Stainless steel sheet for fuel cell separators, and production method therefor

Patent metadata

Field	Value
Publication number	US-10763517-B2
Application number	US-201716307238-A
Country	US
Kind code	B2
Filing date	May 22, 2017
Priority date	Jun 10, 2016
Publication date	Sep 1, 2020
Grant date	Sep 1, 2020

Abstract

A stainless steel sheet for fuel cell separators comprises: a predetermined chemical composition; and fine precipitates containing Cr and Ti at a steel sheet surface, wherein an average equivalent circular diameter of the fine precipitates is 20 nm or more and 500 nm or less, and a number of the fine precipitates existing per 1 μm 2 at the steel sheet surface is three or more.

First claim

The invention claimed is:

1. A stainless steel sheet for fuel cell separators, comprising:
a chemical composition containing, in mass %,
C: 0.003% to 0.030%,
Si: 0.01% to 1.00%,
Mn: 0.01% to 1.00%,
P: 0.050% or less,
S: 0.030% or less,
Cr: 16.0% to 32.0%,
Ni: 0.01% to 1.00%,
Ti: 0.05% to 0.45%,
Al: 0.001% to 0.200%, and
N: 0.030% or less,
with the balance being Fe and inevitable impurities; and
fine precipitates containing Cr and Ti at a steel sheet surface,
wherein an average equivalent circular diameter of the fine precipitates is 20 nm or more and 500 nm or less, and a number of the fine precipitates existing per 1 μm 2 at the steel sheet surface is three or more.

2. The stainless steel sheet for fuel cell separators according to claim 1 ,
wherein the chemical composition further contains, in mass %, one or more selected from
Mo: 0.01% to 2.50%,
Cu: 0.01% to 0.80%,
Co: 0.01% to 0.50%, and
W: 0.01% to 3.00%.

3. The stainless steel sheet for fuel cell separators according to claim 2 ,
wherein the chemical composition further contains, in mass %, one or more selected from
Nb: 0.01% to 0.60%,
Zr: 0.01% to 0.30%,
V: 0.01% to 0.30%,
Ca: 0.0003% to 0.0030%,
Mg: 0.0005% to 0.0050%,
B: 0.0003% to 0.0050%,
REM: 0.001% to 0.100%,
Sn: 0.001% to 0.500%, and
Sb: 0.001% to 0.500%.

4. The stainless steel sheet for fuel cell separators according to claim 3 ,
wherein a ratio [Cr]/[Fe] of an atomic concentration of Cr existing in chemical form other than metal to an atomic concentration of Fe existing in chemical form other than metal at the steel sheet surface is 2.0 or more.

5. A production method for a stainless steel sheet for fuel cell separators, comprising:
preparing a stainless steel sheet having the chemical composition according to claim 3 , as a material;
subjecting the stainless steel sheet to annealing, to obtain an annealed sheet; and
subjecting the annealed sheet to anodic electrolysis,
wherein an atmosphere in the annealing has a dew point of −35° C. or less and a nitrogen concentration of 1 vol % or more, and
a total electric charge applied in the anodic electrolysis is 5 C/dm 2 to 60 C/dm 2 .

6. The production method for a stainless steel sheet for fuel cell separators according to claim 5 , further comprising
after the anodic electrolysis, subjecting the annealed sheet to Cr condensation treatment, the Cr condensation treatment being immersion in an oxidizing solution or electrolysis in a potential range in which the stainless steel sheet is passivated.

7. The stainless steel sheet for fuel cell separators according to claim 2 ,
wherein a ratio [Cr]/[Fe] of an atomic concentration of Cr existing in chemical form other than metal to an atomic concentration of Fe existing in chemical form other than metal at the steel sheet surface is 2.0 or more.

