NSC Mechanical Technology Welding and Metalwork Machine-specific safety measures: QUESTION 9: JOINING METHODS (STR

QUESTION 9: JOINING METHODS (STRESSES AND DISTORTION) (SPECIFIC) 9.1 State THREE purposes of relieving stress caused by the heat treatment process - NSC Mechanical Technology Welding and Metalwork - Question 9 - 2024 - Paper 1

Question 9

QUESTION 9: JOINING METHODS (STRESSES AND DISTORTION) (SPECIFIC) 9.1 State THREE purposes of relieving stress caused by the heat treatment process. 9.2 State THREE... show full transcript

Worked Solution & Example Answer:QUESTION 9: JOINING METHODS (STRESSES AND DISTORTION) (SPECIFIC) 9.1 State THREE purposes of relieving stress caused by the heat treatment process - NSC Mechanical Technology Welding and Metalwork - Question 9 - 2024 - Paper 1

Step 1

State THREE purposes of relieving stress caused by the heat treatment process.

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Answer

To reduce or eliminate residual stresses in welded structures, promoting structural integrity.
To improve the dimensional stability of materials, ensuring they maintain their intended shapes.
To enhance resistance to distortion during subsequent processes.

Step 2

State THREE factors that can contribute to distortion and residual stress in welding.

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Answer

Material properties, including carbon content and alloying elements that influence the welding process.
Joint design, which may create areas with varying heat absorption and cooling rates.
The welding process itself, including the choice of technique and parameters such as heat input and speed.

Step 3

State FOUR mechanical properties that are affected by temperature change during heat treatment.

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Answer

Hardness, which can increase due to certain heat treatments, enhancing wear resistance.
Strength, often improved as the material undergoes microstructural changes.
Ductility, which may diminish or improve depending on the specific heat treatment applied.
Malleability, as this property can also change based on changes in the material’s microstructure.

Step 4

State THREE factors that influence the grain size of cold-worked steel.

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Answer

The amount of temperature and duration of the annealing process, which can coarsen or refine grain structure.
The composition of the steel, as different alloying elements can affect grain size directly.
Its melting point, as materials with lower melting points tend to have finer grains.

Step 5

What is the primary cause of shrinkage in welded joints?

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Answer

The primary cause of shrinkage in welded joints is the cooling of the weld metal, which leads to contraction as it solidifies.

Step 6

State FOUR welding methods to reduce distortion.

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Answer

Tack welding, which can minimize the amount of heat input in specific areas.
Intermittent welding to reduce overall heating and cooling rates.
Back-step welding, allowing for a sequential heating that counters distortion.
Using clamps, jigs, and fixtures for better control of the workpiece during welding.

QUESTION 9: JOINING METHODS (STRESSES AND DISTORTION) (SPECIFIC) 9.1 State THREE purposes of relieving stress caused by the heat treatment process - NSC Mechanical Technology Welding and Metalwork - Question 9 - 2024 - Paper 1

Worked Solution & Example Answer:QUESTION 9: JOINING METHODS (STRESSES AND DISTORTION) (SPECIFIC) 9.1 State THREE purposes of relieving stress caused by the heat treatment process - NSC Mechanical Technology Welding and Metalwork - Question 9 - 2024 - Paper 1

State THREE purposes of relieving stress caused by the heat treatment process.

State THREE factors that can contribute to distortion and residual stress in welding.

State FOUR mechanical properties that are affected by temperature change during heat treatment.

State THREE factors that influence the grain size of cold-worked steel.

What is the primary cause of shrinkage in welded joints?

State FOUR welding methods to reduce distortion.

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