| 摘要 |
PURPOSE:To manufacture a molten zinc plating steel plate which is excellent in corrosion resistance and satisfactory in luster, by controlling an O2 concentration range in plural areas on the bath surface, respectively, until a plating metal is coagulated, in case of melt-plating a band steel by a zinc bath containing Mg and Sn. CONSTITUTION:Molten zinc plating is performed by passing a band steel tape 1 through a zinc bath 4 containing both 0.1-2.0% Mg and 0.1-8% Sn. In this case O2 concentration of a space of the upper maximum 1 meter of the bath surface side including a wiping nozzle 7 is controlled to 100-1,000ppm, by enclosing at least a part by a sealing body 2 until a plating metal which has adhered onto the surface of the steel tape in the upper part from the surface of the bath 4 is coagulated. Also, O2 concentration of the coagulated area side of its upper plating metal is controlled as mentioned below. That is to say, when this O2 concentration is controlled to >=''0''- concentration in the air, >=1,000ppm, and 100ppm- concentration in the air, in case when the plating quantity is <=50g/m<2>, 50-200g/m<2>, and >=200g/m<2>, respectively, it is possible to obtaii a plating band steel which not only has said characteristics but also generates no twist nor hair crack. |
