What process usually follows hardening to decrease hardness?

What process usually follows hardening to decrease hardness?

• A. Quenching
• B. Tempering
• C. Annealing
• D. Normalizing

Answer: (B)

After hardening, tempering is the usual next step when you want to reduce hardness. Hardening creates martensite, which is very hard but also brittle. Tempering involves heating the metal to a temperature below the hardening temperature and holding it there, then cooling. This gives the carbon atoms time to diffuse and form small carbide particles, and it relieves internal stresses. The result is a material that is less hard but tougher and more ductile, which is often more useful in practical use. Quenching would actually increase hardness, not decrease it. Annealing softens the metal but is done under different conditions and isn’t specifically the standard post-hardening step. Normalizing also changes grain structure and properties in a different way, not primarily aimed at reducing hardness after hardening.

After hardening, tempering is the usual next step when you want to reduce hardness. Hardening creates martensite, which is very hard but also brittle. Tempering involves heating the metal to a temperature below the hardening temperature and holding it there, then cooling. This gives the carbon atoms time to diffuse and form small carbide particles, and it relieves internal stresses. The result is a material that is less hard but tougher and more ductile, which is often more useful in practical use.

Quenching would actually increase hardness, not decrease it. Annealing softens the metal but is done under different conditions and isn’t specifically the standard post-hardening step. Normalizing also changes grain structure and properties in a different way, not primarily aimed at reducing hardness after hardening.