Influence of hot rolling and post-tempering on the mechanical properties of duplex stainless steel containing martensite and ferrite

Abstract

In this research, SUS 403 duplex stainless steel containing martensite and ferrite was processed with hot rolling at a range of reductions (15-50%) and post-tempering at a range of temperatures (473-873 K) to investigate microstructural change during tempering and mechanical properties as a function of tempering temperature and ferrite grain size. The results indicate that Cr-rich carbides precipitate when tempering at the range of 473-773 K. The precipitation of fine carbides increases the carbide-ferrite phase boundary area. Again, the hard carbides reinforce the ferrite matrix along the boundaries and, consequently, results in enhancing mechanical properties. A secondary strengthening phenomenon in stress and hardness occurs at 773 K tempered. The ferrite grain size decreases with increasing reduction. Fine grain structure leads to an increase in grain boundaries and homogeneous dispersion of carbides, which provides a dominant action against crack propagation and improves the mechanical properties. Except the hardness, the maximum mechanical properties of each rolling reduction are better than that of the specimens quenched and tempered without hot rolling. © 2006 The Japan Institute of Metals.