8.1 Name TWO factors that should be taken into account during oxy-acetylene welding to ensure high quality welding - NSC Mechanical Technology Welding and Metalwork - Question 8 - 2018 - Paper 1
Question 8
8.1 Name TWO factors that should be taken into account during oxy-acetylene welding to ensure high quality welding.
8.2 What does the abbreviation HAZ stand for wit... show full transcript
Worked Solution & Example Answer:8.1 Name TWO factors that should be taken into account during oxy-acetylene welding to ensure high quality welding - NSC Mechanical Technology Welding and Metalwork - Question 8 - 2018 - Paper 1
Step 1
Name TWO factors that should be taken into account during oxy-acetylene welding to ensure high quality welding.
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Answer
Correct flame for the type of work being performed, ensuring optimal heat distribution.
Proper depth of penetration and an adequate amount of fusion between the materials.
Step 2
What does the abbreviation HAZ stand for with regard to welded joints?
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Answer
HAZ stands for Heat Affected Zone, which is the area of base metal that has not melted but has experienced changes in properties due to the heat of welding.
Step 3
State TWO causes of EACH of the following arc-welding defects:
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Answer
8.3.1 Spatter:
Disturbance in the molten weld pool caused by incorrect settings or disruptions.
Too low welding voltage, leading to unstable weld characteristics.
8.3.2 Undercutting:
Too fast travel speed during the welding process, which does not allow enough fusion.
Too low current or incorrect electrode angle, which impacts the weld formation.
8.3.3 Incomplete penetration:
Insufficient welding current, which does not provide enough heat to penetrate.
Improper electrode size or type, hindering the weld strength.
Step 4
State TWO methods to reduce EACH of the following types of cracks during arc-welding:
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Answer
8.4.1 Transverse cracks:
Pre-heating the base metal before welding to reduce stress.
Ensuring proper cooling conditions to manage the cooling rate post-welding.
8.4.2 Centre-line cracks:
Adjusting welding parameters to control heat input and minimize distortion.
Using a proper workpiece alignment to ensure even joint stress.
Step 5
Explain the difference between a non-destructive test and a destructive test that are conducted on welded joints.
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Answer
A non-destructive test does not damage the welded joint, allowing it to maintain its integrity. In contrast, a destructive test involves applying stress or other conditions that lead to the failure of the joint, which provides insight into the maximum capacity and weaknesses of the weld.
Step 6
What type of welding defect occurs when conducting an ultrasonic test on a welded joint?
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Answer
Ultrasonic tests can detect internal flaws such as porosity, slag inclusions, and cracks that may not be visible on the surface.
Step 7
Name TWO internal defects that may be detected when conducting a nick-break test on a welded joint.
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Answer
Slag inclusions, which occur when slag is trapped within the weld bead, compromising integrity.
Porosity, resulting from trapped gas bubbles during the solidification of the weld.
Step 8
Explain why a machinability test is conducted.
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A machinability test is conducted to evaluate the hardness and strength of the welded joint, ensuring it can withstand machining operations without failing.
Step 9
State TWO visual requirements for an acceptable weld.
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Uniformity of the weld profile, ensuring consistent appearance and thickness.
Absence of surface defects such as cracks or excessive overlaps that could affect performance.
