Abstract: The flexible bearing steel with long fatigue life using for robot harmonic speed reducer has been successfully de⁃ veloped by applying EAF process technology. The ratio of scrap to hot metal was controlled more than 80%. This paper compared the metallurgical quality of flexible bearings and traditional rolling bearings in terms of non-metallic inclusions， austenite grain size and carbide banding structure， the fatigue strength of steel used for flexible bearing and traditional roll⁃ ing bearing under 107  cycles was tested by the method of rotary bending fatigue test. The O content of steel used for flexible bearings of robot harmonic reducer was less than 0. 000 4%， the Ti content was much less than 0. 001%， non-metal inclu⁃ sions of class A sulfide≤1. 0 grade， non-metal inclusions of class B and D oxide ≤0. 5 grade. The size of the maximum spherical inclusion was less than 30 μm. The test results show that the flexible bearings have ultra-high purity. By increas⁃ ing Al and N chemical composition in the smelting process， the austenite grain size was 10 grade in the flexible bearing steel， much higher than 8. 5 grade in the traditional rolling bearing steel. The proportion of carbide banding structure of 7. 1 and 7. 2 grade was higher than that of traditional bearing steel in the means of extending the high temperature diffusion time. The ultra-high austenite grain size and the decrease of the width of carbide banding structure showed that the flexible bearing steel had an ultra-high structure uniformity. In addition， the rotary bending fatigue strength of the flexible bearing steels was 1 016 MPa， its fatigue life was slightly higher than that of the traditional rolling bearing steels.

Key words: Harmonic Speed Reducer, Flexible Bearing Steel, Grain Size, Non-metallic Inclusions, Rotary Bending Fa tigue, Ultra-high Cycle Fatigue

摘要： 采用电弧炉生产工艺，控制废钢/铁水比为80%以上，开发出长寿命机器人谐波减速机柔性轴承用钢，从非 金属夹杂物、奥氏体晶粒度、碳化物带状组织方面对比柔性轴承用和传统滚动轴承用钢的冶金质量，并利用旋转弯 曲疲劳试验的方法测试柔性轴承用和传统滚动轴承用钢在107 循环周次条件下的疲劳强度。机器人谐波减速机柔 性轴承用钢的w［O］＜0. 000 4%，w［Ti］＜0. 001%，A类硫化物类非金属夹杂物≤1. 0级，B类和D类氧化物类非金属 夹杂物≤0. 5级，极值统计法预测最大球状夹杂物的尺寸＜30 μm，检验结果表明柔性轴承具备超高纯净度。通过在 冶炼过程增加Al和N的元素含量，柔性轴承用钢具有10级的奥氏体晶粒度，远高于传统滚动轴承用钢的8. 5级晶 粒度。通过延长高温扩散时间，7. 1和7. 2级别的碳化物带状组织占比要高于传统滚动轴承用钢，超高晶粒度和碳 化物带状组织的带宽减小表明柔性轴承具备超高组织均匀性。柔性轴承用钢在107 循环周次条件下具有超高旋转 弯曲疲劳强度为1 016 MPa，疲劳寿命略高于传统滚动轴承用钢。

关键词: 谐波减速机, 柔性轴承, 晶粒度, 非金属夹杂物, 旋转弯曲疲劳, 超高周疲劳性能