PURPOSE: To stabilize the quality by executing hot-rolling after executing squeezing work specifying the ratio of C content in core part of a cast slab to C content of molten steel in a ladle, to the molten steel containing the specific contents of C, Si, Mn, respectively and one or more kinds of Co, Cu, Nb, B and the balance of Fe.
CONSTITUTION: The molten steel composed of the composition containing 0.4-1.0wt.% C, 0.1-1.5% Si, 0.3-2.0% Mn and at least one kind selected among 0.05-1.00% Co, 0.05-1.00% Cu, 0.010-0.20% Nb, 0.0005-0.0050% B and the balance of Fe with inevitable impurities, is continuously cast at ≥25°C degree of overheat of the molten steel. Then, at near crater end completing solidification of the molten steel in inner part of the cast slab, the squeezing work satisfying C/C0=0.8-1.05 the ratio of C content (C) in the core part of cast slab to the C content (C0) of the molten steel in the ladle, is executed and successively, the hot-rolling is executed. By this method, ductile toughness after wire drawing is improved and this can be worked to the high working ratio without developing disconnection of wire.
AMANO KENICHI
NAKANO SHOZABURO
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