Silicon-deoxidized alloys are widely used for investment casting processes in jewelry manufacturing. Brightening and deoxidizing properties are the most important benefits of such alloys, yet these alloys are also known to have significant drawbacks, especially when used in high-karat gold alloys with large amounts of silver. Furthermore, many factors such as alloy composition, temperature, etc., can affect the critical concentration of silicon at which defective behavior can be triggered. In this research project, a new approach to investment casting alloys will be discussed. A comparison will be made between the characteristics and performance of new formulas and silicon-deoxidized alloys, and conclusions will be drawn as to the ability of new deoxidizing elements to replace silicon in casting alloys. Casting alloys with reduced concentrations of silicon will also be discussed. Encouraging results have been obtained from silicon-free casting alloys in terms of fluidity and deoxidizing properties (less dross in crucible), in addition to very small crystal grain size dimension and good mechanical properties. These alloys help reduce the possibility of gas or shrinkage porosity, thereby bringing further benefits, especially for investment casting of high-karat gold alloys.

Author: Dr. Andrea Basso, Massimo Poliero