| Summary: | 碩士 === 國立高雄應用科技大學 === 模具工程系 === 99 === The effects of different water based colloidal silica on the properties of primary and backup slurries and ceramic shell mold have been studied. In addition, fused silica can instead of zircon within primary slurry and stucco due to a low density, low thermal expansion coefficient, low specific heat and other characteristics, and prices of the zircon flours and zircon stucco soar. Therefore, the effects on the slurry and ceramic shell mold properties after fused silica instead of zircon have also been studied.
There were three variable combinations within the experiment: (1) Type 1, water based colloidal silica A + zircon flours + zircon stucco, (2) Type 2, water based colloidal silica B + zircon flours + zircon stucco and (3) Type 3, water based colloidal silica B + fused silica flours + fused silica stucco, and mullite flours and stucco were uniformly used as backup refractories. About the effects on slurry properties, the viscosity, rheology, pH, sedimentation rate and water-loss rate were investigated. About the effects on ceramic shell mold properties, the four and a half layers ceramic shell mold was principally investigated on the weight, thickness, drying time, MOR (green strength, hot strength and fired strength), permeability, surface roughness, humidity, and sintering duration. Finally, the practical metal pouring experiment was conducted.
The results showed: 1. On the slurry properties, Type 2 and 3 have a slowed rising tendency compared with Type 3. And there is no obvious variation on the slope of pH value, but the slurry slows to gel at high pH. Type 3 can decrease the sedimentation rate and it has a larger amount of water-loss weight. 2. On the ceramic shell mold properties, Type 2 and 3 have a light, thin and drying-time-shorted ceramic shell mold compared with Type 1. On the other hand, Type 2 and 3 also have a higher green strength, lower hot and fired strengths, and a higher hot permeability. MOR has no obvious variation, but permeability increase with sintering duration. And drying time is shorted with the humidity decreased. 3. During the 316L stainless steel casting process, the Type 2 ceramic shell mold can withstand the impact of high temperature liquid metal.
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