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During the production and processing of aluminum castings, many abnormal conditions were discovered, such as black spots, copper-nickel coatings, and mold sticking, etc. The existence of these problems will affect the quality of the castings and thus shorten their service life. Therefore, it is necessary to identify the causes and solve them.

Firstly, when aluminum castings are polished, black spots may appear, which could be due to the formation of silicon oxide or aluminum oxide. The solution is very simple: use fresh aluminium ingots. However, the possibility of the tubular condenser lies in the release agent, such as spraying too much release agent or having an excessively high organic content in the release agent.

At the temperature of hot-melted aluminum, some of these organic substances are reduced to carbon elements, and some are transformed into organic macromolecular polymers. The mixture of these carbon molecules and polymers is contained in the surface layer when the aluminum casting is formed, becoming the black spots we see. The problem can be alleviated by reducing the concentration of the spray agent, switching to another type of spray agent, or increasing the air flow after spraying.

Secondly, the copper-nickel coating on aluminum castings can be removed through certain methods, one of which is electrolysis. At room temperature, the returned piece is used as the anode with a current density of 3 to 5A/dm 2 for electrolytic stripping. This method is prone to copper displacement after complete removal. Copper should be removed in a dilute chromic acid solution after the nickel layer has been completely removed. Another one is the chemical elimination method.

In addition, if mold sticking occurs during the production of aluminum castings, it should also be resolved as soon as possible. On the one hand, the feeding position at the feeding port can be increased to prevent excessive impact due to insufficient feeding. On the other hand, it is necessary to save mold and light. And increase the demolding Angle for quick demolding.