Galvanized steel sheets have over-galvanized edges on the production line in normal operation. When the edges are rolled up, the products produced are all waste products and the loss is large. Therefore, it must first be treated from the perspective of reducing the loss of waste products. However, reducing the speed of the production line will aggravate the over-galvanizing of the edges, so first you can use the method of increasing the atmospheric pressure to reduce the overall galvanizing amount. By producing a part of the products with low galvanizing amount to gain a processing time, so as not to cause a large amount of waste products, but also can deal with the problem leisurely. Generally speaking, edge over-galvanization mostly occurs when the amount of galvanization is high and the air knife pressure is low, so adding atmospheric knife pressure can often produce certain effects.
The next step is to distinguish between raw material problems, zinc pot temperature problems or air knife parameter problems. The method is to observe the edge of the galvanized coil. If the over-galvanization is caused by slag, it is at the edge. If the edge is rough, whitish, and the gloss is not strong, it is often caused by raw material problems. Look for raw materials for verification to see if there is any edge trimming, cracks, jagged edges, etc. Generally speaking, it is difficult to adjust the air knife and use the baffle for the over-galvanizing of the edges caused by the raw materials, and the materials can only be replaced.
If it is obvious that the edge of the steel strip coming out of the air knife has begun to crystallize, and the sprinkles on the edge of the galvanized steel sheet are particularly small after cooling, it is probably caused by the low temperature of the zinc pot, and the temperature of the zinc pot must be increased immediately.
If the edge of the galvanized steel sheet is relatively smooth and the thickness is 4-10mm away from the edge, it may be caused by improper matching of the air knife parameters. At this time, adjust the angle of the air knife and confirm the actual air knife accurately. The angle, especially the domestic imitation Kohler air knife, must be carefully adjusted to ensure that the front and rear angles are staggered by 1°-2°. At the same time, make the distance between the air knife and the steel belt as small as possible.
If the galvanized steel sheet cannot eliminate the problem of zinc transition at the edge by the above methods, the air knife must be stopped to adjust the air knife clearance to make the air knife clearance at the edge larger and further improve the zinc scraping force at the edge.
