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3.1 Explain how you will conduct the following tests to identify various metals: 3.1.1 Sound test 3.1.2 File test 3.2 What is the purpose of the heat treatment of steel? 3.3 What is the purpose of the case hardening of steel? 3.4 Describe the tempering process of steel - NSC Mechanical Technology Welding and Metalwork - Question 3 - 2020 - Paper 1
Question 3
3.1 Explain how you will conduct the following tests to identify various metals: 3.1.1 Sound test 3.1.2 File test 3.2 What is the purpose of the heat treatment of ... show full transcript
Worked Solution & Example Answer:3.1 Explain how you will conduct the following tests to identify various metals: 3.1.1 Sound test 3.1.2 File test 3.2 What is the purpose of the heat treatment of steel? 3.3 What is the purpose of the case hardening of steel? 3.4 Describe the tempering process of steel - NSC Mechanical Technology Welding and Metalwork - Question 3 - 2020 - Paper 1
Step 1
3.1.1 Sound test
Answer
To conduct the sound test, lightly tap the metal with a hammer and listen to the sound produced. If the sound is clear and resonant, the metal is likely to be of higher quality, whereas a dull sound may indicate a lower quality metal. Alternatively, you can drop the metal on the floor, and based on the sound it produces upon impact, you can make a similar assessment about the material.
Step 2
3.1.2 File test
Answer
For the file test, take a metal file and apply it to the surface of the metal. Observe the interaction: if the file bites well into the metal, it indicates that the metal is softer; conversely, if the bite is minimal and effortful, the metal is harder. This helps in determining the hardness and material properties of the metal.
Step 3
3.2 What is the purpose of the heat treatment of steel?
Answer
The purpose of heat treatment of steel is primarily to change the mechanical properties of the steel, such as its strength and ductility. Additionally, heat treatment can modify the grain structure of the steel, enhancing its performance characteristics for specific applications.
Step 4
3.3 What is the purpose of the case hardening of steel?
Answer
Case hardening is used to create a hard, wear-resistant surface on steel components that come into contact with friction or wear. This process gives the outer layer of the steel a tough exterior, while retaining a softer, ductile interior, thus improving the overall durability and longevity of the steel piece.
Step 5
3.4 Describe the tempering process of steel.
Answer
The tempering process involves heating steel to a specific temperature, known as the temper color, below its critical temperature, which is typically between 150 to 650 degrees Celsius depending on the desired properties. Once heated, the steel is maintained at that temperature for a designated period to relieve internal stresses. After this, it is quenched rapidly in water, brine, or oil to achieve the desired hardness and toughness.
Step 6
3.5 Name the THREE factors which need to be taken into consideration when heat treatment of steel is done.
Answer
The three main factors that should be considered during the heat treatment of steel include:
- Heating temperature / Carbon content - The temperature at which the steel is heated should correspond with its carbon content to optimize results.
- Soaking time - This is the period during which the steel is held at the target temperature; it must be sufficient to allow uniform heat distribution.
- Cooling rate / Quenching medium - The method and rate at which steel is cooled have significant effects on its microstructure and mechanical properties, depending on whether water, oil, or air is used.