HIGH-RIGIDITY HIGH-STRENGTH THIN STEEL SHEET AND METHOD FOR PRODUCING SAME

摘要

Disclosed is a high-rigidity high-strength thin steel sheet having a tensile strength of not less than 590 MPa and a Young's modulus of not less than 230 GPa at the same time. The high-rigidity high-strength thin steel sheet has a composition consisting of, in mass%, C:0.02-0.15%, Si: 1.5% or less, Mn: 1.0-3.5%, P: 0.05% or less, S: 0.01% or less, Al: 1.5% or less, N: 0.01% or less, Ti: 0.02-0.50%, and the balance of iron and unavoidable impurities, wherein the C, N, S and Ti contents satisfy the following relations: Ti* = Ti - (47.9/14) x N - (47.9/32.1) x S >= 0.01 and 0.01 <= C - (12/47.9) x Ti* <= 0.05. The structure of such a steel sheet is mainly composed of a ferrite phase, and contains not less than 1% of a martensite phase in the area ratio.