| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To prevent the generation of a defect in appearance such as unplating and plating unevenness and a defect in plating adhesion when a steel sheet comprising≥0.2 mass% Si is subjected to hot-dip galvanizing plating. <P>SOLUTION: When a steel sheet comprising≥0.2 mass% Si in the steel is heated and annealed in a reduction furnace, and is thereafter subjected to hot-dip galvanizing, the dew point of a gas in the furnace within the region of 1/3 at the lower part of the steel sheet-passing region in the height direction of the reduction furnace is controlled to the range of >-30 to≤0°C. When the dew point reaches≤-30°C, the feed of the gas to the reduction gas is performed from the position lower than the 1/2 of the steel sheet passing region in the height direction of the reduction furnace, and also, the exhaust of the gas in the reduction furnace is performed from the position lower than the 1/2 of the steel sheet passing region in the height direction of the reduction furnace. When the dew point reaches >0°C, the exhaust of the gas in the reduction furnace is performed from the position higher than the 1/2 of the steel sheet passing region in the height direction of the reduction furnace, and the amount of the≥1/3 of the feed of the gas to be fed to the reduction furnace is exhausted. <P>COPYRIGHT: (C)2009,JPO&INPIT</p> |
