Control the Defects of Galvanized Steel Coil

user image 2019-06-20
By: Alisajpq
Posted in: galvanized steel coil
Control the Defects of Galvanized Steel Coil

Galvanized steel coil because of its ideal corrosion resistance, forming, welding and coating, and other comprehensive properties and low cost, good appearance, and other advantages, a large number of construction, automobile, household appliances and other industries. In the production of the galvanized coil, there will be linear bulged, raised head grain defects, affecting the quality of products, customer use, need to control.

A. linear projections
The appearance morphology of linear convex defects is generally distributed along the rolling direction in a linear distribution of different lengths, which looks like scratch defects. The difference is that the number of linear convex defects is not fixed, but the relative position is fixed. The cause of the formation of the defect is due to a raw material defect.

Control measures:
1. Optimize composition design of steelmaking process and focus on adjusting manganese sulfur ratio of molten steel; At the same time, the water quantity system of two cold water seasons is formulated to distinguish the disturbance caused by winter and summer season factors.
2. In the continuous casting stage, select the mould without coating on the upper half and coating on the lower half.
3. Strengthen the management of the previous galvanizing process and equipment, and try to avoid scratches caused by the equipment. At the same time, the maximum rolling force of reducing the pass number is considered to reduce the damage of rolled material caused by excessive shearing.

B. defect of forehead wrinkles
Because some of them resemble wrinkles on a person's forehead, they are called forehead wrinkles. Many factors such as transverse striation defect of hot dip galvanizing sheet, the fluidity of zinc solution and the formation of Kirschner air mass in continuous annealing process are easy to lead to the defect of the raised head.

Control measures:
1. Appropriately increase the temperature and steel strip speed of zinc solution, or reduce the aluminum content in zinc solution and increase the height of air knife, so as to increase the fluidity of zinc solution in the air knife area.
2. Increase the press amount of bending roll and improve the bending effect. Increase the number of yield area, reduce the width of yield area, and reduce the forehead wrinkles.
3. Reduce the tensile elongation, that is, reduce the total plastic deformation.
4. Reasonable control of annealing temperature of galvanized steel coil.

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