A New Economical Sigma-Free Duplex Stainless Steel 19Cr-6Mn-1. 0Mo-0. 5Ni-0. 5W-0. 5Cu-0. 2N

A new resource-saving duplex stainless steel with composition of 19Cr-6Mn-1. 0Mo-0. 5Ni-0. 5W-0. 5Cu-0. 2N has been developed, and the microstructure, mechanical properties and corrosion properties have been investigated. The results show that the alloy has a balanced ferrite-austenite relation, and the ferrite content rises with the solution treatment temperature. The designed alloy is free of precipitation of sigma phase when aged at 650, 750 and 850 °C for 3 h, respectively, whereas a few Cr23 C6 precipitates are found after being aged at 750 °C for 8 h. Charpy impact tests indicate that the impact energy of the alloy is 68, 200 and 220 J at −40, 0 and 25 °C, respectively. The designed alloy solution treated at 1050 °C for 30 min has a much higher yield strength and similar corrosion resistance compared with those of AISI 304 austenitic stainless steel. Moreover, the production cost of the alloy is about $ 1000 per ton which is lower than that of AISI 304.