Because the equipment is the core platform for the implementation of the technology, and the composite squeeze casting method is quite different from the traditional squeeze casting method, which also makes the existing squeeze casting equipment difficult to realize the composite squeeze casting method, so it is necessary to design the composite squeeze casting equipment according to the requirements of the composite squeeze casting method, combined with the technical level of the existing squeeze casting equipment. Because the object of composite squeeze casting is a large part, the following key technical problems need to be solved in the overall design:
Large volume molten liquid transportation (determine filling temperature)
Due to the large amount of molten metal required for large parts, in order to ensure the quality of molten metal, it is necessary to reduce the contact between molten metal and air as much as possible to avoid oxidation. At the same time, due to the large amount of infusion, the requirement of quantitative molten liquid is relatively high. The solution to the quantitative transportation of large volume molten liquid and the reduction of oxidation is to transport the molten metal in the closed pipe, and realize the mold pre closing before filling. Mould pre closing means that the mould is closed in a state close to the forming size of the casting, and the extrusion stroke of the mould to the molten metal only reserves the reduction of the cavity volume required by the solidification shrinkage and a small amount of plastic deformation of the molten metal during the extrusion process, that is, the pressure surface of the mould to the molten metal contacts the molten metal completely when the mould is filled, so that when the mould applies the pressure, it can be transferred to the molten metal immediately High static pressure can be maintained to ensure the solidification of molten metal under high pressure, to strengthen the feeding and densification, and to improve the formability of casting.
Filling of large volume molten liquid (determine filling speed)
There is a large amount of molten metal in the mold filling of large parts, but the filling speed of molten metal must be moderate, the filling speed is too slow, and the molten metal entering the mold cavity will solidify too early, which makes it difficult to pressurize or even unable to form; the filling speed is too fast, which is easy to make the molten metal turbulent, involving gas and oxide skin, resulting in stress, crack, bubble, shrinkage and other defects. In order to ensure that the molten metal can fill the mold cavity, the molten metal filling will be slightly larger than the required volume of the casting. At the same time, there are inevitably some errors in the process of large volume molten liquid transportation. Therefore, in addition to ensuring the smooth filling of molten metal, it is necessary to ensure the quantitative filling of molten metal.
Mass melt extrusion (determine specific pressure)
In the compound squeeze, the upper die is used to extrude the molten metal. Because of the large compression area of large parts, the extrusion pressure of the equipment is relatively high. At the same time, after filling, it is necessary to establish a higher extrusion pressure for the molten metal in the mold cavity quickly, and ensure that the extrusion pressure can be uniform and effective on the whole pressure surface of the molten metal. At the same time of applying pressure to the upper die, the filling head must be able to maintain the position in the filling cavity, that is, the filling head has the function of passive pressing.