Causes of surface cracking of 35MnBH steel chain rail joint

The surface of 35MnBH round steel cracked after forging and heat treatment. The causes of surface cracking were analyzed by means of macroscopic observation, chemical composition analysis, metallographic examination and hardenability test. The results show that the surface crack of the chain rail joint was a quenching crack, and the improper heating process was the main reason for the quenching crack.