In recent years, with the rapid development of our national economy, the use of high-pressure cleaner in cleaning equipment of aluminium sheet and strip, the demand for aluminium strip and foil is increasing in aerospace, household appliances, decoration materials and beverage industry, which brings the rapid development of PS base material, aluminium plastic strip, capacitor foil, canning material and other high-precision aluminium sheet and strip. These products have strict requirements for flatness and cleanliness, while high-precision aluminium strips are usually rolled by oil-cooled and smooth rolling. There are a lot of rolling oil and aluminium powder remaining on their surface. Therefore, in order to achieve outstanding appearance quality, it is necessary to clean and remove their surface residues. In order to improve the flatness of aluminium strip during cold working, it is necessary to clean the outer surface of strip firstly considering the straightening process. In addition, the strip should be stretched, bended and straightened. Under the effect of stretching and bending, the plastic extension will occur gradually and the internal stress of the strip will be released to improve the flaws such as waveform, warpage, lateral bending and potential bad shape of the strip.
Cleaning Principle and Theory of Aluminum Plate and Strip
Cleaning Principle Aluminum plate and strip in cold rolling process, because of the surface conflict and rolling between roll and aluminium plate, its appearance will occur slight dropping and adsorption of aluminium oxide powder, rolling oil and its incidental suspended components will remain on the surface of aluminium plate, which will have a negative impact on the processing of aluminium plate and strip composite, coating and other finished products. The tension exerted on the strip is partly transformed into the tension roll of the strip due to the severe bending and deformation of the strip on the roll, which eventually constitutes a conflict force and drives the roll group. Therefore, if the strip surface is not cleaned and alumina powder falls off during deformation, with oil contamination X attached to the roll surface of tension roll, the roll surface will be worn and slightly damaged, so it is necessary to clean the strip by special cleaning device.
Cleaning is to use pressure pump to pressurize the cleaning medium, to spray or brush the surface of the strip with non-touch type, so that the aluminum powder oil pollution on the surface of the strip can be dissolved and dropped into the cleaning medium, and then dried by extrusion roller, high-pressure air blowing and even high-temperature air drying, in order to obtain clean and dry aluminum strip. Together, by continuously compensating for the use of cleaning media in conjunction with the online circulating filtration system, the cleaning media can be maintained in sufficient quantity and cleanliness, and the thermal energy and cleaning media can be greatly saved. Nowadays, the commonly used cleaning media of STRETCH-BEND Leveller in aluminium processing industry are cleaning agent (or solvent oil), softening hot water and chemical solvent, and each has its own advantages and disadvantages.
The high-pressure water jet has a huge impact force due to the direct eruption of a dense beam. Both dense jet and direct eruption are indispensable. The jet beam is symmetrically arranged in the center line of the nozzle, but diverges and disperses. The jet is generally divided into three sections. In the original section, the length of the jet is L, which shows that the dynamic pressure along the axis of the jet is almost constant, and the dynamic pressure at the top of the jet is the same as that at the outlet of the nozzle. Another characteristic is very dense texture, particles hardly mix well with air, so the striking force of this section is the strongest. It is mainly used to clean hard scales. The length of the basic section shows by Lz that the characteristics of this jet are that air begins to mix with water jet, forming cavities and eddies. Therefore, the striking force of this section is moderate and suitable for cleaning various equipment and materials. It should be pointed out that with the increase of the interval, the effective strike force gradually decreases. In divergent section, the length of L3 shows that the jet is characterized by thorough mixing of air and water, thorough atomization of the jet, dramatic decrease in impact pressure and jet velocity, and the jet in this section has no technical value.
The key to the use of water jet cleaning is the selection and matching of pressure and flow rate. However, the pressure and flow rate of the direct effect are different in different jet intervals and divergence angles. Others are affected by the difference of nozzle structure and performance. Even under the same outlet pressure and flow rate conditions, the dynamic pressure has a great difference in the volume distribution.
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