Dr. Yinhui Yang, Associate Professor, School of materials science and engineering, Kunming University of Science and Technology, China

Title: Investigation on the compression dynamic recrystallization softening behavior of 23Cr economical duplex stainless steel with Mn addition

Abstract: Duplex stainless steels (DSS) having the properties of austenitic (γ) and ferritic (δ) stainless steels, which exhibit excellent combination of high mechanical property and resistance to corrosion in presence of chloride-containing environments. The DSS are extensively used in oil, papermaking, petrochemical and shipbuilding industries as one kind of important structural material. The growing price of Ni has made high-Ni-containing DSS cost prohibitive for many industrial applications, the substitution of cheap Mn for Ni can stabilize the austenite phase and increase the solubility of nitrogen in DSS. The rolling step is important in producing high performance dual phase steel plate and sheet. However, the hot working of dual phase presents more complicated deformation behavior than single phase steels, which is associated with their different crystal structures and stacking fault energy (SFE) values. The chemical composition and temperature are the main factors that control SFE, and the additions of Mn can change the austenite stability and deformation properties due to its different austenite stabilized ability compared with Ni. Dynamic recrystallization (DRX) is a common microstructural phenomenon during actual hot working processes of stainless steel. It is helpful to accurately design an industrial process by determining critical strain and completing DRX. In order to better control microstructure and properties of Mn substitution for Ni DSS after compression deformation, to understand the effects of Mn addition on the initiation of DRX, type of DRX flow curves, DRX microstructure, DRX of kinetics are essential in production. In this study, the DRX softening difference in different Mn content addition low nickel type DSS were investigated by isothermal hot compression tests with 50% reduction, which were conducted within the temperature of 850-1150℃ and the strain rate of 0.01-10s-1. Moreover, processing map has been adopted to understand the high-temperature deformation mechanisms with different Mn addition.

Keywords: duplex stainless steel; isothermal compression; Mn addition; dynamic recrystallization; processing map.