	US 12,344,910 B2
	Duplex stainless steel, seamless steel pipe or tube, and a method of manufacturing the duplex stainless steel
Yusuke Yoshimura, Tokyo (JP); Shunsuke Sasaki, Tokyo (JP); and Yuichi Kamo, Tokyo (JP)
Assigned to JFE STEEL CORPORATION, Tokyo (JP)
Appl. No. 17/426,245
Filed by JFE STEEL CORPORATION, Tokyo (JP)
PCT Filed Nov. 14, 2019, PCT No. PCT/JP2019/044765 § 371(c)(1), (2) Date Jul. 28, 2021, PCT Pub. No. WO2020/158111, PCT Pub. Date Aug. 6, 2020.
Claims priority of application No. JP2019-014033 (JP), filed on Jan. 30, 2019.
Prior Publication US 2022/0106659 A1, Apr. 7, 2022
Int. Cl. C21D 9/08 (2006.01); C21D 6/00 (2006.01); C21D 8/10 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/42 (2006.01); C22C 38/44 (2006.01); C22C 38/46 (2006.01); C22C 38/48 (2006.01); C22C 38/50 (2006.01); C22C 38/54 (2006.01)

CPC C21D 9/08 (2013.01) [C21D 6/004 (2013.01); C21D 6/005 (2013.01); C21D 6/008 (2013.01); C21D 8/105 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/005 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/42 (2013.01); C22C 38/44 (2013.01); C22C 38/46 (2013.01); C22C 38/48 (2013.01); C22C 38/50 (2013.01); C22C 38/54 (2013.01)]

7 Claims

1. Duplex stainless steel comprising:

a chemical composition containing, in mass %,

C: 0.03% or less,

Si: 1.0% or less,

Mn: 0.10% to 1.5%,

P: 0.030% or less,

S: 0.005% or less,

Cr: 20.0% to 30.0%,

Ni: 5.0% to 10.0%,

Mo: 2.0% to 5.0%,

Cu: 1.0% or more and less than 2.0%, and

N: less than 0.075%,

with a balance being Fe and inevitable impurities,

a microstructure containing:

an austenite phase in a volume fraction of 30% to 70%; and

a ferrite phase in a volume fraction of 30% to 70%; and

mechanical properties such that a yield strength YS is 862 MPa or more and an absorption energy in a Charpy impact test at −10° C., vE₋₁₀, is 40 J or more.