Abstract：The causes of cracking of 40CrNiMo steel shaft was analyzed and discussed based on chemical composition analysis， hardness testing and metallographic structure inspection as well as fracture morphology observation. Moreover， the improvement measures were proposed. The results showed that the serious segregation of banded structure in the center of the steel shaft was the main reason for the cracking. The upper bainite formed in quenched-tempered heat treatment process further reduced the properties of material， which accelerated the formation and propagation of cracks.
2020, Vol. 38 
