Alternatives for Zircon Stucco and Flour
Casting trials have shown Itochu Ceratech Cerabeads 60 sand to be a successful substitute for zircon sand in many cases, but not 100% of the time. A new product from Itochu Ceratech, Cerabeads 70, has proven to be a more universal solution as a zircon sand substitute. A zircon flour substitute of alumina and alumino-silicates has been developed and tried in production tests. This slurry in combination with Cerabeads 70 has proven to be successful in replacing zircon in prime layers. Casting trials are presented.
The price of zircon flour and sand continues to be high and there are some concerns about long term supply. Many foundries desire a zircon substitute for this reason. This paper is a continuation of a paper presented in 2011 at the Fall ICI Technical Conference. Last year Cerabeads 60 was presented as a potential substitute for zircon sand. While this was true in many cases, there were several instances of rough surface or “burn in” in production trials using standard zircon/fused silica slurry. Presumably, these failures were caused by too thin of a prime coating layer or a reaction of the Cerabeads 60 with the fused silica.
In response to these and other results, Itochu Ceratech developed a new product, Cerabeads 70, which has higher alumina content. Trials using Cerabeads 70 replacing Cerabeads 60 were conducted and some improvement was seen with less instances of “burn in”. Some trials still had “burn-in” using Cerabeads 70, however. In order to have a non-zircon prime slurry and stucco, it became clear that a prime slurry was needed that was not only refractory enough to withstand the molten metal, but that also was capable of leaving a uniform and relatively thick layer of ceramic between the molten metal and the zircon substitute stucco. The slurry presented last year needed to be modified to accomplish this task.
The prime slurry used last year was a blend of Tabular Alumina and lumino-Silicate flour. This slurry was used to make small crucibles in which we melted metal and evaluated the reaction. The problems with this slurry were that slurry life was shorter than desired and the rheology of the slurry did not provide for the thick inert ceramic layer between the molten metal and the Cerabeads 60 stucco.