Coating aluminum coil can not be produced by only one coil equipment. Generally, a coating aluminum coil production line needs four steps: pretreatment, coating, heating and exhaust gas recovery. Next, I will talk about the four steps of coating aluminum coil forming in detail with you.
I. pretreatment of aluminum roll:
Substrate pretreatment technology is produced with the production of coating technology. It serves for coating technology and lays the foundation for the preparation of excellent coating. Some grease and lubricant will remain on the surface of all base plates pre coated with aluminum coil during the production process. Of course, other substances may adhere during the transportation process. If these grease and adhesive are not removed, the coating and use of aluminum coil will be affected. In addition, the clean substrate surface needs to be chemically treated to form a stable conversion film, so as to improve the corrosion resistance of the substrate and the adhesion to the coating.
Due to the fast wire speed of the pre coating line, these process conditions require that all the pre-treatment night must be efficient to ensure that the substrate is clean and the conversion film covers all the substrate surfaces.
The pretreatment section mainly includes several processes, such as hot alkali degreasing, hot water cleaning, chemical treatment and passivation treatment.
II. Coating method:
Coating is the core part of the production line, and the main equipment includes roller coater and dryer. Generally, the front or back coating process is adopted. According to the different direction of coating roller and transmission roller, the process can be divided into forward coating and reverse coating.
(1) coating equipment roller coater is a kind of equipment which uses roller to coat coating on aluminum roll. Kdwa6td, which is the most widely used, is a two roller machine and a three roller machine. The double roll machine is mainly composed of paint trough, material lifting roll, coating roll and transmission roll. During the work, the adjusted coating is pumped into the paint tank by the working pump. The material lifting roller is responsible for sticking the coating in the paint tank and transferring it to the coating roller. The coating roller is responsible for coating the coating on the roll aluminum in the transmission, and the transmission roller is mainly responsible for the transmission of the metal roll. In the actual operation process, there is a certain proportion of the relative rotation speed between the feeding roller, the coating roller and the transmission roller.
Compared with the double roll machine, the three roll machine has one more control roll. The control roll is used to adjust the amount of paint transferred from the lifting roll to the coating roll, which has a certain effect on the accurate control of the amount of paint. If the rotating speed ratio between the three rollers is not reasonable, the coated material will produce horizontal and vertical stripes and other surface problems. In general, the linear speed of three rollers:
It is one of the key factors to control the rotation speed and the proportion of the three rollers reasonably. The three roller machine is mainly used in the occasions with high surface requirements.
(2) generally, the coating process of precoating aluminum coil can be divided into three types according to the number of coating layers: three coating process, two coating process and single coating process. According to the rotation direction of the coating roller and the driving roller, the coating process can be divided into forward coating and reverse coating. The coating way in which the rotation direction of the coating roller is the same as that of the substrate is the forward coating. On the contrary, it is reverse painting. Generally, the wet film thickness can only be coated with a lower one, and the surface appearance of the film coated by this process is not ideal, so the fixation process is not used very much. The reverse coating process is the most widely used coating process at present. By adjusting the rotation ratio between the rollers and the moving speed of the substrate, the required thickness and smooth appearance of the coating can be obtained. Coating is the core part of the whole production line, and this section mainly pays attention to several parts:
1. Relative rotation speed ratio between rollers 2. Balance parameters of substrate thickness and running speed with substrate surface temperature 3. Viscosity of coating and gap between rollers 4. Relationship between dry film thickness of coating and gap between coating and roller 5. Relationship between curing time, drying path length, substrate running speed, substrate thickness and plate surface temperature.
(3) the post-treatment section of post-treatment stage is used for further processing of the produced aluminum coil to give it better protection and decoration effect. There are mainly film, printing, embossing and embossing. In this simple note: the film is to apply the peelable film of polyolefin on the top coat. Printing is to print various patterns and patterns on the finished metal roll. Embossing is hot embossing on the surface of the paint film. Pressing is to press out a three-dimensional pattern through a steel roller matched with a male and a female pattern.
3. The heating mode of production line gas heating gas heating is the most widely used mode at present, mainly using natural gas, gas and other fuels. This method is mainly economic, the other is that the tail gas in the production process can be recycled.
IV. recovery of tail gas:
Because most of the coatings currently used contain a certain amount of organic solvents, Shanghai waste metal recycling experts say that in the production process, it is inevitable to produce tail gas, which contains a large number of organic solvents and carbon dioxide gas, which will cause a certain degree of harm to people's health and the environment. At present, the tail gas is generally treated by incineration. The specific method is to introduce the tail gas produced by the production line into the preheating oxidation device for purification and heat treatment, so as to generate hot air of solvent. The hot air of solvent and fuel gas will be introduced into the combustion chamber for combustion together. After combustion, the tail gas containing organic solvent will be converted into water and carbon dioxide, and the generated heat will be transferred through the heat exchange device It is recycled, so that the content of harmful gas in the exhaust gas discharged into the air is greatly reduced. The main
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