WELDING, MANUFACTURING TECHNOLOGY

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MFT 1 UNIT 2 PART A (Draw diagrams wherever necessary)
23) Limitations of friction welding
 Accurate alignment of job must
 Flash produced ( trimming must )
 High speed, high capacity m/c required.
 Weld may not be strong enough, if sufficient pressure is not applied at the end.
24) Write short notes on Diffusion Welding
Coalescence produced by intergranular atomic diffusion at high pressure and temp. Every
metal surface has a peak and valley point. Initially the faces to be welded are mated
together and held under huge pressure such that the roughnesses of metals are deformed
25) Advantages of AC over DC equipments in arc welding
 Penetration deep and wide
 High efficiency
 Terminals interchangeable
 Stronger weld
 AC equipment is Less expensive and light in weight
26) Why is flux used in Brazing and Soldering
In soldering and bracing, flux protects molten filler material from oxidation.
27) What is fusion welding
A welding process that melts the base metals at the joint. The metal is heated to the
molten state and then solidified. Upon cooling, the welded joint is often stronger
than the base metals is called as fusion welding
28)Applications of friction welding
Drill, tap, reamer etc. joining with shank.
To join steering shaft and worm gear, engine valves, power transmission shaft and
production of bimetallic shaft joining
29) In TIG welding what is the function of Tungsten
In TIG welding, non consumable tungsten electrode is used to establish arc between
the electrode and the workpiece.
30) What is the basic Principle of diffusion welding
At high pressure and temp grain boundaries of job disappear. Coalescence produced by
intergranular atomic diffusion at high pressure and temp

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31,36) What is the principle of resistance welding
Group of welding process wherein coalescence is produced by the heat obtained from
resistance of the work to the flow of electric current in a circuit and by application of
pressure Heat source electrical (i2
r) heating
32) What chemical reaction occurs in Thermit welding
Fe2O3+Al Al2O3+2Fe+heat
3Fe3O4+8Al 4Al2O3+9Fe+heat
33) What are the specific situations where electroslag welding is used
Electro slag welding is a very efficient, single pass process carried out in the vertical or near
vertical position and used for joining steel plates/sections in thicknesses of 25mm and
above. It superseded the very high current submerged arc process for making longitudinal
welds in thick-walled pressure vessels
34,43) Name any four weld defects
 Lack of penetration
 Porosity
 Slag inclusion
 Undercut
 Cracks
 Weld distortion
35,40)Arc welding equipments and Accessories
 Generator(DC), transformer (AC)
 Electrode holder
 Electrode
 Welding table
 Cables
 Goggles
37)Applications of welding
 Automobile industry
 Aerospace industry
 Electronics
 Tool making etc
 Structural works
 Ship building

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38)Write the advantages and dis-advantages of welding process
Advantages of welding
 Strong permanent joint
 Best method for joining metals
 Minimum chances of joint failure
 Homogeneity of finished product
Disadvantages of welding
 Rate of cooling cannot be controlled
 Original properties of job disturbed
 Costly in some cases
39)Classification of welding
 Plastic welding (Pressure)
 Fusion welding (Non Pressure)
41)Advantages of arc welding over gas welding
 Filler rod need not be used (consumable electrode)
 Easier to operate
 Lesser welding cost
 Safer than gas welding
 Distortion in arc welding is less
 HAZ is minimum when compared with gas welding
42) State the functions of coating in electrodes
 flux coating on electrode melts and covers molten pool and protects it from atmosphere
 Increase the deposition efficiency
 Reduce spatter of the weld metal
 Removes oxides and impurities
 Influence the depth of arc penetration
44) Distinguish between welding, soldering and brazing
Welding Brazing & soldering
Base metal melted Base metal not melted
3000 C Brazing > 427 C
Soldering < 427 C
Permanent joint Semi permanent joint
Particularly used to join dissimilar materials
Large amount of diffusion takes place in brazing
Diffusion is secondary in soldering
Brazing produces joints stronger than those made by

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soldering and they can be used in service at higher
temperatures
Distortion is more Distortion is less
It uses the filler metal having the
same composition of base metal
Soldering uses the filler metal of lead and tin
45) Name the fluxes used for welding copper, aluminium and cast iron
Fluxes used to weld copper and its alloys
Boric acid, Borax
Aluminium alloys
Sodium chloride, potassium chloride, Lithium chloride, Sodium fluoride and Barium chloride
Cast Iron
Borax, sodium carbonate, Potassium carbonate and sodium nitrate
A1) Give some example for gas welding.
1. Oxy acetylene welding
2. Oxy hydrogen welding
3. Oxy butane welding.
A2) List the technique used in gas welding
1. Left ward welding.
2. Rightward welding.
3. Vertical welding.
4. Overhead welding
A3) List the types of arc used in the plasma arc welding?
1. Transferred arc
2. Non transferred arc.