6.1 State ONE cause of EACH of the following welding defects: 6.1.1 Porosity 6.1.2 Undercutting 6.1.3 Slag inclusion 6.2 Name THREE destructive tests that can be executed onto a welded joint - NSC Mechanical Technology Fitting and Machining - Question 6 - 2018 - Paper 1

Undercutting is often attributed to improper settings of equipment, which can cause excessive melting of the base metal.

Slag inclusion commonly occurs due to the failure to remove previous weld slag, resulting in impurities being trapped in the weld.

Three destructive tests that can be performed on a welded joint include:

1. Nick break test
2. Bend test
3. Tensile test

The dye penetration test involves several steps:

1. Clean the weld: Ensure the joint is free from contaminants.
2. Apply dye: Spray a dye onto the surface that needs to be tested to allow it to penetrate.
3. Remove excess dye: Clean the surface with a cleaning agent to remove excess dye.
4. Allow surface to dry: Let the surface dry fully to see the results clearly.
5. Develop the surface: Apply a developer to bring out the dye trapped in any cracks.
6. Inspect: The dye will highlight all surface defects, indicating any flaws.

The inert gas serves multiple purposes:

• It stabilizes the arc, ensuring a steady and focused welding process.
• It prevents atmospheric contamination by shielding the weld area from airborne impurities.
• It minimizes weld spatter, leading to cleaner welds.
• It promotes proper fusion of the materials being joined.

Three critical factors to consider during MIG/MAGS welding include:

1. Amount of penetration and fusion required for optimal weld strength.
2. The rate of wire feed to maintain consistent welding speed and quality.
3. The sound of the welding process, which can indicate the stability and quality of the arc.

A: Parent metal / Work piece B: Electrode wire C: Gas shroud D: Contact tube E: Shielding gas F: Earth cable / terminal / ground wire / skelm G: Work piece / welded joint