Engineering Reference

Cold working

Deforming a metal below its recrystallisation temperature to strengthen it.

Definition

Cold working raises strength and hardness by multiplying dislocations, at the cost of ductility. It is how wire, sheet and drawn bar get their properties, and it is why a half-hard temper is stronger than an annealed one of the same alloy.

In machining, cold working appears as a nuisance rather than a process: any rubbing or dwelling at the tool hardens a surface layer, which is the mechanism behind work hardening on stainless and titanium.

Common misuse

Assuming cold-worked and annealed stock of the same alloy machine the same way. Harder tempers machine worse and spring back more.

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