What should be done to improve the quality of galvanizing?
(I) improve the adhesion of the coating:
1. Factors affecting the adhesion of the coating:
(1) steel base chemical composition:
From the point of view of product quality and production cost, it should be mainly used as hot galvanizing plate.However, with the common and development of continuous casting, it is necessary to galvanize all kinds of sedation steel.In addition, due to the need of the application, high strength is required, and the strength adhesion of low alloy steel has a tendency to deteriorate.If C,Si, AL,Cr, Nb and other elements are added in the steel, the viscosity can deteriorate, and the reason for the viscosity deterioration is three:
A) if any of the above elements exist or are precipitated on the surface of the strip, these metals and zinc cannot produce intermetallic compounds, while the zinc coating is slightly less than zinc, resulting in a decrease in adhesion of the coating.
B) in the annealing furnace, a thin film of zinc oxide on the surface of the strip can prevent the formation reaction of the alloy layer and reduce the adhesion of the coating.
C) the above elements accelerate the diffusion of hot galvanizing, thus forming a thicker alloy layer, and even the pure zinc layer is converted into the alloy layer, reducing the processing performance of the coating.
(2) influence of zinc liquefaction.
(3) influence of galvanizing operation conditions.
2. Improve the adhesion of coating.
(1) it is generally used as galvanized steel plate.When the steel is hot galvanizing, the harmful elements must be reduced to a certain amount.
(2) change the composition of zinc liquefaction, so that the zinc liquid is within the required range of chemical composition.At present, we add a small amount of AL to the pan, 0.18~0.2%.
(3) improve the galvanized operating conditions, in the process of production found that coating adhesive, it should be taken to improve the strip into the zinc pot temperature: strip run a little slower, here, is not good for adhesion of galvanized products