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Test: Fabrication Processes (Welding) - 2 - Mechanical Engineering MCQ


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30 Questions MCQ Test - Test: Fabrication Processes (Welding) - 2

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Test: Fabrication Processes (Welding) - 2 - Question 1

 Fabrication weldability test is used to determine     

Detailed Solution for Test: Fabrication Processes (Welding) - 2 - Question 1

The fabrication weldability test is used to determine the susceptibility of the welded joint for cracking. Weldability test may be classified as:

i) Theoretical test

ii) Simulated test

iii) Actual welding tests

a) Fabrication weldability tests that determine the susceptibility of the welded joint to crack. These tests are a hot cracking test, root cracking test, hydrogen-induced tests.

b) Service weldability test that measures mechanical properties which are considered essential for the satisfactory performance of the welded joint during service. These tests are: Tensile, hardness and bend tests, impact tests, fatigue tests, corrosion tests, creep tests etc.

Test: Fabrication Processes (Welding) - 2 - Question 2

Match List I (Welding problems) with List II (Causes) and select the correct answer using the codes given below the Lists: 

[IES - 2004]

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Test: Fabrication Processes (Welding) - 2 - Question 3

 By which one of the following methods gray iron is usually welded? 

Test: Fabrication Processes (Welding) - 2 - Question 4

Preheating before welding is done to         

Test: Fabrication Processes (Welding) - 2 - Question 5

In a gas welding of mild steel using an oxy-acetylene flame, the total amount of acetylene consumed is 10 litre. The oxygen consumption from the cylinder is

Test: Fabrication Processes (Welding) - 2 - Question 6

In arc welding, d.c. reverse polarity is used to hear greater advantage in 

Detailed Solution for Test: Fabrication Processes (Welding) - 2 - Question 6

Direct current reversed polarity (DCRP) : It is also known by the name of direct current electrode positive (DCEP) process. As name suggests, the electrode in the straight polarity process is on the positive terminal while the workpiece is connected with the negative terminal.
Reverse polarity is advantageous in overhead welding because in reverse polarity work piece is made negative (at positive electrode). So less amount of metal is melted.

Test: Fabrication Processes (Welding) - 2 - Question 7

In an arc welding process, the voltage and current are 25 V and 300 A respectively. The arc heat transfer efficiency is 0.85 and welding speed is 8 mm/see. The net heat input (in J/mm) is 

Detailed Solution for Test: Fabrication Processes (Welding) - 2 - Question 7

Effective heat transfer per second (P) = η VI =0.85x25x300 J/s

Speed (c) = 8 mm/s

Net heat input 

Test: Fabrication Processes (Welding) - 2 - Question 8

Arc blow is more common in       

Test: Fabrication Processes (Welding) - 2 - Question 9

An arc welded joint is shown in the above figure. The part labelled 'B' in the figure is known as

 

Test: Fabrication Processes (Welding) - 2 - Question 10

In which of the following welding processes, flux is used in the form of granules? 

Test: Fabrication Processes (Welding) - 2 - Question 11

In resistance welding, heat is generated due to the resistance between 

Test: Fabrication Processes (Welding) - 2 - Question 12

Assertion (A): Spot welding is adopted to weld two overlapped metal pieces between two electrode points. Reason (R): In this process when current is switched on, the lapped pieces of metal are heated in a restricted area.  

Test: Fabrication Processes (Welding) - 2 - Question 13

Two 1 mm thick steel sheets are to be spot welded at a current of 5000 A. Assuming effective resistance to be 200 micro-ohms and current flow time of 0.2 second, heat generated during the process will be   

Detailed Solution for Test: Fabrication Processes (Welding) - 2 - Question 13

Q = I2Rt = 50002 × (200 ×10−6 ) × 0.2J = 1000J

Test: Fabrication Processes (Welding) - 2 - Question 14

Assertion (A): In electron beam welding process, vacuum is an essential process parameter

Reason (R): Vacuum provides a highly efficient shield on weld zone  

Detailed Solution for Test: Fabrication Processes (Welding) - 2 - Question 14

Correct Answer :- B

Explanation : EBW is carried out in vacuum to avoid dispersion or deviation from the focus.

Test: Fabrication Processes (Welding) - 2 - Question 15

Match List I (Welding processes) with List II (Features) and select the correct answer using the codes given below the Lists: 

Codes:

Test: Fabrication Processes (Welding) - 2 - Question 16

Which one of the following is a solid state joining process?                 

Test: Fabrication Processes (Welding) - 2 - Question 17

The strength of a brazed joint     

Test: Fabrication Processes (Welding) - 2 - Question 18

Consider the following statements: The magnitude of residual stresses in welding depends upon                                  

1. design of weldment  

2. support and clamping of components

3. welding process used  

4. amount of metal melted / deposited

Which of the statements given above are correct?  

Detailed Solution for Test: Fabrication Processes (Welding) - 2 - Question 18

Correct Answer :- b

Explanation : Residual stress depends on welding parameters such as current, voltage, speed, current.

Test: Fabrication Processes (Welding) - 2 - Question 19

The ratio of acetylene to oxygen is approximately………. for a neutral flames used in gas welding.     


