The raw materials for the production of optical glass are oxides, hydroxides, nitrates and carbonates, and phosphate or fluoride is introduced according to the formulation requirements. In order to ensure the transparency of the glass, the content of the colored impurities such as iron, chromium, copper, manganese, cobalt, nickel, etc. must be strictly controlled. When weighing, it is required to accurately weigh and evenly mix. The main production processes are melting, forming, annealing and inspection.
1 smelting has a single enthalpy intermittent smelting method and a pool kiln (see kiln) continuous smelting method. The single smelting method can be further divided into a clay smelting method and a platinum smelting method. No matter which kind of smelting method is used, it needs to be stirred by a stirrer, and the temperature and stirring are strictly controlled to make the optical glass glass liquid highly uniform. Clay bismuth can smelt most of bismuth glass and flint glass at a low cost and is used when the melting temperature of the glass exceeds the use temperature of platinum.
Platinum rhodium can be used to smelt high quality glass that has a severe erosive effect on clay crucibles, such as heavy enamel, heavy strontium, rare earth glass and fluorophosphorus glass. Platinum crucibles are electrically heated, generally using a silicon carbon rod or a silicon molybdenum rod electric furnace. However, high-frequency heating can be employed for glass having a large tendency to devitrify, requiring rapid cooling, and having a certain atmosphere.
Since the 1960s, countries have successively used continuous kiln lining with platinum to make the output of optical glass greatly improved and the quality is good. This is the main trend of optical glass production process development.
2 molding optical glass molding methods include classical breaking method, rolling method and casting method, but at present, more and more leakage molding (using single or continuous flow of liquid) can be used to directly pull the rod or drip. Pressing or leaking material to form large-sized blanks, improving the feed rate utilization and yield.
3 Annealing In order to minimize the internal stress of the glass and improve the optical uniformity, a strict annealing system must be established to perform precision annealing.
4 The indicators measured by the test are: optical constant, optical uniformity, stress birefringence, streaks, bubbles, and the like.
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