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Name and describe the heat treatment process required to achieve each of the following: (i) soften copper before hollowing; (ii) reduce the hardness in the point of a centre punch - Leaving Cert Engineering - Question 3 - 2010
Question 3
Name and describe the heat treatment process required to achieve each of the following: (i) soften copper before hollowing; (ii) reduce the hardness in the point o... show full transcript
Worked Solution & Example Answer:Name and describe the heat treatment process required to achieve each of the following: (i) soften copper before hollowing; (ii) reduce the hardness in the point of a centre punch - Leaving Cert Engineering - Question 3 - 2010
Step 1
(i) soften copper before hollowing
Answer
The heat treatment process required to soften copper before hollowing is called Annealing.
Description:
Annealing is a process that softens the metal and relieves internal stresses. To anneal copper, it is heated to a dull red color, approximately 600°C to 700°C, and then allowed to cool slowly in air or water. This process makes the copper more malleable and easier to work with.
Step 2
(ii) reduce the hardness in the point of a centre punch
Answer
To reduce the hardness of the point of a centre punch, the process called Tempering is used.
Description:
First, the point of the centre punch should be polished with emery cloth until the tempering colours become visible. The point is then heated slowly, allowing the temperature to increase gradually. As the temperature rises, the metal's hardness decreases. Once the correct colour is reached, typically a brown hue, the punch should be cooled in oil or water.
Step 3
Describe how the mild steel shaft of the screwdriver shown is case-hardened.
Answer
The mild steel shaft of the screwdriver is case-hardened through a process called Carburising.
Description:
In this method, the shaft of the screwdriver is first increased in temperature within a carbon-rich environment. This is done by heating the steel to a cherry red and then quenching it in oil or water. The outer surface absorbs carbon, making it hard while the inner core remains softer. This provides a durable exterior while maintaining toughness in the interior.
Step 4
List two reasons why it is necessary to wear protective clothing when heat treating metals.
Answer
- Protection against burns: Heat treating processes involve high temperatures, which can lead to severe burns if protective clothing is not worn.
- Protection against splashes and fumes: Protective clothing safeguards against harmful splashes from liquids and toxic fumes that may be released during the heating processes.
Step 5
State the main difference between low carbon steel and high carbon steel.
Answer
The primary difference between low carbon steel and high carbon steel lies in their carbon content:
- Low carbon steel typically contains less than 0.3% carbon and is more ductile and malleable.
- High carbon steel, on the other hand, has a carbon content ranging from 0.6% to 1.0% or more, making it harder but less ductile.