A Study On Vacuum Die-casting Process For Aluminum Oil Pan

Die-casting process has the characteristics of high production efficiency,dimensional precision and surface quality. However, owing to the high filling speed andunstable flow state during the filling process of die-casting process, castings cannot beheat-treated as pores are often developed inside. As a development of die-castingprocess, vacuum die-casting process decreases the porosity of castings and improves themechanic properties by pumping the air in the cavity and die chamber. In this paperengine oil pan was produced using the vacuum die-casting process in order to eliminateporosity which was easily developed with die-casting process.Firstly, the influences of vacuum degree on the quality of castings were discussedbased on the numerical simulation of non-ferrous die casting alloys test specimen withthe MAGMA software. Secondly, forming process and distribution characteristics ofdie-casting defects were analyzed by visual simulation of engine oil pan die-castingprocess with finite difference method. The reliability of simulation result was confirmedaccording to the comparison between the simulation result and defects of castings in theproduction field. Thirdly, the gating system and exhaust system were developed and thenumerical simulation of engine oil pan vacuum die-casting process was performed. Thedie-casting mould was optimized based on the numerical simulation result and avacuum die-casting process of aluminum alloy engine oil pan was developed. The mainachievements in this paper were listed as follows:①The vacuum die-casting process of non-ferrous die casting alloys test specimenwere designed according to the newly developed high-speed vacuuming method. Theconsequence of numerical simulation of non-ferrous die casting alloys test specimenindicates that as the vacuum degree increases, the resistance of air on the molten metalreduces, the filling speed increases and thus the filling period reduces; and also as thevacuum degree increases, the gas between molten metal and the cavity wall reduces, theheat transfer between them increases and thus the chilling speed of molten metalincreases.②Through numerical simulation of engine oil pan die-casting process, it wasfound that air entrainment occurred at pin holes, screwed holes and oil ducts, whichcoincided with the actual die-casting product.③The optimized technical parameters based on the numerical simulation was as follows: vacuum degree10KPa, pouring temperature670℃, mold temperature230℃,velocity of slow shooting0.5m/s, velocity of high-speed shooting4.8m/s, specificpressure of shooting60MPa. With the above technical parameters, the filling progress isstable, solidification sequence is rational and feeding effect is good.④Pores and shrinkage defects of aluminum alloy engine oil pans were reduced bythe vacuum die-casting process. The leakage detection indicates that no leakage wasfound. Therefore, the products are qualified.