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Name and describe the FOUR tests used to distinguish between the different types of materials - NSC Mechanical Technology Automotive - Question 3 - 2019 - Paper 1
Question 3
Name and describe the FOUR tests used to distinguish between the different types of materials. Give the reason why the following heat-treatment processes are perfor... show full transcript
Worked Solution & Example Answer:Name and describe the FOUR tests used to distinguish between the different types of materials - NSC Mechanical Technology Automotive - Question 3 - 2019 - Paper 1
Step 1
Tests to distinguish between the different types of materials
Answer
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Bending Test: This test involves hitting the material with a hammer to observe its responsiveness to bending. A material that easily bends is likely to be softer.
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Filing Test: In this test, a file is used to assess the material. The ease with which the file cuts into the material can indicate its hardness or softness. The color of the file material and the effort required for filing are also important.
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Machining Test: This test involves using a machine tool to shave off material. The ease of machining and the resultant surface finish provide insights into the material's properties, like toughness or brittleness.
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Sound Test: Dropping the material on a hard surface allows one to listen to the sound produced. The frequency of the sound can help in differentiating between materials with different hardness levels.
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Spark Test: This test involves applying a grinding wheel to the material and observing the shape and color of the sparks produced. This can help identify the type of metal.
Step 2
Give the reason why the following heat-treatment processes are performed on steel:
Answer
3.2.1 Tempering: Tempering is performed after hardening to relieve the internal strains induced during the hardening process and to reduce brittleness in the steel.
3.2.2 Normalising: Normalising is essential for relieving internal stresses that may have developed during fabrication. This process restores the steel's ductility and mechanical properties.
3.2.3 Hardening: Hardening is performed to produce extremely hard steel, which is essential for applications requiring high wear resistance. It also enables the material to resist wear and tear effectively.