Industry news

　　Because aluminum alloy has severe oxidation and aspiration tendency, and directly contacts with furnace gas or external atmosphere in the melting process, it is easy for aluminum alloy to absorb gas and form pores, especially pinholes, if the control is slightly improper in the melting process. Pinholes usually refer to the precipitated pores less than 1 mm in the casting, which are mostly round and unevenly distributed in the whole section of the casting, especially in the thick section and the parts with low cooling rate of the aluminum alloy die casting. According to the distribution and shape characteristics of precipitation pores in aluminum alloy, pinholes can be divided into three types.

　　1. Reticular pinholes: in the macrostructure, pinholes are densely connected to form a network, and there are a few large holes, so it is not convenient to check the number of pinholes per unit area, and it is difficult to measure the diameter of pinholes.

　　2. Punctate pinholes: in macrostructure, pinholes are round and punctate, with clear and discontinuous pinholes. It can count the number of pinholes per square centimeter and measure their diameter. This kind of pinhole is easily distinguished from shrinkage, porosity, etc.

　　3. Comprehensive stomata: it is the middle type of punctate pinhole and reticular pinhole. From the macrostructure, there are many large pinholes, but they are not round, but polygonal.

　　The production practice of aluminum alloy die casting has proved that the main gas component of the air hole formed by air suction is hydrogen, and there is no certain rule to follow for its occurrence, and pinholes often exist in all or most of the castings in one heat; Materials are no exception, all kinds of aluminum alloys are prone to pinholes.