Differential Pressure Casting Equipment for Active Metals

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A prototype equipment for differential pressure casting of titanium and other active metals was designed and constructed for the purpose of successfully casting thin-walled castings.1) Design, construction and setup.The equipment consists of a tank, power source and vacuum pumps. High frequency induction coil for melting 1.5kg of metal in a calcia crucible and mold chamber were installed. Casting fluidity was ensured by applying differential pressure to the melt by controlling the tank pressure and mold cavity pressure.2) Function testing : Designed functions were checked.3) Test melting and casting : Titanium, steel and aluminum alloys were successfully melted and cast.4) mold making and permeability : Calcia moldS were made and mermeability was measured.5) Experiments using the equipment : The following results were obtained ;Mold filling ability of titanium alloys are affected by melt head, gate size and back pressure. Effects of back pressure in cavity was examined by a mold without gas vent. Fluidity was measured and theoretically analyzed. Surface quality is affected by using zirconia mold, while it is not affected when using mold of calcia. Pressure casting is necessary for preventing shrinkage in titanium castings, whereas, with pressure, the shrinkage behavior is comparable to taht of steel.