| 摘要 |
PURPOSE:To considerably enhance the corrosion resistance, workability and coatability of a steel plate, by plating the surface of the plate with a Zn-Al-Si- Mg alloy having a specified composition by hot dipping. CONSTITUTION:In the manufacture of a one-side hot dipped steel plate for a car member or an external material for household electric appliances, one side of a steel plate is covered with a masking agent, and the plate is dipped in a molten Zn alloy bath consisting of 3-40% Al, 0.05-2.0% Mg, 0.005-0.1 time as much Si as Al, <0.02% Pb and the balance Zn to carry out hot dipping at 480-680 deg.C bath temp. The amount of the Zn alloy stuck by the hot dipping is controlled to <=30g/m<2>, and by apraying cooling water or the like, the Zn alloy layer is solidified by rapid cooling. The plate is then heated to 550-900 deg.C in a heating furnace to alloy the layer with the surface of the plate. Materials used in the hot dipping vessel are made of Cr cast steel or stainless cast steel to prevent corrosion. A hot dipped steel plate with superior corrosion resistance, workability and coatability is obtd. |
