tempering curve

例句：

1. 1. The steel was tempered to increase its strength and toughness.
   钢材经过回火以提高其强度和韧性。
2. 2.The engineer used a tempering curve to determine the optimal temperature for tempering.
   工程师使用回火曲线来确定最佳回火温度。
3. 3.During the manufacturing process, the metal is subjected to a tempering curve to achieve the desired properties.
   在制造过程中，金属受到回火曲线的作用以获得所需性质。