The Role of Process Parameters in Platinum Casting

The Research Institute for Precious Metals and Metals Chemistry (FEM), Katharinenstrasse 17, D-73525 Schwabisch Gmund, Germany; *E-mail: klotz@fem-online.de Platinum is a challenging material for casters because of its physical properties, which result in possible crucible and flask reactions during melting and casting, high shrinkage porosity and difficulties in filling of filigree items. This paper summarises the results of a collaborative research effort by several industrial partners and FEM on the influence of casting process parameters. Two common platinum jewellery alloys (platinum with 5 wt% cobalt and platinum with 5 wt% ruthenium) and four different investment materials were used for casting experiments with variation of atmosphere, casting and flask temperature, tree design and centrifugal machine parameters. Detailed sample investigation found shrinkage porosity and surface defects to be the main problems. Optimised process parameters for heavy and filigree items were identified. Future research on platinum casting should focus on casting simulation in order to reduce experimental effort and costs.