Coated coils are widely used in manufacturing industries such as construction, trolleys, home appliances, etc. due to their comprehensive advantages such as corrosion resistance, forming, electric welding and spray coating. During the production of galvanized steel, strips and wrinkles on the forehead are constantly emerging, which jeopardizes the quality of the material. The use of customers must be controlled.
1. Bars stand out
The appearance of the strip-shaped protruding defects is usually heavy along the cold rolling, and it is spreading like a canine tooth. It looks like a scratch defect. The difference is that the number of strip-shaped protruding defects is never fluid, so it greatly affects the analogy fluidity. The cause of the defect is due to a defect in the material.
Control countermeasures:
(1) Improve the composition scheme of ironmaking process, and demonstrate the adjustment of iron-manganese-sulfur ratio. In addition, a two-season water flow track system shall be formulated to distinguish the intrusion caused by seasonal factors throughout the year.
(2) In the steel rolling stage, the upper part of the five teeth is never coated with a mold in the lower half.
(3) Improving the processing of the prior galvanizing process and the improvement of weapons and equipment, and minimizing the continuous scratching of the natural environment due to the continuous emergence of weapons and equipment. In addition, the cold rolling production starts with a large cold rolling force that reduces the number of passes, thereby replacing the natural environment caused by the rolling material that is roughly cut by cutting.
2. Forehead wrinkle defect
It is called a forehead wrinkle because it looks like a wrinkle on a person's forehead. The hot-dip galvanized steel sheet contains transverse pattern defects and the liquidity of its zinc solution. Coriolis agglomerates generated during the re-quenching process are also likely to cause continuous wrinkle defects on the galvanized steel sheet due to cold rolled coils.
Control countermeasures:
(1) Properly increase the temperature of the zinc liquid and the speed of the hot-rolled strip, or reduce the aluminum moisture content in the zinc liquid and increase the aspect ratio of the demister, so as to expand the zinc liquid circulation in the demister area.
(2) Increase the amount of pressing of the bump roller to increase the adverse impact of bump. Increase the number of flexion areas, reduce the total width of flexion areas, and relieve forehead wrinkles.
(3) Reduce the tensile strength, instead of the total plastic deformation.
(4) Galvanized coil controls fair annealing temperature of hot-rolled strip.