New technology for surface treatment of mold springs
The current mold is the main process equipment for industrial production. The development of modern industrial products and the improvement of technical level depend to a large extent on the development level of the mold industry. Since the Second World War, the improvement of automation has led to the rapid development of foreign molds. Although China is a big mold producing country, it is not a mold manufacturing power. For the springs that match the mold, this detail is also the key to quality. Affect the performance of the entire mold.
The author himself is engaged in surface treatment engineering, and has conducted market research on the surface treatment of mold springs, that is, rectangular springs. I found the following questions and asked to discuss them.
The surface of the spring is identified by various lacquer layers, such as light and small load, which is represented by yellow lacquer; light load is indicated by blue lacquer; medium load is indicated by red lacquer; and extreme load is indicated by brown lacquer;
Performance analysis: a good paint layer to match the surface treatment of the spring, can be described as two-pronged, using color to identify various technical parameters, to facilitate industrial production operations, but also to ensure the corrosion resistance of the spring surface is better.
At present, the main manufacturers that successfully use the above methods are many foreign manufacturers, such as Japan's Dongfa Company.
In China, there are only a small number of manufacturers' effective visits. At present, there are some fixed technical requirements, such as the use of imported materials to reach foreign levels, but there is a clear gap in the overall surface treatment effect of the spring.
Domestically, artificial spray painting is used, and the appearance will be sag, leaking, and poorly combined, and the rust prevention ability is poor. The limitations of its own process have caused a large number of products to be stripped and reworked.
Electrophoresis paint is used in foreign countries. In the water-soluble paint tank, the workpiece is used as a cathode, and a certain voltage and time can be applied to form a uniform thickness paint layer on all surfaces of the spring, and then cleaned and dried. Its appearance is clean and bright, no particles, no bottoming phenomenon, good bonding force is not easy to fall off, hardness is good 3-4H, if the British LVH company polyurethane cathodic electrophoretic paint, its softness is quite good. The operating environment has no rich solvent smell, less air pollution, and the wastewater treatment discharge process is simple, as long as the resin of the PH sedimentation electrophoresis paint is adjusted, and then the water is discharged.
We design the process for a domestic manufacturer: forming spring → shot peening → → hanging tools → alkaline degreasing → double washing → (micro acid 1% neutralization) phosphating → double washing → double deionized water washing → cathode system polyurethane Color electrophoretic paint → recycling → double water washing → assisting washing → baking curing → lower hanging tools.
result:
Shot peened particles are caught in the gap between the ends of the spring.
Shot peening leads to a rough surface, and the lacquer layer is correspondingly thickened to have a bright and flat appearance, which is 10-20 microns thick, which in turn causes the shrinkable thickness of the spring to become smaller.
Phosphating causes hydrogen embrittlement and reduces the life of the spring.
Improvement process: forming spring → lye liquid decoration degreasing → centrifugal water drop → hanging up → alkaline degreasing → double water washing → (micro acid neutralization 1%) phosphating → double water washing → double deionized water washing → cathode system polyurethane Color electrophoretic paint → recycling → double water washing → assisting washing → baking curing → lower hanging tools.
analysis:
The finishing process is to place the spring directly into a series of slanting centrifugal or spiral vibration type, eddy current type, etc., and add appropriate amount of abrasive, abrasive and water for finishing. The surface after finishing is smoother than the surface of the shot.
Moreover, the conventional processes such as degreasing, washing, pickling, phosphating, dehydrogenation, etc. are reduced, the production process is simplified, and the spring has less chance of rust in the production process, and does not need pickling. The thickness of the lacquer on the surface can be controlled to about 10 microns.
The author used Geely's cathodic electrophoretic paint from Haojin Fine Chemicals (Shanghai) Co., Ltd. as an experiment. Its performance in all aspects is better and the coating rate: when the coating is 10 microns, 45-50 square meters can be coated per kilogram of paint. Salt spray test: 500-1000H.
However, subtracting the shot peening process may reduce the strength of the spring itself. It is best to select a steel shot of a suitable diameter according to different spring specifications, such as the size of the gap, to avoid the steel shot being clamped in the spring gap.
Unqualified paint removal method:
At present, some factories use oil-painted paint layers, and then use shot peening to clean the surface, but the operation process is quite polluting, and the fire is prone to occur during manual operation.
The lacquer layer is carbonized with concentrated sulfuric acid, but the strong acid itself causes hydrogen embrittlement and is not suitable for springs.
Using KRT paint remover, using the swelling method, peeling off the paint layer, not hurting the spring substrate, the operation is simple, it is a relatively advanced method, but the use of the commercial paint remover may lead to an increase in cost, but if the scrap rate is reduced, the overall The cost will not rise.
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