Ferritic stainless steel having excellent salt corrosion resistance
This ferritic stainless steel includes: in terms of % by mass, C: 0.001% to 0.100%; Si: 0.01% to 5.00%; Mn: 0.01% to 2.00%; P: 0.050% or less; S: 0.0100% or less; Cr: 9.0% to 25.0%; Ti: 0.001% to 1.00%; Al: 0.001% to 5.000%; and N: 0.001% to 0.050%, with a balance being Fe and impurities, wherein in a region from a steel surface to a depth of 5 nm, and not exceeding a thickness of a passive film, a total amount of Al and Si is 1.0 atomic % or more, an amount of Cr is 10.0 atomic % or more, and an amount of Fe is 85.0 atomic % or less, in terms of cation fraction.
1. A ferritic stainless steel having excellent corrosion resistance against salt damage, comprising: in terms of % by mass,
C: 0.001% to 0.100%;
Si: 0.01% to 5.00%;
Mn: 0.01% to 2.00%;
P: 0.050% or less;
S: 0.0100% or less;
Cr: 9.0% to 25.0%;
Ti: 0.001% to 1.00%;
Al: 1.050% to 5.000%;
N: 0.001% to 0.050%;
Ni: 0% to 1.00%;
Mo: 0% to 3.00%;
Sn: 0% to 1.000%;
Cu: 0% to 2.00%;
B: 0% to 0.0050%;
Nb: 0% to 0.500%;
W: 0% to 1.000%;
V: 0% to 0.500%;
Sb: 0% to 0.100%;
Co: 0% to 0.500%;
Ca: 0% to 0.0050%;
Mg: 0% to 0.0050%;
Zr: 0% to 0.0300%;
Ga: 0% to 0.0100%;
Ta: 0% to 0.050%; and
REM: 0% to 0.100%,
with a balance being Fe and impurities,
wherein a passive film is present in a steel surface, and
in a region ranging from the steel surface to a depth of 5 nm, and not exceeding a thickness of the passive film, Al and Si are present in a total amount of 1.0 atomic % or more, Cr is present in an amount of 10.0 atomic % or more, and Fe is present in an amount of 85.0 atomic % or less, in terms of cation fraction.
2. The ferritic stainless steel having excellent corrosion resistance against salt damage according to claim 1 ,
wherein after the ferritic stainless steel is subjected to a heat treatment at 400° C. for 8 hours in air, a concentrated layer of Al and Si is present at an interface between a base material and an oxide film at a volume ratio of 10% or more.
3. The ferritic stainless steel having excellent corrosion resistance against salt damage according to claim 1 , comprising: in terms of % by mass, one or more selected from the group consisting of:
Ni: 0.01% to 1.00%,
Mo: 0.01% to 3.00%,
Sn: 0.001% to 1.000%,
Cu: 0.01% to 2.00%,
B: 0.0001% to 0.0050%,
Nb: 0.001% to 0.500%,
W: 0.001% to 1.000%,
V: 0.001% to 0.500%,
Sb: 0.001% to 0.100%, and
Co: 0.001% to 0.500%.
4. The ferritic stainless steel having excellent corrosion resistance against salt damage according to claim 1 , comprising: in terms of % by mass, one or more selected from the group consisting of:
Ca: 0.0001% to 0.0050%,
Mg: 0.0001% to 0.0050%,
Zr: 0.0001% to 0.0300%,
Ga: 0.0001% to 0.0100%,
Ta: 0.001% to 0.050%, and
REM: 0.001% to 0.100%.
5. The ferritic stainless steel having excellent corrosion resistance against salt damage according to claim 2 , comprising: in terms of % by mass, one or more selected from the group consisting of:
Ni: 0.01% to 1.00%,
Mo: 0.01% to 3.00%,
Sn: 0.001% to 1.000%,
Cu: 0.01% to 2.00%,
B: 0.0001% to 0.0050%,
Nb: 0.001% to 0.500%,
W: 0.001% to 1.000%,
V: 0.001% to 0.500%,
Sb: 0.001% to 0.100%, and
Co: 0.001% to 0.500%.
6. The ferritic stainless steel having excellent corrosion resistance against salt damage according to claim 2 , comprising: in terms of % by mass, one or more selected from the group consisting of:
Ca: 0.0001% to 0.0050%,
Mg: 0.0001% to 0.0050%,
Zr: 0.0001% to 0.0300%,
Ga: 0.0001% to 0.0100%,
Ta: 0.001% to 0.050%, and
REM: 0.001% to 0.100%.
7. The ferritic stainless steel having excellent corrosion resistance against salt damage according to claim 3 , comprising: in terms of % by mass, one or more selected from the group consisting of:
Ca: 0.0001% to 0.0050%,
Mg: 0.0001% to 0.0050%,
Zr: 0.0001% to 0.0300%,
Ga: 0.0001% to 0.0100%,
Ta: 0.001% to 0.050%, and
REM: 0.001% to 0.100%.