Test: Fabrication Processes (Welding) - 2 - Question 20

In Oxyacetylene gas welding, temperature at the inner cone of the flame is around 

Test: Fabrication Processes (Welding) - 2 - Question 21

In oxy-acetylene gas welding, for complete combustion, the volume of oxygen required per unit of acetylene is        

Test: Fabrication Processes (Welding) - 2 - Question 22

Oxyacetylene reducing flame is used while carrying out the welding on 

Test: Fabrication Processes (Welding) - 2 - Question 23

Assertion (A): The electrodes of ac arc welding are coated with sodium silicate, whereas electrodes used for dc arc welding are coated with potassium silicate binders.

Reason (R): Potassium has a lower ionization potential than sodium.  

Detailed Solution for Test: Fabrication Processes (Welding) - 2 - Question 23

Let's analyze the Assertion (A) and Reason (R):

Assertion (A):

"The electrodes of AC arc welding are coated with sodium silicate, whereas electrodes used for DC arc welding are coated with potassium silicate binders."

  • This statement is true. In AC arc welding, electrodes are typically coated with sodium silicate because sodium helps stabilize the arc in alternating current. In DC arc welding, potassium silicate is preferred because potassium provides better arc stability with direct current due to its ionization properties.

Reason (R):

"Potassium has a lower ionization potential than sodium."

  • This statement is false. In fact, potassium has a higher ionization potential than sodium. Sodium has a lower ionization potential, meaning it requires less energy to remove an electron from a sodium atom compared to potassium.

Conclusion:

  • Assertion (A) is true, but Reason (R) is false.

Thus, the correct answer is:

Option 1: A is true but R is false.

Test: Fabrication Processes (Welding) - 2 - Question 24

In d.c. welding, the straight polarity (electrode negative) results in    

*Multiple options can be correct
Test: Fabrication Processes (Welding) - 2 - Question 25

Which one of the following statements is correct?        

Detailed Solution for Test: Fabrication Processes (Welding) - 2 - Question 25

Correct Answer :- a,b

Explanation : Although the classic flux for steel was borax, and the filler rod is dipped in a can of borax, while the rod is still very hot. The shielding gas is supplied by the torch itself as the work is done inside the area covered by the flame.

So the flux took care of minor oxide contamination, and the torch flame kept the weld puddle from seeing atmospheric oxygen.

Generally DCSP is used in GTAW with the exception of AC being used in aluminium and Magnesium.

Test: Fabrication Processes (Welding) - 2 - Question 26

In MIG welding, the metal is transferred into the form of which one of the following?   

Detailed Solution for Test: Fabrication Processes (Welding) - 2 - Question 26

Explanation:

Gas metal arc welding (GMAW) or Metal inert gas arc welding (MIG)

  • In this process, the arc is formed between a continuous, automatically fed, metallic consumable electrode and welding job in an atmosphere of inert gas, and hence this is called metal inert gas arc welding (MIG) process.
  • In this process small droplets of molten metal from the electrode are transferred to the weld area, at ratio of several hundred droplets per second, the transfer is spatter free and very stable, high dc current, high voltage, and large diameter electrode are used along with the shielding gas.
  • The shielding gases for MIG welding are mixtures of argon, oxygen, and CO2, and special gas mixtures may contain helium. 
Test: Fabrication Processes (Welding) - 2 - Question 27

For butt -welding 40 mm thick steel plates, when the expected quantity of such jobs is 5000 per month over a period of 10 year, choose the best suitable welding process out of the following available alternatives. 

Detailed Solution for Test: Fabrication Processes (Welding) - 2 - Question 27

We need maximum metal deposition rate so choice SAW.
Note: You know maximum metal deposition rate of all welding is SAW and it may joint 40 mm thick plates easily.

Test: Fabrication Processes (Welding) - 2 - Question 28

Resistance spot welding is performed on two plates of 1.5 mm thickness with 6 mm diameter electrode, using 15000 A current for a time duration of 0.25 seconds. Assuming the interface resistance to be 0.0001 Ω , the heat generated to form the weld is       

Detailed Solution for Test: Fabrication Processes (Welding) - 2 - Question 28

H = I2Rt = 150002 × 0.0001× 0.25J = 5625 W − s

Test: Fabrication Processes (Welding) - 2 - Question 29

Which one of the following is not an electric resistance method of welding? 

Detailed Solution for Test: Fabrication Processes (Welding) - 2 - Question 29

Electro slag welding is not a type of electric resistance method of welding.

  • Percussion welding

    Uses a short electrical discharge to create a high temperature arc, then applies pressure to forge the materials together. This method is often used to join dissimilar metals or when flash isn't needed at the joint.

  • Flash welding

    Doesn't use filler metals, but instead creates an arc by applying current to the metals while they're separated by a predetermined distance. Once the metals reach the right temperature, they're pressed together to forge them together.

  • Seam welding

    Uses a series of continuous spot welds to create a leak-proof joint between two overlapping pieces of sheet metal. The workpiece is placed between two wheels that apply pressure and carry current to produce the welds.

Test: Fabrication Processes (Welding) - 2 - Question 30

In which one of the following welding techniques is vacuum environment required? 

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