Repiakh S. Advancement of manufacturing process of large-scale thin-walled investment castings for special purposes

Advanced technological methods of ceramic shell moulds preparing for tem-pering and casting as well as modern theories of shrinkage porosity formation are analyzed. The dissertation investigates the influence of casting parameters on shrinkage porosity flaw appearing in large-scale thin-walled investment castings made of high-alloyed chrome-nickel steel. Parameters of quartz shell moulds heating, providing its integrity while casting, are defined. The research shows that the method of preparing of the quartz shell moulds for casting has its influence on its proportional heating and on homogeneousness of its temperature field while casting. The paper investigates the influence of the quartz shell mould formation method on gas permeability and gassing ability of the moulds. The heating regimes of thermostatic quartz shell moulds are developed.The author provides physical and mathematic model of shrinkage porosity flaw appearing in large-scale thin-walled castings in conditions of pulse velocity of casting flow. The paper investigates the kinetics of thickness changing of the casting crust, depending on the parameters of casting flow in the mould and type of casting alloy. The author focuses on the influence of the way of casting flow ve-locity on shrinkage porosity in the thin walls of the cast.The dissertation contains recommendations for quality increasing of the large-scale thin-walled investment castings made of high-alloyed chrome-nickel steel. The results of industrial approbation of the given recommendations are presented.