This set of Engineering Materials & Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Welding”.
1. The welding process in which no filler metal is used is classified as ___________
Explanation: Welding is basically classified into fusion and plastic types. The plastic type of welding is further classified as autogenous, homogeneous, and heterogeneous. In the autogenous process, no filler metal is used, whereas the other two processes involve usage of filler metal.
2. The pressure of acetylene in welding torch for oxy-acetylene welding is maintained at _________
a) 0.66-1.0 bar
b) 0.1-3.5 bar
c) 0.5-3.5 bar
d) 1.0-4.5 bar
Explanation: The oxy-acetylene system is employed depending on the manner in which acetylene is supplied for welding. In the high-pressure system, the pressure of acetylene at the welding torch is 0.66-1.0 bar and it is 0.1-3.5 bar for oxygen. The low-pressure system pressure for oxygen should be 0.5-3.0 bar.
3. What is the color of an acetylene cylinder in case of gas welding?
d) Light blue
Explanation: For gas welding, a head of oxygen and acetylene are used for the process. Both the gases are stored in separate cylinders. The standard color for oxygen cylinder is black, where the oxygen is stored at a pressure of 125-140 kg/cm2. The acetylene cylinder has a standard color of maroon and is fitted with a fusible light to avoid the explosion.
4. What is the temperature of arc needed for arc welding?
Explanation: In the arc welding process, the heat for joining the metals is developed using an electric arc. The workpiece is melted by the arc and the electrode also melts, making the two join together. The temperature of the arc is about 5000-6000oC.
5. A small depression formed in the parent metal is called _________
a) Arc length
b) Arc carter
c) Depth of fusion
d) Slag length
Explanation: Depth of fusion is defined as the depth to which the metal is melted and deposited. The molten metal is forced out of the pool by an electric arc, which forms a small depression in the parent metal where the molten metal is piled up. This is known as arc carter. The distance between the tip of the electrode and the bottom of the arc crater is called arc length.
6. What is the level of efficiency of a transformer as a welding machine?
Explanation: An AC machine (transformer) is preferred for welding as it has a higher efficiency of 80-85%. Moreover, it has a lower power consumption and low cost of equipment. The efficiency for a DC machine (generator) is a low 30-60%.
7. Which electrode material is used for welding of wrought iron?
a) Cast iron rods
b) Low carbon steel rod
c) Mild steel copper coated rod
d) Low alloy steel rod
Explanation: The metal of the electrode depends on the kind of parent metal used. For wrought iron, low carbon steel rods are used. Cast iron rods, mild steel copper coated rods, and low alloy steel rod containing 0.25% carbon are used for cast iron, mild steel, and alloy steel workpieces respectively.
8. Which electrode material is used for welding of carbon steel?
a) Cast aluminum alloy rod
b) Soft steel wire
c) Copper rod
d) Drawn brass rod
Explanation: The metal of the electrode depends on the kind of parent metal used. For carbon steel, soft steel wires containing 0.1-0.18% carbon and 0.0025-0.04% phosphorus and sulfur are used. Cast aluminum alloy rods, copper rods, drawn brass rods containing are used for aluminum, copper casting, and brass workpieces respectively.
9. ___________ is used as an inert gas for metal inert gas welding.
Explanation: Gas metal arc welding or MIG welding is a common welding process where an electric arc is produced between a consumable metal electrode and the workpiece. The arc and welding zone are surrounded by an inert gas. For MIG welding, argon or helium are used as the inert gas.
10. Which electrode is used in the process of TIG welding?
Explanation: Tungsten inert gas welding or TIG welding is a common welding process where an electric arc is produced between a non-consumable tungsten electrode and the workpiece. The electrode used in this process is tungsten. As it has a high melting point of 330oC, it will not melt during welding.
11. The heat released in plasma arc welding is about ____________
Explanation: Plasma is a high temperature ionized gas which is passed through the torch. The arc is initiated in the beginning by supplying electrical energy between the nozzle and tungsten electrode. This will release a high amount of heat, usually between 10000 and 30000oC.
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