The production process of optical glass

The raw materials for the production of optical glass are some oxides, hydroxides, nitrates and carbonates, and depending on the requirements of the formulation, phosphates or fluorides are introduced. In order to ensure the transparency of glass, the content of coloring impurities, such as iron, chromium, copper, manganese, cobalt, nickel, etc., must be strictly controlled. Accurate weighing and uniform mixing are required when batching. The main production processes are melting, molding, annealing, and inspection.

(1) There are single crucible intermittent smelting method and pool kiln (see kiln) continuous smelting method. The single crucible smelting method can be divided into clay crucible smelting method and platinum crucible smelting method. Regardless of the melting method, it needs to be stirred with a stirrer, and the temperature and stirring are strictly controlled to achieve a high degree of uniformity of the molten glass. Clay crucibles can melt most crown glass and flint glass at a low cost and are used when the melting temperature of the glass exceeds the temperature at which platinum is used. Platinum crucibles can be used to melt glass with high quality and severe erosion of clay crucibles, such as heavy crowns, heavy barium flints, rare earth glasses and fluorophosphorus glasses. The platinum crucible is heated by electricity, and the silicon carbon rod or silicon molybdenum rod electric furnace is generally used. However, high-frequency heating can be used to manufacture glass with a large tendency to crystallide, rapid cooling and certain requirements for atmosphere.

Since the 60s, countries have successively adopted platinum-lined continuous pool kiln smelting, which has greatly increased the output of optical glass and the quality is good, which is the main trend of the current development of optical glass production technology.

(2) The forming methods of forming optical glass include classical breaking method, rolling method and pouring method, but at present, leakage molding (with a single crucible or continuous melt flowing out of the material liquid) is more and more widely used, which can directly pull the rod or drip to form a large-size blank or leakage material, so as to improve the utilization rate of material droplets and the yield rate.

(3) AnnealingIn order to eliminate the internal stress of the glass to the greatest extent and improve the optical uniformity, it is necessary to formulate a strict annealing system and carry out precision annealing.

(4) The indicators of inspection and measurement are: optical constant, optical uniformity, stress birefringence, fringes, bubbles, etc.