Hot rolled ferritic stainless steel sheet, method for producing same, and method for producing ferritic stainless steel sheet
This hot-rolled ferritic stainless steel sheet has a steel composition containing, in terms of % by mass: 0.02% or less of C; 0.02% or less of N; 0.1% to 1.5% of Si; 1.5% or less of Mn; 0.035% or less of P; 0.010% or less of S; 1.5% or less of Ni; 10% to 20% of Cr; 1.0% to 3.0% of Cu; 0.08% to 0.30% of Ti; and 0.3% or less of Al, with the balance being Fe and unavoidable impurities, and the hot-rolled ferritic stainless steel sheet has a Vickers hardness of less than 235 Hv.
1. A hot-rolled ferritic stainless steel sheet having a steel composition containing, in terms of % by mass:
0.02% or less of C;
0.02% or less of N;
0.1% to 1.5% of Si;
1.5% or less of Mn;
0.035% or less of P;
0.010% or less of S;
1.5% or less of Ni;
10% to 15.1% of Cr;
1.0% to 3.0% of Cu;
0.08% to 0.30% of Ti;
0.3% or less of Al; and
0.0002% to 0.0030% of B,
with the balance being Fe and unavoidable impurities,
wherein the hot-rolled ferritic stainless steel sheet has a Vickers hardness of less than 235 Hv, and
an impact value is in a range of 55 J/cm 2 or more.
2. The hot-rolled ferritic stainless steel sheet according to claim 1 , which further contains one or more selected from a group consisting of, in terms of % by mass:
0.3% or less of Nb;
0.3% or less of Mo;
0.3% or less of Zr;
0.5% or less of Sn; and
0.3% or less of V.
3. A method for producing a hot-rolled ferritic stainless steel sheet, the method comprising:
subjecting a slab, which is obtained by casting a ferritic stainless steel having a steel composition according to claim 1 or 2 , to finish rolling of hot rolling so as to form a hot-rolled steel sheet;
subsequently coiling the hot-rolled steel sheet under a condition where a coiling temperature is set to be in a range of 620° C. to 750° C.; and
subjecting a hot-rolled coil to hot idling or cooling while controlling a temperature T (K) of the hot-rolled steel sheet and a holding time t (h) such that the following relation (Expression 1) is fulfilled with respect to the entirety of the hot-rolled coil,
T (20.24+log( t ))≥17963 . . . (Expression 1).
4. A method for producing a hot-rolled ferritic stainless steel sheet, the method comprising:
after subjecting a slab having a steel composition according to claim 1 or 2 to finish rolling of hot rolling, setting an average cooling rate between 850° C. and 450° C. to be in a range of 10° C./s or more; and
coiling a hot-rolled ferritic stainless steel sheet under a condition where a coiling temperature is set to be in a range of 350° C. to 450° C.
5. A method for producing a ferritic stainless steel sheet, the method comprising:
subjecting the hot-rolled steel sheet produced by the method according to claim 3 to hot-rolled sheet pickling, cold rolling, cold-rolled sheet annealing, and cold-rolled sheet pickling.
6. A method for producing a ferritic stainless steel sheet, the method comprising:
subjecting the hot-rolled steel sheet produced by the method according to claim 3 to hot-rolled sheet annealing, hot-rolled sheet pickling, cold rolling, cold-rolled sheet annealing, and cold-rolled sheet pickling.
7. The method for producing a ferritic stainless steel sheet according to claim 5 ,
wherein when performing the cold rolling, rolling work rolls having a roll diameter of 400 mm or more are used.
8. A method for producing a ferritic stainless steel sheet, the method comprising:
subjecting the hot-rolled steel sheet produced by the method according to claim 4 to hot-rolled sheet pickling, cold rolling, cold-rolled sheet annealing, and cold-rolled sheet pickling.
9. A method for producing a ferritic stainless steel sheet, the method comprising:
subjecting the hot-rolled steel sheet produced by the method according to claim 4 to hot-rolled sheet annealing, hot-rolled sheet pickling, cold rolling, cold-rolled sheet annealing, and cold-rolled sheet pickling.
10. The method for producing a ferritic stainless steel sheet according to claim 6 ,
wherein when performing the cold rolling, rolling work rolls having a roll diameter of 400 mm or more are used.
11. The method for producing a ferritic stainless steel sheet according to claim 8 ,
wherein when performing the cold rolling, rolling work rolls having a roll diameter of 400 mm or more are used.
12. The method for producing a ferritic stainless steel sheet according to claim 9 ,
wherein when performing the cold rolling, rolling work rolls having a roll diameter of 400 mm or more are used.