Casting pressure in two types of titanium casting equipment

This study theoretically examined the relationship between mold permeability and the casting pressure acting on the molten titanium in two types of pressure casting equipment [two-chamber and one-chamber] for preparing titanium dental castings in order to select the most effective mvestment material and optimal casting conditions. The casting pressure exerted on the melt can be defined as the pressure difference between the melting chamber and the mold cavity after the molten titanium drops and seals the entrance to the cavity sprue. Differential equations describing the pressure in the mold cavity were derived from the equation of the state of gas as a function of time. Analysis revealed that mold permeability and the operation of each casting unit affect how the casting pressure acts on the melt: a low-permeability mold is appropriate for the one-chamber type but intermediate permeability molds are desirable for the two-chamber type. Using the results of this study and published permeability data on investments, an optimum investment material can be selected for each type of equipment.