回火是在冶金学当中，一种改善金属材料性质的热处理技术。

回火是将淬火钢加热到奥氏体转变温度以下的适当温度，保持高温加热1到2小时后冷却。经过回火，钢的结构趋于稳定，其脆性降低，韧性与塑性提高。回火往往与淬火相伴，并且是热处理的最后一道工序，能消除或者减少淬火应力，稳定钢的形状与大小，防止淬火零件变形和开裂。高温回火还可以改善切削加工性能。

依据加热的温度不同，回火分为：

Tempering is a process of heat treating, which is used to increase the toughness of iron-based alloys. Tempering is usually performed after hardening, to reduce some of the excess hardness, and is done by heating the metal to some temperature below the critical point for a certain period of time, then allowing it to cool in still air. The exact temperature determines the amount of hardness removed, and depends on both the specific composition of the alloy and on the desired properties in the finished product. For instance, very hard tools are often tempered at low temperatures, while springs are tempered to much higher temperatures.