Tempering steel after hardening serves to relieve internal stresses and reduce brittleness.

Tempering steel after hardening serves to relieve internal stresses and reduce brittleness.

• A. Increase hardness
• B. Relieve internal stresses and reduce brittleness
• C. Increase brittleness
• D. Improve machinability

Answer: (B)

Tempering after hardening is about improving the metal’s toughness by relaxing internal stresses that build up during quenching. When steel is quenched, it becomes martensitic—very hard but full of internal stresses and a brittle structure. Heating to a moderate temperature below the critical point allows slight atomic rearrangement and diffusion of carbon, which reduces dislocations and relieves those stresses. The result is a tougher, less brittle steel, though it does lose some hardness in the process. So the goal is to relieve internal stresses and reduce brittleness, not to increase hardness or make the metal more brittle. It can also make the material easier to machine because it’s less prone to cracking during cutting.

Tempering after hardening is about improving the metal’s toughness by relaxing internal stresses that build up during quenching. When steel is quenched, it becomes martensitic—very hard but full of internal stresses and a brittle structure. Heating to a moderate temperature below the critical point allows slight atomic rearrangement and diffusion of carbon, which reduces dislocations and relieves those stresses. The result is a tougher, less brittle steel, though it does lose some hardness in the process. So the goal is to relieve internal stresses and reduce brittleness, not to increase hardness or make the metal more brittle. It can also make the material easier to machine because it’s less prone to cracking during cutting.