8. A production method for a stainless steel sheet for fuel cell separators, comprising:
preparing a stainless steel sheet having the chemical composition according to claim 2 , as a material;
subjecting the stainless steel sheet to annealing, to obtain an annealed sheet; and
subjecting the annealed sheet to anodic electrolysis,
wherein an atmosphere in the annealing has a dew point of −35° C. or less and a nitrogen concentration of 1 vol % or more, and
a total electric charge applied in the anodic electrolysis is 5 C/dm 2 to 60 C/dm 2 .

9. The production method for a stainless steel sheet for fuel cell separators according to claim 8 , further comprising
after the anodic electrolysis, subjecting the annealed sheet to Cr condensation treatment, the Cr condensation treatment being immersion in an oxidizing solution or electrolysis in a potential range in which the stainless steel sheet is passivated C/dm 2 .

10. The stainless steel sheet for fuel cell separators according to claim 1 ,
wherein the chemical composition further contains, in mass %, one or more selected from
Nb: 0.01% to 0.60%,
Zr: 0.01% to 0.30%,
V: 0.01% to 0.30%,
Ca: 0.0003% to 0.0030%,
Mg: 0.0005% to 0.0050%,
B: 0.0003% to 0.0050%,
REM: 0.001% to 0.100%,
Sn: 0.001% to 0.500%, and
Sb: 0.001% to 0.500%.

11. The stainless steel sheet for fuel cell separators according to claim 10 ,
wherein a ratio [Cr]/[Fe] of an atomic concentration of Cr existing in chemical form other than metal to an atomic concentration of Fe existing in chemical form other than metal at the steel sheet surface is 2.0 or more.

12. A production method for a stainless steel sheet for fuel cell separators, comprising:
preparing a stainless steel sheet having the chemical composition according to claim 10 , as a material;
subjecting the stainless steel sheet to annealing, to obtain an annealed sheet; and
subjecting the annealed sheet to anodic electrolysis,
wherein an atmosphere in the annealing has a dew point of −35° C. or less and a nitrogen concentration of 1 vol % or more, and
a total electric charge applied in the anodic electrolysis is 5 C/dm 2 to 60 C/dm 2 .

13. The production method for a stainless steel sheet for fuel cell separators according to claim 12 , further comprising
after the anodic electrolysis, subjecting the annealed sheet to Cr condensation treatment, the Cr condensation treatment being immersion in an oxidizing solution or electrolysis in a potential range in which the stainless steel sheet is passivated C/dm 2 .

14. The stainless steel sheet for fuel cell separators according to claim 1 ,
wherein a ratio [Cr]/[Fe] of an atomic concentration of Cr existing in chemical form other than metal to an atomic concentration of Fe existing in chemical form other than metal at the steel sheet surface is 2.0 or more.

15. A production method for a stainless steel sheet for fuel cell separators, comprising:
preparing a stainless steel sheet having the chemical composition according to claim 1 , as a material;
subjecting the stainless steel sheet to annealing, to obtain an annealed sheet; and
subjecting the annealed sheet to anodic electrolysis,
wherein an atmosphere in the annealing has a dew point of −35° C. or less and a nitrogen concentration of 1 vol % or more, and
a total electric charge applied in the anodic electrolysis is 5 C/dm 2 to 60 C/dm 2 .

16. The production method for a stainless steel sheet for fuel cell separators according to claim 15 , further comprising
after the anodic electrolysis, subjecting the annealed sheet to Cr condensation treatment, the Cr condensation treatment being immersion in an oxidizing solution or electrolysis in a potential range in which the stainless steel sheet is passivated.

Assignees

• Jfe Steel Corp

Inventors

• Yano Takayoshi
• Ishikawa Shin

Classifications

• Y02P70/50

  Manufacturing or production processes characterised by the final manufactured product · CPC title

• C22C38/00

  Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00) · CPC title

• H01M8/0254

  corrugated or undulated · CPC title

• C21D9/46 Primary

  for sheet metals · CPC title

• H01M8/1006

  Corrugated, curved or wave-shaped MEA · CPC title