Hot-rolled steel sheet

Abstract

The hot-rolled steel sheet according to the present invention contains as chemical components, in mass%, 0.030-0.250% of C, 0.05-2.50% of Si, 1.00-4.00% of Mn, 0.001-2.000% of sol. Al, 0.100% or less of P, 0.0200% or less of S, 0.01000% or less of N, 0-0.20% of Ti, 0-0.20% of Nb, 0-0.010% of B, 0-1.0% of V, 0-1.0% of Cr, 0-1.0% of Mo, 0-1.0% of Cu, 0-1.0% of Co, 0-1.0% of W, 0-1.0% of Ni, 0-0.01% of Ca, 0-0.01% of Mg, 0-0.01% of REM, and 0-0.01% of Zr, the balance being Fe and impurities, wherein the percentage by area of scale defects that are a portion lower by 10 [mu]m or more than the average height of a surface of the steel sheet is 20% or less, and the steel sheet has a tensile strength of 780 MPa or more.

Description

technical field [0001] The present invention relates to a high-strength hot-rolled steel sheet excellent in bending workability. [0002] This application claims priority based on Japanese Patent Application No. 2019-43961 for which it applied in Japan on March 11, 2019, and uses the content here. Background technique [0003] So-called hot-rolled steel sheets produced by hot rolling are widely used as raw materials for structural members of automobiles and industrial equipment as relatively inexpensive structural materials. In particular, hot-rolled steel sheets used in automobile running part parts, shock absorber parts, shock absorbing members, etc. have progressed in increasing their strength from the viewpoints of weight reduction, durability, and shock absorbing energy. Excellent formability that can withstand forming into a complex shape is required. [0004] However, since the formability of a hot-rolled steel sheet tends to decrease as the strength of the material...

AI Technical Summary

Problems solved by technology

[0004] However, since the formability of hot-rolled steel sheets tends to decrease as the strength of the material increases, it is difficult to achieve both high strength and good formability

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