Ferrite-based stainless steel plate having excellent resistance against scale peeling, and method for manufacturing same
This ferritic stainless steel sheet contains, by mass %: C: 0.02% or less, N: 0.02% or less, Si: 0.05% to 0.80%, Mn: 0.05% to 1.00%, P: 0.04% or less, S: 0.01% or less, Cr: 12% to 20%, Cu: 0.80% to 1.50%; Ni: 1.0% or less, Mo: 0.01% to 2.00%, Nb: 0.30% to 1.00%, Ti: 0.01% to less than 0.25%, Al: 0.003% to 0.46%, V: 0.01% to less than 0.15%, and B: 0.0002% to 0.0050%, with a remainder of Fe and inevitable impurities, wherein the following formulae (1) and (2) are satisfied, and an average Cu concentration in an area from a surface to a depth of 200 nm is 3.00% or less, in the case of Mn<0.65%, 1.44×Si−Mn−0.05≥0 (1), and in the case of Mn≥0.65%, 1.10×Si+Mn−1.19≥0 (2).
1. A ferritic stainless steel sheet comprising, by mass %:
C: 0.02% or less;
N: 0.02% or less;
Si: 0.05% to 0.80%;
Mn: 0.05% to 1.00%;
P: 0.04% or less;
S: 0.01% or less;
Cr: 12% to 20%;
Cu: 0.80% to 1.50%;
Ni: 1.0% or less;
Mo: 0.01% to 2.00%;
Nb: 0.30% to 1.00%;
Ti: 0.01% to less than 0.25%;
Al: 0.003% to 0.169%;
V: 0.01% to less than 0.15%; and
B: 0.0002% to 0.0050%,
with a remainder of Fe and inevitable impurities,
wherein the following formulae (1) and (2) are satisfied, and an average Cu concentration in an area from a surface to a depth of 200 nm is in a range of 3.00 mass % or less,
in the case of Mn<0.65%,
1.44×Si−Mn−0.06>=0 (1) and
in the case of Mn>=0.65%,
1.10×Si+Mn−1.19>=0 (2),
herein, element symbols in the formulae represent mass % of the corresponding elements.
2. The ferritic stainless steel sheet according to claim 1 ,
wherein a mass gain is in a range of 1.50 mg/cm 2 or less and a mass of spalled scale is in a range of 0.30 mg/cm 2 or less after a continuous oxidation test in air at 900° C. for 200 hours.
3. The ferritic stainless steel sheet according to claim 1 , which further comprises, by mass %, one or two of W: 5% or less and Sn: 1% or less.
4. A method for manufacturing the ferritic stainless steel sheet according to claim 1 ,
the method comprising: final annealing; and finishing pickling, wherein the ferritic stainless steel sheet of claim 1 is produced,
wherein the final annealing is carried out in an oxidizing atmosphere having an oxygen proportion of 1.0 vol % or more and a volume ratio of oxygen/(hydrogen+carbon monoxide+hydrocarbon) of 5.0 or more, an annealing temperature T is set to be in a range of 850° C. to 1100° C., and an annealing time A is set to be in a range of 150 seconds or less,
the finishing pickling is carried out through dipping treatment in a nitric hydrofluoric acid aqueous solution or electrolytic treatment in a nitric acid aqueous solution,
in the case where the dipping treatment in a nitric hydrofluoric acid aqueous solution is carried out, a nitric acid concentration N is set to be in a range of 3.0 mass % to 20.0 mass %, a hydrofluoric acid concentration F is set to be in a range of 3.0 mass % or less, and a pickling time P is set to be in a range of 240 seconds or less,
in the case where the electrolytic treatment in a nitric acid aqueous solution is carried out, a nitric acid concentration N is set to be in a range of 3.0 mass % to 20.0 mass %, an electrolysis current density J is set to be in a range of 300 mA/cm 2 or less, a current applying time I is set to be in a range of 50 seconds or less, and a pickling time P is set to be in a range of 240 seconds or less, and conditions of the final annealing and the finishing pickling fulfill the following formula (3),
T×log A×((4.3×F+0.12×N)×P+0.24×J×I)×10 −6 <=5.0 (3).
5. The ferritic stainless steel sheet according to claim 2 , which further comprises, by mass %, one or two of W: 5% or less and Sn: 1% or less.
