Production Method of Optical Glass

The raw materials for the production of optical glass are some oxides, hydroxides, nitrates and carbonates, and phosphates or fluorides are introduced according to the requirements of the formulation. In order to ensure the transparency of glass, the content of colored impurities, such as iron, chromium, copper, manganese, cobalt, and nickel, must be strictly controlled. Ingredients are required accurate weighing and uniform mixing. The main production processes are smelting, forming, annealing and inspection.

①Smelting: 

There are single crucible batch smelting method and tank kiln (see kiln) continuous smelting method. Single crucible smelting method can be divided into clay crucible smelting method and platinum crucible smelting method. No matter what kind of smelting method is used, it needs to be stirred with a stirrer, and the temperature and stirring are strictly controlled to make the glass liquid reach a high degree of uniformity. The clay crucible can smelt most crown glass and flint glass, with low cost, and is used when the melting temperature of the glass exceeds the service temperature of platinum. The platinum crucible can smelt high-quality glass that has a serious corrosive effect on the clay crucible, such as heavy crown, heavy barium flint, rare earth glass and fluorophosphorous glass. Platinum crucibles are heated by electricity, generally silicon-carbon rods or silicon-molybdenum rod electric furnaces are used. However, high-frequency heating can be used to manufacture glass that has a high tendency to crystallize, requires rapid cooling, and has certain requirements on the atmosphere.Since the 1960s, various countries have successively adopted continuous smelting with platinum lining, which greatly increased the output and quality of optical glass. This is the main trend in the development of the current optical glass production process.

②Forming

The molding methods of optical glass include classical crucible method, rolling method and pouring method. However, leakage molding (using a single crucible or continuous melt flow out) is more and more widely used, and it can be directly drawn or dripped. Large-size blanks are formed by molding or leaking materials, which improves the utilization rate of gobs and the rate of finished products.

③ Annealing 

In order to clean the internal stress of the glass to a greater extent and improve the optical uniformity, it is necessary to formulate a strict annealing system for accurate annealing.

④Inspection 

The indicators measured are: optical constant, optical uniformity, stress birefringence, streaks, bubbles, etc.

optical glass balls