Facing the increasingly severe crisis of energy and environmental, lightweight has become an important direction in the development of parts industry. Because of that, people are committed to the development and utilization of lightweight and high-strength materials, such as high-strength steel or alloy materials such as aluminum and magnesium. Because of a series of excellent characteristics, aluminum alloy has become one of the most ideal materials for automobile lightweight. In recent years, aluminum castings developed rapidly.
The increasing demand for aluminium castings has promoted the development of foundry enterprises, but the problems of environmental protection and high energy consumption have also become potential threats. Green casting is the inevitable direction of the development of foundry enterprises. Therefore, in order to survive and maintain high competitiveness, foundry enterprises should realize green from many aspects, angles and directions.
Because the furnace charge and die cast aluminium alloy liquid absorb gas and produce inclusions during melting, transportation and pouring, the melt purity decreases and the fluidity becomes worse, which leads to casting defects after pouring, affecting mechanical properties, machinability, corrosion resistance, air tightness and surface quality.
(1) In order to obtain pure aluminum liquid, on the one hand, it is necessary to "prevent", that is, make full preparation before smelting.
It is necessary to dewater, degrease and preheat the furnace charge and clean, coat, dry and preheat the melting tools. Reasonable selection of recycled materials and their consumption are also very important. If the prevention is proper, the subsequent refining process can be simplified, thus reducing the environmental pollution caused by refining.
(2) In order to obtain pure aluminum liquid, on the other hand, "removing" is also necessary, that is, refining.
Hydrogen and oxide inclusions (mainly Al ₂O ₃) in aluminum melt exist at the same time with strong interaction. The hydrogen content in aluminum melt is greatly affected by the inclusion content. When the inclusion content is 0.002% and 0.02%, the corresponding hydrogen content of 100g aluminum is 0.2cm³ and 0.35cm³. Under the same hydrogen content, the higher the inclusion content, the higher the pinhole rate. Therefore, degassing and refining are often combined together, so it is customary to call these two processes refining.