| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a hot-rolled steel plate superior in workability. SOLUTION: A steel slab is made from steel comprising 0.10 to 0.20% C, 0.50 to 1.30% Mn, 0.010 to 0.030% Nb, 0.005% or less N, 0.5% or less Si, 0.03% or less P and 0.01% or less S; and has a thickness of 220 to 300 mm. The method for manufacturing the hot-rolled steel plate having a tensile strength of 490 MPa or more includes heating the slab so that the surface temperature T can be in a range of T(solution)≤T(surface)<T(solution)+(0.6t-60). By thus controlling the temperature of the surface of the slab and the central part of the slab thickness, Nb dissolves into the matrix on the slab surface having a high temperature, but does not dissolve into the matrix in the slab center having a low temperature. As a result, the hot-rolled steel plate acquires less planar anisotropy and consequently higher workability. COPYRIGHT: (C)2008,JPO&INPIT
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