| 摘要 |
PURPOSE:To obtain the titled cold rolled steel sheet by limiting the contents of C, N, S, Ti and Nb of a specifically composed dead soft steel added with Ti and Nb in combination and limiting strictly the coiling conditions in hot rolling and the holding and cooling conditions for continuous annealing. CONSTITUTION:The steel contg., by weight, <=0.0050% C, <=1.5% Si, <=1.5% Mn, formula I Ti, formula II Nb, 0.005-0.10% Al, <=0.20% P, <=0.0050% N and <=0.015% S is hot rolled and is then coiled at <=710 deg.C. The steel sheet is thereafter subjected to cold rolling at >=50% draft and is held for >=1sec in the temp. region of >=850 deg.C and up to the Ac3 point, then the steel sheet is cooled at 5-300 deg.C/s down to <=500 deg.C. The cold rolled steel sheet having the higher effect of the combined addition of Ti and Nb and assuring the BH characteristic without deteriorating the material quality is thus obtd.
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