Research Of Aluminum Alloy Tilted Casting Technology For Large Sized Complex Castings

Aluminum alloy case is the essential part of engine fuel attachment for aircraft.It develops towards integration,enlargement and complexity,with the rising requirement of fuel economy and low weight of the engine parts.Under this background,some aluminum alloy engine cases were designed to an integrated casting part,which were machined in separated parts and oil channels then assembled before.It induced the cases consisting of varies hollows,bosses,large thin walls and complex inner oil channels.The complexity of aluminum alloy case makes that it is hardly manufactured using normal casting technology.Moreover,the high air impermeability and mechanical properties are required.The casting of aluminum alloy engine case has become the limitation and critical problem for the manufacture of air aircraft engine.In this work,the casing technology of aluminum alloy engine case was studied and modified with the help of casting simulation,and high quality casting case was obtained,which meets the requirement of the designed aircraft engine.It is also helpful to solve the casting problems of this kind of engine cases.First,on the basis of consulting a large number of literatures,the tilt casting technology,the main auxiliary materials used for casting and the application of simulation were discussed.The detailed experimental scheme was designed.According to the structural characteristics of the castings,the advantages and disadvantages of gravity casting and tilt casting were analyzed,and three process methods were designed.The casting processes simulations were carried out using the simulation software.The advantages of tilt casting method was determined.Then,a detailed simulation was performed,and the filling process,solidification process,temperature field,and defect conditions of the tilt casting were systematically analyzed.According to the simulation results and the characteristics of the tilt casting process,the design of tilt casting mold and shell cores was carried out.A die casting mold,and a dispersion core manufacturing method for integrally assembling the cores were designed.The first casting found a slight cold septum and “white” defects.According to the mechanism of defects and the simulation results,it is considered that the pouring pouring speed and mold temperature are the key factors affecting the defects.Based on microscopic analysis,“white” defects were porosities casued by local overheating of the mold.For eliminating these two kinds of defects,the pouring speed and mold temperature were increased,and partially using cooling water and cold iron.The modified casting processes were simulated and analyzed.After optimization,the casting defects were eliminated,and castings with excellent internal quality were obtained.Furthermore,in order to avoid deformation caused by changes in the size of the castings,two different heat treatment simulation methods were compared and studied.The heat treatment placement methods were determined after threedimensional scanning and comparison.the mechanical properties of the casting at different locations under different cooling conditions were compared and tested.It was found that,the mechanical properties of the casting obvious changed with the solidification conditions.When the function of the various parts of the casting varies greatly,the solidification should be fully considered.The casting parts with high requirments of mechanical properties should be casted by metal mold.The casted engine case was machined after casting,the casting dimensions and surface quality are good,which fully meet the requirements of design.and Xray inspection,air impermeability test at 0.5 MPa for 5min and strength test at 22.5 MPa for 5min of the castings were conducted according to the requirements.No casting defects and leakage were found,indicating that the casting is dense and the casting process is fine.