Hot ductility of Cr15Mn7Ni4N austenitic stainless steel slab

Abstract

Hot ductility tests of Cr15Mn7Ni4N austenitic stainless steel slab were performed in a Gleeble-3500 thermomechanical simulator at a strain rate of 1×10−3s−1 and at temperatures ranging from 650°C to 1400°C, which are close to the continuous casting conditions of steel. The fracture morphology of tensile samples was examined using a scanning electron microscope (SEM). The ferrite structure of tensile samples was observed by using an optical microscope (OM). From 750°C to 1300°C, the reduction of area (RA) of tensile samples ranged from 50% to 70%. The hot ductility of Cr15Mn7Ni4N stainless steel is not appreciable with most of the reduction of area lower than 50% in the temperature range of 650–750°C. The volume fraction of ferrite of the tensile sample at 750°C was 5.8%, which was lower than 10 % of the tensile sample at 700°C. The equilibrium phase diagram indicated that ferrite began to form at 708°C and increased with the decrease of temperature. Meanwhile, the reduction of area decreased from 51.56% at 750°C to 39.68% at 700°C, which indicated that the formation of ferrite could lead to the decrease of the hot ductility at the temperature lower than 750°C.