DUPLEX STAINLESS STEEL
A duplex stainless steel excellent in the weldability during large heat input welding and in the stress corrosion cracking resistance in a chloride environment containing corrosive associated gases has a chemical composition consisting, by mass %, of C: 0.03% or less, Si: 0.2 to 1%, Mn: 5.0% or less, P: 0.040% or less, S: 0.010% or less, sol. Al: 0.040% or less, Ni: 4 to 8%, Cr: 20 to 28%, Mo: 0.5 to 2.0%, Cu: more than 2.0% and 4.0% or less and N: 0.1 to 0.35%, and optionally contains one or more selected from among V, Ca, Mg, B and a rare earth metal(s), with the balance being Fe and impurities; wherein the duplex stainless steel satisfies the following formulas: 2.2Cr+7Mo+3Cu>66 (1) Cr+11Mo+10Ni<12(Cu+30N) (2), wherein the symbols represent mass % of the elements in the steel.
1 . A duplex stainless steel that has a chemical composition consisting, by mass %, of C: 0.03% or less, Si: 0.2 to 1%, Mn: 5.0% or less, P: 0.040% or less, S:
0 . 010% or less, sol. Al: 0.040% or less, Ni: 4 to 8%, Cr: 20 to 28%, Mo: 0.5 to 2.0%, Cu: more than 2.0% and 4.0% or less and N: 0.1 to 0.35%, with the balance being Fe and impurities; wherein the duplex stainless steel satisfies the relations of the following formulas (1) and (2):
2Cr+7Mo+3Cu>66 (1)
Cr+11 Mo+10Ni<12(Cu+30N) (2)
wherein the symbols of elements in formulas (1) and (2) respectively represent the contents (unit: mass %) of the elements in the steel.
2 . The duplex stainless steel according to claim 1 , which further contains, by mass %, V: 1.5% or less, in place of part of Fe.
3 . The duplex stainless steel according to claim 1 , which further contains, by mass %, one or more selected from among Ca: 0.02% or less, Mg: 0.02% or less and B: 0.02% or less, in place of part of Fe.
4 . The duplex stainless steel according to claim 1 , which further contains, by mass %, rare earth metal(s): 0.2% or less, in place of part of Fe.