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3.1 Name ONE property of steel that is tested by conducting a bending test on steel - NSC Mechanical Technology Fitting and Machining - Question 3 - 2018 - Paper 1
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3.1 Name ONE property of steel that is tested by conducting a bending test on steel. 3.2 Give TWO reasons for conducting EACH of the following heat-treatment proces... show full transcript
Worked Solution & Example Answer:3.1 Name ONE property of steel that is tested by conducting a bending test on steel - NSC Mechanical Technology Fitting and Machining - Question 3 - 2018 - Paper 1
Step 1
Name ONE property of steel that is tested by conducting a bending test on steel.
Answer
One property of steel that is tested by conducting a bending test is its ductility. This measures the ability of the steel to deform under tensile stress, which is crucial for understanding its performance in various applications.
Step 2
Give TWO reasons for conducting EACH of the following heat-treatment processes on steel: 3.2.1 Annealing
Answer
- To relieve internal stresses: This process helps to reduce the residual stresses developed during previous working of the material.
- To soften the steel: Annealing makes the steel easier to work with in subsequent manufacturing processes.
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: Case hardening improves the wear resistance of the surface while retaining toughness at the core.
- To ensure toughness at the core: This is necessary to withstand applied loads despite having a hard surface layer.
Step 4
Explain why the tempering of steel is done after the hardening process.
Answer
Tempering is done after the hardening process to reduce the brittleness caused by hardening. It also allows for relief of internal strain and increases the toughness of the steel, ensuring better performance under load.
Step 5
State the THREE factors that must be considered during all heat-treatment processes.
Answer
- Heating temperature / Carbon content: The temperature at which the steel is heated affects its microstructure.
- Soaking time: The duration for which the steel is maintained at temperature is critical for even heat distribution.
- Cooling rate / Quenching rate: The rate at which the steel is cooled significantly impacts its mechanical properties.
Step 6
Explain the hardening process of steel.
Answer
The hardening process involves several steps:
First, the steel is heated to a temperature range of 30 – 50°C above the critical temperature (Ac3).
Once the desired temperature is reached, it is maintained for a soaking period to ensure uniform heating.
After soaking, the steel is rapidly cooled by quenching it in water, brine, or oil, which transforms the structure of the steel into a hard form.