Development of an easy-deformable Cr21 lean duplex stainless steel and the effect of heat treatment on its deformation mechanism

A novel lean duplex stainless steel with the composition of Fe-0.11C-21.8Cr-4.52Mn-1.16Ni-0.40Mo-0.16 N has been developed, which can be easily deformed during hot rolling without forming edge cracks. It has been found that the volume fraction of austenite was decreased with the increase of heat treatment temperatures. After having been annealed at 1050 ℃ for 5 min, the cold rolled and annealed band exhibited an excellent combination of strength and ductility, with the ultimate tensile strength and elongation having been measured to be 860 MPa and 63%, respectively. Its yield strength and pitting corrosion potential are higher than those of SUS304 by more than 100% and 60%, respectively. As compared to the conventional LDX 2101, the present steel possesses lower deformation resistance and higher ductility with higher fraction of ferrite during the hot deformation, and exhibits more excellent combination of strength and plasticity with slight decrease in corrosion resistance. The behavior of plastic deformation was studied, in which the effect of transformation induced plasticity (TRIP) had been observed with the orientation relationships between α´-martensite and austenite matrix being close to the K-S and N-W relationships. The stability of austenite for the present steel was found to be increased with increasing annealing temperature, resulting in slower strain induced martensite (SIM) transformation.