What is called air knife in galvanizing production line?
A nozzle with a zinc-coated strip thickness controlled by fluid impingement is called an air knife.
What are the types of air knives?What are their characteristics?
Type of air knife: since the air knife was used in continuous hot galvanizing production of strip steel, there have been two types of uniform gap air knife, which later developed into two types of non-uniform gap air knife with medium and narrow edge width.
(1) characteristics of uniform gap air knife: the nozzle gap is uniform and equidistant, but the pressure of the spray gas is large in the middle, and the pressure on both sides is low, the plating layer of the product is thin in the middle and thick on both sides.
(2) characteristics of non-uniform gap air knife with narrow edge width: the nozzle gap is narrow in the middle and wide on both sides. Although the pressure distribution in the air knife is still high in the middle and low on both sides, the impulse of blown air is uniform, so the coating thickness of the product is uniform.
How to control the surface quality of strip steel reasonably?
Poor operation of zinc pot is an important cause of surface defects of galvanized sheet.As follows:
(1) scum on both sides of the strip should be cleaned regularly. Special tools can be used to scrape the scum to the non-operating side for centralized removal.
(2) refractory fragments and other dirty things on the inner wall of the furnace and the top of the furnace are easily brought into the zinc pot by the strip steel and deposited on the zinc level in the nose of the furnace. Every certain time, especially when dealing with the broken belt in the furnace, special dust hooks should be used to remove the dirty things on the surface of zinc liquid on the inner wall of the furnace.
(3) should be regular dregs, iron zinc pot every 10 days to salvage, sometimes the induction zinc pot also need 3~ 6 months dregs, do not make the bottom slag contact sink roll, if sink roll and stability roll adhere to zinc and timely scraping.(distance between bottom dregs and sunk rolls shall not be less than 200 MMM
(4) pay attention to adjust the air knife height, in a certain range of the air knife height has little effect on the coating thickness, but when the speed of the strip increases, it is necessary to increase the air knife injection pressure, in order not to make the spatter zinc liquid blocking air knife nozzle caused by air knife striation, must adjust the air knife height in time.