cold hardening

例句：

1. 1. The steel was cold hardened to increase its strength.
   钢材被冷硬处理以增加其强度。
2. 2. During the manufacturing process, the metal is often cold hardened to improve its durability.
   在制造过程中，金属经常被冷硬处理以提高其耐用性。
3. 3. Cold hardening is a technique used in metallurgy to strengthen materials.
   冷硬是一种在冶金中使用的技术，用于增强材料。