Reasons and Solutions of Oxidation Spot in Automobile Castings
Automobile Castings and their alloys are much more difficult to silver than copper, the process is also more complex. The main reason is that the performance of castings and their alloys is not the same as other metals, aluminum is a two-sex metal, and acid and alkali are the reaction, pretreatment slightly improper, it will cause the surface over corrosion. And cast and its alloys, whether in the air or in the solution are easy to produce oxide film, this layer of oxide film if not removed, will affect the adhesion of the coating. casting Common defects Features: Oxidation slag is mostly distributed on the upper surface of the casting, in the corner of the Mold is not ventilated. Fracture mostly gray or yellow, by x-ray or in the mechanical processing found, can also be in alkaline washing, pickling or anodizing found. The experimental results show that the addition of the appropriate additives in NaOH solution can produce good polishing effect.
The exploratory experiment also found that the surface reflectivity of the aluminum surface can reach 90% after DC constant pressure electrolysis with NaOH solution under certain conditions, but there are still some unstable factors due to the experiment, which needs further study. The feasibility of using DC pulsed electrolytic polishing method to polish aluminum under basic conditions is explored. The results show that the pulse electrolysis polishing method can achieve the leveling effect of DC constant voltage electrolytic polishing, but its leveling speed is slow.
Package casting part of the aluminum layer was cut off, the outer package of aluminum is high quality aluminum, the inner layer of the package is miscellaneous aluminum, two different materials, so the oxidation of "vitiligo" like spots.
Solution: This phenomenon is often not too much understanding of customers, manufacturers should do more to explain the work, clear the whole story, so as not to cause misunderstanding. On the other hand, the aluminum industry analysis predicts that the use of Automobile Castings will rise by 50% in five years, from 250 pounds / vehicle in 2000 to 380 / vehicles by 2005. A large number of production and processing of castings, the need for polycrystalline diamond (PCD) tool. The main cause of chip PCD damage during processing. To keep the PCD tool cutting edge intact, it is best to distribute the cutting load evenly to each milling cutter.
Automobile Casting annealing: the aluminum alloy castings heated to a higher temperature, generally about 300 ℃ or so, after a certain period of time, with the furnace cooling to room temperature process known as annealing. During the annealing process, the solid solution decomposes, and the second phase of the particle is aggregated, which can eliminate the internal stress of the casting, stabilize the casting size, reduce the deformation and increase the plasticity of the casting.
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