Application of brush roller in electrolytic alkaline washing process of cold rolled strip steel_faq

Electrolytic alkaline washing relies on the electrode polarization and the mechanical stirring and stripping of the gas evolved on the electrode to remove oil. Therefore, the NaOH content in the electrolytic alkaline washing solution should be appropriately low. The use of surfactants should prevent the generation of a large amount of foam, otherwise it will be generated. Hydrogen and oxygen are difficult to escape and mix in the foam layer. If the electrode is in poor contact and ignites, it will explode. The most commonly used method in electrolytic alkaline washing is the intermediate conductor method, that is, the strip is not directly connected to the power source, and the power source is connected to the electrode plate. When the electrode plate of the inlet part is connected to the anode, the electrode plate of the outlet part is connected to the cathode. At this time, the current flows from the anode to the strip through the alkaline washing solution, and from the strip to the cathode through the alkaline washing solution. In the inlet part, the strip steel corresponding to the anode plate serves as the cathode, and hydrogen is precipitated on the strip steel; when the strip steel runs to the position corresponding to the cathode electrode plate in the outlet part, the strip steel acts as a positive plate, and oxygen is precipitated on the strip steel . Therefore, when the strip passes through the electrolytic cleaning tank, it undergoes a process of first cathode and then anode. In the intermediate conductor method, the polarity of the two electrode plates can be automatically switched, usually every 2 hours. The polarity conversion can also remove some impurities that precipitate on the surface of the strip when the strip is the cathode. The amount of hydrogen precipitated when the strip is the cathode is twice the amount of oxygen that is precipitated when the strip is the anode. Therefore, when the strip is the cathode, the oil removal speed is fast and the effect is good. Steel produces hydrogen embrittlement. Influencing factors of electrolytic alkaline washing effect: (1) When selecting current density for current density, ensure that enough bubbles can be precipitated to increase the alkaline washing speed. Generally, the current density should be controlled at 011～013A/cm2. The current density calculation formula is: J u003d Iη/ (2 · L · B) where J is the current density, A/ cm2; I is the current, A; η is the electrolysis efficiency; L is the electrode length, cm; B is Strip width, cm. Increasing the current density can increase the degreasing speed, the hydrogen permeation effect of the cathode degreasing increases, and the degreasing ability to remove the oil stains rolled into the surface of the strip steel is improved. However, the current density is too high, which causes the electrolytic cell voltage to be too high; when the strip steel is used as the cathode, a large amount of hydrogen gas is precipitated and a large amount of alkali mist is brought out to pollute the air. When the strip steel is anode, it may corrode the surface of the strip steel. In severe cases, pitting corrosion may occur. Therefore, the appropriate current density should be selected according to the amount of oil on the surface of the strip. (2) Electrolysis time The combined effect of electrolysis time and current density affects the cleaning effect of the strip surface. The larger the current, the better the cleaning effect. The calculation method of the current is as follows: C u003d JL / V where C is the current, A/ (cm2·s); J is the current density, A/cm2; L is the total length of the electrode, cm; V is the operating speed of the unit ,cm/ s. At present, there is no uniform limit to the electrolysis time, but according to experience, the duration of hydrogen bubble development should not be less than 0125s, and the standard residence time for hydrogen bubble development is generally 013～015s. In fact, most designs make the total time that the strip stays between the electrode plates in the electrolytic cell (the duration of hydrogen bubble development + the duration of oxygen bubble development) greater than 1s. (3) Electrolytic alkaline washing temperature The electrolytic alkaline washing temperature is generally controlled at 40～80 ℃. The high temperature of electrolytic alkaline washing can strengthen the emulsification effect and enhance the degreasing effect. It can also reduce the resistance of the solution, increase the conductivity, and speed up the degreasing process, but the temperature is too high, just like the chemical alkaline washing, the heat energy consumed increases, and the solution Large amounts of evaporation will worsen the working environment. (4) Electrolyte The electrolyte of cold-rolled strip steel generally uses NaOH solution with a concentration of 2% to 5%. NaOH can saponify oil and gas. In addition, NaOH is a strong electrolyte, which can be completely ionized in the solution, so that the solution has good conductivity. Therefore, increasing the concentration of NaOH can increase the current density during degreasing and speed up the degreasing speed; at the same time, the solution has a passivation effect on the surface of the strip, which can prevent the strip from being corroded during cathode degreasing. (5) Electrolyte circulation The circulation of the electrolytic solution plays the role of stirring the solution, because the stirring solution can replace the emulsion layer around the high-speed running strip steel; at the same time, due to the mechanical force, the oil droplets can be taken away from the surface of the strip steel , In addition, it can increase the current density used. (6) Other factors: When the strip steel contacts the strip steel in the electrolytic cell, and the strip steel plate shape is too poor or the strip is broken, as long as these grids have voltage, the strip steel will have burn marks. At this time, the rectifier must be automatically controlled. Disconnect in time. The electrolytic alkaline washing of cold-rolled steel strip is a relatively mature process, and its equipment and control system have been fully mastered in China. The equipment can be domestically produced. Electrolytic alkaline washing