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某M131W万能外圆磨床,使用约半年后,一次在开车2小时左右时突然发生闷车。当即停车,加4～5公斤的5号机械油入磨头油槽,再次开车亦未能启动。经拆机检查,发现砂轮主轴已损坏,见图1。由图1可见,主轴及轴瓦表面有明显回火色、裂纹及脱落层,轴瓦上有脱落物嵌入痕迹。显微镜下观察,主轴未烧蚀区组织为回火细马氏体和碳化物(见图2)。经硬度测定HRC62～64;烧蚀区组织为回火细马氏体、屈氏体和碳化物(见图3),HRC48～58;主轴心部为索氏体,HRC34。经化学成分分析:C 1.00%;Cr 1.48%,符合Cr2钢成分。对主轴进行磁力探伤,未发现微裂纹及原材料缺陷。
A M131W Universal Cylindrical Grinder, the use of about six months, once in about 2 hours driving suddenly stuffy car. Immediately stop, plus 5 to 5 kg of mechanical oil into the grinding tank, drive again failed to start. After teardown inspection, found that the wheel spindle has been damaged, shown in Figure 1. Can be seen from Figure 1, the surface of the spindle and bearing significantly temper color, cracks and shedding layer, there are embedded traces on the bearing. Microscopically, the ablated areas of the spindle were tempered by fine martensite and carbides (see Figure 2). The hardness of HRC62 ~ 64 was determined. The ablated area was tempered martensite, troostite and carbide (see Fig. 3), and HRC48 ~ 58. Sorbite and HRC34 were the main part of the spindle. The chemical composition analysis: C 1.00%; Cr 1.48%, in line with Cr2 steel composition. Magnetic testing of the spindle, found no microcracks and raw material defects.