US 12,264,376 B2
Duplex stainless steel and method for manufacturing same, and duplex stainless steel pipe
Kazuki Fujimura, Tokyo (JP); Kenichiro Eguchi, Tokyo (JP); Yusuke Yoshimura, Tokyo (JP); and Masao Yuga, Tokyo (JP)
Assigned to JFE Steel Corporation, Tokyo (JP)
Appl. No. 17/613,316
Filed by JFE Steel Corporation, Tokyo (JP)
PCT Filed Apr. 9, 2020, PCT No. PCT/JP2020/015983
§ 371(c)(1), (2) Date Nov. 22, 2021,
PCT Pub. No. WO2020/241084, PCT Pub. Date Dec. 3, 2020.
Claims priority of application No. 2019-099955 (JP), filed on May 29, 2019.
Prior Publication US 2022/0228231 A1, Jul. 21, 2022
Int. Cl. C21D 9/08 (2006.01); C21D 6/00 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (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 38/52 (2006.01); C22C 38/54 (2006.01); C22C 38/58 (2006.01)
CPC C21D 9/08 (2013.01) [C21D 6/004 (2013.01); C21D 6/005 (2013.01); C21D 6/007 (2013.01); C21D 6/008 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/005 (2013.01); C22C 38/008 (2013.01); C22C 38/02 (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 38/52 (2013.01); C22C 38/54 (2013.01); C22C 38/58 (2013.01); C21D 2211/001 (2013.01); C21D 2211/005 (2013.01)] 6 Claims
 
1. A duplex stainless steel having a composition comprising, in mass %,
C: 0.03% or less,
Si: 1.0% or less,
Mn: 0.10 to 1.5%,
P: 0.040% or less,
S: 0.01% or less,
Cr: 20.0 to 28.0%,
Ni: 2.0 to 10.0%,
Mo: 2.0 to 5.0%,
Cu: 2.0 to 6.0%,
Al: 0.001 to 0.05%, and
N: less than 0.070%,
and in which the balance is Fe and incidental impurities,
the duplex stainless steel having a microstructure containing an austenitic phase and a ferrite phase, and satisfying the following contents for C, Si, Mn, Cr, Mo, Ni, N, Cu, and W in the formula (1) below,
the duplex stainless steel having a yield strength YS of 655 MPa or more, and an absorption energy vE−10 of 40 J or more as measured by a Charpy impact test at a test temperature of −10° C.,
0.55[% C]−0.056[% Si]+0.018[% Mn]−0.020[% Cr]−0.087[% Mo]+0.16[% Ni]+0.28[% N]−0.506[% Cu]−0.035[% W]+[% Cu*F]≤0.94  (1),
wherein [% symbol of elements] represents the content (mass %) of the element in the steel, [% symbol of elements *F] represents the content (mass %) of the element in the ferrite phase, and the contents are zero for elements that are not contained.