DUPLEX STAINLESS STEEL, AND ITS MANUFACTURING METHOD

摘要

PCT No. PCT/KR96/00084 Sec. 371 Date Feb. 4, 1997 Sec. 102(e) Date Feb. 4, 1997 PCT Filed Jun. 5, 1996 PCT Pub. No. WO96/39543 PCT Pub. Date Dec. 12, 1996A duplex stainless steel consisting of a ferrite phase and an austenite phase is disclosed which is superior in the hot ductility, the high temperature oxidation resistance, the corrosion resistance and the impact toughness. The duplex stainless steel is applied to marine facility and the like. The duplex stainless steel which consists of a ferrite phase and an austenite phase is composed of in weight %: less than 0.03% of C, less than 1.0% of Si, less than 2.0% of Mn, less than 0.04% of P, less than 0.004% of S, less than 2.0% of Cu, 5.0-8.0% of Ni, 22-27% of Cr, 1.0-2.0% of Mo, 2.0-5.0% of W, and 0.13-0.30% of N. Or there are further added one or two elements selected from a group consisting of: less than 0.03% of Ca, less than 0.1% of Ce, less than 0.005% of B and 0.5% of Ti. Further, the ratio (Creq/Nieq) of the Cr equivalent (Creq) to the Ni equivalent (Nieq) is 2.2-3.0. Further, the weight ratio (W/Mo) of the W to Mo is 2.6-3.4. That is, the duplex stainless steel of the present invention satisfies the above condition, and the Nieq and Creq are defined as follows: Nieq=%Ni+30x%C+0.5x%Mn+0.33x%Cu+30x(%N-0.045), Creq=%Cr+Mo+1.5x%Si+0.73x%W.