1. Normal zinc plating
During the normal solidification process of zinc coatings on galvanized coils, zinc grains grow and form self-growing coatings with obvious zinc flower morphology.
2. Small zinc flower coating
In the solidification process of zinc layer, the zinc grain is artificially limited, forming as fine as possible zinc flower coating.
3. Zinc-free plating
The coating obtained by adjusting the chemical composition of the plating solution does not have the visual appearance of zinc flower, and the appearance of the coating is average divergent.
4. Zinc-Iron Alloy Coating
The hot treatment of steel strip after galvanizing bath is stopped so that the whole coating can form an alloy layer of zinc and iron. The coating has dark gray appearance and no metallic luster. It is easy to be powdered in the process of violent forming. It is suitable for coating which can be directly coated without further treatment except for ordinary cleaning.
5. Differential Thickness Coating
For both sides of galvanized steel sheet, coatings with different weight of galvanized layer are required.
Finishing is a cold rolling process that stops a small amount of deformation of galvanized steel sheets for one or more of the following purposes. Improve the appearance of galvanized steel sheet or suitable for decorative coatings; make the phenomenon of slip lines or folds produced when waste products are not processed temporarily to a minimum.
What is the use of galvanized coils?
Galvanized coil is a thin steel sheet which is immersed in molten zinc bath to make its surface adhere to a layer of zinc. Galvanized coil can be divided into hot-rolled galvanized coil and cold-rolled galvanized coil. At present, continuous galvanizing process is mainly used for consumption, that is, continuous immersion of coiled steel sheets in galvanized bath to make galvanized steel sheets.
Galvanized coils are widely used in construction, household appliances, automobiles, containers, transportation and household industries because of their strong corrosion resistance, good appearance, good processing and economic applicability. Especially in steel construction, automobile manufacturing, steel silo manufacturing and other industries.
Defects of galvanized coil
Galvanized coil has defects such as easy to fall off, scratch, passivation spot, zinc grain, thick edge, air knife blade mark, air knife scratch, exposed steel, inclusion, mechanical damage, poor performance of steel base, wave edge, ladle bending, dimension incompatibility, stamping, zinc layer thickness incompatibility, roll printing, etc.
The main reasons for the scattering of zinc layer in galvanized coil are surface oxidation, silicon compounds, dirty cold-binding emulsifier, too high oxidation atmosphere in NOF section and dew point of maintenance gas, unreasonable air-fuel ratio, low hydrogen flow rate, oxygen infiltration into furnace, low temperature of steel strip entering pot, low furnace pressure in RWP section, low furnace door suction, low furnace temperature in NOF section, oil and grease. The evaporation is inexhaustible, the aluminium content of the zinc pot is low, the speed of the unit is too fast, the recovery is not sufficient, the residence time in zinc solution is too short, and the coating is too thick.
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