| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-strength cold rolled steel sheet having good deep- drawability and also excellent formability in pressing such as low yield strength and large elongation. SOLUTION: A steel consisting of, by mass, <=0.005% C, 0.05-2.0% Mn, <=1.0% Si, 0.03-0.15% P, <=0.02% S, 0.04-0.1% Al, <=0.005% N, x-0.1% Ti (Where, x=4[C]+3.43[N]+1.5 [S], and [C], [N] and [S] are respectively the percentages of C, N and S.), as necessary, >=1 kinds of 0.004-0.05% Nb, 0.0003-0.0025% B and the balance Fe with inevitable impurities is coiled at 550-630 deg.C after hot rolling and the hot rolled steel sheet whose Fe-Ti-P base chemical compound of <=15nm diameter is reduced to <=200 particles perμm<2> is cold-rolled and annealed.
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