Duplex stainless steel
View Patent ↗Provided is duplex stainless steel having high strength, SCC resistance and SSC resistance excellent in a high-temperature chloride environment, and capable of suppressing precipitation of a σ phase. The duplex stainless steel of the present embodiment includes, in mass %, of: C: at most 0.03%; Si: 0.2 to 1%; Mn: more than 5.0% to at most 10%; P: at most 0.040%; S: at most 0.010%; Ni: 4.5 to 8%; sol. Al: at most 0.040%; N: more than 0.2% to at most 0.4%; Cr: 24 to 29%; Mo: 0.5 to less than 1.5%; Cu: 1.5 to 3.5%; W: 0.05 to 0.2%; the balance being Fe and impurities, wherein the duplex stainless steel satisfies Formula (1): Cr+8Ni+Cu+Mo+W/2≥65 . . . (1), where a symbol of each element in Formula (1) represents a content of the element (in mass %).
1. Duplex stainless steel consisting of, in mass %,
C: at most 0.03%;
Si: 0.2 to 1%;
Mn: 6.1 to 10%;
P: at most 0.040%;
S: at most 0.010%;
Ni: 4.5 to 8%;
sol. Al: at most 0.040%;
N: more than 0.2% to at most 0.4%;
Cr: 26.85 to 29%;
Mo: 0.5 to less than 1.5%;
Cu: 1.5 to 3.5%;
W: 0.05 to 0.2%;
the balance being Fe and impurities,
wherein
the duplex stainless steel has a yield strength of at least 550 MPa, and
the duplex stainless steel satisfies Formula (1):
Cr+8Ni+Cu+Mo+W/2≥65 (1),
where a symbol of each element in Formula (1) represents a content of the element (in mass %).
2. Duplex stainless steel consisting of, in mass %,
C: at most 0.03%;
Si: 0.2 to 1%;
Mn: 6.1 to 10%;
P: at most 0.040%;
S: at most 0.010%;
Ni: 4.5 to 8%;
sol. Al: at most 0.040%;
N: more than 0.2% to at most 0.4%;
Cr: 26.85 to 29%;
Mo: 0.5 to less than 1.5%;
Cu: 1.5 to 3.5%;
W: 0.05 to 0.2%;
V: at most 1.5%;
the balance being Fe and impurities,
wherein
the duplex stainless steel has a yield strength of at least 550 MPa, and
the duplex stainless steel satisfies Formula (1):
Cr+8Ni+Cu+Mo+W/2≥65 (1),
where a symbol of each element in Formula (1) represents a content of the element (in mass %).
3. Duplex stainless steel consisting of, in mass %,
C: at most 0.03%;
Si: 0.2 to 1%;
Mn: 6.1 to 10%;
P: at most 0.040%;
S: at most 0.010%;
Ni: 4.5 to 8%;
sol. Al: at most 0.040%;
N: more than 0.2% to at most 0.4%;
Cr: 26.85 to 29%;
Mo: 0.5 to less than 1.5%;
Cu: 1.5 to 3.5%;
W: 0.05 to 0.2%;
one or more types selected from a group of Ca: at most 0.02%, Mg: at most 0.02%, and B: at most 0.02% instead of part of Fe;
the balance being Fe and impurities,
wherein
the duplex stainless steel has a yield strength of at least 550 MPa, and
the duplex stainless steel satisfies Formula (1):
Cr+8Ni+Cu+Mo+W/2≥65 (1),
where a symbol of each element in Formula (1) represents a content of the element (in mass %).
4. Duplex stainless steel consisting of, in mass %,
C: at most 0.03%;
Si: 0.2 to 1%;
Mn: 6.1 to 10%;
P: at most 0.040%;
S: at most 0.010%;
Ni: 4.5 to 8%;
sol. Al: at most 0.040%;
N: more than 0.2% to at most 0.4%;
Cr: 26.85 to 29%;
Mo: 0.5 to less than 1.5%;
Cu: 1.5 to 3.5%;
W: 0.05 to 0.2%;
V: at most 1.5%;
one or more types selected from a group of Ca: at most 0.02%, Mg: at most 0.02%, and B: at most 0.02% instead of part of Fe;
the balance being Fe and impurities,
wherein
the duplex stainless steel has a yield strength of at least 550 MPa, and
the duplex stainless steel satisfies Formula (1):
Cr+8Ni+Cu+Mo+W/2≥65 (1),
where a symbol of each element in Formula (1) represents a content of the element (in mass %).
5. The duplex stainless steel according to claim 1 , wherein the Ni content is 4.5 to 6.5 mass %.
6. The duplex stainless steel according to claim 1 , wherein the N content is more than 0.2 mass % to at most 0.35 mass %.
7. The duplex stainless steel according to claim 1 , wherein the duplex stainless steel is a steel pipe.
8. The duplex stainless steel according to claim 2 , wherein the duplex stainless steel is a steel pipe.
9. The duplex stainless steel according to claim 3 , wherein the duplex stainless steel is a steel pipe.
10. The duplex stainless steel according to claim 4 , wherein the duplex stainless steel is a steel pipe.
11. The duplex stainless steel according to claim 1 , wherein the duplex stainless steel is a line pipe.
12. The duplex stainless steel according to claim 2 , wherein the duplex stainless steel is a line pipe.
13. The duplex stainless steel according to claim 3 , wherein the duplex stainless steel is a line pipe.
14. The duplex stainless steel according to claim 4 , wherein the duplex stainless steel is a line pipe.