Reason for shear cracking of 40Cr steel bars

A certain company produced 40Cr steel bars that cracked during the cold shear cutting process. The cause of cracking in the bar was analyzed using methods such as macroscopic observation, chemical composition analysis, scanning electron microscopy analysis and metallographic examination. The results show that there was a localized work hardening layer on the surface of the bar, which led to shear cracking of the bar. The reason for the formation of work hardening layer was improper straightening and grinding wheel peeling process during the finishing process of the bar.