| 摘要 |
PURPOSE:To improve the workability, chemical conversion treatment property, material quality, etc. of plating layers by subjecting a steel plate carried out with zinc hot dipping to a primary heat treatment of annihilate spangles then to secondary annealing on the outside of the line thereby forming alloyed layers. CONSTITUTION:In a continuous type zinc hot dipping line, zinc plating is carried out on a steel plate by using a plating bath contg. 0.08-0.20% Al in molten zinc. The steel plate is heat treated by holding the same for 10-60 seconds at 460-600 deg.C in a primary heating furnace, whereby the spangles on the surface layers of the plating are annihilated. The steel plate is fed to an open coil annealing furnace installed on the outside of the furnace, where the plate is subjected to a secondary heat treatment by holding the same for 30min-4hr at 350-400 deg.C, whereby uniform Fe-Zn alloy layers are formed over the entire surface of the steel plate. By such method, the galvanealed steel having excellent chemical conversion treatment property, and the workability of the plating layers is produced stably without any limitation for the compsns. of steel materials. |
