Performance characteristics: the single side of galvanized steel sheet is uneven in size or the size of zinc flake on the upper and lower surfaces is inconsistent.
The most fundamental reason for affecting the uniformity of zinc flake is the inconsistency of the external environment during the process of zinc flower nucleation and growth, which is usually manifested in the uneven stress, roughness
or temperature on the surface of strip steel.
When the stress on the surface of the strip steel is uneven, such as the air knife is not parallel to the strip steel, the angle difference between the two air knives is too large, the cooling speed
of the area with high injection gas pressure on the plate surface is fast, and the zinc flake has solidified before it grows; the cooling speed of the area with low pressure is slow, the temperature is high, and the zinc flake size is large. The vibration
and bad shape of strip caused by wear of sink roll and stabilizer roll will cause uneven stress on the surface of strip steel.
In the production of aluminized zinc products, the cooling rate of the strip after leaving the zinc pot and the temperature
fluctuation of the strip in the annealing furnace lead to the rapid nucleation and small size of the zinc flake in the low temperature region, while the zinc flower nucleation is slow and the size is large in the high temperature area.
the surface roughness of raw steel strip is, the more nucleation and the smaller the zinc flake; the smaller the surface roughness is, the less nucleation is and the larger the zinc flake is. The main reasons for uneven roughness are as follows:
1) Strip steel shaking caused by wear of sink roll and stabilizing roll or inflexible rotation of stabilizing roll of sink roll will cause Scratch on strip steel surface;
2) When the surface cleanliness of raw steel strip is poor or the cleaning
section is not clean, the oil on the steel plate surface is carbonized before volatilization in the annealing furnace, which is wrapped on the surface of steel-based iron particles, making the reduction process difficult to carry out, resulting in excessive
crystallization points on the surface of steel strip;
3) The surface roughness of the coating will be uneven due to the nodulation on the surface of the furnace roll, the scratch of the strip in the furnace and the increase of the oxide scale on
the surface of the original plate;
4) The roughness of raw materials is uneven.
1) Adjust the distance and parallelism between the air knife and the strip steel, and the air knife angle is generally between - 4 ° and
+ 1 °;
2) Improve the stability of the mechanical system of zinc pot, control the shape of the incoming material and avoid the steel strip shaking;
3) Reduce sratch on the surface of strip steel;
4) Improve the cleaning capacity of cleaning
5) The temperature control of strip steel zinc pot should be strengthened to ensure the uniformity of plate surface temperature;
6) Improve the uniformity of raw material roughness.