Study On Vacuum Die-casting Exhaust Theory And Design Of Vacuum Die-casting System

Light alloy is the key structure material of manufacturing light weight, and die casting is the most widely-used liquid molding method. But the cavity air will decrease the technical and economic index of die casting light alloy and damage the internal technological quality What’s more, because of interception of air in the casting, heat treatment cannot be applied to improve the microstructure and mechanical property. So vacuum die casting becomes one of the main research directions of the die casting industry technology.To ensure the vacuum degree of the cavity during the high speed die casting process, the cavity air must be pumped in a very short time after casting and the vacuum degree should be maintained until the filling process finishes. What’s more, to avoid the melt flow into the external vacuum system, vacuum pumping channel should be closed in time and stably.This paper focuses on the problems of the vacuum die casting such as imperfect vacuum pumping theory, low reliability of vacuum system, and a low vacuum degree of vacuum pumping. New thoughts and methods are put up to realize rapid vacuum pumping of the cavity and maintain a high vacuum degree of cavity after analyzing present commercial vacuum-aided system. A air pumping system model of high pressure casting is built which can effectively inhibit secondary pollution of casting melt and has high vacuum pumping ability. The reliability of the model is high, and it can maintain the vacuum degree of the cavity well during the filling process.① With full respect to its characteristics, a physical model of die-casting process was developed. Following the principle of fluid hydrodynamics, a dynamic theoretical vacuuming model was established. With the models, the vacuum die casting process was expressed in a scientific view, followed by systematic discussion of influence vacuuming processing parameters on the cavity vacuuming speed and vacuum degree to lay a foundation for the design of vacuuming system.② A prototype vacuuming system was constructed and used to verified the predictions of the established theory and to systematically analysis the influence of vacuuming processing parameters.③ To overcome the poor reliability, low achievable vacuum degree of the present commercial vacuuming systems, an integrate vacuum channel closure insert was develop.④ To prevent melt oxidation during pouring, an air-proof pouring technique was jointly developed with Chongqing Sino ST Co. Ltd..With the newly developed high pressure vacuum die casting machine, casting die, and dosing furnace with air-proof pouring function, the Changan auto Mg wheel was experimentally produced. The processing quality of the prototype wheels is encouraging.