tip of inner cone is obtained. Carburising Flame  When the quantity of oxygen is less than required for complete combustion we get carburizing flame. This 2800oC - 3150oC at the tip of inner cone is obtained. type of flame is used for welding lead. 9/27/2015 36 BASICS OF MANUFACTURING PROCESS
  37. 37. 9/27/2015 37 BASICS OF MANUFACTURING PROCESS
  38. 38.  Mainly two types of weld joints are made by gas welding :- ◦ Butt Welds i.e. welding two pieces of metal without any overlap. ◦ Fillet Welds i.e. joining two pieces perpendicular to each other or with an over lap. 9/27/2015 38 BASICS OF MANUFACTURING PROCESS
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  43. 43.  Resistance welding processes are pressure welding processes in which heavy current is passed for short time through the area of interface of metals to be joined. The basic governing equation  H = I 2 R T, H- total heat generated  These processes differ from other welding processes in the respect that no fluxes are used, and filler metal rarely used. 9/27/2015 43 BASICS OF MANUFACTURING PROCESS
  44. 44.  All resistance welding operations are automatic and, therefore, all process variables are preset and maintained constant.  Heat is generated in localized area which is enough to heat the metal to sufficient temperature, so that the parts can be joined with the application of pressure. Pressure is applied through the electrodes. 9/27/2015 44 BASICS OF MANUFACTURING PROCESS
  45. 45. The heat generated during resistance welding is given by following expression: H = I 2 R T  Where, H is heat generated  I is current in amperes  R is resistance of area being welded  T is time for the flow of current. 9/27/2015 45 BASICS OF MANUFACTURING PROCESS
  46. 46. 9/27/2015 46 BASICS OF MANUFACTURING PROCESS
  47. 47. Spot welding Seam welding Butt welding Projection welding 9/27/2015 47 BASICS OF MANUFACTURING PROCESS
  48. 48.  In resistance spot welding, two or more sheets of metal are held between electrodes through which welding current is supplied for a definite time and also force is exerted on work pieces 9/27/2015 48 BASICS OF MANUFACTURING PROCESS
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  54. 54.  In seam welding overlapping sheets are gripped between two wheels or roller disc electrodes and current is passed to obtain either the continuous seam i.e. overlapping weld nuggets or intermittent seam i.e. weld nuggets are equally spaced 9/27/2015 54 BASICS OF MANUFACTURING PROCESS
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  58. 58.  In this process projections are provided in one of the work piece at the place of intended welding. Thus surface of the work pieces come in contact with each other only at the tip of these projections. As the current is switched on the projection are melted and the work pieces are pressed together to complete the weld. The melted projection form the spot welds simultaneously. The electrodes and the holding fixtures are suitably designed as per the shape of the weld. 9/27/2015 58 BASICS OF MANUFACTURING PROCESS
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  65. 65.  Very little skill is required to operate the resistance welding machine  Process is suitable for high production rate  HAZ (Heat affected Zone) is very small.  No filler metal is required  Possible to weld two dissimilar metals or sheets of different thickness  Semi-automatic equipment are available  No consumable other than electricity is required. 9/27/2015 65 BASICS OF MANUFACTURING PROCESS
  66. 66. 9/27/2015 66 BASICS OF MANUFACTURING PROCESS
  67. 67.  Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint. Filler metal has relatively low melting point. Bond is through wetting action. Resulting joints are not as strong as the base metal but they have adequate strength.  It is often confused with welding but the difference between them is, in soldering the work piece is not melted, they are joined using a filler metal, but in welding work piece is joined by melting. 9/27/2015 67 BASICS OF MANUFACTURING PROCESS
  68. 68.  This method is used for joining metals particularly when they are in the form of sheets or wires, by using another metal or alloy which has fairly low melting point compared to the base metal to be joined. The metal or alloy used for this purpose is known as solder. There are two types of solders soft solder and hard solder. 9/27/2015 68 BASICS OF MANUFACTURING PROCESS
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  72. 72.  It is a process of joining metals with the help of hard solder. Brass is generally the main constituent of this solder. Brazing solder is commonly known as spelter which is an alloy of copper, zinc and tin. Hard solder provides much stronger joint as compared to soft soldering. However in this case the metal piece to be joined is heated to slightly above the melting point of the filler metal. 9/27/2015 72 BASICS OF MANUFACTURING PROCESS
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  76. 76.  Cracks may be of micro or macro size and may appear in the weld metal or base metal or base metal and weld metal boundary.  Different categories of cracks are longitudinal cracks, transverse cracks or radiating/star cracks and cracks in the weld crater.  Cracks occur when localized stresses exceed the ultimate tensile strength of material. These stresses are developed due to shrinkage during solidification of weld metal. 9/27/2015 BASICS OF MANUFACTURING PROCESS 76
  77. 77. 9/27/2015 BASICS OF MANUFACTURING PROCESS 77
  78. 78.  Porosity results when the gases are entrapped in the solidifying weld metal.  These gases are generated from the flux or coating constituents of the electrode or shielding gases used during welding or from absorbed moisture in the coating. Rust, dust, oil and grease present on the surface of work pieces or on electrodes are also source of gases during welding.  Porosity may be easily prevented if work pieces are properly cleaned from rust, dust, oil and grease.  Futher, porosity can also be controlled if excessively high welding currents, faster welding speeds and long arc lengths are avoided flux and coated electrodes are properly baked. 9/27/2015 BASICS OF MANUFACTURING PROCESS 78
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  80. 80.  Slag inclusions may be in the form of slag or any other nonmetallic material entrapped in the weld metal as these may not able to float on the surface of the solidifying weld metal.  During arc welding flux either in the form of granules or coating after melting, reacts with the molten weld metal removing oxides and other impurities in the form of slag and it floats on the surface of weld metal due to its low density.  However, if the molten weld metal has high viscosity or too low temperature or cools rapidly then the slag may not be released from the weld pool and may cause inclusion.  Slag inclusion can be prevented if proper groove is selected, all the slag from the previously deposited bead is removed, too high or too low welding currents and long arcs are avoided. 9/27/2015 BASICS OF MANUFACTURING PROCESS 80
  81. 81. 9/27/2015 BASICS OF MANUFACTURING PROCESS 81
  82. 82.  Lack of fusion is the failure to fuse together either the base metal and weld metal or subsequent beads in multipass welding because of failure to raise the temperature of base metal or previously deposited weld layer to melting point during welding.  Lack of fusion can be avoided by properly cleaning of surfaces to be welded, selecting proper current, proper welding technique and correct size of electrode. 9/27/2015 BASICS OF MANUFACTURING PROCESS 82
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  85. 85.  Imperfect shape means the variation from the desired shape and size of the weld bead.  During undercutting a notch is formed either on one side of the weld bead or both sides in which stresses tend to concentrate and it can result in the early failure of the joint.  Main reasons for undercutting are the excessive welding currents, long arc lengths and fast travel speeds.  Underfilling may be due to low currents, fast travel speeds and small size of electrodes. Overlap may occur due to low currents, longer arc lengths and slower welding speeds. 9/27/2015 BASICS OF MANUFACTURING PROCESS 85
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