Fig. 2. These silica sands from Oregon, Ill., (left) and Roff, Okla., have been used successfully as a substitution for olivine sand.


castings with 75% new olivine sand and 25% new silica sand had a slightly dull appearance with a few small sand particles adhering to the surface but a reduced number of surface pinholes. Test castings with a 50/50 mixture of olivine and silica sand had a smooth but dull finish, with a small amount


of adhering sand but no pinholes. Test castings made with 100% new silica sand exhibited a clean surface with some adhering sand (Figs. 3-6). According to the authors, maturity and continued use in the green sand system would bring improved prop- erties and better casting results. A


test casting from a mature operating sand system using 100% silica sand exhibited a surface superior to that of a mature olivine sand system (Fig. 7). For some metalcasting facilities,


such as Pride Cast Metals, the use of silica sand brings with it certain health concerns. Although silica


22 | MODERN CASTING December 2012


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