Study On Thermal Stress Formation And Heat Treatment Process Of Quartz Glass

In recent years,China has seen an increasing demand for high quality quartz glass in areas such as national defense,military and aerospace.High quality quartz glass blanks(quartz glass lump)are usually made of high purity silicon tetrachloride as raw material and synthesized by chemical vapor deposition process with high temperature fusion,which mainly includes three processes such as high temperature melting,deposition and cooling.During the cooling process of quartz glass lump,there is a large temperature gradient,which in turn generates thermal stresses that greatly reduce the performance of quartz glass.This thermal stress must be reduced by a subsequent heat treatment process.In this paper,a theoretical analysis and numerical simulation study of the formation of thermal stress and heat treatment process of quartz glass is carried out to address the problem of excessive thermal stress and high production cost of quartz glass due to the existing production process proposed by the quartz glass production plant.Firstly,a theoretical analysis of the cooling and heat transfer processes and the formation of thermal stress in the production of glass in the existing vertical quartz glass block making process of the factory is carried out;then the production cooling process and the heat treatment process of the quartz glass block are simulated numerically;finally,the production cooling process and the heat treatment process are improved.the specific contents studied in this paper are as follows:By using finite element software,the thermal stress generated during the cooling process of quartz glass lead is numerically simulated,and the influence law of temperature distribution on the thermal stress of quartz glass lead is obtained.The simulation results show that excessive temperature gradient in the process of production cooling has a great influence on the thermal stress of quartz glass lead.The thermal stress preconditioning device of quartz glass is designed and its effect is simulated.The heat treatment process of quartz glass in the factory was studied,the fluid dynamics model,three-dimensional turbulence model and fluid-structure coupling heat transfer model in the annealing furnace were defined,and the temperature field in the furnace was simulated and analyzed and the temperature measurement experiment was conducted.In addition,the stress test of annealed quartz glass samples was carried out.In order to improve the production efficiency of quartz glass,the structure of quartz glass heat treatment furnace was designed and improved.The distribution of pressure field and flow field in furnace,temperature field and stress field of quartz glass in annealing process are simulated and analyzed.At the same time,based on the improved annealing furnace,the influence of quartz glass size and ventilation rate on the cooling process is analyzed.It is found that with the increase of quartz glass size and ventilation rate,the maximum stress in the cooling process increases,and ventilation can significantly reduce the maximum stress in the annealing process of quartz glass.It provides reference for improving the quality and production efficiency of quartz glass.