Reason for cracking of 45Mn2 steel circular tube

Cracks were found on the surface of a 45Mn2 steel billet processed into a circular tube. The cause of surface cracking of steel pipes was analyzed using methods such as macroscopic observation, chemical composition analysis, microscopic analysis, and electron probe microanalysis. The results show that the abnormal metal did not fuse with the substrate, and during the grinding treatment of the steel tube, the abnormal metal experienced detachment. The structure and chemical composition of the abnormal metal were different from those of the substrate. Different metals were pressed into the surface of the steel tube, causing cracking on the surface of the steel tube.