| 摘要 |
PROBLEM TO BE SOLVED: To provide a cold-rolled steel sheet which has high hardness and exhibits excellent edge properties in blanking and excellent flatness even at enhanced temperatures and which is suitable for use in a clutch plate or ring, a clutch disc, or the like. SOLUTION: The cold-rolled steel sheet has a composition containing, by mass%, 0.01 to 0.15% C, ≤0.03% Si, 0.10 to 0.70% Mn, ≤0.025% P, ≤0.025% S, 0.01 to 0.05% Al, ≤0.008% N snd satisfying the relationship of (C%)+0.15x(Mn%)+0.85x(P%)≥0.21 with the balance consisting of Fe and unavoidable impurities, and a partially recrystallized structure having a mean ferrite grain diameter of 2 to 10 um and a degree of unrecrystallization of ≥25 to ≤90% and which exhibits Rockwell hardness HRB of ≥83 or above by virtue of the composition and the structure. COPYRIGHT: (C)2010,JPO&INPIT
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