Analysis and interpretation of aluminum die casting porosity phenomenon
Because aluminum has a tendency to severe oxidation and inspiration, smelting process has direct contact with the gas furnace or the outside air, so as to control the process of melting slightly inappropriate, it is easily absorbed by the gas and aluminum form pores, the most common pinhole.
Pinhole usually refers to castings precipitation of less than 1mm holes, mostly round, not evenly distributed throughout the casting section, particularly in smaller casting heavy section and the cooling rate of the site. According to the distribution and shape of the pores of the precipitation characteristics aluminum, pinholes can be divided into three categories.
1. pinhole mesh: at low magnification dense pinhole connected into a network, there are a few larger holes, the inconvenience of pinholes on the inventory quantity per unit area, it is difficult to measure the diameter of the pinhole.
2. dot pinhole: at low magnification punctate circular pinhole, pinhole outline clear and mutually continuous, can count on the number of pinholes per square centimeter, and can measure the results of its diameter. This pinhole easily be the difference between shrinkage, shrinkage and so open.
3. Comprehensive pores: it is dotted pinhole and pinhole mesh intermediate point of view from a low magnification, large pinhole more, but not a dot shape, and polygonal. Aluminum die-casting production practice confirmed that the main component of aluminum due to the intake of gas and the formation of pores is hydrogen, and it thrown no certain rules to follow, often all or most aluminum die casting one heats are there needles hole phenomenon; the material is no exception, aluminum various components are prone to pinholes.
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