通过断口宏微观分析、金相检验、化学成分分析以及硬度测试等方法对某9Cr18MoV钢丝杠耳轴在联合试验过程中早期断裂原因进行了分析。结果表明: 该丝杠耳轴断裂主要是因为其原材料碳含量高于标准要求, 使其显微组织中存在大量的网状共晶碳化物, 大大降低了钢的强度和塑性; 另丝杠耳轴R角处的过渡圆弧半径小于设计图纸技术要求, 使该处产生应力集中, 造成丝杠耳轴在试验过程中的双向弯曲应力作用下过早断裂失效。

By means of fracture macro and micro analysis, metallographic examination, chemical compositions analysis and hardness testing, the early fracture failure reasons of 9Cr18MoV steel screw trunnion during combined testing were analyzed. The results show that the screw trunnion fracture was mainly because that the carbon content of raw material was beyond standard requirement, which made the microstructure have a large number of network eutectic carbide and greatly reduced the strength and plastic of the steel. At the same time, the transition arc radius of the screw trunnion was less than technical requirement of the design drawings, which resulted in stress concentration. So, under the action of biaxiality bending stress during the test, the screw trunnion fractured early.