Which statement best describes cold working?

• A. It hardens metal and increases strength
• B. It causes work hardening and increases strength
• C. It softens metal
• D. It causes cracking

Answer: (B)

Cold working involves deforming metal at room temperature, which creates and tangles dislocations inside the crystal structure. This increasing obstacle to further dislocation movement is called strain hardening, or work hardening. As a result, the metal becomes stronger and harder, but more brittle with reduced ductility. That is why the statement describing cold working as causing work hardening and increasing strength is the best description. It doesn’t soften the metal, and cracking would only be a risk if the material is deformed beyond its limit; in typical forming, the key idea is the rise in strength from work hardening.