Quartz glass production process, especially the use of electrical melting method to produce transparent quartz glass, widely used graphite crucible, graphite heating body, graphite insulation sleeve and so on. In the production of opaque quartz glass, often using a single rod method of production, that is, using a graphite rod (including the Round rod and U-shaped rod), ohmic heating, quartz sand fused into quartz glass, and in the production of quartz glass in the gas refining process, but also the use of graphite materials to make the pallet.
In the “Gas refining trough sinking method”, the quartz block of an air smelting shall be placed in a graphite box coated with a tungsten sintering layer, and the box is pressurized with a graphite block, heated to a high frequency furnace or a resistance furnace to dissolve and flatten the material block, and then a power outage. Cooling and annealing, so that a slender quartz block can be suppressed into large diameter optical quartz glass (also can be profiled), and can reduce the particle inhomogeneity of the gas refining glass. It can be seen that graphite has become an indispensable material during the production of quartz glass.
1. Production of transparent quartz glass by vacuum pressure method
It is the pure processed natural crystal Material block (5 ~ 25 mm) into the graphite crucible, in the vacuum resistance Furnace rapid melting (15-45 minutes per furnace), and directly drawn into transparent quartz glass tube method.
Graphite crucible is generally used barrel type, both the container and the heating body, as shown in Fig. 3-8.
In order to eliminate the bubbles, the insulation structure of the furnace and the shape of graphite crucible should conform to the principle of high temperature and low temperature in the upper part.
2. Production of quartz glass by vacuum pressurization
It is the fine crushing material vacuum melting, immediately filled with high-pressure gas, and then put gas tube or made of infrared optical quartz glass.
At present, the graphite crucible used in the vacuum pressurized flushing pipe is generally used in the cylindrical spindle-shaped Guo, the thin middle thickness of the Guo wall ends, and the Guo shape is chosen mainly to reduce the longitudinal temperature difference of the crucible heating body. Because of the existence of longitudinal temperature difference, the material layer near the core rod is not completely deoxidation. Because the local material layer glass melts after sinking, the core bar around the material layer to form bubbles, even if the delay in degassing time, the bubble can not be discharged.
