temper-hardening

例句：

1. 1. The steel is tempered to improve its strength and toughness.
   这种钢经过回火处理，以增强其强度和韧性。
2. 2. Quenching the metal in water helps to temper it and prevent cracking.
   将金属在水里淬火有助于回火，防止开裂。
3. 3.Tempering is a process that involves heating and cooling the metal to achieve a hardened state.
   回火是一种过程，涉及加热和冷却金属以达到硬化状态。