Vibration improved the fluidity of aluminum alloys in thin wall investment casting

Abstract

Misrun is a term used to describe the incomplete filling of the mould cavity. It is a major defect in the investment casting process when used to produce turbine blades, impellers and impulse blades for turbo pumps which have complex profiles, thin walls and sharp edges. From the casting engineering point of view, poor fluidity characteristics are a major factor leading to the occurrence of misrun defects in thin wall casting. The technique to "increase" the metal head during casting and improve the fluidity in thin sections are explored in this paper by the application of vibration during the pouring process. A mathematical model that enable to calculate the fluidity length in thin wall investment casting consider the effect of both mould surface, roughness and vibration has been developed. Surface roughness has been studied with the objective to calculate the Interfacial Heat Transfer Coefficient (IHTC) during liquid contact and subsequent by the IHTC during separation of solidifying metal from the mould (gap formation). The obtained data are applied in a one dimensional model of solidification during filling of a channel. The effect of vibration is quantified and incorporated into the fluidity model, such that the velocity with and without vibration can be considered in the fluidity model. High pouring temperature aluminum alloy in thin wall investment casting, fluidity characteristic is improved by application of vibration.