PROBLEM TO BE SOLVED: To provide a cold rolled steel sheet manufacturable by a steel mass-production manufacturing process, having an extralow carbon concentration and an extralow Al concentration, an having high drawability, and to provide a method for refining a molten steel for the steel sheet.;SOLUTION: The extralow carbon steel sheet has a chemical composition comprising, by mass, 0.0005 to 0.025% C, 0.003 to 0.15% Si, 0.3 to 2.5% Mn, ≤0.15% P, ≤0.02% S, ≤0.006% N, 0.0002 to 0.005% sol.Al, 0.005 to 0.05% Ti, 0.020 to 0.20% Nb, and the balance Fe with impurities, and in which an Nb/Ti ratio is ≥2.0, and inclusions satisfy inequalities (1) to (3): NTi≥30 pieces/mm2 (1), NTi/(NTi+NAl)≥0.80 (2), NTi/NTotal≥0.65 (3), wherein NTi, NAl and NTotal all denote inclusions with a major axis of ≥1 μm in the longitudinal face parallel to the rolling direction, and are the one comprising ≥50% Ti oxide, the one comprising ≥50% Al oxide and the average numerical density of all oxide inclusions, respectively.;COPYRIGHT: (C)2009,JPO&INPIT
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机译：解决的问题：提供一种可通过钢的批量生产制造工艺制造的冷轧钢板，该钢板具有极低的碳浓度和极低的Al浓度，并具有较高的可拉伸性，并提供一种精炼用于该钢的钢水的方法。解决方案：极低碳钢板的化学成分按质量计包括0.0005至0.025％C，0.003至0.15％Si，0.3至2.5％Mn，0.15％P，0.02％S， ≥0.006％N，0.0002至0.005％sol.Al，0.005至0.05％Ti，0.020至0.20％Nb和余量的Fe和杂质，其中Nb / Ti比为2.0且夹杂物满足不等式（1）至（3）：N Ti ＆ge; 30个/ mm 2 （1），N Ti /（N Ti + N Al ）＆ge; 0.80（2），N Ti / N Total ＆ge; 0.65（3），其中N Ti ，N Al 和N Total 均表示长轴为＆ge; 1μm的夹杂物在平行于长轴的纵向面上。滚动方向分别是50％的Ti氧化物，50％的Al氧化物和所有氧化物夹杂物的平均数值密度。;版权所有：（C）2009，JPO＆INPIT
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