6.1 What welding defect is described as non-metallic solids trapped in the weld metal? 6.2 Name FOUR defects that may be observed during visual inspections - NSC Mechanical Technology Automotive - Question 6 - 2017 - Paper 1

During visual inspections, the following defects may be observed:

1. Shape of profile: Irregularities in the geometric shape of the weld.
2. Uniformity of surface: Variability in the surface texture and appearance of the weld.
3. Overlap: Metal not properly fused to the base material, leading to a protruding weld.
4. Crack free: Identifying surface cracks that may indicate weakness in the weld.

Two common causes of incomplete penetration in a welded joint are:

1. Weld speed too fast: This can prevent sufficient heat from being generated to penetrate the base metal adequately.
2. Electrode too large: Using an electrode that is too large may result in insufficient melting of the base material, leading to incomplete penetration.

To prevent a lack of fusion in a welded joint, the following measures can be implemented:

1. Correct preparation of joint: Ensuring that the surfaces to be welded are properly cleaned and aligned can enhance fusion.
2. Correct weld speed: Maintaining an appropriate speed during the welding process helps achieve good fusion between the weld metal and base metal.

The test used to determine the weld hardness and strength is the machinability test. This test assesses how easily the welded material can be machined and provides insight into the hardness and general properties of the weld.

The test used to reveal internal defects is the nick-break test. This technique involves breaking the welded joint to visually inspect for internal flaws or weaknesses.

The bend test is conducted to evaluate the ductility of the weld deposit and the heat-affected zone. This test involves bending the welded joint to assess its ability to withstand deformation without breaking.

To conduct a dye penetration test on a welded joint, follow these steps:

1. Clean the weld: Ensure that the weld area is clean from contaminants like oil, grease, and dirt.
2. Apply the dye: Spray a penetrant dye onto the weld and allow it to seep into any surface cracks or defects.
3. Cleanup: After a specified time, clean the excess dye from the surface using a suitable cleaner.
4. Developer application: Apply a developer to the weld surface to make defects visible. The dye trapped in any cracks will appear against the contrasting background, highlighting any flaws.

The wire feed controller is responsible for feeding the consumable electrode wire to the welding gun at a constant predetermined speed, which is crucial for maintaining a stable arc during the welding process.

The welding gun activates the supply of gas, power, and wire feed to facilitate the welding process. It also provides the mechanism for directing the welding arc and ensuring efficient welding operations.

The function of the inert gas used during the MIG/MAGS welding process is to shield the molten pool from atmospheric gases. This prevents contamination and oxidation, which can adversely affect the quality and properties of the weld.