Reasons for cracking of 904L stainless steel pierced billet

Cracking was found on the inner wall of a 904L stainless steel pierced billet after perforation process. The reason for the cracking of the pierced billet was analyzed using methods such as macroscopic observation, chemical composition analysis, mechanical property testing, scanning electron microscopy and energy spectrum analysis, and metallographic examination. The results show that there were loose defects on the inner surface of the pierced billet before perforation. Under the stress of the perforation process, cracks initiated along the loose defects, ultimately led to cracking of the pierced billet.