| 摘要 |
PURPOSE:To produce a cold rolled steel sheet having excellent corrosion resistance and phosphatability by maintaining a reducing atmosphere in the soaking zone and cooling zone of a continuous annealing furnace, reducing the oxide layer formed in the heating zone and annealing the steel sheet then cleaning electrolytically the steel sheet in a basic soln. CONSTITUTION:The gaseous atmosphere in the soaking zone and cooling zone is formed of the reducing atmosphere of H2, gaseous H2-N2 mixture, gaseous H2-CO-N2 mixture, etc. to reduce thoroughly the oxide layer formed on the surface of the steel sheet in the heating zone in the stage of annealing the cold- rolled steel sheet in the continuous annealing furnace having at least the heating zone, soaking zone and cooling zone. The steel sheet, after annealing, is electrolytically cleaned for about >=3sec at about >=2A/dm<2> current density with the steel sheet as anode in the basic soln. such as NaOH soln. having >=8, if necessary about >=10pH. The electrolytically cleaned steel sheet is rinsed with hot water and water and is then subjected to temper rolling at >=0.3% by which the cold-rolled steel sheet having the excellent corrosion resistance and chemical conversion treatability is obtd. |
