Investigation of the Crack Initiation and Propagation in Super Duplex Stainless Steel During Hot Working

A better understanding of crack initiation and propagation in duplex stainless steel (DSS) during hot working process is significant for improving production efficiency, due to the frequent occurrence of cracking during deformation process of duplex stainless steels. In this work, the cracking mechanism of S32750 super duplex stainless steel (SDSS) during hot rolling was researched in detail. The results showed that uneven deformation can easily cause the crack initiation and propagation. The hard and brittle sigma phases with high Cr and Mo, which were observed near the cracks, seriously damaged the hot working properties of SDSS. During hot deformation, nitride, as another high temperature phases, precipitated along grain boundaries to prevent grain boundary migration, and further to reduce the hot ductility of steel. Inclusions can also cause crack initiation and propagation, especially Al2O3. In addition, the surface microcracks resulting from oxide layer rolled into the matrix.