Ferritic stainless steel casting and sheet and method for producing the same

A method for producing a ferritic stainless steel sheet having an average r-value of 2.0 or more, an ridging height of 5 μm or less and an elongation of 35% or more, comprising using a casting wherein:

• said casting contains, in mass, 0.001 to 0.010% C, 0.01 to 0.30% Si, 0.01 to 0.30% Mn, 0.01 to 0.04% P, 0.0010 to 0.0100% S, 10 to 20% Cr, 0.001 to 0.020% N, 0.05 to 0.30% Ti, 0.0002 to 0.0050% Mg, and further contains Al and/or Ca, with a balance consisting of Fe and unavoidable impurities, and the value of Σ defined by the expression <1> is 0.70 or less,
• Σ=0.9[Si]+8.6[P]+2[Ti]+0.5[Mn]−0.5 <1>;
• wherein [Si], [P], [Ti], and [Mn] represents contents of Si, P, Ti and Mn in said steel, respectively, and the average composition of the Mg containing oxides dispersing in said casting satisfies the expressions <2> and <3>,
• 17.4(Al2O3)+3.9(MgO)+0.3(MgAl2O4)+18.7(CaO)≦500 <2>,
• (Al2O3)+(MgO)+(MgAl2O4)+(CaO)≧95 <3>,
• wherein the chemical components in the parentheses mean mol % of the relevant chemical components, respectively, said method comprising
• hot rolling the casting by a method comprising heating said casting to temperature T1 within the range defined by the expression <4>, subjecting said heated casting to rough rolling of plural passes, and finishing rolling of plural passes at a temperature of 850° C. or lower;
• coiling said hot-rolled steel sheet at a temperature of 700° C. or lower;
• annealing said hot-rolled steel sheet at a heating temperature T2 in the range defined by the expression <5>;
• cold rolling said annealed steel sheet;
• and
• subsequently annealing said cold-rolled steel sheet at a heating temperature T3 in the range defined by the expression <6>,
• 1,000≦T1(° C.)≦−100−8,714/(log([Ti]×[C]0.5×[S]0.5)−3.4) <4>,
• −5,457/(log([T1]×[C])−2.6)≦T2(° C.)≦1,000 <5>,
• −100−5,457/(log([Ti]×[C])−2.6)≦T3(° C.)≦−5,457/(log([Ti]×[C])−2.6) <6>
• wherein [Ti], [C], and [S] represents contents of Ti, C, and S in said steel, respectively.