22Cr High-Mn-N Low-Ni Economical Duplex Stainless Steels

A new family of economical duplex stainless steels in which N or Mn was substituted for Ni with composition of 22Cr-8.0Mn-xNi-1.0Mo-0.7Cu-0.7W-0.3N (x = 0.5 – 2.0) have been developed by examining the micro-structure, mechanical and corrosion properties of these alloys. The results show that these alloys have a balanced ferrite-austenite relation. In addition, the alloys are free of precipitation of sigma phase and Cr-nitride when solution-treated at 750 to 1300°C for 30 min. The yield strength, tensile strength and fracture elongation values of experimental alloys solution-treated at 1050°C for 30 min are about 500, 750 MPa and 40.0%, respectively. Low-temperature impact properties can be improved distinctly with the increase of nickel content. Among the designed DSS alloys, the alloy with Ni of 2.0% is found to be an optimum alloy with proper phase proportion, better low-temperature impact properties and higher pitting corrosion resistance compared with those of other alloys. The mechanical and corrosion properties and lower production cost of the designed DSSs are better than those of AISI 304.