The Technology and Performance Influencing Factor of Hot Dip Galvanizing
Sep 04, 2017Keywords: hot galvanized steel, performance, influencing factor
Hot dip galvanized steel plate is the most important material for the construction of steel silo. Hot-galvanize technology is one of the most effective means to delay the steel material environmental corrosion, there is nothing comparable to this anchoring strength, durability and economical, widely used in the construction, machinery, transport and oceanographic engineering etc.
Main technological process of hot dip galvanizing: degreasing- washing- pickling- washing-dipping- plating-drying and preheating- hot galvanizing- sorting out- cooling- passivation- rinsing, drying - testing.
During hot galvanizing, complex physical and chemical reactions between iron and zinc happened lead to the formation of iron zinc intermetallic compounds. On the one hand, the zinc plating separates the steel matrix and the surrounding corrosion environment and can also produce the electrochemical protection to the steel base in the aggressive medium. Due to the existence of the Fe Zn alloy layer, the coating has higher hardness and bonding with the steel matrix, has good wear resistance and subsequent processing performance.
Factors influencing the hot-galvanizing structure property
1. Alloying Element
The addition of alloying elements can affect the melting point, viscosity and surface tension of zinc, and can change the growth behavior of metal compounds in the coating, and then change the properties of the coating. For example, Al, Mg and Ni can improve the corrosion resistance of the coating; Al, Pb, Sn and Sb can improve the appearance quality of the coating.
2. The chemical composition of steel matrix.
Among the elements of steel, C and Si have the biggest influence on the coating, and Mn, P and S have less influence. When C exists in the form of beaded pearlite and lamellar pearlite, the reaction of Fe-Zn is intensified, resulting in thicker metal compound layer and worse performance. Therefore, it is essential to choose the suitable carbon steel to produce galvanized steel sheet.
3. Hot-dip Galvanized Temperature
When galvanized, it will have the bad effect to the coatings performance if the zinc liquid temperature too high or too low :if the zinc liquid temperature is too high, the coating thickness and brittleness increased and ductility decreased, affect the surface quality of components, easy to produce cracks in the process of using. When the liquid temperature is too low and the fluidity is poor, the chemical composition of the coating is uneven.
4. Hot-Dip Galvanizing Time
The time of zinc dipping is short, which results in uneven distribution of alloy layer； The time of zinc dipping is long, resulting in brittle layer too thick of alloy layer and easily flaking when bent.
5. Flux and Passivating
Solvent plating is the most important technology in the pretreatment of galvanization, at present widely adopt the zinc chloride plating. The alloy coating can be passivated to improve the corrosion resistance.
SRON steel silo adopt the high quality hot-dip galvanizing coil, greatly improve the using performance of the silo, and reduce the later maintenance cost, SRON is the right choice for the silo system solution.
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