What is the production and processing method of optical glass?

There are many types of glass that play a pivotal role in various industries. In addition to the insulating glass and laminated glass used to make doors and Windows, there are many types of art ornaments used to make, such as hot melt glass and embossed glass. These glass products have their own characteristics and can be used for various occasions.

First, optical glass production and processing methods

The raw materials for the production of optical glass are some oxides, hydroxides, nitrates and carbonates, and according to the requirements of the formula, the introduction of phosphate or fluoride. In order to ensure the transparency of the glass, the content of coloring impurities must be strictly controlled, such as iron, chromium, copper, manganese, cobalt, nickel and so on. It is required to weigh accurately and mix evenly when dosing. The main production processes are melting, forming, annealing and inspection.

① There are single crucible intermittent melting method and pool kiln (see kiln) continuous melting method. The single crucible melting method can be divided into clay crucible melting method and platinum crucible melting method. No matter what kind of melting method is used, it is necessary to stir with a mixer, and strictly control the temperature and stirring, so that the glass liquid can reach a high degree of uniformity. Clay crucible can melt most of the crown glass and flint glass, low cost, and when the melting temperature of the glass exceeds the use temperature of platinum. Platinum crucible can melt high quality, clay crucible has serious erosion of glass, such as heavy crown, heavy barium flint, rare earth glass and fluorophosphate glass. Platinum crucible is heated electrically, generally using silicon carbon rod or silicon molybdenum rod electric furnace. However, the manufacture of glass with large crystallization tendency, rapid cooling and certain requirements for the atmosphere can use high-frequency heating.

Since the 1960s, countries have successively used platinum-lined continuous pool kiln smelting, so that the output of optical glass greatly improved, the quality is good, which is the main trend of the development of optical glass production process.

② The forming method of forming optical glass has the classical breaking cauldron method, rolling method and pouring method, but at present, the leakage molding is more and more widely used (with a single crucible or continuous melting of the outflow of the material liquid), which can directly pull the rod or drop press type or leak molding large size blank, improve the material drop utilization rate and yield.

③ Annealing In order to eliminate the internal stress of the glass to a greater extent and improve the optical uniformity, a strict annealing system must be developed for precision annealing.

④ The index of inspection and determination are: optical constant, optical uniformity, stress birefringence, fringe, bubble and so on.