| 摘要 |
PURPOSE:To produce a high carbon steel strip having good cold formability easily and inexpensively by subjecting the high-carbon hot-rolled steel strip which is stuck with black skin scale to annealing in a specific condition range in a dry inert gaseous atmosphere. CONSTITUTION:A high carbon hot rolled steel strip contg. >=0.3% C which is stuck with black skin scale is annealed for 1-50hr in a 600-1,000 deg.C temp. range in a dry inert gaseous atmosphere lower than 0 deg.C dew point. If the conditions for the annealing are specified as mentioned above, the black skin scale consisting essentially of Fe3O4 causes reaction of the formula 4C+Fe3O4 3Fe+ 4CO with C in the surface of the steel strip, whereby a uniform surface decarburized layer is formed and the cold formability of the high-carbon steel strip is improved. At the same time, the black skin scale is reduced and converted to metal. Since the reacting source exists beforehand on the steel strip, the annealing treatment is applied immediately in the state of tight coil. |
