热处理是为了赋与材料强度、耐磨性、耐热性、抗蚀性等而施行的工艺过程。从汽车工业开始,一般机器工业结构上的重要部份,都要用经过热处理的材料。而且,热处理的优劣,是对产品性能产生直接影响的重要的加工。尤其是近来有这样的倾向:由热处理弥补其强度而使材料低级化、轻量化,事先根据需 Heat treatment is a process that is performed to impart material strength, wear resistance, heat resistance, corrosion resistance, and the like. Starting from the automotive industry, heat-treated materials are used in the most important parts of the general machine industry. Moreover, the quality of heat treatment is an important process that has a direct impact on product performance. In particular, recently, there is a tendency that the strength is reduced by the heat treatment to make the material lower in weight and lighter in weight.