	US 11,834,725 B2
	Martensitic stainless steel material
Daisuke Matsuo, Tokyo (JP); and Yusaku Tomio, Tokyo (JP)
Assigned to NIPPON STEEL CORPORATION, Tokyo (JP)
Appl. No. 16/973,231
Filed by NIPPON STEEL CORPORATION, Tokyo (JP)
PCT Filed Sep. 26, 2019, PCT No. PCT/JP2019/037770 § 371(c)(1), (2) Date Dec. 8, 2020, PCT Pub. No. WO2020/067247, PCT Pub. Date Apr. 2, 2020.
Claims priority of application No. 2018-181109 (JP), filed on Sep. 27, 2018.
Prior Publication US 2021/0238705 A1, Aug. 5, 2021
Int. Cl. C21D 9/46 (2006.01); C21D 1/18 (2006.01); C21D 6/00 (2006.01); C21D 8/00 (2006.01); C22C 38/00 (2006.01); C21D 8/02 (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 38/50 (2006.01); C22C 38/52 (2006.01)

CPC C21D 9/46 (2013.01) [C21D 1/18 (2013.01); C21D 6/004 (2013.01); C21D 6/005 (2013.01); C21D 6/007 (2013.01); C21D 6/008 (2013.01); C21D 8/0205 (2013.01); C21D 8/0226 (2013.01); C21D 8/0263 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (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 38/50 (2013.01); C22C 38/52 (2013.01); C21D 2211/008 (2013.01)]

4 Claims

1. A martensitic stainless steel material, comprising a chemical composition consisting of: in mass %,

C: 0.030% or less,

Si: 1.00% or less,

Mn: 1.00% or less,

P: 0.030% or less,

S: 0.005% or less,

Al: 0.010 to 0.100%,

N: 0.0010 to 0.0100%,

Ni: 5.00 to 6.50%,

Cr: 10.00 to 13.40%,

Cu: 1.80 to 3.50%,

Mo: 1.00 to 4.00%,

V: 0.01 to 1.00%,

Ti: 0.050 to 0.300%,

Co: 0.300% or less,

Ca: 0.0006 to 0.0030%,

O: 0.0050% or less, and

W: 0 to 1.50%, with the balance being Fe and impurities, and satisfying Formulae (1) and (2), wherein

a yield strength is 724 to 861 MPa,

a volume ratio of martensite is 80% or more in the microstructure,

an area of each intermetallic compound and each Cr oxide in the steel material is 5.0 m²or less, and a total area fraction of intermetallic compounds and Cr oxides is 3.0% or less, and

a maximum circle-equivalent diameter of an oxide containing Ca is 9.5 m or less in the steel material:

11.5≤Cr+2Mo+2Cu−1.5Ni≤14.3 (1)

Ti/(C+N)≥6.4 (2)

where, each symbol of element in Formulae (1) and (2) is substituted by the content, in mass %, of the corresponding element.