起重机减速机齿轮轴断裂原因分析及改进措施

Cause analysis and improvements on gear shaft fracture of crane main hoist reducer

起重机主起升减速机在工作时由于高速齿轮轴突然断裂,致使起重机主钩发生溜钩事故。通过对高速齿轮轴材质、力学性能、断口微观电镜以及制造、安装精度检查、分析,发现齿轮轴力学性能检验不合格,热处理未达到锻件调制处理技术要求,金相组织从表面至心部均以极少量回火索氏体+大量针状铁素体(呈魏氏组织形态分布)和珠光体存在,降低了齿轮轴的抗疲劳强度和抗冲击能力。轴肩位置的应力集中,成为齿轮轴受扭转作用时的薄弱位置。同时安装同轴度误差超标,使齿轮轴工作时承受较大的旋转弯曲应力。本文提出齿轮轴采用840℃淬油,再480°回火处理,硬度可达HRC35~45,获得良好的综合机械性能,对轴身、轴肩等关键位置进行优化,提高加工和安装精度,减少应力集中,减少齿轮轴在工作中承受的旋转弯矩载荷,能有效解决齿轮轴的断裂问题。

Due to the high speed gear shaftof the main hoist reducer suddenly broke, themain hook occurs unhook accidentwhen the crane is working. Throughinspection and analysis of high-speed gear shaft material, mechanical properties, fracture micro-morphologyelectron microscopy, manufacturing and installation precision, it is found that the materialofthe gear shaftmechanical properties are not qualified, and the heat treatment failed to meet the technical requirements forforgings thermal refining.The microstructure, from the surface to the core, are very littletempering sorbite + a large number ofacicular ferrite(distributed widmanstatten structure form) and pearlite, which reduces the fatigue strength and impact resistance of gear shaft. The stress concentrationinshaft shoulderbecomes the weak position of gear shaft undertorsion. At the same time, the coaxiality error out of limitmake the gear shaftbear large rotating bending stress.This paper advances some methods of good comprehensive mechanical properties of gear shaft, it is quenched at 840 ℃ and tempered at 480 ℃. Meawhile, it put forward some suggestions, such asoptimizing key positions( shaft and shoulder), improving machining and installation accuracy, reducing local stress concentration and rotating moment load, can effectively solve thegear shaft fractureproblem..