The image below shows a part of the MIG welding apparatus - NSC Agricultural Technology - Question 4 - 2024 - Paper 1

The MIG welding process involves several steps:

• The MIG welding machine sends a continuous feed of positive wire into the welding area when the operator presses the trigger on the gun.
• An electric arc is formed between the filler wire and the workpiece, creating a short circuit as the wire melts.
• As the wire melts, the heat generated allows it to mix with the base metal, forming a welded joint.
• An inert shielding gas surrounds the weld area to protect it from oxygen and other contaminants in the atmosphere.
• Once welding is done, the molten metal cools and solidifies to form a strong bond.

Common components of MIG welding shielding gas include:

• Argon
• Helium
• Carbon Dioxide (CO₂)

Problems that can prevent wire feeding include:

1. Blocked or defective contact tip.
2. Loose or broken wire drive rollers.
3. Entangled wire in the delivery pipe.
4. Wire jammed on the spool.

The welding defect indicated by A is undercutting. Possible causes for undercutting can include:

1. Excessive travel speed of the torch.
2. High current settings during the welding process.

Three common pipe welding positions are:

1. Horizontal fixed position.
2. Horizontal movable position.
3. Vertical position.

Metals that should not be cut with oxyacetylene cutting apparatus include:

1. Aluminum: Its high thermal conductivity causes it to melt too quickly, which results in a porous cut.
2. Stainless steel: The presence of nickel and molybdenum creates an oxide film on the base metal, making it difficult to cut accurately.

When the torch is moved too fast while cutting:

• The molten puddle may not have sufficient time to form properly, potentially sticking to one another.
• The flame may not penetrate adequately through the metal, resulting in a poor cut and producing slag.

The material used for manufacturing the plasma-cutting nozzle is porcelain.

Properties of porcelain include:

1. Heat resistant: Can withstand high temperatures without deforming or melting.
2. Durable: Exhibits high strength and abrasion resistance.
3. Non-conductive: Does not conduct electricity, making it safe for use in plasma-cutting applications.