汽车摇臂轴开裂原因分析与改进

Analysis and improvement on cracking cause for automobile rocker shaft

针对汽车转向器摇臂轴在机加工过程中发现的螺纹孔端部出现批量裂纹的现象,通过宏观形貌分析、裂纹部位扫描电镜及能谱分析、金相显微组织分析等方法对裂纹的形成原因进行了深入检测和分析。结果表明,裂纹均存在于一个较规整的四边形区域内,裂纹产生的原因在于摇臂轴毛坯存在中心偏析,裂纹萌生于心部偏析严重处,在后续热锻三向不等拉应力作用下,进一步沿偏析走向扩展,形成宏观裂纹。并针对裂纹的产生原因提出了改进措施,经现场生产验证,棒料中心偏析不明显、金相组织均匀、硬度差别较小,后续机加工端面螺纹孔时,未发现开裂情况,改进效果良好。

For the occurrence of batch cracks at the end of threaded hole in the machining process of rocker shaft for automobile steering gear,the causes of crack formation were detected and analyzed deeply by means of macro morphology analysis,scanning electron microscope and energy spectrum analysis of crack positions and metallographic microstructure analysis.The results show that the cracks all exist in a relatively regular quadrilateral area.The crack is caused by the existence of center segregation in the rocker shaft blank,and the crack is initiated at the center where the segregation is serious.Under the action of three-dimensional unequal tensile stress in the subsequent hot forging,the crack further expands along the segregation direction to form macroscopic cracks.According to the causes of cracks,the improvement measures are put forward.The on-site production verification shows that the central segregation of bar is not obvious,the metallographic structure is uniform,and the hardness difference is small.In addition,when the end threaded holes are machined subsequently,no cracks are found,and the improvement effect is good.