| 摘要 |
PURPOSE:To obtain a cold rolled steel sheet for press working having improved suitability to chemical conversion treatment as well as high press formability by adding a very small amount of Ca to a steel having a very low C content and by further adding Ti or Nb. CONSTITUTION:This cold rolled steel sheet contains, by weight, <=0.050% C, <=1.0% Si, <=1.0% Mn, <=0.15% P, 0.010% S, 0.010-0.100% Al, <=0.0050% N, 0.010-0.050% Ti and/or 0.004-0.30% Nb and 0.0009-0.0025% Ca. A steel contg. said components refined as usual in a converter or an electric furnace is formed into a slab by ingot making-cogging or continuous casing, and the slab is hot rolled, cold rolled and annealed to manufacture the cold rolled steel sheet. This steel sheet has superior suitability to chemical conversion treatment as well as superior deep drawability and aging resistance.
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