| 摘要 |
Galvanized ferrous sheet or strip has on one of its sides a layer of zinc with an interface alloy layer lying between the zinc and the base, and has on its other side a thin coating of zinc wholly alloyed with the base. The product is made by (a) subjecting the sheet or strip to a cleaning and oxidizing operation, (b) reducing the oxide layer on the sheet by passing it through a furnace containing reducing gases, (c) passing the sheet through a cooling hood containing reducing gases into a bath of molten zinc optionally containing a minor amount of aluminium, (d) withdrawing the coated sheet from the bath through exit rolls and scraping one surface of the sheet above one of the rolls so as to remove the greater part of the zinc coating metal therefrom, and (e) subjecting the same surface of the sheet to localized heat, e.g. by means of gas ribbon burners or electrical means. In a modification of step (d), differential coating may be effected by grooving the exit rolls or by using an air blast on the meniscus at the exit rolls. |
