Definition of galvanized coil coating
1, normal zinc coating
In the normal solidification process, the zinc grains grow freely and form a coating with obvious zinc flower morphology.
2, small zinc coating
During the solidification process of zinc layer, the zinc grains are artificially limited to form the smallest zinc flower coating as possible.
3, no zinc coating
By adjusting the chemical composition of the plating solution, there is no visible zinc flower morphology, and the surface is uniform.
4, zinc iron alloy coating
Heat treatment of the steel strip after the galvanized bath, so that the entire coating to produce zinc and iron alloy layer, this coating appearance is dark gray, no metallic luster, easy to powder in the vigorous forming process, suitable for in addition to general cleaning, without further treatment can be directly painted coating.
5. Differential thickness coating
On both sides of the galvanized steel sheet, a coating with different zinc layer weights is required.
6. Finish
Finishing is a cold rolling process of small deformation on galvanized steel plates for one or more of the following purposes. Improve the surface appearance of galvanized steel or suitable for decorative coating; To temporarily minimize the phenomenon of slip lines or creases that occur when the finished product is not processed.
What is the use of galvanized coil
Galvanized coil is a thin steel plate that is immersed in a melted zinc tank and adhered to a layer of zinc on its surface. Galvanized coil can be divided into hot-rolled galvanized coil and cold-rolled hot-galvanized coil. At present, continuous galvanizing process is mainly used to produce galvanized steel sheet, that is, the steel sheet into a coil is continuously dipped in the plating tank with zinc melting. Because galvanized coil has the characteristics of strong corrosion resistance, good surface quality, conducive to deep processing, economic and practical, it is widely used in construction, home appliances, automobiles, containers, transportation and home industry and other fields. Especially steel structure construction, automobile manufacturing, steel silo manufacturing and other industries.
Defects of galvanized coil
The galvanized coil is easy to fall off, scratch, passivation spot, zinc particle, thick edge, air knife stripe, air knife scratch, exposed steel, inclusion, mechanical damage, poor steel base performance, wave edge, bending, improper size, impression, zinc layer thickness, roll printing and other defects.
The main reasons for the falling off of the galvanized coil zinc layer are surface oxidation, silicon compounds, cold binding emulsion too dirty, NOF oxidation atmosphere and protective gas dew point is too high, air fuel ratio is unreasonable, hydrogen flow rate is low, furnace aerobic infiltration, low temperature of strip steel into the pot, low furnace pressure and door suction in RWP section, and low furnace temperature in NOF section. Grease evaporation is not enough, the zinc pot aluminum content is low, the unit speed is too fast, the reduction is insufficient, the residence time in the zinc liquid is too short, and the coating is thick.
