| 摘要 |
PROBLEM TO BE SOLVED: To provide an apparatus that prevents the direct blowing of fine dust, dirt, iron oxide, sea salt particles, etc., to steel sheet surface and eventually avoides the generation of black dot defects on a galvannealed steel sheet which is produced. SOLUTION: This apparatus prevents black dot defects to be generated on the surfaces of a galvannealed steel sheet, which is produced by heating, holding and cooling or heating and cooling in an alloying furnace, after subjecting a steel sheet 1 to hot dip galvanizing, then adjusting zinc coating weights with a coating weight controller. The gas contact sections from the gases suction sections of a cooling zone 7 in common use as a holding zone and Nos. 1, 2 air cooling zones 8, 9 for cooling the steel sheet 1 to blowing nozzles to the steel sheet 1 are made of stainless steel sheets. The duct diameters in the inlet side parts of filter boxes 7f, 8e, 9e are made large in order to maintain the velocities of flow of the cooling gases on the inlet side of blowers 7c, 8b, 9c at 1.0 to 3.0 m/s. In addition, filters for removing the dust of >=15μm are arranged in the enlarged duct parts.
|