6. A method for manufacturing the ferritic stainless steel sheet according to claim 2 ,
the method comprising: final annealing; and finishing pickling, wherein the ferritic stainless steel sheet of claim 2 is produced,
wherein the final annealing is carried out in an oxidizing atmosphere having an oxygen proportion of 1.0 vol % or more and a volume ratio of oxygen/(hydrogen+carbon monoxide+hydrocarbon) of 5.0 or more, an annealing temperature T is set to be in a range of 850° C. to 1100° C., and an annealing time A is set to be in a range of 150 seconds or less,
the finishing pickling is carried out through dipping treatment in a nitric hydrofluoric acid aqueous solution or electrolytic treatment in a nitric acid aqueous solution,
in the case where the dipping treatment in a nitric hydrofluoric acid aqueous solution is carried out, a nitric acid concentration N is set to be in a range of 3.0 mass % to 20.0 mass %, a hydrofluoric acid concentration F is set to be in a range of 3.0 mass % or less, and a pickling time P is set to be in a range of 240 seconds or less,
in the case where the electrolytic treatment in a nitric acid aqueous solution is carried out, a nitric acid concentration N is set to be in a range of 3.0 mass % to 20.0 mass %, an electrolysis current density J is set to be in a range of 300 mA/cm 2 or less, a current applying time I is set to be in a range of 50 seconds or less, and a pickling time P is set to be in a range of 240 seconds or less, and conditions of the final annealing and the finishing pickling fulfill the following formula (3),
T×log A×((4.3×F+0.12×N)×P+0.24×J×I)×10 −6 <=5.0 (3).
7. A method for manufacturing the ferritic stainless steel sheet according to claim 3 ,
the method comprising: final annealing; and finishing pickling, wherein the ferritic stainless steel sheet of claim 3 is produced,
wherein the final annealing is carried out in an oxidizing atmosphere having an oxygen proportion of 1.0 vol % or more and a volume ratio of oxygen/(hydrogen+carbon monoxide+hydrocarbon) of 5.0 or more, an annealing temperature T is set to be in a range of 850° C. to 1100° C., and an annealing time A is set to be in a range of 150 seconds or less,
the finishing pickling is carried out through dipping treatment in a nitric hydrofluoric acid aqueous solution or electrolytic treatment in a nitric acid aqueous solution,
in the case where the dipping treatment in a nitric hydrofluoric acid aqueous solution is carried out, a nitric acid concentration N is set to be in a range of 3.0 mass % to 20.0 mass %, a hydrofluoric acid concentration F is set to be in a range of 3.0 mass % or less, and a pickling time P is set to be in a range of 240 seconds or less,
in the case where the electrolytic treatment in a nitric acid aqueous solution is carried out, a nitric acid concentration N is set to be in a range of 3.0 mass % to 20.0 mass %, an electrolysis current density J is set to be in a range of 300 mA/cm 2 or less, a current applying time I is set to be in a range of 50 seconds or less, and a pickling time P is set to be in a range of 240 seconds or less, and conditions of the final annealing and the finishing pickling fulfill the following formula (3),
T×log A×((4.3×F+0.12×N)×P+0.24×J×I)×10 −6 <=5.0 (3).
8. A method for manufacturing the ferritic stainless steel sheet according to claim 5 ,
the method comprising: final annealing; and finishing pickling, wherein the ferritic stainless steel sheet of claim 5 is produced,
wherein the final annealing is carried out in an oxidizing atmosphere having an oxygen proportion of 1.0 vol % or more and a volume ratio of oxygen/(hydrogen+carbon monoxide+hydrocarbon) of 5.0 or more, an annealing temperature T is set to be in a range of 850° C. to 1100° C., and an annealing time A is set to be in a range of 150 seconds or less,
the finishing pickling is carried out through dipping treatment in a nitric hydrofluoric acid aqueous solution or electrolytic treatment in a nitric acid aqueous solution,
in the case where the dipping treatment in a nitric hydrofluoric acid aqueous solution is carried out, a nitric acid concentration N is set to be in a range of 3.0 mass % to 20.0 mass %, a hydrofluoric acid concentration F is set to be in a range of 3.0 mass % or less, and a pickling time P is set to be in a range of 240 seconds or less,
in the case where the electrolytic treatment in a nitric acid aqueous solution is carried out, a nitric acid concentration N is set to be in a range of 3.0 mass % to 20.0 mass %, an electrolysis current density J is set to be in a range of 300 mA/cm 2 or less, a current applying time I is set to be in a range of 50 seconds or less, and a pickling time P is set to be in a range of 240 seconds or less, and conditions of the final annealing and the finishing pickling fulfill the following formula (3),
T×log A×((4.3×F+0.12×N)×P+0.24×J×I)×10 −6 <=5.0 (3).