Duplex stainless steel

Patent metadata

Field	Value
Publication number	US-10000832-B2
Application number	US-201214342039-A
Country	US
Kind code	B2
Filing date	Aug 28, 2012
Priority date	Sep 6, 2011
Publication date	Jun 19, 2018
Grant date	Jun 19, 2018

Abstract

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 %).

First claim

The invention claimed is:

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.

Assignees

• Takabe Hideki
• Amaya Hisashi
• Ogawa Kazuhiro
• Nippon Steel & Sumitomo Metal Corp

Inventors

• Takabe Hideki
• Amaya Hisashi
• Ogawa Kazuhiro

Classifications

• C21D2211/004

  Dispersions; Precipitations · CPC title

• C21D6/005

  containing Mn · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• C21D9/08

  for tubular bodies or pipes · CPC title

• C22C38/02

  containing silicon · CPC title