| 摘要 |
PROBLEM TO BE SOLVED: To provide a hot rolled steel sheet in which cracking and galling on rotary ironing can be suppressed, and which combines excellent workability (local ductility) and excellent dimensional precision by uniform working in a peripheral direction. SOLUTION: The hot rolled steel sheet having excellent rotary ironing workability comprises, by mass, 0.02 to 0.10% C,≤1.0% Si, 0.1 to 2.5% Mn,≤0.05% P,≤0.01% S, 0.01 to 0.10% sol.Al and≤0.006% N, and the balance substantially iron. The steel sheet has a microstructure comprising a ferrite phase and the second phase consisting of one or more selected from pearlite, bainite and martensite. The volume ratio of the second phase is 3 to 30%, and the mean particle diameter of the second phase is≤5μm. In the hot rolled steel sheet having excellent rotary ironing workability, the plane anisotropyΔn of the work hardening index, n value satisfies ¾Δn¾≤0.015 as well. COPYRIGHT: (C)2004,JPO
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