Investigation of Causes for Cracking of S32750 Seamless Steel Tube during Cold-rolling Process and Relevant Control Measures

Investigated are the specific causes for cracking of the S32750 seamless steel tube during cold-rolling process by means of relevant process analysis and physiochemical tests. Accordingly，it is concluded that the coldrolling process itself and the inclusions produce no influences on the cracking，whereas the intermetallic phase plays a major role in developing the cracking. The intermetallic phase is formed during the hot-extrusion process，and it is by no means avoided，and can only be eliminated by the subsequent solid solution process. The results from the solid solution tests of different processes demonstrate that the best solid solution temperature for the S32750 seamless steel tube is 1 100 益，and the holding time is （W.T.×2） min. In this case，it is ensured that the precipitated phases are completely dissolved，while the tube can be cold-rolled smoothly，and finally possesses excellent micro structure.