Analysis and improvement on cracking cause for automobile rocker shaft

ZHAO Hong-li, WU Mei, ZHANG Hong-xia, WANG Dian, SHEN Pei-zhi, WANG Long, JIANG Sen

Forging & Stamping Technology ›› 2022, Vol. 47 ›› Issue (8) : 15-21.

PDF(2474 KB)
PDF(2474 KB)
Forging & Stamping Technology ›› 2022, Vol. 47 ›› Issue (8) : 15-21. DOI: 10.13330/j.issn.1000-3940.2022.08.003

Analysis and improvement on cracking cause for automobile rocker shaft

  • ZHAO Hong-li1, WU Mei2, ZHANG Hong-xia1, WANG Dian1,3, SHEN Pei-zhi1, WANG Long1, JIANG Sen1
Author information +
History +

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.

Key words

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

Cite this article

EndNote

Ris (Procite)

Bibtex

Download Citations
ZHAO Hong-li, WU Mei, ZHANG Hong-xia, WANG Dian, SHEN Pei-zhi, WANG Long, JIANG Sen. Analysis and improvement on cracking cause for automobile rocker shaft[J]. Forging & Stamping Technology, 2022, 47(8): 15-21 https://doi.org/10.13330/j.issn.1000-3940.2022.08.003

References

[1] GB/T 1979—2001,结构钢低倍组织缺陷评级图[S].GB/T 1979—2001,Standard diagrams for macrostructure and defect of structural steels[S].
[2] GB/T 5216—2014,保证淬透性结构钢[S].GB/T 5216—2014,Structural steels with specified hardenability bands[S].
[3] 谢仲豪,何杨,刘建华,等.大断面连铸圆坯中心裂纹的成因和控制研究[J].炼钢,2021,37(3):51-57.Xie Z H,He Y,Liu J H,et al.Research on causes and coutrol of central cracks in large section continuous castin ground billets [J].Steelmaking,2021,37(3):51-57.
[4] 田亚强,张宏军,宋进英,等.成分及偏析带对65Mn钢热处理后组织性能的影响[J].热加工工艺,2015,44(18):218-220.Tian Y Q,Zhang H J,Song J Y,et al.Effect of composition and segregated band on microstructure and properties of 65Mn steel after heat treatment [J].Hot Working Technology,2015,44(18):218-220.
[5] 黄贞益,陈光,牛亚然,等.连铸坯凝固偏析和高强热轧盘条的组织遗传性[J].钢铁研究学报,2007,19(1):44-47.Huang Z Y,Chen G,Niu Y R,et al.Solidification segregation of continuous cast steel billets and structure heredity of high strength hot rolled rods [J].Journal of Iron and Steel Research,2007,19(1):44-47.
[6] 于志敏.连铸轴承钢中心偏析缺陷探讨[J].哈尔滨轴承,2019,40(4):36-37,42.Yu Z M.Discussion on central segregation defects of continuous casting bearing steel [J].Journal of Harbin Bearing,2019,40(4):36-37,42.
[7] 梁文,刘永前,胡俊,等.影响低碳高强钢中心偏析和带状组织的因素及改进措施[J].上海金属,2019,41(5):66-72,80.Liang W,Liu Y Q,He J,et al.Factors influencing center segregation and banded structure in low-carbon high-strength steel and measures improving them [J].Shanghai Metals,2019,41(5):66-72,80.
[8] 王胜利,汪洪峰.连铸板坯内部裂纹的形成机制及控制实践[J].连铸,2019,44(2):53-57.Wang S L,Wang H F.Formation mechanism of internal cracks in continuous casting slab and the controlling practice [J].Continuous Casting,2019,44(2):53-57.
[9] 谢金鹏,冯冉,杨春,等.阀箱开裂原因分析[J].金属热处理,2017,42(7):176-179.Xie J P,Feng R,Yang C,et al.Failure analysis on cracking of valve housing [J].Heat Treatment of Metals,2017,42(7):176-179.
[10] 胡连新,周健,刘建雄,等.H13钢退火材心部微裂纹缺陷成因分析[J].金属热处理,2018,43(6):232-236.Hu L X,Zhou J,Liu J X,et al.Failure analysis on microcrack in the center of H13 hot working die steel[J].Heat Treatment of Metals,2018,43(6):232-236.
[11] 张振学,李鹏飞,赵志刚,等.GCr15轴承钢大方坯宏观碳偏析的分析[J].热加工工艺,2020,49(7):74-77.Zhang Z X,Li P F,Zhao Z G,et al.Analysis on carbon macro-segregation in large square billets of GCr15 bearing steel [J].Hot Working Technology,2020,49(7):74-77.
[12] 邵龙刚.电磁搅拌器控制系统对大方坯中心偏析的改善[J].世界有色金属,2019,34(23):49-52.Shao L G.Improvement of central segregation of blooms by electromagnetic stirrer control system[J].World Nonferrous Metals,2019,34(23):49-52.
[13] 姬颍伦,左秀荣,洪良,等.连铸坯中心偏析控制技术的新进展[J].热加工工艺,2017,46(7):17-20.Ji Y L,Zuo X R,Hong L,et al.New progress of control technology of center segregation of continuous casting slab[J].Hot Working Technology,2017,46(7):17-20.
[14] 施琦,章小峰,赵丹丹,等.加热工艺对SUP6弹簧钢连铸坯成分偏析影响的研究[J].热加工工艺,2017,46(9):101-104.Shi Q,Zhang X F,Zhao D D,et al.Research on effects of heating process on composition segregation of spring steel SUP6 continuous casting billet[J].Hot Working Technology,2017,46(9):101-104.
PDF(2474 KB)

256

Accesses

0

Citation

Detail
Sections
Recommended
　 Copyright © Forging & Stamping Technology, All Rights Reserved.
Powered by Beijing Magtech Co. Ltd,.

/

〈 〉