Cast aluminum alloy is an aluminum alloy filled with molten metal to obtain the blank of parts of various shapes. It has the advantages of low density, high specific strength, good corrosion resistance and casting process, and little restriction by the structural design of parts. It is divided into Al-Si and Al-Si-Mg-Cu based medium strength alloys. Al-cu-based high strength alloy; Corrosion resistant alloy based on Al-Mg; Thermal strength alloy based on Al-Re. Most require heat treatment to strengthen the alloy, eliminate the internal stress of the casting, stabilize the structure and part size. Used in the manufacture of beams, turbine blades, pump bodies, racks, hubs, intake lips and engine casings. It is also used to manufacture the cylinder head, transmission and piston of the automobile, the housing of the instrument gauge and the supercharger pump body.

Casting aluminum alloy has good casting performance and can be made into parts with complex shapes; There is no need for bulky add-ons; It has the advantages of saving metal, reducing costs, and reducing man-hours, and has been widely used in the aviation industry and civil industry. It is used in the manufacture of beams, gas turbine blades, pump bodies, pylons, wheel hubs, intake lips and engine casings, etc. It is also used in the manufacture of cylinder heads, gearboxes and pistons of automobiles, the housing of instruments and meters, and the pump body of superchargers.

The earliest is industrial customized cast aluminum alloy. The alloys have high strength and thermal stability, but poor cast ability and corrosion resistance. The copper content is generally lower than the solubility limit of copper in aluminum (5.85%), there is no eutectic in the equilibrium structure, and a small amount of eutectic may appear under non-equilibrium conditions. After solution treatment, the solid solution can be supersaturated and the aging strengthening effect can be obtained. The addition of manganese and titanium to the alloy can refine the grain, strengthen and improve the corrosion resistance.

The alloy has the characteristics of quenching micro-structure in the casting state, and high strength can be obtained without heat treatment, but the density of the alloy is large, and it is not suitable for the production of aircraft parts. The alloy system is made of zinc on the basis of silica-aluminum alloy, so it is also called “zinc-silica-aluminum” alloy.

Aluminum alloy refining is mainly to remove the gas and non-metallic inclusions in the alloy liquid. The gas in aluminum alloy is mainly hydrogen (accounting for more than 85%), and the inclusion is mainly alumina. Because the saturation solubility difference of hydrogen in liquid and solid aluminum alloy is nearly 20 times, it is easy to precipitate hydrogen during the solidification process of aluminum alloy, resulting in pinholes in the casting. Inclusions and gases interact, and pores appear when the hydrogen content per 100 g of aluminum alloy liquid in industrial pure aluminum is higher than 0.1 m L, and when the hydrogen content per 100 g of aluminum alloy liquid in high purity aluminum is as high as 0.4 m L, pores will appear. It can be seen that degassing must be slag removed, and slag removal is the basis of degassing.

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