The Flow Field Simulation And Research On Control System Of Shielding Gas For Magnesium Alloy

Magnesium and magnesium alloys have been widely used in spaceflight and automobile making for its excellent properties such as low density, high specific strength and high specific rigidity. Due to their chemical active nature, Mg alloys are prone to oxidation and ignition. Therefore, the technique of gas protected melting become part of the key techniques in Mg production and application. In terms of the present developing and research conditions of shielding gas for magnesium alloys, most of the focus is concentrated on protective mechanism. Whereas, it is not very mature in terms of the characteristics on flow field of shielding gas in magnesium alloy melting furnace and the apparatus for the shielding gas. This work is involved in the characteristics on flow field of shielding gas in magnesium alloy melting furnace and the control system apparatus is design base on the melting process.In this work, shielding gas flow process in magnesium alloy melting furnace is analyzed. With the aid of the software—FLUENT, the mathematical model of turbulent flow in the magnesium alloy melting furnace is established. The governing equations are solved with SIMPLE algorithm in finite volume way. According to the simulation result, the factors affecting the component of flow field are discussed such as process parameters (e.g. inlet velocity, concentration ratio) and working condition (e.g. the temperature of molten magnesium alloy, the liquid height). The results are displayed by TECPLOT, so the flow fields and gas distribution are showed directly to realize the visualization of the calculations. The results of numerical simulation indicate that inlet velocity should be controlled within certain range, the rising phenomenon will occurred due to the buoyancy force if the inlet velocity was too small and the phenomenon of uneven distribution above the magnesium alloy molten surface will occurred when the inlet velocity was too high. The concentration of the effective component above the magnesium alloy molten surface can change along with the inlet concentration. Good protective effect can be obtained by changing the process parameters when the working condition is changed.Aiming at the phenomenon of uneven distribution above the magnesium alloy molten surface, the apparatus of multihole diverter is put forward. It adoptes theoretical model and finite element numerical simulation to achieve the distribution of multihole diverter and the premises for uniform distribution of flow. Research shows that the pressure drop of the shielding gas in the multihole can be reduced by increasing the diameter of multihole main pipe, and the outflow uniformity is improved effectively.The steady of gas flow and good system performance are very important during the magnesium alloys melting process. A reasonable scheme is designed by using PLC and Touch-screen as the core of control unit. The accurate control of flow is achieved by adopting Mass flow controller.