Effects of Calcium Carbonate Additives on the Properties of the Slurry and Ceramic Shell Mold of the Investment Casting

• Main Authors: Y.R.Lin, 林祐任
• Other Authors: Koho Yang
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/04706023510608007122

碩士 === 國立高雄應用科技大學 === 模具工程系碩士班 === 95 === The effects of the nano-precipitated calcium carbonate and heavy calcium carbonate additives on the properties of backup slurry and ceramic shell mold of the investment casting have been studied. The ceramic shell mold consisted of five and a half layers (two layers for primary slurry, three and a half layers for backup slurry). The materials used for primary slurry were zircon flour and water based colloidal silica (mix ratio was 3.8:1), and for backup slurry were molochite and colloidal silica (mix ratio was 2:1). The main effects of the additive on the slurry were the measurement of the variations occurred by the rheology, pH and temperature. The effects on the ceramic shell mold were the measurement of the MOR (green strength, hot strength and fired strength) and high temperature permeability. The rheology of the slurry was measured by the rheometer and the Zahn cup, respectively. The data obtained were double checked. The results showed, either the addition of heavy calcium carbonate or the nano-precipitated calcium carbonate on the slurry, both have the similar effect: the anti-setting effect. Comparing the setting of the slurry, the time required for the 12wt% nano-precipitated calcium carbonate was 4 times longer than that of non- nano-precipitated calcium carbonate added slurry; and for 12wt% heavy calcium carbonate, the time required was 1.4 times longer than that of the non-heavy calcium carbonate added slurry. Both the addition of the heavy calcium carbonate and nano-precipitated calcium carbonate on the backup slurry prolonged the life of the slurry and changed the rheological properties (lowered the viscosity), so that, during premixing, the time required to meet the necessary viscosity of the slurry was less, resulted in reducing the required time for mixing slurry. The addition of the 12wt% nano-precipitated calcium carbonate had the most prominent effect. The additives somewhat affected the MOR of the ceramic shell mold and high temperature permeability. The addition of 6wt% nano-precipitataed calcium carbonate had the better overall effect. When the amount of the additives was too much, it caused more vacancies on the ceramic shell mold; on the other hand, when the amount was too little, then, the effect was not obvious.