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

Patent metadata

Field	Value
Publication number	US-10930940-B2
Application number	US-201716307578-A
Country	US
Kind code	B2
Filing date	May 22, 2017
Priority date	Jun 10, 2016
Publication date	Feb 23, 2021
Grant date	Feb 23, 2021

Abstract

A stainless steel sheet for fuel cell separators comprises: a predetermined chemical composition; and Cr-containing fine precipitates 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 26.0%,
Ni: 0.01% to 1.00%,
Al: 0.001% to 0.200%,
N: 0.030% or less, and
one or two selected from the group consisting of Ti: 0.01% to 0.45% and Nb: 0.01% to 0.60%,
with the balance being Fe and inevitable impurities; and
Cr-containing fine precipitates at a steel sheet surface of the stainless steel sheet,
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, and
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.

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 the group consisiting of
Zr: 0.01% to 0.40%,
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 1 ,
wherein the chemical composition further contains, in mass %, one or more selected from the group consisiting of
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. 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;
subjecting the annealed sheet to anodic electrolysis; and
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,
wherein a dew point of an atmosphere in the annealing is −30° C. or less, and
a total electric charge applied in the anodic electrolysis is 5 C/dm 2 to 60 C/dm 2 .

5. 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 the group consisting of
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%.

6. 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;
subjecting the annealed sheet to anodic electrolysis; and
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,
wherein a dew point of an atmosphere in the annealing is −30° C. or less, and
a total electric charge applied in the anodic electrolysis is 5 C/dm 2 to 60 C/dm 2 .

7. 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;
subjecting the annealed sheet to anodic electrolysis; and
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,
wherein a dew point of an atmosphere in the annealing is −30° C. or less, and
a total electric charge applied in the anodic electrolysis is 5 C/dm 2 to 60 C/dm 2 .

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 5 , as a material;
subjecting the stainless steel sheet to annealing, to obtain an annealed sheet;
subjecting the annealed sheet to anodic electrolysis; and
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,
wherein a dew point of an atmosphere in the annealing is −30° C. or less, and
a total electric charge applied in the anodic electrolysis is 5 C/dm 2 to 60 C/dm 2 .

Assignees

• Jfe Steel Corp

Inventors

• Yano Takayoshi
• Ishikawa Shin

Classifications

• Y02P70/50

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

• C25D11/00

  Electrolytic coating by surface reaction, i.e. forming conversion layers · CPC title

• C22C38/50

  with titanium or zirconium · CPC title

• C21D6/007

  containing Co · CPC title

• C23G1/085

  solutions containing HNO3 · CPC title