Transactions of Materials and Heat Treatment

Title：Analysis on bulging fracture defects for medium carbon microalloy non-quenched and tempered steel 36MnVS4 connecting rod

Authors： Huang Boyuan Dong Shuaijun Sun Jianlin Zhang Chaolei

Unit： School of Materials Science and Engineering University of Science and Technology Beijing

KeyWords： non-quenched and tempered steel bulging fracture processing slag dropping irregular fracture thermo mechanical control process

ClassificationCode：TG142.1

year,vol(issue):pagenumber：2023,48(7):228-233

Abstract：

Through analysis of alloy composition, quantitative characterization of microstructure, observation of fracture morphology and measurement of mechanical properties, the slag dropping at fracture and irregular fracture defects of medium carbon microalloy non-quenched and tempered steel 36MnVS4 connecting rod were analyzed. Under VW 50030 and TCCMI 13.1—2021 standards, the results show that the structures of four connecting rods are pearlite+ferrite without abnormal structure, and the grain size is all Grade 5.5-6.0, which does not meet the standard requirements. The tensile strength, yield strength and elongation after fracture of the defective connecting rods meet the standards, but the section shrinkage is 26.5%-27.4%, which is significantly lower than that (32.8%-33.5%) of the qualified connecting rods and does not meet the requirements. The main reason of irregular fracture is the Ca and Si oxide inclusions near the fracture. The position of laser cut groove is found to be deep on the side of fracture, which not only changes the bulging fracture trajectory, but also reduces the section shrinkage. The main reason of slag dropping is that microporous fracture dimples appears near the fracture, which changes the surface state of fracture. Finally, it is proposed that the use of thermo mechanical control process to accurately control the microstructure and properties is the key to solve the problem.

Funds：

作者简介：黄博远（1996-），男，博士研究生 E-mail：597707542@qq.com 通信作者：张朝磊（1984-），男，博士，副教授 E-mail：zhangchaolei@ustb.edu.cn

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