Hot -soaking galvanized is a metallurgical reaction process. From a micro perspective, the hot -dip galvanized process is two dynamic balance: thermal balance and zinc iron exchange balance. When the steel workpiece is immersed in a melting zinc solution of about 450 ° C, the workpiece at room temperature absorbs the heat of zinc liquid to reach more than 200 ° C. The interaction of zinc and iron gradually becomes obvious, and zinc seep into the surface of the iron worker.
As the temperature of the workpiece gradually approach the temperature of the zinc liquid, the surface of the workpiece forms a alloy layer containing a different zinc and iron ratio, which constitutes a layered structure of the zinc coating. Over time, different alloy layers in the plating layer show different growth rates. From a macro perspective, the above process is manifested in the zinc fluid of the workpiece, and the zinc liquid surface is boiling. When the zinc and iron reaction gradually balances, the zinc surface gradually calms. When the workpiece is proposed, when the temperature of the workpiece is gradually decreased to below 200 ° C, the zinc iron reaction stops, and the hot -dip galvanized coating is formed, and the thickness is determined.
The factors that affect the thickness of zinc plating are: matrix metal components, surface roughness of steel, active element silicon and phosphorus content and distribution status in steel, the internal stress of steel, workpiece geometry, and heat -immersed galvanized process.
The current international and Chinese hot -dip galvanized standards are divided into sections according to the thickness of the steel. The thickness and local thickness of the zinc plating level should reach the corresponding thickness to determine the corrosion performance of the zinc plating. Workpons with different thickness of steel, the time required to achieve heat balance and zinc iron exchange balance, the thickness of the coating is also different.
The average thickness of the coating in the standard is based on the industrial production experience value of the above -mentioned galvanized mechanism. The local thickness is considering the unevenness of the thickness distribution of the zinc coating layer and the experience value required for corrosive corrosion requirements for coating. The average thickness of the coating in the standard is based on the industrial production experience value of the above -mentioned galvanized mechanism. The local thickness is considering the unevenness of the thickness distribution of the zinc coating layer and the experience value required for corrosive corrosion requirements for coating.
