New surface treatment technology of mould spring
The current mold is the main process equipment for industrial production. The development of modern industrial products and the improvement of technical level depend largely on the development level of the mold industry. Since the Second World War, the increase in automation has led to the rapid development of foreign molds. Although my country is a big country in mold production, it has never been a strong country in mold manufacturing. For springs that match the mold, this detail is also the key to achieving quality. Affect the performance of the entire mold.
I am engaged in surface treatment engineering, and have conducted market research on the surface treatment of mold springs, that is, rectangular springs. I found the following questions and raised them for discussion.
The surface of the spring is identified by various paint layers. For example, light and small loads are represented by yellow paint; light loads are represented by blue paint; medium loads are represented by red paint; extremely heavy loads are represented by brown paint;
Performance analysis: A good paint layer is used to match the spring surface treatment, which can be described as two birds with one stone. Colors are used to identify various technical parameters, which is convenient for industrial production and operation, and the anti-corrosion performance of the spring surface can be better guaranteed.
At present, the main manufacturers that successfully use the above methods are many foreign manufacturers, such as Japan’s Dongfa Company.
In China, only a small number of manufacturers have effectively visited. At present, it is mainly due to some fixed technical requirements, such as the use of imported materials to reach foreign levels, but there is an obvious gap in the surface treatment effect of the entire spring.
Manual painting is generally used in China, and the appearance will appear sagging, leaking, poor combination, and poor rust resistance. The limitations of its own process caused a large number of products to be stripped and reworked.
Electrophoretic paint is used abroad. The workpiece is used as a cathode in a water-soluble paint tank, and a certain voltage and time are applied to form a paint layer with uniform thickness on all surfaces of the spring, which can then be cleaned and dried. Its appearance is clean and bright, no particles, no bottoming phenomenon, good binding force, it is not easy to fall off, and the hardness is 3-4H. If the polyurethane cathodic electrophoretic paint from UK LVH company is used, its flexibility is quite good. The operating environment has no strong solvent smell, less air pollution, and simple waste water treatment and discharge process. Just adjust the resin of the PH sedimentation electrophoretic paint, and then discharge the clear water.
We design the process flow for a domestic manufacturer: forming spring → shot blasting → upper hanger → alkaline degreasing → double water washing → (slightly acid 1% neutralization) phosphating → double water washing → double deionized water washing → cathode system polyurethane Color electrophoretic paint→recycling→double water washing→assisting washing→baking and curing→under hanging tools.
The peened particles will be caught in the gap between the two ends of the spring.
Shot blasting causes a rough surface, and the paint layer should be thickened accordingly to have a bright and flat appearance, with a thickness of 10-20 microns, which in turn causes the shrinkable thickness of the spring to become smaller.
Phosphating can cause hydrogen embrittlement and reduce the service life of the spring.
Improvement process: forming spring → lye polish degreasing → centrifugal water drop → hanging → 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 and curing→under hanging tools.
The finishing (finishing) process is to put the spring directly into the inclined centrifugal, spiral vibrating, vortex and other series of finishing machines, and add an appropriate amount of abrasive, abrasive and water for finishing. The surface after finishing is smoother than that of shot blasting.
Moreover, traditional processes such as degreasing, cleaning, pickling, phosphating, dehydrogenation, etc. are reduced, the production process is simplified, and there is less chance of corrosion of the spring during the production process, so pickling is not required. The thickness of the paint on the surface can be controlled at about 10 microns.
The author used Hawking Fine Chemicals (Shanghai) Co., Ltd.’s Geelylon cathodic electrophoretic paint for the experiment. It has better performance in all aspects and the coating rate: when the coating is 10 microns, 45-50 square meters per kilogram of paint can be coated. Salt spray test: 500-1000H.
However, subtracting the shot peening process may reduce the strength of the spring itself. It is best to choose a steel shot with a suitable diameter according to different spring specifications, such as the size of the gap, to avoid the steel shot being caught in the spring gap.
Unqualified paint removal method:
At present, some factories use oil to burn the paint layer, and then use shot blasting to clean the surface, but the operation process causes considerable pollution, and fire is prone to occur during manual operation.
Use concentrated sulfuric acid to carbonize the paint layer, but strong acid itself can cause hydrogen embrittlement, so spring is not suitable.
The use of KRT paint remover, the swelling method, peel off the paint layer, does not damage the spring substrate, simple operation, is a relatively advanced method, but the use of commercial paint remover may lead to increased costs, but if the scrap rate is reduced, the overall The cost will not rise.