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Name ONE property of steel that is tested by conducting a bending test on steel - English General - NSC Mechanical Technology: Fitting and Machining - Question 3 - 2018 - Paper 1
Question 3
Name ONE property of steel that is tested by conducting a bending test on steel. Give TWO reasons for conducting EACH of the following heat-treatment processes on s... show full transcript
Worked Solution & Example Answer:Name ONE property of steel that is tested by conducting a bending test on steel - English General - NSC Mechanical Technology: Fitting and Machining - Question 3 - 2018 - Paper 1
Step 1
Step 2
Step 3
Give TWO reasons for conducting EACH of the following heat-treatment processes on steel: 3.2.2 Case hardening
Answer
- To require a wear-resistant surface while maintaining toughness within the core to withstand applied loads.
- To create a hard case that offers high abrasion resistance, ensuring longevity in service.
Step 4
Explain why the tempering of steel is done after the hardening process.
Answer
Tempering is performed post-hardening to reduce the brittleness caused by the hardening process. It relieves internal strain, allowing the steel to regain some ductility while retaining its hardness, which enhances its overall toughness.
Step 5
State the THREE factors that must be considered during all heat-treatment processes.
Answer
- Heating temperature: The temperature should be controlled to avoid unwanted reactions in the steel.
- Soaking time: The duration the steel is held at the target temperature must be adequate to achieve the desired properties.
- Cooling rate: The rate at which the steel is cooled impacts its microstructure and resultant characteristics.
Step 6
Explain the hardening process of steel.
Answer
The hardening process involves heating steel to a temperature between 30 and 50°C above its critical temperature (Ac3). After reaching this temperature, the steel is held to allow the transformation of its structure. It is then rapidly cooled by quenching it in a medium such as water, oil, or brine, locking in a hard microstructure and enhancing its strength.