1. The substrate is scratched
Substrate scratches are scratches on the surface of cold-rolled substrates caused by rolling mill coiling. Since the zinc-iron reaction speed at the scratched part of the substrate is significantly higher than the normal surface, the defects on the substrate will be more obvious after the strip is hot-dip galvanized.
By strengthening the inspection of the incoming material quality in the previous process, it is possible to completely prevent the scratched substrate from entering the galvanized line.
2. Scratches caused by zinc pot rollers
Zinc pot roller scratches are the main source of scratches on galvanized products, accounting for more than 70% of scratch defects. The zinc pot roller consists of three rollers: sinking roller, correcting roller and stabilizing roller. It is in a special position in the zinc liquid, which is not conducive to the installation of the motor for transmission. Therefore, most of the zinc pot rollers are passive rollers. The friction between the surface of the strip steel and the surface of the zinc pot roller makes the zinc pot roller the same as the strip steel. Speed movement; but sometimes due to changes in the composition of the zinc liquid, the use of zinc pot rolls, changes in process speed and other factors, the strip steel and the sunken roll are relatively sliding due to insufficient transmission friction, resulting in scratches on the zinc pot roll Surface defects. In addition, the zinc slag adhering to the zinc pot roller is also the main factor causing scratches.
The solution to the scratches of the zinc pot roller: properly increase the tension of the zinc pot area to increase the transmission friction; appropriately increase the temperature of the zinc solution, and at the same time appropriately increase the content of aluminum and antimony in the zinc solution, and reduce the iron content, which is beneficial to reduce The viscosity of the zinc liquid increases the fluidity of the zinc liquid, thereby enhancing the transmission of the zinc pot roller. In addition, the zinc slag adhering to the zinc pot roller can also be properly cleaned by the immersion roller scraper and spatula.
3. Other rollers are scratched
Other roller scratches refer to the scratches caused by the whole line of idler rollers, steering rollers, tension rollers, and correcting rollers. It is divided into drive roller scratches and non-drive roller scratches. The main reason for this kind of scratches is the inconsistency between the rotating speed of the roller contacting the strip and the running speed of the strip, and the strip and the roller are relatively sliding.
Solution: If scratches are found, immediately confirm whether it is scratches before or after plating, and then determine the scratch area. The scratches caused by the driving roller can be solved by matching the speed; the scratches caused by the non-driving roller should be checked by maintenance personnel. If there is no problem with the bearing, you can increase the tension in the area and increase the transmission friction of the roller and the belt. Power to reduce scratches.
