Historically, both zircon flour and stucco have been considered a requirement for good casting surface finish on numerous steel alloys. As flour in prime slurry it affords improved slurry draining characteristics.

Zircon prices are once again on the rise and, more importantly, domestic supplies are becoming tight. In 2005 Minco presented a paper at the 53rd ICI Technical Conferences and Expo in which we concluded that reducing the amount of zircon used in prime dip applications was the strongest recommendation we had to offer to address increasing price and reduced availability. With the increased tightening of domestic supplies of zircon for use as a sand and flour we feel that investigation into the use of un-calcined sands and flours is necessary.

The first stage of this study will be to compare offshore zircon flour with our domestic zircon flour in a typical prime slurry formula (60/40 zircon/ fused silica both 200 mesh). In this study all prime slurry dips will be coated with domestic calcined zircon sand. The surface finish of the castings from these molds will then be compared.

Next, offshore calcined and un-calcined zircon sand will be compared with the domestic calcined source. The prime slurry for these shells will be made from domestic zircon flour using the same 60/40 formula above. This stucco comparison will include both calcined and non-calcined sands as well as one non-zircon refractory. The surface finish of the castings from these molds will be compared as well.