The production process of glass bottles includes: batching, melting, forming, annealing and other processes. They are introduced as follows:
According to the designed material list, the various raw materials are weighed and mixed uniformly in a mixer. The main raw materials of glass are: quartz sand, limestone, feldspar, soda ash, boric acid and so on.
The prepared raw materials are heated at high temperature to form a uniform and bubble-free glass liquid. This is a very complicated physical and chemical reaction process. The melting of the glass takes place in the furnace.
There are two main types of furnaces:
1. Crucible kiln, glass frit is contained in the crucible and heated outside the crucible. The small crucible kiln only puts one crucible, and the large one can have as many as 20 crucibles. Crucible kiln is produced in gap type, and now only optical glass and colored glass are produced in crucible kiln.
2. In the kiln, the glass frit is melted in the kiln, and the open flame is heated on the upper part of the glass surface. The melting temperature of glass is mostly 1300~1600°C. Most of them are heated by flames, and a few are heated by electric current, which are called electric melting furnaces.
It transforms the molten glass into a solid product with a fixed shape. Forming must be carried out within a certain temperature range. This is a cooling process. The glass first changes from a viscous liquid state to a plastic state, and then into a brittle solid state.
The forming method can be divided into two categories: artificial forming and mechanical forming.
A. Artificial forming
B. Mechanical forming
Because of the high labor intensity, high temperature and poor conditions of artificial forming, most of them have been replaced by mechanical forming except for free forming.
The glass undergoes drastic temperature changes and shape changes during the forming process, and this change leaves thermal stress in the glass. This thermal stress will reduce the strength and thermal stability of the glass container bottles. If it is cooled directly, it is likely to rupture on its own during the cooling process or later during storage, transportation and use. In order to eliminate the phenomenon of cold explosion, glass container and bottle products must be annealed after being formed. Annealing is to keep the temperature in a certain temperature range or slowly cool down for a period of time to eliminate or reduce the thermal stress in the glass to allowable value.
In addition, some glass bottle products can be rigidified in order to increase their strength. Including: physical rigidization (quenching), used for thicker glasses, desktop glass, car windshields, etc.; and chemical rigidization (ion exchange), used for watch surface glass, aviation glass, etc. The principle of stiffening is to generate compressive stress on the surface of the glass to increase its strength.
