What Should Be Done To Improve The Quality Of Galvanizing?
- Jun 01, 2018 -
What should be done to improve the quality of galvanizing?
(I) improve the adhesion of the plating layer:
1. Factors influencing coating adhesion:
(1) steel base chemical composition:
From the point of view of product quality and production cost, we should mainly use zeolite as hot-dip galvanized sheet.However, with the development of continuous casting, all kinds of calm steel should be hot-galvanized.In addition, due to the need of application, when high strength is required, the strength adhesion of low alloy steel will tend to deteriorate.For example, the addition of C,Si, AL,Cr, Nb and other elements in steel will lead to the deterioration of viscosity adhesion, which is caused by three reasons:
A) if the above elements are present or precipitated on the surface of strip steel, these metals and zinc cannot form intermetallic compounds, and where the zinc coating is slightly plated without zinc, the adhesion of the coating is reduced as a result.
B) in the annealing furnace, the zinc-sparing oxide film of zinc layer on the surface of the strip steel hinders the formation of the alloy layer and reduces the coating adhesion.
C) some of the above elements accelerate the diffusion of hot galvanizing, thus forming a thicker alloy layer, and even facilitating the conversion of pure zinc layer into alloy layer, reducing the processing performance of the coating.
(2) effects of zinc liquefaction components.
(3) influence of galvanized operating conditions.
2. Methods to improve the adhesion of coating
(1) effervescent steel is generally used as the original galvanized sheet.When the steel is hot galvanized, the harmful elements must be reduced below a certain amount.
(2) change the chemical composition of zinc liquefaction so that the zinc solution is within the required range.At present, a small amount of AL is added to the pot, 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