Three Hot Aluminizing Processes for Steel Wire
According to the different ways of wire surface purification and activation, there are three hot aluminizing processes for steel wire.
1. Flux method
According to the condition of oil stain and oxide film on the steel wire surface, the rolling oil, lubricant and other contaminants can be removed by acid erosion, molten lead treatment, direct fire heating combustion, alkali washing and other methods. When molten lead is used, the temperature of molten lead shall be kept at 400-430 ℃. When the steel wire passes through the molten lead bath, the high temperature lead liquid can evaporate or burn the oil stain on the surface of the steel wire, and the dirt or drawing lubricant adhering to the surface of the steel wire can also be easily "scraped" by the lead liquid. The molten lead treatment has a great effect on removing oil dirt on the surface of steel wire, but this method has not been widely used due to the toxic problem of lead vapor.
2. Molten salt preheating method
Moeler, an American researcher, put forward in 1953 an aluminum plating method that uses molten salts to preheat steel wires and then immerse them in aluminum solution. The essence of this method is to use the low melting point and high specific gravity of the eutectic composition of two kinds of salts to make the aluminum liquid float on the surface of the molten salt. After the steel wire is preheated by the molten salt, it enters the aluminum liquid above it for aluminum plating without contacting the air. After degreasing and pickling, the steel wire is dipped with water solution flux, dried and immediately immersed in the molten mixed molten salt. In the molten salt, the steel wire is heated to the aluminizing temperature by the salt, bypasses the sinking roller (pressing roller) and directly passes through the aluminum liquid layer on the upper part of the molten salt. The steel wire is aluminized in the molten aluminum layer, and then is vertically lifted to the air for cooling and coiling.
3. Ultrasonic vibration method
The essence of ultrasonic vibration method is to increase the contact density between molten metal and steel wire surface by using the ultrasonic vibration transmitted to liquid aluminum and steel wire. When the steel wire enters the aluminum solution, because the steel wire is cold, ultrasonic vibration can prevent the molten metal adhering to the steel wire surface from rapidly forming a solidified layer, which will benefit the heat transfer effect of dry aluminum on the steel wire and improve the speed of aluminum plating. In addition, ultrasonic vibration can also make the solid particles separated from the steel wire surface, mainly the iron oxide film particles automatically gather and stay away from the moving steel wire, so as not to adhere to the dry steel wire surface. With the continuous addition of aluminum alloy ingots to the plating pot, it can be ensured that there is sufficient molten metal around the steel wire to avoid contamination by the above solid particles. Therefore, the obtained coating is free of impurities and has a smooth surface. To promote the destruction of the oxide film on the steel wire surface and the diffusion of molten metal to the steel wire surface.