Numerical Study On Gating System Design Criteria For Mg Die Casting

The main shaping method of magnesium alloy is high pressure die casting, but there is few technological criteria of die casting process designing of large complex casting parts for reference. To reduce the cost of production, and strengthen the competitive advantage of magnesium alloys, studying the technological criterion of die casting process designing is inevitable.To study the relationship between the filling quality and the filling characteristic of the melt which is drove by pressure; the text abstracts different and representative structural units through modularing the complex structure of die casting parts. Then, different gates are designed for each unit according to the filling principle (the gates include different ingate thickness, different length-width ratio and reduction of ratio of cross-sectional area of fan runner , different flow angle of tangential runner and two fan runners with different flow angle and distance of each runner), and the filling mold, the tendency of gas entapment and the change of the gas pressure of the cavity are analyzed numerically, when the ingate speed and temperatures of melt and mold of the high presssure die casting process parameters are 40m/s, 680℃and 200℃. Hope it is helpful for forming the guidance of die casting process design of magnesium alloy, the research results are as follows:①The main cavity is divided based on the quality requirement of castings, and the castings are modulared based on the coincidence of the main cavity with the high-quality fields of the gating system, the casting units are categorized into three categories: flat, half-frameⅠandⅡtype.②The size and distribution of the region of air entrapment percentage which is more than 20% and the peak percentage of air entrapment are used to evaluate the quality of filling. When the two parameters are small , the result is the best; When the former one is small and the latter one is big, the result is the second; When the two parameters are big, the result is the worst.③The parameters of the ingate: when flow angle of the fan runner is 28°, the quality of filling of plate parts alters for the better first then goes to the bad, as"r"(the ratio of the thickness of ingate and casting) increases. The filling quality of the half-frame parts goes to the bad, as"r"(the ratio of the thickness of ingate and casting) increases. ④The parameters of the fan runner: at the condition of r=0.25, the quality of filling of plate part goes to the bad as"α"(reduction of ratio of cross-sectional area of fan runner) increases at the condition of w=1.25(w is length-width ratio of fan runner), and alters for the better as"α"increases at the condition of w=0.75, and alters for the better first and then goes to the bad as"α"increases at the condition of w=1; The quality of filling of half-frame parts goes to the bad as"α"increases at the condition of w=1.25, and goes to the bad first and then alters for the better as"α"increases at the condition of w=1, the quality is worse than the former and changes little at the conditon of w=0.75.⑤The parameters of the tangential runner: at the condition of r=0.25, the quality of filling of plate part alters for the better first and then goes to the bad as"θ"(the flow angle of the tangential runner) increases; The quality of filling of half-frame parts alters for the better as"θ"increases.⑥The interaction of two runners: at the condition of r=0.25, the quality of filling of plate part alters for the better as the flow angle of the fan runner increases at the condition of L=5mm (the"L"is the length between two runner), and alters for the better first and then goes to the bad as the angle increase at the conditon of L=10mm, and goes to the bad as the angle increases at the condition of L=20mm; The quality of filling of half-frameⅠpart alters for the better as the flow angle of the fan runner increases at the condition of L=5mm, and alters for the better first and then goes to the bad as the angle increase at the conditon of L=20mm, and the quality changes little at the conditon of L=10mm. The quality of filling of half-frameⅡpart alters for the better as the flow angle of the tangential runner increases.