| 摘要 |
To provide a continuously cast IF slab and a thin IF steel sheet in which drawbacks encountered in a thin IF steel sheet, such as surface defect, manufacturing difficulty and a low strength are fundamentally eliminated, and a method of manufacturing the same slab and steel sheet. A continuously cast slab of extremely low carbone steel containing Si <= 1.5 %, Mn <= 2.0 %, P <= 0.15 %, Al = 0.01 - 0.15 % and N <= 0.0050 % in mass ratio, a superficial layer containing 0.01 - 0.08 % of C as cementite, an inner layer containing C <= 0.0050 % and one or not less than two kinds of elements out of Ti = 0.02 0.10 %, Nb = 0.01 - 0.10 %, V = 0.02 - 0.10 % and Zr = 0.03 - 0.10 %, the carbon existing substantially in the form of carbides of these elements, the superficial layer preferably further containing B = 0.0001 - 0.0015 %, the rest comprising Fe and unavoidable impurities, and a thin steel sheet produced from the same slab; and a method of manufacturing the same slab and thin steel sheet combined with continuous casting powder, an electromagnetic brake or an alloy-adding wire. The IF steel and high-strength IF steel, which have been unable to be mass-produced, and unable to attain a high yield and perfect performance, have been improved and recognized as reliable basic metal materials. |
