| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel material to be three-dimensionally hot-bent which is sufficiently quenched even by heating at a low temperature and for a short period of time, and can be produced into a high-strength formed article.SOLUTION: This steel material has a chemical composition containing, by mass%, 0.05-0.35% C, 0.5% or less Si, 0.5-2.5% Mn, 0.03% or less P, 0.01% or less S, 0.1% or less sol.Al, 0.01% or less N and one or more elements selected from 0.005% or less B, 0.1% or less Ti, 0.5% or less Cr, 0.1% or less Nb, 1.0% or less Ni and 0.5% or less Mo in some cases; and has a steel structure in which a spheroidized rate of carbides in the steel is 0.60-0.90. The number density of the carbides is preferably 0.50 pieces/μmor more, and the number ratio of coarse carbides having particle diameters of 0.5 μm or more occupying in all carbides is preferably 0.15 or less. |
