AZ91 Magnesium Alloy Smelting Without Flux

In this paper, purification the magnesium alloy melt and improving the quality of magnesium alloy are researched for the most part. In the process of melting, the traditional protection often uses flux in order to prevent the Oxidative combustion of magnesium liquid surface. However, the density of flux generally greater than the density of magnesium alloy. Therefore, in the process of melting the flux will sink, and we needs to add flux Continuously. Part of flux left in the liquid alloy as slag and form inclusions, which reduce the performance of alloy, becomes common defects of magnesium alloy castings melted by flux, and reduce the alloy's corrosion resistance at the same time. The experiment uses tetrafluoroethane gas mixture to protect the magnesium alloys melting and then studies. Compared to traditional smelting protection, this method not only reduce the melt pollution but also reduce the environmental pollution and cost, increase economic efficiency.After analyzing magnesium and its alloy's classification, the thesis discuss the basic principles of Refining processing, and process magnesium alloy through a variety of refined methods in order to remove gas and impurities, improve the quality of magnesium alloy.The thesis choose AZ91 magnesium alloy material for experiments to explore the magnesium alloy melt refining technology, And we design a comparison experiment as follows: in the process of melting, spinning inject Ar, selecting different inflatable volume and different spinning speed. obtain AZ91 magnesium alloy specimen by means of filtering solution. Compare and analyze metallurgical structure and mechanical properties of obtained specimen, and then we analyze its strengths and weaknesses. Research the refining effect of the main Refining technology of magnesium alloy at present. And explore magnesium alloy fining and heat treatment technology in the condition of smelting technology without flux. At last ascertain the optimal process parameters, formulate reasonable smelting process and improve Technological devices.We obtain specimen from different forms of smelting technologies. Basing on tensile experiment and hardness experiment and combining with metallurgical experiment, we process the specimen using metalloscope, scanning electron microscopy and mechanical properties testing machine and other equipment. And then discuss The distribution of alloy metallurgical and Mechanical Properties of alloy under different technology Condition. Finally we obtain the best smelting technology and the best heat treatment technology according to the orthogonal and level analyzing method. The best method is as follows: purge argon for 30min with inflatable volume 10L/min, speed of 240 r / min, foam ceramic filtering, adding MgCO3 metamorphism of 0.5%. The best heat treatment technology is as follows: 350 degrees solution 14h, 180 degrees aging 24h. At last under two best technologies, the tensile strength of specimen reached 235Mpa and it is improved nearly 30% comparing with cast state.