Why the aluminum die casting hole can be processed beyond 0.25mm?
In order to be suitable for die casting on the die casting machine, humans have added a lot of bismuth (si) to the aluminum alloy for die casting. When the aluminum alloy is condensed in the mold, these sputum will float to the surface to form a thin ruthenium film. This layer of enamel film is very hard and very wear resistant. Some OEM designers use this feature. The inner surface of the hole of the die casting is directly counted as a bearing surface. This crucible surface layer is generally only 0.2 to 0.9 mm thick. Too much processing, the life of this bearing surface will be shortened.
Why do my aluminum die castings have black spots when they are polished?
There are several reasons for this. It is possible that yttrium oxide or aluminum oxide is formed. The solution is simple, using fresh aluminum ingots. However, the biggest possibility comes from the release agent. Maybe, we spray too much release agent. It is also possible that the organic content of the release agent is too high. Some of these organic substances are reduced to carbon at the temperature of hot-melt aluminum, and some become organic macromolecular polymers. The mixing of these carbon molecules and polymers, when formed in aluminum castings, is contained in the surface layer and becomes the dark spot we see. We can reduce the concentration of the spray agent, switch to another spray, or lengthen the blow time after spraying. To reduce the formation of carbon, and to prevent the accumulation of macromolecular polymers.