| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a high-strength steel sheet which is suppressed in occurrence of peeling in shear and punched end surfaces and improved in surface quality, hole expandability and slag encapsulation properties in arc welding.SOLUTION: A high-strength steel sheet has a composition comprising, by mass%, 0.04-0.06% C, 0.02-0.15% Si, 1.6-2.0% Mn, 0.20-0.50% Al, 0.020-0.05% Nb, 0.10-0.15% Ti, 0.02% or less P, 0.005% or less S, 0.005% or less N and remaining Fe and unavoidable impurities. Taking contents of Mn, Si and Al as [Mn], [Si] and [Al], respectively, the ratio of [Mn]/([Si]+[Al]) is 3.4-6.7. The structure is a ferrite/bentonite composite structure which is based on bentonite and has a ferrite fraction is 5-30%.</p> |
