| Description |
x, 97 leaves : illustrations, photographs ; 29 cm |
| Summary |
"The effects of zircon refractories in the prime coats of commercial type investment shell molds on solidification and fluidity were investigated. The results of this research may eventually help to enable the zircon portion of investment shells to be minimized and/or recovered. Zircon is used as a prime coat refractory because of its highly refractory properties, low thermal expansion, high thermal conductivity, and resistance to wetting by molten metals. The high heat transfer characteristics of zircon had little effect after mold temperatures had risen. The zircon showed greater chilling effects in the smaller section sizes. The zircon prime coats also allowed peak mold temperatures to be reached more quickly than in molds with other prime coat compositions. A mixture of fused silica and zircon acted as a thermal insulator, providing slower cooling than the pure fused silica prime coat. This behavior of the fused silica/zircon prime coat is likely due to additional porosity in the fused silica/zircon prime coat mixture. The fluidity spirals fed to greater lengths when a zircon prime coat was used; however, the effect diminished with a smaller cross-sectional area of the spiral. Although some chilling effect of zircon was found, the necessity for a zircon prime coat instead of fused silica for chilling or fluidity advantages is questionable"--Abstract, leaf iii. |
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