Abstract： The material 4140 hanger forgings were subjected to surface magnetic particle inspection after finishing, and the cracks were observed on the end surfaces. In order to find out the causes, the anatomical sampling inspection and analysis were carried out. The results showed that the cracks were formed before quenching or tempering, and belonged to the end cracks caused by the stress of the quenched structure. Most of the cracks were located in the dark segregation bands, indicating that dark segregation band was one of the causes of crack formation. The crack was mainly propagated along the grains, and it was related to the precipitation of trace harmful elements along the grain boundaries in the dark segregation band.
2021, Vol. 39 
