250+ TOP MCQs on Welding of Various Metals and Answers

Welding Question Bank on “Welding of Various Metals”.

1. Which of the following methods cannot be used for welding carbon steel?
a) Arc welding
b) Gas welding
c) Ultrasonic welding
d) Forge welding
Answer: c
Clarification: For the welding of carbon steel material, one may use the arc welding method. To gas weld carbon steel is also a feasible option and carbon steels can be treated using forge welding also, but it cannot be welded using ultrasonic welding.

2. High alloys steels are preheated up to what temperature?
a) 350°C
b) 400°C
c) 450°C
d) 500°C
Answer: b
Clarification: High alloy steels are those steels which contain high amount of carbon in them. These alloys need to be preheated before welding in order to avoid cracking. The temperature up to which these alloys are preheated is 400°C.

3. Up to what percent of carbon content in steel, it is not required to preheat it?
a) 0.25% – 0.3%
b) 0.3% – 0.35%
c) 0.35% – 0.4%
d) 0.4% – 0.45%
Answer: a
Clarification: Low carbon steels are the ones containing low amount of carbon in them, which does not require preheating. The amount of carbon content needed in low carbon steels, is 0.25% to 0.3%, if preheating is to be avoided.

4. Which of the following material is not used in alloy steels?
a) Molybdenum
b) Nickel
c) Chromium
d) Sodium
Answer: d
Clarification: In alloy steels, there is a big composition used up by iron. Along with iron, there vitally has to be carbon in alloy steels. Along with carbon, there is a presence of other elements such as, molybdenum, nickel and chromium in small amounts.

5. Which among the following methods is best suited for stainless steels?
a) Electric butt welding
b) Seam welding
c) Flux coated arc welding
d) Oxy-hydrogen welding
Answer: a
Clarification: There are a few methods of treating stainless steels for welding, such as, any of the metal arc welding methods or the oxy-acetylene welding method, but the one best suited for this alloy is electric butt welding.

6. Stainless steels are annealed at what temperature?
a) 650°C – 700°C
b) 700°C – 750°C
c) 750°C – 800°C
d) 800°C – 850°C
Answer: c
Clarification: Stainless steels are hardened by constant heating and cooling and the best method suited for this alloy is electric butt welding. As soon as the stainless steel alloy is electric butt welded, it needs to be annealed at a temperature in between 750°C to 800°C.

7. Which of the following is not a material used for making an electrode in metal arc welding, for treating stainless steels?
a) Niobium
b) Columbium
c) Titanium
d) Potassium
Answer: d
Clarification: Stainless steels are best welded using the electric butt welding method and then followed by annealing at around 750°C to 800°C. Stainless steels can also be welded using the metal arc welding methods. For this the electrode which is needed is made up of niobium, titanium and columbium. These materials avoid the occurrence of the defect called weld decay.

8. What is the temperature needed for preheating in cast irons?
a) 550°C
b) 600°C
c) 650°C
d) 700°C
Answer: b
Clarification: Cast irons, upon the removal of welding heat, get solidified very quickly. This solidification takes place due to the surrounding cold mass and the air around. Because of such quick cooling, the carbon gets retained and hard metal stays in the weld. To overcome this, cast irons have to be preheated to 600°C.

9. Low carbon steels need not be preheated before welding.
a) True
b) False
Answer: a
Clarification: Carbon steels which contain carbon in a very low amount are not compulsorily required to be preheated before undergoing welding if the large runs are made. This is because, in low carbon steels, unlike high carbon steels, there is no cracking seen on welding.

10. Carbon steels can be fusion welded.
a) True
b) False
Answer: b
Clarification: Carbon steels are best treated using forge welding, resistance welding, arc welding or by gas welding. Carbon steels essentially cannot be fusion welded, because, of the occurrence of cracks which may cause due to carbon pick up.

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