8.1 State THREE welding aspects that must be focused on during the arc welding procedure - NSC Mechanical Technology Welding and Metalwork - Question 8 - 2021 - Paper 1

1. Adjusting the welding parameters: By controlling the current and voltage, welders can avoid excessive penetration which can lead to cracking.
2. Slowing down the travel speed: A slower travel speed allows for better heat distribution, reducing the likelihood of cracks forming.

1. Travel speed too slow: If the welder moves too slowly, there may not be enough heat to create a strong bond, leading to lack of fusion.
2. Weld current too low: Insufficient welding current can also prevent adequate fusion between the base materials.

1. Contaminated weld surface: Dirt, oil, or moisture on the surface can trap gas and create porosity in the weld.
2. Wet or dirty electrodes: Using electrodes that are contaminated can introduce hydrogen into the weld puddle, resulting in porosity.

1. Welding current too low: If the current is insufficient, the weld might not penetrate fully into the joint.
2. Incorrect electrode angle: An improper angle can result in a shallow weld that does not penetrate into the base materials.

1. Open the acetylene torch valve: Start by opening this valve about half a turn and ignite the gas.
2. Adjust the oxygen torch valve: Slowly open the oxygen valve until the flame is no longer burning yellow, which indicates excess acetylene.
3. Final adjustment: Adjust until the inner cone of the flame appears rounded and has a clear blue color, ensuring a neutral flame for optimal welding.

1. Placement of the specimen: The welded sample is placed across supports of the bend die.
2. Applying force: Apply a bending force to the specimen to shape it according to the die.
3. Assessment of the bend: Observe the specimen for cracks or defects and determine the percentage elongation of the weld metal.

1. Ductility of the weld: The test evaluates how much the welded joint can deform without cracking.
2. Percentage elongation: Measure the amount of elongation to determine the weld's ability to withstand stress.

1. Fluorescent dye: This type emits visible light when exposed to ultraviolet light, facilitating the identification of defects.
2. Regular liquid dyes: These can be inspected in regular light and are used to detect surface flaws.

The nick-break test is performed to evaluate the internal soundness of the weld. It helps identify any internal defects such as slag inclusions, porosity, and lack of fusion by breaking the joint and allowing inspection of the weld's cross-section.