Ferritic stainless steel and component for exhaust gas

Patent metadata

Field	Value
Publication number	US-2023383390-A1
Application number	US-202118032771-A
Country	US
Kind code	A1
Filing date	Oct 22, 2021
Priority date	Oct 23, 2020
Publication date	Nov 30, 2023
Grant date	—

Abstract

This ferritic stainless steel has a predetermined chemical composition, at least one type of oxides of oxides containing 5 mass % or more of Al and oxides containing 5 mass % or more of Si are present on the surface, and, among the oxides present on the surface, the number of oxides having a diameter D of 0.1 μm or more and 2.0 μm or less is 10 or more per 93 μm 2 , the diameter D being represented by D=(Dmax+Dmin)/2 where Dmax is the maximum diameter of the oxide on the surface and Dmin is the minimum diameter of the oxide on the surface.

First claim

1 . A ferritic stainless steel comprising, as a chemical composition:
0.05 mass % or more and 2.50 mass % or less of Si; 0.05 mass % or more and 1.50 mass % or less of Mn; 0.025 mass % or less of C; 0.040 mass % or less of P; 0.003 mass % or less of S; 0.025 mass % or less of N; 0.01 mass % or more and 0.50 mass % or less of Ni; 10.50 mass % or more and 25.00 mass % or less of Cr; 0.01 mass % or more and 1.80 mass % or less of Cu; 0.002 mass % or more and 0.200 mass % or less of Al; 0.001 mass % or more and 1.00 mass % or less of Nb; 0 mass % or more and 2.5 mass % or less of W; 0 mass % or more and 3.00 mass % or less of Mo; 0 mass % or more and 0.500 mass % or less of Ti; 0 mass % or more and 0.0100 mass % or less of B; 0 mass % or more and 0.0030 mass % or less of Ca; 0 mass % or more and 0.50 mass % or less of Hf; 0 mass % or more and 0.40 mass % or less of Zr; 0 mass % or more and 0.50 mass % or less of Sb; 0 mass % or more and 0.30 mass % or less of Co; 0 mass % or more and 1.0 mass % or less of Ta; 0 mass % or more and 1.00 mass % or less of Sn; 0 mass % or more and 0.30 mass % or less of Ga; 0 mass % or more and 0.50 mass % or less of V; 0 mass % or more and 0.003 mass % or less of Mg; 0 mass % or more and 0.20 mass % or less of REM; and a remainder including Fe and an impurity, wherein at least one type of oxides of oxides containing 5 mass % or more of Al and oxides containing 5 mass % or more of Si are present on a surface, and, among the oxides present on the surface, the number of oxides having a diameter D of 0.1 μm or more and 2.0 μm or less is 10 or more per 93 μm 2 , the diameter D being represented by the following formula (1)
D =( D max+ D min)/2  (1)

in the formula (1), Dmax is a maximum diameter of the oxide on the surface, and Dmin is a minimum diameter of the oxide on the surface.

2 . The ferritic stainless steel according to claim 1 ,
wherein, regarding the surface, CIE1976 luminosity L* that is measured using a D65 light source in a diffuse lighting mode by receiving light in a direction at 8° with respect to a normal line to the surface at a visual field angle of 10° visual field for a measurement time of one second is 60 or more.

3 . The ferritic stainless steel according to claim 1 ,
wherein the chemical composition contains one or more of: 0.01 mass % or more and 2.5 mass % or less of W; 0.01 mass % or more and 3.00 mass % or less of Mo; 0.001 mass % or more and 0.500 mass % or less of Ti; 0.0002 mass % or more and 0.0100 mass % or less of B; 0.0002 mass % or more and 0.0030 mass % or less of Ca; 0.001 mass % or more and 0.50 mass % or less of Hf; 0.01 mass % or more and 0.40 mass % or less of Zr; 0.005 mass % or more and 0.50 mass % or less of Sb; 0.01 mass % or more and 0.30 mass % or less of Co; 0.001 mass % or more and 1.0 mass % or less of Ta; 0.002 mass % or more and 1.00 mass % or less of Sn; 0.0002 mass % or more and 0.30 mass % or less of Ga; 0.01 mass % or more and 0.50 mass % or less of V; 0.0003 mass % or more and 0.003 mass % or less of Mg; and 0.001 mass % or more and 0.20 mass % or less of REM.

4 . The ferritic stainless steel according to claim 1 ,
wherein, in a range from the surface to 1.0 μm after the ferritic stainless steel is held in an atmosphere of 300° C. to 900° C. for 100 hours or longer, when a Cr content is represented by [Cr], a Si content is represented by [Si] and an Al content is represented by [Al] by unit mass %, the following formula (2) is satisfied,
[Cr]+[Si]+[Al]≥18.0  (2).

5 . A ferritic stainless steel,
wherein, in a range from a surface to 1.0 μm, when a Cr content is represented by [Cr], a Si content is represented by [Si] and an Al content is represented by [Al] by unit mass %, the following formula (2) is satisfied,
[Cr]+[Si]+[Al]≥18.0  (2).

6 . A component for exhaust gas comprising:
the ferritic stainless steel according to claim 1 .

7 . The ferritic stainless steel according to claim 2 ,
wherein, in a range from the surface to 1.0 μm after the ferritic stainless steel is held in an atmosphere of 300° C. to 900° C. for 100 hours or longer, when a Cr content is represented by [Cr], a Si content is represented by [Si] and an Al content is represented by [Al] by unit mass %, the following formula (2) is satisfied,
[Cr]+[Si]+[Al]≥18.0  (2).

8 . The ferritic stainless steel according to claim 3 ,
wherein, in a range from the surface to 1.0 μm after the ferritic stainless steel is held in an atmosphere of 300° C. to 900° C. for 100 hours or longer, when a Cr content is represented by [Cr], a Si content is represented by [Si] and an Al content is represented by [Al] by unit mass %, the following formula (2) is satisfied,
[Cr]+[Si]+[Al]≥18.0  (2).

9 . A component for exhaust gas comprising:
the ferritic stainless steel according to claim 2 .

10 . A component for exhaust gas comprising:
the ferritic stainless steel according to claim 3 .

11 . A component for exhaust gas comprising:
the ferritic stainless steel according to claim 4 .

12 . A component for exhaust gas comprising:
the ferritic stainless steel according to claim 5 .

13 . A component for exhaust gas comprising:
the ferritic stainless steel according to claim 7 .

14 . A component for exhaust gas comprising:
the ferritic stainless steel according to claim 8 .

Assignees

• Nippon Steel Stainless Steel Corp

Inventors

• Fujimura Yoshitomo
• Hamada Takahito

Classifications

• C21D8/02

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• C22C38/52

  with cobalt · CPC title

• C22C38/60

  containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur · CPC title

• C22C38/001

  containing N · CPC title

• C21D8/0236

  Cold rolling · CPC title