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Describe the changes in the mechanical properties of high carbon steel: (i) if it is heated to a cherry red and cooled quickly; (ii) if it is heated to a cherry red and cooled slowly - Leaving Cert Engineering - Question Question 1 - 2008
Question Question 1
Describe the changes in the mechanical properties of high carbon steel: (i) if it is heated to a cherry red and cooled quickly; (ii) if it is heated to a cherry re... show full transcript
Worked Solution & Example Answer:Describe the changes in the mechanical properties of high carbon steel: (i) if it is heated to a cherry red and cooled quickly; (ii) if it is heated to a cherry red and cooled slowly - Leaving Cert Engineering - Question Question 1 - 2008
Step 1
Describe the changes in the mechanical properties of high carbon steel: (i) if it is heated to a cherry red and cooled quickly
Answer
When high carbon steel is heated to a cherry red temperature and cooled quickly (quenched), it undergoes a transformation that makes it hard and brittle. This process, known as hardening, increases the material's wear resistance significantly. However, the brittleness also means that the steel becomes more susceptible to breaking under shock or stress, which can be detrimental in practical applications.
Step 2
Describe the changes in the mechanical properties of high carbon steel: (ii) if it is heated to a cherry red and cooled slowly
Answer
If high carbon steel is heated to a cherry red and then cooled slowly, it is subjected to a process called annealing. This results in a reduction of internal stresses, making the steel softer and more ductile. The malleability and toughness are improved, allowing the material to be machined more easily and withstand blows or shocks better than hardened steel.
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Step 5
Identify two safety precautions to be observed when using oil for cooling during heat treatment.
Answer
- Ensure good ventilation to allow fumes to dissipate, preventing the buildup of potentially harmful vapors.
- Hold the component securely to avoid accidental slips or drops, which can lead to injuries.
Step 6
Describe the case hardening process which can be carried out on low carbon steel.
Answer
Case hardening is a process used to harden the outer surface of low carbon steel while leaving the core softer. This is typically achieved by increasing the carbon content in the surface layer through a process known as 'carburizing'. The part is heated to a cherry red temperature and then quenched, resulting in a hardened skin with a tough core. This method enhances wear resistance without compromising the toughness of the steel.