Analysis Of The Fluid Dynamics Gas Entrapment Behavior And Hole Morphology In Vacuum Die Casting

With the constant improvement of the lightweight requirements, large-scale, integrated and thin wall is the inevitable trend in the design of die castings, which puts forward higher requirements on die-casting molding technology. High vacuum die casting technology is one of the most promising means to achieve this goal. But in our country, there are some problems about theories and technology on HVDC remain to be solved, some mechanisms on air entrapment in die casting process need to be analyzed, and how to improve the quality of components by HCDC.Based on numerical simulation and test results on Engine block casting, and aimed at the inadequate HVDC theory and no deep understanding on air entrapment in die casting process, the theory of the fluid flow dynamics behavior of HVDC was analyzed, results are as follows:① Based on the thorough analysis of the current situation of the die casting technology, the further theory on high vacuum die casting was proposed.② The numerical simulation of the engine crankcase cylinder on both normal die casting and high vacuum die casting were taken. Results show that Vacuum can reduce the gas but not affect the filling flow pattern of the fluid in the cavity, and the tensile properties of the samples are raised with the increase of the density.③ Numerical simulation experiments of pressure chamber, mold, exhaust trough in die casting were designed, and flow characteristics and fluid flow rule in every die casting regions were analyzed. Fluid tends to be overturn wave in pressure Chambers, the interaction of the fluid result in eddy current ring and primary air in the cavity, and disturbance phenomena of gas is easily happened in exhaust trough.④ The gas behavior in the die cavity was analyzed deeply. Results indicate that the vortex formed in fluid motion has important influence on gas volume, and the formation, evolution, rupture and diffusion of the vortex were also discussed.⑤ The calculation of the fractal dimension on the porosity of die castings were taken based on the fractal theory, and the pore morphology properties were characterized.