| 摘要 |
With this heat treatment process the semi-product of the glass-silicate plate consists of a bottom layer, made up of sand or other silicate material, with a top layer, containing glass granulate. After compression the aggregate of both layers is heated until reaching temperature Tf at the bottom layer and Tg at the top layer, which is lower than the transformation temperature of the glass granulate. A negative temperature gradient is maintained along the thickness of the semi-product in the direction from the surface. At temperatures Tf and Tg there follows retardation and pressing of the semi-product by a plate, which is gas permeable and has a temperature of Tg. After that the bottom layer is heated to T1 - the Littleton Point - and the surface of the top layer to the temperature (Tf) of sintering of sintered glass. Then there is a second retardation and reheating to maintain temperature T4.5 in the surface layer. T4.5 corresponds to the logarithm of viscosity expressed in Pa.s of sintered glass is 4.5. There then follows a retardation with positive temperature gradient for the period required to form a smooth surface on the top layer, whereas the current temperature of the bottom layer is controlled so that at the end of the retardation it is lower than T5.5, where the logarithm of viscosity expressed in Pa.s. of the sintered glass equals 5.5. Following that there is a sharp drop in temperature to T1 on the surface of the top layer and retardation in order to balance the temperature in the whole volume of the semi-product and cooling to the upper temperature T12, followed by two-phase cooling to room temperature.<IMAGE> |
