Explain how you will conduct the following tests to identify various metals: 3.1.1 Sound test 3.1.2 File test What is the purpose of the heat treatment of steel? What is the purpose of the case hardening of steel? Describe the tempering process of steel - NSC Mechanical Technology Automotive - Question 3 - 2020 - Paper 1

For the file test:

1. Use a file to scratch or bite into the metal.
2. Observe the bite of the file: if the bite is big, this indicates a softer metal; if the bite is smaller, the metal is harder.

The purpose of the heat treatment of steel is twofold:

1. To change the properties of steel, enhancing its strength, ductility, and hardness.
2. To alter the grain structure of steel, allowing for better performance under different conditions.

The purpose of case hardening is to create a hard wear resistance surface while maintaining a tough core, thereby enhancing the durability and performance of steel components.

The tempering process of steel involves:

1. Heating the steel to a specific temperature, which is below the critical temperature, depending on the desired properties.
2. Holding it at that temperature for a predetermined period.
3. Quenching or cooling it in an appropriate medium, such as water, brine, or oil.

The three important factors to consider during the heat treatment of steel include:

1. Heating temperature/Carbon content – ensuring proper balance for desired properties.
2. Soaking time – the duration the steel is held at the target temperature.
3. Cooling rate – determining the best method (e.g., slow cooling vs. quenching) based on the required characteristics.