Lean duplex stainless steel excellent in corrosion resistance and toughness of weld heat affected zone

摘要

The present invention provides a lean duplex stainless steel able to suppress the drop in corrosion resistance and toughness of a weld heat affected zone comprising, by mass %, C: 0.06% or less, Si: 0.1 to 1.5%, Mn: 2.0 to 4.0%, P: 0.05% or less, S: 0.005% or less, Cr: 19.0 to 23.0%, Ni: 1.0 to 4.0%, Mo: 1.0% or less, Cu: 0.1 to 3.0%, V: 0.05 to 0.5%, Al: 0.003 to 0.050%, O: 0.007% or less, N: 0.10 to 0.25%, and Ti: 0.05% or less, having a balance of Fe and unavoidable impurities. An Md30 value is 80 or less, an Ni-bal is −7.1 to 4, an austenite phase area percentage is 40 to 70%, and a 2×Ni+Cu is 3.5 or more: Md30=551−462×(C+N)−9.2×Si−8.1×Mn−29×(Ni+Cu)−13.7×Cr−18.5×Mo−68×Nb; Ni-bal=(Ni+0.5Mn+0.5Cu+30C+30N)−1.1(Cr+1.5Si+Mo+W)+8.2 and N(%)≦0.37+0.03×(Ni-bal).