Investigation of Interface Agent for Investment Casting With Ice Patterns

Abstract

Investment casting with ice patterns is similar to that with wax patterns but with significant process differences. A major difference in our developed method is that an interface agent needs to be coated around the ice pattern to protect it from damage during the process. We have studied the criteria for choosing the interface agent and discovered that the most important factor is the cohesion parameter. The thickness of the interface agent affects the dimensional accuracy of the generated metal casting. To compensate for this, mathematical models have been constructed to predict the thickness of the interface agent for a large cylindrical part and for a small part. The interface layer thickness and the temperature distribution within the ice part and the solidifying interface agent have been investigated. For solid ice cylinders, both the immersion time and the cylinder diameter affect the interface layer thickness. For small parts, the interface thickness is mainly dependent upon the ratio between the volume and surface area of the ice part and to a lesser extent upon the physical properties of the materials. Superheat has little influence on the interface layer thickness. Based on the analysis, the dimensional accuracy of the metal castings for small parts can be much improved by compensating the interface layer thickness. The analytical results agree well with experimental observations.