Explain why a fully hardened steel would need to be tempered.
Support your answer with a labelled sketch of the resulting tempered microstructure. (4 marks)
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Exemplar solution 1:
→ Steel in its fully hardened state exhibits extreme brittleness, limiting its practical applications and making it vulnerable to failure.
→ When exposed to abrupt forces or stress concentrations, fully hardened steel can develop cracks or break catastrophically due to its inability to deform.
→ The tempering process plays a vital role in optimising steel’s mechanical properties, creating an essential balance between hardness and toughness.
→ Through careful tempering, the steel’s characteristics can be precisely tuned to match specific operational requirements, ensuring reliable performance across diverse applications.
→ Martensite by hardening:
Exemplar solution 2:
→ The tempering process serves as a crucial follow-up treatment after quenching, specifically designed to mitigate the steel’s brittle characteristics.
→ The procedure involves carefully reheating the hardened steel to a temperature below its critical point, followed by another cooling cycle.
→ This methodical heating and cooling sequence helps release internal stresses that developed during the initial quenching phase.
→ Through tempering, manufacturers can precisely adjust the balance between the steel’s hardness and toughness to achieve desired mechanical properties.
→ Ferrite and finely dispersed cementite:
Exemplar solution 1:
→ Steel in its fully hardened state exhibits extreme brittleness, limiting its practical applications and making it vulnerable to failure.
→ When exposed to abrupt forces or stress concentrations, fully hardened steel can develop cracks or break catastrophically due to its inability to deform.
→ The tempering process plays a vital role in optimising steel’s mechanical properties, creating an essential balance between hardness and toughness.
→ Through careful tempering, the steel’s characteristics can be precisely tuned to match specific operational requirements, ensuring reliable performance across diverse applications.
→ Martensite by hardening:
Exemplar solution 2:
→ The tempering process serves as a crucial follow-up treatment after quenching, specifically designed to mitigate the steel’s brittle characteristics.
→ The procedure involves carefully reheating the hardened steel to a temperature below its critical point, followed by another cooling cycle.
→ This methodical heating and cooling sequence helps release internal stresses that developed during the initial quenching phase.
→ Through tempering, manufacturers can precisely adjust the balance between the steel’s hardness and toughness to achieve desired mechanical properties.
→ Ferrite and finely dispersed cementite:
