High formability and high tensile strength hot rolled steel sheet having excellent material uniformity, production method therefor, and working method therefor

TLDR: In this paper, the authors proposed a hot-rolled steel sheet having excellent material uniformity which has a reduced variation in material in a coil, particularly that of yield strength in the width direction and can be industrially put into practical use.

Abstract: PROBLEM TO BE SOLVED: To provide a high formability, high tensile strength, hot rolled steel sheet having excellent material uniformity which has a reduced variation in material in a coil, particularly that of yield strength in the width direction and can be industrially put into practical use, to provide a production method therefor, and to provide a working method therefor. SOLUTION: The steel containing, by weight, ≤0.1% C and 0.02 to 0.2% Ti, and containing one ore more kinds of metals selected from 0.05 to 0.6% Mo and 0.01 to 1.5% W is cast. The steel is thereafter hot-rolled, is coiled round a coil, and is heat-treated. By the process, carbides containing Ti and one or more kinds of metals selected from Mo and W are dispersively precipitated in the ranges satisfying the following (1) into a structure mainly made up of ferrite, and the difference in yield stress between the central part and edge parts in the width direction of the steel sheet is ≤30 MPa: 0.1≤Ti/[48{(Mo/96)+(W/184)}]≤3.5 (1). COPYRIGHT: (C)2004,JPO