First, the flux method According to the oil stain and oxide film on the surface of the steel wire, acid corrosion, molten lead treatment, direct fire heating, alkali washing, etc. can be used to remove rolling oil, lubricant and other contaminants. When treated with molten lead, the temperature of the molten lead is maintained at 400-430 degrees Celsius. When the steel wire passes through the molten lead tank, the high-temperature lead liquid can evaporate or burn off the oil on the surface of the steel wire, and the dirt adhered to the surface of the steel wire or the drawn lubricant is also easily scraped by the lead liquid. The treatment of molten lead has a great effect on the removal of grease on the surface of the steel wire, but this method is not used because of the poisoning problem of lead vapor.
Second, molten salt preheating method The American researcher Moeler proposed in 1953 that the molten salt was used to preheat the steel wire and then immersed in the aluminum liquid. The essence of the method is to use the low melting point of the eutectic composition of the two salts and its high specific gravity to float the aluminum liquid on the surface of the molten salt. The steel wire is preheated by the molten salt and then enters without contact with air. The aluminum liquid in the upper part is plated with aluminum. The degreased, pickled steel wire is dip coated with the aqueous solution flux, dried and immediately immersed in the molten mixed molten salt. In the molten salt, the steel wire is heated by the salt to the aluminizing temperature, bypassing the sinking roll (pressing roll) directly through the aluminum liquid layer on the upper part of the molten salt, the steel wire is plated with aluminum in the molten aluminum layer, and then vertically raised to the air. Medium cooling and coiling. Third, ultrasonic vibration method The essence of the ultrasonic vibration method is to increase the contact density of the molten metal with the surface of the steel wire by using ultrasonic vibration transmitted to the aluminum liquid and the steel wire. When the steel wire enters the aluminum liquid, the ultrasonic vibration can prevent the molten metal adhered to the surface of the steel wire from rapidly forming a solidified layer due to the cold steel wire, which is advantageous for the heat transfer effect of the dry aluminum on the steel wire and the speed of the aluminum plating. In addition, the ultrasonic vibration can also cause the solid particles removed from the surface of the steel wire, mainly the iron oxide film particles to automatically gather and stay away from the moving steel wire, so as not to adhere to the dry steel wire surface. As the metal aluminum alloy ingot is continuously replenished to the plating pot, it is ensured that the molten metal around the steel wire is not contaminated by the solid particles or the like, and thus the resulting plating layer contains no impurities and has a smooth surface. To promote the destruction of the oxide film on the surface of the steel wire and the diffusion of molten metal to the surface of the steel wire.