What is 'cold working' in metallurgy?

• A. Heating metals above their melting point
• B. Plastic deformation below recrystallization temperature
• C. A process of forging at high temperatures
• D. Combining different metals at high temperatures

Answer: (B)

Cold working refers to the process of deforming metals at temperatures below their recrystallization point, typically at or near room temperature. This technique enhances the strength of the metal through dislocation movement, leading to increased hardness and improved properties. As the metal is subjected to mechanical stress—such as rolling, bending, or drawing—its microstructure changes, which results in strain hardening. This is crucial in industrial applications, where enhanced strength without the need for high-temperature processing can be beneficial.

On the contrary, the other options pertain to different processes in metallurgy. Heating metals above their melting point is related to melting and casting rather than cold working. Forging at high temperatures refers to hot working, which involves shaping metals while they are above their recrystallization temperature and allows for significant changes in shape without much resistance. Combining different metals at high temperatures is typically associated with processes like welding or alloying, not cold working.