Wuxi Delixin Automation Equipment Co., Ltd.


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The general principles of the coating pre-treatment process design
News Source: Suntory Xin   2013-2-5 13:09:27
To create a coating treatment production line, first complete the process design, before non-standard equipment design, manufacture and installation. Process design is the basis for the establishment of production lines, correct, reasonable route will have a positive impact on manufacturing operations and product quality. Process design should include: processing methods, processing time, process.
  1 Treatment
   The approach of the workpiece, the workpiece to achieve the purpose of chemical pretreatment, the manner in which in contact with the bath full immersion, spray, spray soaked modular, brushing type. It mainly depends on the workpiece geometry and the shape of the area, the scale of investment, production and other factors. E.g. the complexity of the geometry of the workpiece, is not suitable for spray mode; tank, barrel, the workpiece is not easy to sink into the liquid, and thus is not suitable for dipping.
  1.1 Full immersion
  The workpiece is completely immersed in the bath to be treated for a period of time, removed after completion of the the degreasing or rust phosphating target a common approach, Traditional and Simplified different geometry of the workpiece, as long as the liquid can reach the place,achieve treatment goals, which is the unique advantages of dipping, spray, brush can not be compared. Its shortcomings, is not supporting the use of mechanical erosion, the processing speed is relatively slow, long processing time, especially as continuous suspension conveying the workpiece, in addition to the workpiece in the tank run time, as well as on the workpiece downhill making equipment growth, site area and increased investment. Only phosphide abroad tend full immersion, allegedly full immersion phosphating easy to form a high iron content granular crystalline phosphate coating, with the cathodic electrodeposition good supporting sexual.
  1.2 Full spray
   With a pump to pressurize the liquid, and the liquid forming the mist is sprayed on the workpiece to achieve the processing effect to a pressure of from 0.1 ~ 0.2Mpa. A mechanical erosion profile and the liquid spray, therefore, the processing speed, shorten the time. Shorten the length of the production line, the corresponding section of the first space, equipment, inadequate, the more complex geometry of the workpiece, such as cavity around the corner and liquid is not easy to reach, the treatment effect is not good, so is only suitable for simple workpiece geometry processing . Shower system is not very suitable for pickling rust, it will bring a series of problems of corrosion of the equipment, in-process rust must be very careful in the choice of spray pickling. According to reports, the full spray phosphating easy to form crystalline dendritic thick, low iron content of the phosphate coating, pre-treatment do not advocate abroad as cathodic electrophoretic paint base. The full spray method is mainly used in household appliances, parts powder coating, electrostatic painting, anode electrophoresis.
  1.3 The spray - soak binding type
  Sprinkler - soaking binding formula is generally in a procedure, when the workpiece is first spray, soak and then into the groove, out of the groove and then spray all the spray, soak the same bath. This combination retains the the spray high efficiency, improve processing speed, but also has the soaking process, so that all parts of the workpiece can be effectively addressed. Therefore spray - an soak binding front that is able to complete the treatment process in a relatively short period of time, equipment space occupied relatively small, at the same time be satisfied with the treatment effect. At home and abroad for higher pre-treatment requirements of the automotive industry, generally tend to take the spray - soak binding way.
  1.4 Brushing way
  Directly to the treatment solution by hand brush to the surface, to achieve the purpose of chemical treatment, this approach is generally difficult to get good treatment effect is rarely applied in the factory. For some large, relatively simple shape of the workpiece can be considered in this way.
  2 Processing temperature
  Save energy, improve the working environment, reduce production costs, the chemical reaction rate, the processing time and the speed of production requirements, commonly used in the production and application of low or medium temperature pre-treatment process.
  Workpiece in addition to liquid oil, as well as a small amount of solid fats at low temperature, solid oils are difficult to remove, so the degreasing temperature either immersion or spray should select a temperature range. If only liquid oils and fats, the choice of defatted can meet the requirements.
   General corrosion and oxide workpiece temperature pickling, be guaranteed to completely get rid of the rust, and oxide in 10min. Unless there is sufficient reason, generally do not choose low or unheated, pickling rust, low temperature the pickling limited to: workpiece corrosion few non-oxide; rust unrestricted; allow the use of hydrochloric acid pickling.
  Surface of the adjustment process, usually without heating, the general is at room temperature.
