Foaming Mould Design And Pouring Process Simulation Of The LFC Impeller Part

Lost Foam Casting process is a kind of material shaping method by which high precision castings without the need of mechanical machining allowance can be got. While with the advanced technology, the cost is rather low. Foam polystyrene is commonly used as the material of expandable patterns for metal castings. When the metal melt is poured, foamed polystyrene will vaporize., and then the metal melt fills the resulting void to produce the desired cast shape. It is so complicated a process with chemical reactions like gasification and decomposition of foam pattern as well as physical changes, such as solidification and contraction of the metal liquid. Therefore, there are many factors influencing the quality of castings among which the quality of foamed polystyrene pattern and the pouring process parameters.are the most significant.The object of our research is a closed impeller with a diameter of275mm used in slurry pumps. How to get a normally workable impeller with both good surface quality and mechanical properties is what we focused on. In order to improve the existing technology accurately and efficiently, we adopted CAD/CAE integration technology and tracked all through the process from foaming mold design to the pouring procedure to optimize the whole manufacturing technology, achieving the organic unity between the new cast technology and computer technology which helped to improve the efficiency of optimization and to reduce scrap.(1) Reasonable mold design. Initial foaming mold scheme was quickly designed by UG software at first. To combat the demolding problem of the blade passage, we changed the parting surface position and increased loose pieces in the mold cavity. At the same time, the pattern was divided twice to produce the oil-way at the end of axle hole. And finally, we produced well-shaped foam pattern.(2) According to design method of the gating system for malleable iron, we calculated parameters such as gate ratio, runner diameters and feeder size etc. Meanwhile, runner diameters were magnified by30%to50%because of the large foaming capacity during pouring process. Thus, initial schemes of gating system and feeding system were determined.(3) After the gating system model was imported from Pro/E to MAGMA soft, single factor experiment method was adopted to simulate the influence law of different pouring temperatures and runner heights on castings’quality, which helped to find proper range of pouring temperature and runner height. What’s more, proper form and size of feeder were finally determined after being optimized twice according to filling solidification criterion(4) Appearance observation of the impeller acquired under laboratory condition and analysis of metallographic organization were conducted. We found that the casting had good surface quality without significant defects and the metallographic showed that the iron matrix was covered with diffused eutectic carbide---M7C3. The carbide with a six square structure can protect the substrate while being supported by it, offering the casting outstanding wear-resisting performance. Hardness testing was also done to spaceman obtained from one runner blade. The average hardness was HRC61.7, meeting the performance requirements of the casting.