大尺寸石英玻璃冷却过程的优化

Optimizing the Cooling Process of the Quartz Glass in an Electric Furnace

大尺寸石英玻璃在航空航天和核能领域有着广泛的应用,但是大尺寸石英玻璃在冷却过程中会由于较大的温差产生较高的热应力,这会导致石英玻璃内部或者表面产生裂缝并且降低石英玻璃的质量。对这个过程的精确控制能够降低过程热应力。本文中研究了石英玻璃冷却动态过程温度和应力的变化情况,考虑加热器功率、位置和样品尺寸的影响,在加快冷却速率的前提下降低石英玻璃的过程应力,优化石英玻璃的冷却过程。

Large size quartz glass is widely used in aerospace and nuclear energy fields.The thermal stress in the quartz ingot,generated by nonlinear temperature gradients during cooling process,and stress-related defects critically degrade its optical performance.Precise control of the cooling process becomes an emergent task in the production.In this paper,a transient model is firstly proposed,combining heat transfer and stress evolution to investigate changes of temperature and stress in the ingot during cooling.Influences of the heater power profile,the heater position and the ingot size on the stress evolution have been well examined further.The maximum stress in the ingot is chosen as an evaluating indicator of the stress level.The results show that a step function not only can notably reduce the maximum stress,but also cool down the ingot in a shorter period.Furthermore,the heater is found better at the same horizontal position of the ingot,indicating that an adjustment of the heater at the cooling stage is required.The proposed cooling strategies provide a valuable direction for improving quality and productivity of the quartz glass in industry.