6.1 State TWO causes of undercutting in an arc-welded joint - NSC Mechanical Technology Automotive - Question 6 - 2017 - Paper 1
Question 6
6.1 State TWO causes of undercutting in an arc-welded joint.
6.2 How would you prevent slag inclusion in an arc-welded joint?
6.3 Describe how the liquid dye penet... show full transcript
Worked Solution & Example Answer:6.1 State TWO causes of undercutting in an arc-welded joint - NSC Mechanical Technology Automotive - Question 6 - 2017 - Paper 1
Step 1
State TWO causes of undercutting in an arc-welded joint.
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Answer
The current setting is too high, which results in excessive heat and melting of the base material, leading to undercutting.
If the arc length is too long, it can cause excessive heat input, diminishing the weld’s integrity.
Step 2
How would you prevent slag inclusion in an arc-welded joint?
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Answer
Ensure that the joint is properly cleaned before welding to remove any contaminants.
Use direct electrodes and maintain the correct current setting to minimize slag entrapment.
Step 3
Describe how the liquid dye penetration test is done on a welded joint.
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Answer
Begin by cleaning the surface of the welded joint to remove any contaminants.
Spray the dye onto the clean surface and allow it to penetrate for a short time.
Remove any excess dye using a solvent.
After cleaning, apply a developer to highlight any penetrated dye, revealing cracks or imperfections.
Step 4
Name THREE advantages of the use of MIG/MAGS welding rather than arc welding.
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Answer
MIG/MAGS welding requires less skill from the operator compared to traditional arc welding.
It allows for continuous welds without the need to change electrodes, improving efficiency.
The process can be performed quickly and can weld materials in various positions.
Step 5
State TWO functions of the gas flow meter.
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Answer
To control the flow of shielding gas to ensure adequate protection during welding.
To measure the gas flow rate for optimal welding conditions.
Step 6
Label the parts A–E in the illustration of the MIG/MAGS-welding process in FIGURE 6.6 below.
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Answer
A = Melted welding pool / Parent metal / Weld metal / Weld
B = Contact nozzle / Weld pistol / Gun
C = Gas shroud / Weld pistol / Gun
D = Shielding gas
E = Earth clamp / Skelm / Earth cable.
Step 7
What is the purpose of the shielding gas in the MIG/MAGS welding process?
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Answer
The shielding gas is used to protect the molten weld pool from contamination by atmospheric gases, which can negatively impact the quality of the weld.
Step 8
Why must the earth cable be properly connected to the parent metal?
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The earth cable must be properly connected to complete the welding circuit, ensure a consistent current flow, and prevent electric shock.
Step 9
Name THREE types of gases used for MIG/MAGS welding.
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