1. Why is electrode coated with a flux in shielded metal arc welding?
a) for shiny appearance of electrode
b) to make welding faster
c) to increase the melting of electrode
d) to protect the electrode
Explanation: The electrode is coated with a flux in shielded metal arc welding. Heat from electric current causes the combustion and decomposition of electrode. This creates a gaseous shield to protect the electrode, metal and molten pool from atmospheric contamination due to oxidation.
2. Which of the following can be non-low hydrogen process?
a) Shielded metal arc welding
b) Submerged arc welding
c) Gas-shielded metal arc welding
d) Flux core arc welding
Explanation: Shielded metal arc welding can be a low hydrogen process or non-low hydrogen process, while submerged arc welding, gas-shielded metal arc welding, flux core arc welding are low hydrogen process.
3. Why hydrogen not used excessively for welding?
a) increases welding rate
b) decreases welding rate
c) destroys the metal plate
d) affects the weld
Explanation: Hydrogen causes weld to crack. Hence most of the welding processes are low hydrogen welding process.
4. Which of the following is true about shielded metal arc welding?
a) equipment cost is high
b) cannot weld different types of metals
c) cannot be used for metal sheets under 1.5mm thickness
d) entire electrode can be used
Explanation: The following are some advantages of shielded metal arc welding : (i)low equipment cost, (ii)welds many different metals, (iii)welds can be performed in any position, (iv)process less affected by wind, (v)can be performed under most weather conditions. SomeThe disadvantages are : (i)not suitable for metal sheets under 1.5mm thickness,(ii) entire electrode cannot be used, about 25-50mm electrode is wasted.
5. Which of the following is not correct about submerged arc welding?
a) high deposition rate
b) short set-up time
c) high quality welds
d) slag removal needed
Explanation: The following are some advantages of submerged arc welding: (i) high deposition rate, (ii)high quality welds with good ductility, high impact strength, good corrosion resistance, (iii)good for welding long joints(in excess of 1m), (iv)no eye protection required. Some disadvantages are : (i) long set-up time, (ii)slag removal needed, (iii)used for flat or horizontal fillets only.
6. Choose the correct option regarding metal-active gas welding?
a) not suitable for thin metal sheets
b) need to stop welding to change the consumed electrode
c) equipment is not expensive
d) high deposition rate
Explanation: Gas-shielded metal arc welding is also called metal-active gas welding. The following are some advantages of gas-shielded metal arc welding : (i) suitable for metals as thin as 0.58mm, (ii)all welding positions can be used, (iii) no need to stop welding to change the consumed electrode, (iv)high deposition rates. Some disadvantages are : (i)welding equipment is expensive and complicated, (ii)cannot be performed outdoors in greater than 8km/hr breeze.
7. What is the differentiating factor between flux core arc welding and gas-shielded metal arc welding processes?
a) structure and chemical composition of electrode
b) structure and chemical composition of metal plate
c) time of welding
d) process of welding
Explanation: The structure and chemical composition of electrode wire is the differentiating factor between flux core arc welding and gas-shielded metal arc welding processes. Unlike gas-shielded metal arc welding, flux core arc welding electrode wire is not solid and consists of thin-walled metal tube filled with flux.
8. Which of the following is true about flux core arc welding?
a) low deposition rate
b) cannot weld narrow angles
c) slag removal required
d) generates less volume of fumes and smoke.
Explanation: The following are some advantages of flux core arc welding: (i)high deposition rates, (ii)can be used to groove angles as narrow as 30˚, (iii)welds in all positions can be made, (iv)has excellent weld pool control. Some disadvantages are: (i) slag removal required, (ii) generates large volume of fumes and smoke.
9. Which of the following welding process is preferred for field application?
a) Shielded metal arc welding
b) Submerged arc welding
c) Gas-shielded metal arc welding
d) Flux core arc welding
Explanation: Submerged arc welding, gas-shielded metal arc welding, flux core arc welding, electro slag welding can be used when welding is done in fabrication shop. For field applications, shielded metal arc welding is preferred.
10. Which of the following is not correct about electro slag welding?
a) high deposition rates
b) welds flat or vertical joints only
c) multiple electrodes may not be used
d) complicated set-up
Explanation: The following are some advantages of electro slag welding: (i) high deposition rates, (ii) multiple electrodes may be used, (iii)low distortion. Some disadvantages are: (i) welds flat or vertical joints only, (ii) complicated set-up, (iii)cooling water is needed.