(1) Surface pretreatment process section. It includes hot water cleaning, degreasing treatment, water cleaning, pickling treatment, water cleaning, water storage, plating flux treatment and drying processes of steel pipes. Hot water cleaning is to remove metal filings, dust, rust and cutting iron filings on the surface of steel pipes. During processing, the steel pipe is first immersed in a hot water tank for cleaning, and the steel pipe is preheated to enhance the effect of the next degreasing and pickling processes. The cleaned steel pipes are cleaned in a chemical degreasing tank in order to remove the grease present on the surface. The degreased steel pipe is washed with hot water again to remove the residual alkaline degreasing solution and degreasing sediment on the steel pipe. In order to remove rust and iron oxide scale on the surface of steel pipes, the steel pipes are pickled in a pickling tank, usually in a pickling solution with corrosion inhibitors added. After pickling and rust removal, the steel pipes must be washed with water to remove the residual solution and sediment of the pickling (for steel pipes washed with sulfuric acid, they are sometimes rewashed in a 5% hydrochloric acid solution tank to make the surface of the steel pipe bright and helpful. to clean the iron sulfate). The pickled steel pipes are then immersed in a weakly acidic cold water tank for storage in preparation for the next process of dipping flux. The main function of dip coating flux is to remove oxides and iron salts on the surface of the steel pipe, thereby ensuring that the surface of the steel pipe remains clean and will not be re-oxidized before being dipped in zinc.
(2) Galvanizing process section. The galvanizing process section includes hot-dip galvanizing of steel pipes. The steel pipe dip-coated with plating flux is dried in a drying furnace and preheated to about 200°C. Steel pipe preheating can reduce the heat consumption in the zinc pot and reduce the intensity of heating the zinc pot, thereby extending the service life of the zinc pot and improving working conditions. The baked steel pipe is sent into the zinc pot by the galvanizing machine and then removed from the zinc pot. The surface of the steel pipe is immersed in a liquid zinc layer. Immediately after the steel pipe is dipped in galvanizing, steam and compressed air are used to spray the coating externally and internally. This is to remove excess zinc on the surface and make the coating surface uniform and smooth.
(3) Post-plating treatment process section. The post-plating treatment process section includes the process from the steel pipe leaving the zinc pot to cooling to room temperature. That includes the air cooling, water cooling, drying, passivation treatment and other processes after the steel pipe is blown outside and blown inside. Cooling after the injection treatment can cool down the steel pipe quickly and stop the growth of the iron-zinc alloy layer. Galvanized steel pipes can be passivated as needed. After passivation, immerse the steel pipe in a hot water tank to wash away the passivation residue. Hot water is used for cleaning because hot water is easy to dry quickly. If passivation treatment is not required, oiling treatment can also be carried out as required.
(4) Post-processing process section. The post-processing technology of steel pipes refers to the inspection, wire turning, straightening, printing, weighing, bundling and packaging of steel pipes after hot-dip galvanizing.
