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The illustration below shows the nozzle of a MIG welding apparatus - NSC Agricultural Technology - Question 4 - 2018 - Paper 1
Question 4
The illustration below shows the nozzle of a MIG welding apparatus. 4.1.1 Describe the origin and purpose of the shielding gas cloud that forms around the welding a... show full transcript
Worked Solution & Example Answer:The illustration below shows the nozzle of a MIG welding apparatus - NSC Agricultural Technology - Question 4 - 2018 - Paper 1
Step 1
Describe the origin and purpose of the shielding gas cloud that forms around the welding area.
Answer
The shielding gas cloud is created when the inserted gas is fed through the nozzle and exits through the holes. Its primary purpose is to protect the molten weld pool from contamination, specifically from oxygen and other atmospheric impurities.
Step 2
Explain the procedure that must be followed when the feed wire burns onto the copper welding tip.
Answer
When the feed wire burns onto the copper welding tip, the first step is to release the trigger of the welding gun. Next, one must take a pair of pliers to carefully cut the outburned wire. Then, use a file to clean the tip to ensure a proper connection. Finally, the feeding wire should be separated from the tip and the welding can continue.
Step 3
Name TWO circumstances that can cause the feed wire to melt onto the welding tip.
Answer
- If there is a gap between the nozzle and the workpiece that is too small, it can create excessive heat.
- If the wire feed speed is set too low, it may not keep up with the melting rate of the wire, resulting in it bonding to the tip.
Step 4
Name THREE causes of cracks forming on the welding bead when performing MIG welding.
Answer
- A root gap in a restrained joint can lead to stress accumulation.
- Excessive heat during the welding process can cause overheating and vulnerable areas in the weld.
- Inadequate pre-heating can lead to thermal shock and cracks in high tensile and low alloy materials.