38CrMoAl钢镗杆断裂原因分析

Analysis on breakage cause of 38CrMoAl steel boring bar

38CrMoAl镗杆在使用过程中突然断裂,从化学成分、显微组织、力学性能和冲击性能对其进行了分析。结果表明,钢的化学成分符合标准,镗杆为脆性断口,组织异常,冲击吸收能量很低,冲击断口也为脆性。断裂主要原因是镗杆有明显的上贝氏体组织,而且晶粒粗大。经分析是因加热温度高,冷却速度慢所致。提出了相应的改进措施。

A 38 CrMoAl steel boring bar was suddenly broken during service. The chemical composition,microstructure,mechanical properties and impact properties of the steel were investigated. The results show that the chemical composition meets the requirements,the fracture surface is brittle failure,microstructure is abnormal,and the impact energy is very low,and the impact fracture is also brittle one,which indicates that the main breaking reason is the upper bainite existing in the boring bar,and coarse grains,results from high austenitizing temperature and low cooling speed during quenching. The countermeasures are given according to this analysis result.