What are the factors that affect the structure of the galvanizing layer?
(1) is affected by temperature temperature < 480 ℃, the Fe loss coefficient is smaller.The temperature > 480 ℃, the Fe - zinc diffusion, thickening of the brittle phase alloy layer, and reduce the plastic coating.
(2) under the influence of zinc immersion time at fixed temperature, prolonged zinc immersion time will promote the thickness of fe-zn alloy layer. Therefore, when hot-galvanizing, the zinc immersion time should be shortened as much as possible to reduce the thickness of the alloy layer, so as to increase the toughness of the coating.
(3) effects of aluminum in zinc liquid
A. Aluminum containing 0.1 ~0.2% in zinc solution can cause significant changes in the coating.
B. When the content of aluminum in zinc solution reaches 0.2%, the brittle 5 phases can be completely eliminated.
C. When the content of aluminum reaches 0.2%, the coating is composed of eutectic mixture +n and n, with good plasticity.
D. when aluminum content reaches 0.2%, 5A1+ 2fezn-fe2als +14Zn
E. AL can inhibit iron loss in zinc solution.
Note: aluminum inhibits the formation of alloy layers. This delay time is called incubation period.The inhibiting effect of aluminum on alloy layer growth is related to the following factors:
a. The higher the content of AL in the zinc solution at a given temperature, the longer the inhibition time.
b. Under certain AL content, the inhibition time of AL on alloy layer decreases with the increase of temperature.
c. At each temperature, there is a limit of AL content, and further increase of AL content will not increase the inhibition time of the alloy layer.
d. The higher the galvanizing temperature, the lower the limit AL content.
e. The rougher the surface of the steel base, the higher the Fe content in the zinc liquid, the shorter the inhibition time of AL on the alloy layer.
(1) AL will cause the alloy layer to be thinner, while the pure zinc layer will be thicker, which is favorable for general bending molding.
2) because the alloy layer is resistant to Cus0 and has better erosion than pure zinc layer, when the content of AL is high, the galvanized product is resistant to CusO and its erosion ability is weakened. Therefore, for galvanized products that are resistant to Cus0 and erosion, the method without AL galvanization should be adopted.