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

Patent metadata

Field	Value
Publication number	US-2019296369-A1
Application number	US-201716307238-A
Country	US
Kind code	A1
Filing date	May 22, 2017
Priority date	Jun 10, 2016
Publication date	Sep 26, 2019
Grant date	—

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 μm2 at the steel sheet surface is three or more.

First claim

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 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%.

4 . 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.

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 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 .

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 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%.

8 . 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.

9 . 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.

10 . The stainless steel sheet for fuel cell separators according to claim 7 ,
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.

11 . 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 .

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 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 .

13 . 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 7 , 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 .

14 . The production method for a stainless steel sheet for fuel cell separators according to claim 11 , 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 .

15 . 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 .

16 . The production method for a stainless steel sheet for fuel cell separators according to claim 13 , 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

• H01M8/0254

  corrugated or undulated · CPC title

• H01M8/1006

  Corrugated, curved or wave-shaped MEA · CPC title

• H01M8/021 Primary

  Alloys based on iron · CPC title

• H01M2008/1095

  Fuel cells with polymeric electrolytes · CPC title

• C22C38/50 Primary

  with titanium or zirconium · CPC title