tempering metals

例句：

1. 1. The steel was tempered to increase its strength and hardness.
   钢材经过回火以提高其强度和硬度。
2. 2.The engineer used a new process to temper the metals.
   工程师采用了一种新的工艺来对金属进行回火处理。
3. 3.The chef carefully tempered the steak before serving it to the guests.
   厨师在将牛排端给客人之前，仔细地对其进行了回火处理。