曲轴用非调质钢38MnVS失效分析

Failure Analysis of 38MnVS Non-quenched Non-tempered Steel for Crankshaft

曲轴用非调质钢38MnVS在大样疲劳试验时发生断裂,对断裂部位进行显微组织分析、扫描分析、淬硬层分析等,结果表明:失效部位为疲劳失效,曲轴淬硬层组织为马氏体组织,淬硬层无明显异常硬度点,淬硬层深约为5.5 mm,曲轴拐角处和打字号处应力集中明显造成裂纹的萌生,油管处存在粗大晶粒,与基体组织连续性差,在弯矩和扭矩的共同作用下应力集中而造成裂纹源的萌生。

The 38MnVS non-quenched and tempered steel for crankshaft was fractured during a fatigue test of large sample.Microstructure analysis,scanning analysis and hard⁃ened layer analysis were carried out on the fracture part.The results show that it was a fa⁃tigue failure,the hardened layer structure of crankshaft was martensite,there was no obvi⁃ous abnormal hardness point in the hardened layer,and the depth of hardened layer was about 5.5mm.The stress concentration at the corner and type number of crankshaft obvious⁃ly caused the crack initiation,and there were coarse grains at the oil pipe,which have poor continuity with the matrix structure.Under the combined action of bending moment and torque,the stress concentration caused the crack initiation.