Aluminum-silicon alloy has good mechanical properties such as low density, dimensional stability, good wear resistance and high specific strength, as well as excellent corrosion resistance, so it is widely used in casting industries such as automobiles and aerospace. The application of computer batching software provides a technical basis for precise control of the chemical composition of castings. The research on the types of modifiers and the solidification process has significantly improved the microstructure of the castings. However, in actual production due to the existence of metallurgical defects such as gases and inclusions in the metal It will destroy the continuity of the metal material, reduce the effective cross section of the casting, and cause stress concentration around the pores, greatly reducing the mechanical properties of the casting. Therefore, in order to obtain high-quality products, it is necessary for purifying aluminum melt during smelting.
According to measurements, more than 85% of the gas content in the aluminum alloy is hydrogen, and the rest is nitrogen, oxygen, carbon monoxide, etc., so the hydrogen content is considered the gas content. Since the solubility of hydrogen in liquid aluminum is about 20 times that of solid, during the solidification process, [H] will be precipitated to form H2 and remain in the casting, resulting in pores of different sizes. In order to purify the alloy liquid and reduce the gas content in the alloy liquid before casting, scholars at home and abroad have carried out a lot of theoretical and technological research. According to the working principle, it can be divided into two categories: adsorption purification and non-adsorption purification. Among them, adsorption purification includes bubble floatation method, ceramic foam filter filtration method, flux refining method. Non-adsorption purification mainly includes static method, vacuum method, ultrasonic purification and electromagnetic purification.
At present, the bubble floatation method is widely used in purifying aluminum melt. The principle is to pass inert gas or active gas insoluble in the aluminum liquid into the aluminum liquid, or add chlorine salt (chloride) to react with the aluminum liquid to generate gas, which is generated in the aluminum liquid. A large number of bubbles, because the hydrogen partial pressure in the bubbles is zero, the hydrogen in the molten aluminum will diffuse into the bubbles and overflow.