为了评定残余奥氏体对渗碳处理钢疲劳强度的影响,对船舶推进装置齿轮用钢进行了旋转弯曲疲劳试验。在有效渗碳层深度的试样中,发现了残余奥氏体量为某一定最时疲劳强度具有最大值。根据渗碳表面层的残余应力、显微结构和断口表面研究了出现最佳残余奥氏体量的原因。 In order to evaluate the effect of residual austenite on the fatigue strength of carburized steel, the rotating bending fatigue test was carried out on the gear steel of ship propulsion device. In the sample of effective depth of carburized layer, it is found that the residual austenite amount has a maximum value at a certain maximum fatigue strength. The reason for the presence of the optimum amount of retained austenite was investigated based on the residual stresses in the carburized surface layer, the microstructure and the fracture surface.