What role does Pb add to zinc solution in hot galvanizing production?
(1) Pb in 450 ℃ of liquid zinc, the solvent is 1.5%
(2) in modern hot-dip galvanizing, Pb in the zinc liquid presents an unsaturated state, generally 0.1-0.22%
(3) effect of adding Pb:
A.P b can reduce the melting point of zinc solution, prolong the solidification time of zinc and promote the formation of large zinc flowers.
B. the presence of b.b. can reduce the viscosity and surface tension of zinc liquid, and thereby increase the infiltration capacity of zinc liquid to iron surface.
When the content of c.Pb exceeds 1.0%, it may cause the corrosion of the coating grain boundary.To avoid this, 0.05% Sb can be added to galvanize.
How does iron content of zinc solution in hot dip galvanization affect product quality?
(1) Fe in 450 ℃ liquid zinc solubility was 0.03%.
(2) when the Fe content is >.03%, fe-zn alloy will be generated and sink to the bottom of the pot to form bottom slag, resulting in defects such as zinc scars in the galvanized products.
(3) in the zinc solution, Fe will combine with AL to form scum, reducing the effective content of aluminum in the zinc solution.
(4) the presence of iron will increase the viscosity and surface tension of zinc-liquid, thus worsening the wetting conditions of zinc-liquid on steel plate. It is inconvenient for high-speed production.