Development Status Hot Dip Galvanized Coils Equipment
The air knife is a crucial component to control the thickness and uniformity of the coating. The new air knife adopts a flexible overall frame structure, which can reliably and accurately adjust the gap and angle between the air knife and the steel belt and adjust the distance between the air knife and the zinc pot. In addition, the knife lip gap can automatically control to ensure the flatness and uniformity of the coating.
The zinc slag in the zinc bath is the most critical factor affecting the surface quality of the galvanized sheet. In modern production lines, the iron-zinc pot replaces by a ceramic-lined pot, and a removable or liftable double zinc pot is used to replace the conversion of the plating solution. , Using the online measuring probe (Al sensor) and the corresponding zinc liquid composition control system can strictly determine the aluminum and related iron content in the zinc liquid, which can effectively reduce the influence of zinc dross on the surface quality of the galvanized sheet.
The vertical zinc pot designed by the magnetic fluid dynamic closure (NHD) created by the electromagnetic moving field can eliminate the parts in the original zinc pot and obtain the advantages of high speed, no zinc slag, energy-saving, and improvement of the surface quality of the zinc layer. [9] . The working principle of this method is: when the liquid Zn (or Al, ZnAl) alloy flows from the bottom of the pot and enters the MHD channel to a certain depth (this depth depends on the specific gravity of the molten metal, the height of the liquid level, the size of the current and other factors), due to AC induction. The external electromagnetic moving field generated by the device generates an induced current in the zinc liquid. The interaction of this current with the external electromagnetic field generates electromagnetic force, which acts on the metal fluid to move it upward. Therefore, the zinc liquid cannot flow out from the opening at the bottom of the pot. When the steel strip enters the zinc pot from its bottom channel, the zinc liquid is always in one position at the channel, and there is no need for any steel structure in the zinc pot.
To improve the unit's operating speed and production efficiency and reduce the formation of surface slag and bottom slag, relevant foreign research units have successively developed "zinc pad" technology and "vertical zinc pot technology." The "Zinc Pad" technology works on a liquid metal pad principle. The steel strip is pressed down by the pressure of the liquid metal to pass through the zinc pad. Since no sinking roller is used, the surface quality of the product is improved, the production efficiency is improved, and the cost reductions. It is especially suitable for high speeds. Unit.
Due to the emergence and application of tailor-made laser welding technology, automobile factories can weld narrow-width plates together and use them. This makes the production of small-volume wide-width plates (with a width of 1800mm or more) no longer necessary, but cold rolling mills. The product's width reaches 1550mm, producing galvanized steel sheets for automobiles.
The continuous development and application of these advanced technologies and equipment have increased the proportion of hot-dip galvanized steel used in automobile manufacturing. For example, Japan has reached 81%, Canada 76%, Italy 71, France 70%, Germany 60%, and the United States 45%. Due to the superiority of the cost and quality of the alloyed galvanized sheet, the Japanese automobile industry decided to replace the existing electro-galvanized alloy sheet with all the alloyed galvanized sheets for automobiles by 2005.
