In the electroplating line, it is necessary to carry out reasonable degreasing before plating the workpiece. Today we will take a look at the method of removing organic solvents:
(1) Impregnation method. In the impregnation method, the metal material is immersed in the cleaning tank, the entire surface is contacted with the organic solvent, and stirred, and the oil on the surface of the base material is dissolved by the organic solvent, and the undissolved dirt is simultaneously taken away. In order to improve the degreasing efficiency, the immersion time may be heated and extended, and a method of increasing the flow rate of the organic solvent may also be employed. The immersion cleaning is sometimes assisted by the mechanical action of a brush or squeegee to increase the rate of degreasing. Various organic solvents can be used for the impregnation method.
(2) Spray method. The spraying method uses a water pump to spray an organic solvent through the nozzle onto the surface of the metal workpiece, the grease is continuously dissolved, and the dirt is also taken away, and the spray is repeatedly sprayed until the oil is completely removed. Generally, the pressure range is 70-120 kPa. The greater the injection pressure, the greater the proportion of mechanical detergency in degreasing. The impact of jetting during high-pressure jet degreasing is a decisive effect. Granular dirt such as dust, carbon particles and quartz sand has a good removal effect. In addition to volatile solvents such as gasoline, acetone and methylene chloride, other organic solvents can be used in this process, but must be handled in a closed container.
(3) Vapor method. In the steam cleaning tank, the organic solvent cleaning liquid is heated to become a vapor to form a gas phase region. The workpiece is placed in the gas phase zone, and the grease adhering to the surface is dissolved by the vapor. When the vapor is condensed by the workpiece, the solvent and the grease and the like fall back into the cleaning liquid below the tank. Then the solvent is heated and vaporized to bring the vapor into contact with the workpiece, and the circulation is continued. Therefore, the solvent vapor contacted by the workpiece during the degreasing of the steam is always clean, so that the degreasing and degreasing process can be overcome in the degreasing and degreasing process. The disadvantage of contamination and the high cleanliness of the workpiece surface.
The organic solvent used for steam degreasing requires the following characteristics:
1 has a high ability to dissolve oil.
2 Lower heat of vaporization and specific heat capacity, the same quality metal workpiece condenses the most solvent and requires the least amount of heat.
3 has a high enough boiling point to ensure the final effect of solvent vapor rinsing. Make the workpiece easy to dry.
4 The boiling point is not particularly high in order to separate the solvent from the oil by simple distillation.
5 The relative density of vapor is larger than that of air, and the loss of diffusion into the air is small.
6 can maintain chemical stability during degreasing.
7 No corrosion to workpieces and equipment.
8 Safe and harmless under working conditions, non-flammable, non-explosive, non-toxic.
From the current use, the organic solvent meeting the above requirements is mainly a halogenated hydrocarbon solvent. The disadvantage of a single vapor degreasing is that the condensation and cleaning stops when the workpiece temperature rises to the vapor temperature, so it is often not suitable for cleaning heavy greased workpieces.
(4) Joint processing method. The combined treatment method includes three methods of impregnating a vapor, spraying a vapor or vapor, impregnating and spraying. The combined treatment method has better degreasing effect. For workpieces with complex shapes, such as deep holes, concave surfaces and old grease stains, joint treatment should be used, that is, the workpiece is impregnated or steamed before degassing. Spray degreasing.
1 impregnation-steam combined degreasing: the workpiece is first de-oiled by de-oiling and then degreased by steam. A part with a thick dirt or dirt and a particularly strong bond is first degreased by immersion. In a near-boiling organic solvent, metal scraps and insoluble impurities on the workpiece and most of the grease are removed; The oil is removed to remove the residual dirty solvent and the workpiece is cooled. Finally, the workpiece is transferred to the steam deoiling tank, and the residual dirt is actually removed by rinsing, and the workpiece is dried.
2 injection-steam combined degreasing: In order to improve the degreasing effect, the combination of jet degreasing and steam degreasing can be combined. However, the composition of the degreasing device is relatively complicated, and the requirements for daily use maintenance management are higher than that of dipping and degreasing. The workpiece with complicated shape and old grease stains can be degreased by spraying, and then degreased by steam to achieve better degreasing effect. When the fuel is degreased, it is usually operated manually, and the injection pressure is 0.
12~0.20MPa is suitable, and the nozzle position should be lower than the vapor deoiling area. Similarly, the workpiece that has been degreased by steam can be further removed by spraying and de-oiling to achieve better decontamination effect.
3 Vapor-impregnation-spray combined degreasing: Vapor-impregnation-spray combined degreasing is mainly based on steam degreasing, and has the advantages of immersion degreasing, jet degreasing, thus ensuring high cleanliness requirements of the workpiece. This degreasing method is highly adaptable and suitable for workpieces with complex shapes and serious surface oils and which are batch-produced. The order of degreasing is to first immerse and degrease, then spray and degrease, and finally perform steam degreasing.
The above is the method of removing oil by using organic solvents on the electroplating line.
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Label: degreasing efficiency specific heat capacity vaporization heat organic solvent workpiece
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