How does the brush roller in the scrubbing unit work?_FAQ

The good surface condition and cleanliness of the brush roll strip steel before hot-dip galvanizing are the prerequisites for obtaining a good coating. On the surface of the strip steel with oil stains, it is impossible to obtain a bright, good bonding force, and superior corrosion resistance coating. Therefore, the brush roller must pass through the cleaning section of the scrubbing unit before the strip steel enters the annealing furnace. The cleaning section mainly includes chemical alkaline washing, electrolytic alkaline washing and brush roller cleaning.　 (1) Spray cleaning and cyclic spray cleaning are mainly to complete the heating and rough washing of strip steel.　 It is carried out in the form of spraying, using the chemical action of hot lye to remove thick rolling oil and iron powder on the surface of cold rolled strip steel. These rolling oils are often contaminated by lubricating oil and hydraulic oil, and must be removed by chemical alkaline washing first, and then electrolytic alkaline washing. Grease is divided into two categories: saponified oil and non-saponified oil. The main component of saponified oil is glyceride containing various higher fatty acids, its general formula is (RCOO)3C3H3, which can react with alkali to produce soap and glycerin. Non-saponified oil refers to mineral oil, which cannot react with alkali, but they can form an emulsion under certain conditions, and the non-saponified oil can be removed from the surface of the steel strip by emulsification. The function of chemical alkaline washing is to use hot lye to remove saponified oil and emulsifier to remove non-saponified oil. The important thing in the spray cleaning section is to control the concentration and temperature. If the concentration is too high, the solubility of the soap and the stability of the emulsion will decrease, and the cleaning effect will be reduced. At the same time, the degreaser will be wasted. If the concentration is too low, the cleaning will not be effective. Generally, the concentration of lye is controlled at 2~3%. From the perspective of energy conservation, the oil removal temperature should be as low as possible, but lowering the temperature and improving the oil removal effect are contradictory. The higher the temperature, the faster the physical and chemical reaction between the grease on the surface and the degreasing agent, and the easier it is to remove the oil. To lower the temperature, a surfactant must be added to the degreasing agent. For the cleaning section of this unit, the temperature should be controlled at 60~80℃.　 (2) Alkaline scrubbing 　 Due to the large amount of grease and iron powder adhered to the surface of the rolled hard coil, only the chemical caustic scrubbing effect is not very good, and the chemical caustic scrubbing and brush roller cleaning must be used for treatment together. Brush roller cleaning can mechanically remove oil and dust to improve the cleaning effect. For the brushing of this unit, in addition to controlling the concentration, temperature and spray pressure, the brush roller current must also be controlled. The brush roller current reflects the degree of compression of the brush roller on the strip steel, and the reduction of the brush roller can be adjusted by the motor. During the brushing process, the bristles of the brush roller will continue to wear out, and the length of the bristles of the brush roller must be checked frequently. When the bristles are too short, the brush roller should be replaced in time. (3) Electrolytic cleaning 　 The mechanism of electrolytic cleaning is that when strip steel is used as a cathode or anode, hydrogen bubbles or oxygen bubbles are correspondingly precipitated on the surface of the strip steel due to the electrolyzed water, which destroys the oil film attached to the surface of the strip steel. Small bubbles break away from the steel strip to which the oil droplets are attached and stay on the surface of the oil droplets, and stay at the interface between the oil and the degreasing liquid. As new bubbles continue to precipitate out, the small bubbles gradually become larger, so the oil droplets stay in the bubbles. It is separated from the surface of the steel strip under the action of, and is carried into the degreasing liquid by air bubbles. At the same time, the generated small bubbles can bring out the oxide scale on the surface and some dirt in the voids. The commonly used methods of electrolytic degreasing are: the intermediate conductor method and the conductive roller method. This unit uses the intermediate conductor method. That is, the strip steel is not directly connected to the power source. The power source is connected to the electrode plates located above and below the strip steel. When the upper electrode plate is connected to the anode, the lower electrode plate is connected to the cathode. Compared with the anode plate, if the strip steel potential is negative, it is the cathode. At this time, the reaction on the strip steel surface is: 4OH- — 4e u003d O2 + 2H2O, which means that oxygen is precipitated on the strip steel. Compared with the cathode plate, if the potential of the strip steel is positive, it is the anode. At this time, the reaction of the strip steel is: 4H2O + 4e u003d 2H2 + 4OH- that is, hydrogen is precipitated on the strip steel. In this way, water is decomposed through an electrochemical reaction to generate hydrogen and oxygen. In the electrolytic cleaning section, the concentration and temperature of the lye should be slightly increased to enhance conductivity. Since a large amount of hydrogen and oxygen are produced in the electrolysis process, and hydrogen is a flammable and explosive gas, the electrolysis cleaning section must have an exhaust device to extract the gas in time. Welcome to www.mxbrushmachinery.com