Galvanized coils are made by dipping thin steel sheets into a molten zinc bath to adhere a layer of zinc thin steel sheets on their surface. Currently, the continuous galvanizing process is mainly used for production, that is, the rolled steel sheets are continuously dipped into a molten zinc plating bath to make galvanized steel sheets; alloyed galvanized steel sheets. This type of steel sheet is also made by hot dip method, but after leaving the bath, it is immediately heated to about 500℃ to form an alloy film of zinc and iron. This type of galvanized coil has good coating adhesion and weldability.