  Low or medium temperature phosphate, phosphate speed are not significantly different from the rapid formation of phosphate coating can in a short period of time. Phosphating workpiece, requires a longer storage time between processes, should select a temperature phosphating, will have a better anti-corrosion effect.
  Throughout the pre-treatment process can be used at room temperature without heating the wash and final rinse hot water dry, the water temperature should be above 80 ℃.
  3 Processing time
  Treatment, the treatment temperature Once selected, the processing time should be based on the oil of the workpiece, the extent of corrosion. Pre-treatment generally reference the Pharmacy manual processing time requirements.
  4 Process
  According to the workpiece oil, the extent of corrosion and primer requirements, divided into different process.
  4.1 No rust workpiece
   Pre-skimmed - degreasing - water cleaning - table adjustment - phosphate - water cleaning - drying (electrophoretic primer time to dry, directly into the electrophoresis tank). This is a standard four-station process, a wide range of applications, pre-treatment is suitable for all kinds of cold-rolled sheet and machined stainless workpiece table transfers can also be added to the skim tank to reduce a table adjustment process.
  4.2 General oil, rust, scale mixed workpiece
  Degreasing rust "Combo" - water cleaning - and - table adjustment - phosphate - water washing - drying (or direct electrophoresis). The set of process is the most widely pre-treatment process, suitable for all types of workpiece (except heavy oil); phosphating temperature, can also dispense with the table adjustment step, a simple plate-type workpiece, can also be omitted and process, a standard four-place process rusted parts
  4.3 Heavy oil, rust, scale workpieces
   Pre-degreasing - water cleaning - degreasing rust "Combo" - water cleaning - and - table adjustment - phosphate - water cleaning - drying (or directly into the electrophoresis tank). For heavy oil workpiece, should first be pre-degreasing, removing most of the oil to ensure that the degreasing rust "Combo" Next treated to obtain a completely clean metal surface.
  5 Few notes
  In some small place in the process design should pay great attention, even if some are associated with equipment design, ill-considered, it will run and workers on the production line operation produces many adverse effects, such as processes interval overflow washing, phosphorus,of slag, the process of the workpiece hole, tank and heating pipe materials.
  5.1 Step interval
  If it is too long, the interval between the various processes cause the workpiece during operation secondary rust, especially in the pickling process, the workpiece after pickling rust easily oxidized in air pan-green, the best feature processbetween the film of water protection can reduce rusting. The rusty yellow pan-green workpiece seriously affect the phosphate effect cause the workpiece hanging gray, yellow, can not form a complete phosphate coating, it should be possible to shorten the interval between the process. If too short, the time interval between the step of the workpiece retention at the water, can not be completely drained, resulting in the string groove phenomenon will have a mutual ejection splash string groove, so that the bath composition is difficult to control, especially in the spray mode, or even destruction bath. Therefore, in considering the step interval should be based on the geometry of the workpiece shape to select an appropriate step interval.
  5.2 Overflow water cleaning
  Promote the overflow of washing, in order to ensure that the work is thoroughly cleaned to reduce the phenomenon of channeling. Should overflow water from the bottom of the upper part of the diagonal open the overflow hole overflow.
  5.3 Technical hole of the workpiece
  For some of the tubular member or easy to form water of the dead ends of the workpiece must select an appropriate location drilled hole process, to ensure fully shed hydropower in a shorter time. Otherwise it will cause channeling or in the air for a long time and drain, produce secondary rusty, impact of phosphate effect.
  5.4 Phosphate slag
   For any kind of phosphate solution will be more or less sediment (the LRT color phosphide to sediment few), should specify a process to design phosphate cleaning plant, especially spray phosphatingcleaning plant is essential, typical cleaning plant: inclined plate settler, high precipitate tower, centrifugal cleaners, paper bag residues are available.
  5.5 Tank and heating pipe materials
  Although for tank heating pipe material selection is not the content of the process design, process design not remind may be caused by the negligence of the equipment designers, affect the operation of the entire production line. For sulfuric acid, hydrochloric acid, the tank material can only use glass, steel, granite, plastic, heating tube can only use lead-antimony alloy tube, ceramic tube, and can not be made ​​of stainless steel materials. If you are using phosphoric acid pickling tank and heating pipe material can be made ​​of stainless steel material, of course, glass, steel, plastic, granite can be.


 

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