Transactions of Materials and Heat Treatment

Title：Analysis and improvement on cracking cause for automobile rocker shaft

Authors： Zhao Hongli Wu Mei Zhang Hongxia Wang Dian Shen Peizhi Wang Long Jiang Sen

Unit： Hubei University of Automotive Technology Dongfeng Forging Co. Ltd. Wuhan University of Science & Technology

KeyWords： rocker shaft continuous casting center segregation central crack hot forging tensile stress

ClassificationCode：TG142.1

year,vol(issue):pagenumber：2022,47(8):15-21

Abstract：

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.

Funds：

湖北省十堰市科技项目（21Y111）；湖北汽车工业学院国家级大学生创新创业训练项目（DC2021044）；湖北汽车工业学院国家级汽车产业实验实训教学中心项目（2021025）；湖北省教育厅科技项目（B2013081）

作者简介：赵红利（1972-)，女，硕士，正高级实验师，E-mail：475383962@qq.com；通信作者：沈培智（1971-），男，博士，副教授，E-mail： 382744969 @qq.com

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