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.
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Answer
The shielding gas cloud is created when the inserted gas is fed through the pipe and nozzle, exiting through the holes in the nozzle. Its primary purpose is to protect the molten weld pool from exposure to oxygen and other contaminants in the atmosphere.
Step 2
Explain the procedure that must be followed when the feed wire burns onto the copper welding tip.
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When the feed wire burns onto the copper welding tip, the following procedure should be followed:
Release the trigger to stop the welding process.
Using pliers, carefully cut the blob formed on the welding tip.
Use a file to clean the welding tip.
Ensure that the feeding wire is properly separated from the tip before resuming welding.
Step 3
Name TWO circumstances that can cause the feed wire to melt onto the welding tip.
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If the gap between the nozzle and workpiece is too small, it can lead to overheating.
If the wire feed speed is too slow, this can also cause excessive heat buildup and melting.
Step 4
Name THREE causes of cracks forming on the welding bead when performing MIG welding.
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A root gap that is too small in a restrained joint can lead to stress and cracking.
Excessive heat during welding can cause the metal to become too hot and brittle.
Inadequate pre-heating can affect the material's tensile strength, contributing to cracking.
Step 5
Describe shrinking as it occurs in a welding joint.
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When metal is heated, it expands, and when it cools down, it contracts. This process leads to the distortion of the welded metal, as different areas may shrink at varying rates, causing a range of distortions.
Step 6
Make a freehand drawing to illustrate longitudinal angular shrinking on a welded project.
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A freehand drawing must include two pieces of metal, a clear representation of the welding bead, indications of the shrinking effect, and the original shape of the metals marked for comparison.
Step 7
State TWO measures that can be taken to prevent metal from distorting when welding is performed.
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Answer
Pre-setting the metal pieces can help mitigate distortion.
Using techniques such as spot welding to minimize heat input and allow the work pieces to maintain their shape.
Step 8
Why is the use of sunglasses not recommended when cutting with the oxy-acetylene set?
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Sunglasses do not effectively filter ultraviolet light, which can lead to eye damage. Moreover, they do not protect the eyes from sparks generated during cutting.
Step 9
Describe the possible outcome for the gas cylinder if it accidentally topples over.
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If the gas cylinder topples over, it may break off the main valve, resulting in the cylinder turning into a missile and potentially causing significant damage or explosion.
Step 10
Name TWO types of metal that can be cut with an oxy-acetylene welding set.
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Mild steel
Carbon steel
Step 11
Give technical advice to a farmer who wants to purchase a plasma cutting machine for general use on the farm.
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Choose a machine suited to the thickness of the metal that needs to be cut.
Ensure a compressor is available that can provide sufficient air pressure for the cutting process.
Step 12
Name FOUR pieces of personal protective equipment (PPE) that must be used when doing plasma cutting.
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Fireproof gloves
Face shield
Flame-resistant clothing
Leather shoes
Step 13
State TWO factors that cause poor cutting performance when using the plasma cutting machine.
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If the working pressure of the machine is too low, cutting efficiency is reduced.
A clogged air filter can impede airflow, compromising cut quality.
