| 摘要 |
PURPOSE:To permit sure and quick changing over of both-faces plating and one-face plating by controlling both the temp. of a molten metal and the pressure of a vapor deposition chamber in the stage of subjecting a steel sheet to vacuum deposition plating of a metal such as zinc. CONSTITUTION:The vapor deposition plating of zinc is executed at a specific sheet thickness and width and line speed as well as under the conditions of 460 deg.C molten zinc temp. by using a vapor deposition device as shown in the figure with the relation between the pressure regulation of a vapor deposition chamber 10 and evaporation rate with the evaporation rate of zinc when the pressure in the chamber 10 is changed to 0.1-1.0Torr, the evaporation rate of the zinc decreases sharply under 0.4-0.5Torr pressure in the chamber 10 as shown in the figure. The evaporation rate decreases to <=1kg/hr and can be considerably suppressed under >=0.5Torr. The flow of the vapor to a duct 13 is, therefore substantially eliminated and the sure sealing is attained when a shutter 17 of an evaporation vessel 14 is fully closed. Since the evaporation rate can be more suppressed under the higher pressure of the chamber 10, the pressure in the chamber 10 is particularly held 2-3 timers larger than the satd. vapor pressure of the zinc bath, for example, >=3Torr. Both faces plating can be made again after the one-face plating simply by resetting the chamber 10 in which the vapor deposition is paused to the operating state of vapor deposition.
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