| 摘要 |
The invention relates to a method for hot dip coating a strip of heavy-duty steel with various alloy constituents comprising zinc and/or aluminium. According to the invention, the strip is first heated in a continuous furnace in a reductive atmosphere to a temperature of approx. 650 °C, at which only negligible quantities of the alloy constituents diffuse to the surface of the strip. The surface that predominantly consists of pure iron is converted into an iron oxide layer by an extremely short thermal treatment at a temperature of up to 750 °C in a reaction chamber that is integrated into the continuous furnace and contains an oxidising atmosphere. Said iron oxide layer prevents the diffusion of the alloy constituents to the surface of the strip during a subsequent annealing treatment at a higher temperature in a reductive atmosphere. The iron oxide layer is converted in the reductive atmosphere into a pure iron layer, to which the zinc and/or aluminium are applied in the molten bath with optimum adhesion. |
