Ferritic stainless steel sheet and production method
There is provided a ferritic stainless steel sheet including a magnetized area fraction of 50% or more wherein the ferritic stainless steel sheet chemical composition includes, in mass %: C: 0.015% or less, Si: 3.0% or less, Mn: 1.0% or less, S: 0.0040% or less, P: 0.08% or less, Al: 0.80% or less, N: 0.030% or less, Cr: 15.0 to 25.0%, Mo: 0.5 to 3.0%, Ti: 0 to 0.50%, Nb: 0 to 0.50%, Ni: 0 to 0.50%, Cu: 0% or more to less than 0.1%, Zr: 0 to 1.0%, V: 0 to 1.0%, REM: 0 to 0.05%, and B: 0 to 0.01%, with the balance: Fe and impurities, and satisfies Formula (i): 0.10≤Ti+Nb≤0.50.
1 . A ferritic stainless steel sheet, wherein
a chemical composition consists of, in mass %:
C: 0.015% or less,
Si: 3.0% or less,
Mn: 1.0% or less,
S: 0.0040% or less,
P: 0.08% or less,
Al: 0.80% or less,
N: 0.030% or less,
Cr: 15.0 to 25.0%,
Mo: 0.5 to 3.0%,
Ti: 0 to 0.50%,
Nb: 0 to 0.50%,
Ni: 0 to 0.50%,
Cu: 0% or more to less than 0.1%,
Zr: 0 to 1.0%,
V: 0 to 1.0%,
REM: 0 to 0.05%, and
B: 0 to 0.01%,
with the balance: Fe and impurities, and
satisfies Formula (i) shown below:
0.10≤Ti+Nb≤0.50 (i)
where symbols of elements in the formula indicate contents (mass %) of the elements contained in the steel, and when an element is not contained, zero will be set to the corresponding symbol;
a maximum grain size of grains is 343 μm or more; and
the ferritic stainless steel sheet comprises a magnetized area fraction of 70% or more, wherein the magnetized area fraction is an area fraction of a magnetized region, the magnetized region being determined by the following steps using a magnetic domain observation microscope:
(a) an amount of change in reflection light intensity is measured in a state where no magnetic field is applied to a sample, and a threshold is specified for an amount of change in reflection light intensity with which 99% of an observation region is determined to be unmagnetized;
(b) with a magnetic field of 1000 Oe applied to the sample, a region having an amount of change in reflection light intensity exceeding the specified threshold of step (a) is extracted as a magnetized region; and
(c) the observation is performed in three visual fields with a magnification within a range of x1000 to x2500, and
in a rolling direction crystal orientation,
F1 that is given by Formula (iii) shown below and is a ratio between a total area S <00> of grains having orientations parallel to a <001> direction and a total area S 111> of grains having orientations parallel to a <111> direction is 5.0 or more:
F1=S <001> /S <111> (iii)
2 . The ferritic stainless steel sheet according to claim 1 , wherein the chemical composition contains, in mass %,
Si: 0.60% or less.
3 . The ferritic stainless steel sheet according to claim 1 , wherein the chemical composition contains one or more elements selected from, in mass %:
Ni: 0.05 to 0.50%,
Cu: 0.01% or more to less than 0.1%,
Zr: 0.01 to 1.0%,
V: 0.01 to 1.0%,
REM: 0.005 to 0.05%, and
B: 0.0002 to 0.01%.
4 . The ferritic stainless steel sheet according to claim 1 , wherein
a pitting resistance equivalent number PREN that is calculated by Formula (ii) shown below is 20.0 or more:
PREN=Cr+3.3Mo+16N (ii)
where symbols of elements in Formula (ii) shown above indicate contents (mass %) of the elements contained in the steel, and when an element is not contained, zero will be set to the corresponding symbol.
5 . The ferritic stainless steel sheet according to claim 1 , wherein a maximum grain size of grains observed is 500 μm or more.
6 . The ferritic stainless steel sheet according to claim 2 , wherein the chemical composition contains one or more elements selected from, in mass %:
Ni: 0.05 to 0.50%,
Cu: 0.01% or more to less than 0.1%,
Zr: 0.01 to 1.0%,
V: 0.01 to 1.0%,
REM: 0.005 to 0.05%, and
B: 0.0002 to 0.01%.
7 . The ferritic stainless steel sheet according to claim 2 , wherein
a pitting resistance equivalent number PREN that is calculated by Formula (ii) shown below is 20.0 or more:
PREN=Cr+3.3Mo+16N (ii)
where symbols of elements in Formula (ii) shown above indicate contents (mass %) of the elements contained in the steel, and when an element is not contained, zero will be set to the corresponding symbol.
8 . The ferritic stainless steel sheet according to claim 3 , wherein
a pitting resistance equivalent number PREN that is calculated by Formula (ii) shown below is 20.0 or more:
PREN=Cr+3.3Mo+16N (ii)
where symbols of elements in Formula (ii) shown above indicate contents (mass %) of the elements contained in the steel, and when an element is not contained, zero will be set to the corresponding symbol.
9 . The ferritic stainless steel sheet according to claim 6 , wherein
a pitting resistance equivalent number PREN that is calculated by Formula (ii) shown below is 20.0 or more:
PREN=Cr+3.3Mo+16N (ii)
where symbols of elements in Formula (ii) shown above indicate contents (mass %) of the elements contained in the steel, and when an element is not contained, zero will be set to the corresponding symbol.