Glass production technology includes: batching, melting, forming, annealing and other procedures.
They are introduced as follows:
1. Ingredients: Weigh all kinds of raw materials according to the designed recipe and mix them evenly in a mixing machine.
The main raw materials of glass are: quartz sand, limestone, feldspar, soda ash, boric acid and so on.
Second, melt, the raw materials will be prepared after high temperature heating, the formation of uniform bubble-free liquid glass.
This is a very complex physical and chemical reaction process.
The glass is melted in the furnace.
There are two main types of melting kilns: one is crucible kilns, in which glass material is held in the crucible and heated outside.
Small crucible kilns put only one crucible, large ones can be up to 20 crucible.
Crucible kilns are interstitial, now only optical glass and color glass are produced by crucible kilns.
The other kind is the pool kiln, the glass material melts in the kiln, the open flame heats in the glass liquid surface.
Most of the glass temperature of the melted in 1300 ~ 1600 ゜ c.
Most are heated by flame, but a few are heated by electric current, called electromelting kilns.
Now, the pool kiln is continuous production, small pool kiln can be a few meters, the large can be more than 400 meters.
Three, forming, is to melt the glass liquid into a fixed shape of solid products.
Forming takes place within a certain temperature range, a cooling process in which the glass first changes from a viscous liquid to a plastic state and then to a brittle solid state.
Forming methods can be divided into two categories: artificial forming and mechanical forming.
There is also (1) blowing, using a ni-Cr blow pipe, pick a ball of glass in the mold while turning and blowing.
It is mainly used for forming glass bubbles, bottles and balls (for cutting glasses), etc.
(2) Drawing. After blowing into bubbles, the other worker sticks them with the top plate. While blowing, the two workers pull them mainly for making glass tubes or rods.
(3) Press, take a ball of glass, cut with scissors to make it fall into the die, then press with the punch.
Mainly used to form cups, plates and so on.
(4) Free shaping, after picking materials, directly make handicrafts with pliers, scissors, tweezers and other tools.
Because artificial forming labor intensity, high temperature, poor conditions, so, in addition to free forming, most have been replaced by mechanical forming.
Mechanical forming in addition to pressing, blowing, drawing, there are (1) calendering method, used to produce thick plate glass, cut glass, wire glass, etc.
(2) Casting process to produce optical glass.
(3) Centrifugal casting method, used for the manufacture of large diameter glass tubes, vessels and large capacity reaction POTS.
This involves injecting the glass melt into a rapidly rotating mold, where centrifugal force forces the glass against the mold wall and the rotation continues until the glass hardens.
(4) Sintering method, used for producing foamed glass.
It is added in the glass powder foaming agent, heating in the metal mold with a lid, the glass in the heating process to form a lot of closed air bubbles, which is a good insulation, sound insulation material.
In addition, the formation of plate glass has vertical lead method, pull method and float method.
Float is a method of forming plate glass by floating glass liquid on the surface of molten metal (tin). Its main advantages are high quality glass (smooth and smooth), fast drawing speed and high yield.
4. Annealing, during forming, the glass undergoes drastic temperature and shape changes, which leave a thermal stress in the glass.
This thermal stress reduces the strength and thermal stability of the glass.
If it is cooled directly, it is likely to break itself (commonly known as cold burst of glass) during the cooling process or during subsequent storage, transportation and use.
In order to eliminate the phenomenon of cold burst, glass products must be annealed after forming.
Annealing is to hold or cool slowly for a period of time within a certain temperature range in order to eliminate or reduce the thermal stress in glass to a permissible value.
In addition, some glass products can be rigid in order to increase their strength.
Including: physical rigidity (quenching), used for thicker glass, table glass, car windshield, etc.;
And chemical rigid (ion exchange), used for watches, glass, aviation glass, etc.
The principle of rigidization is to create compressive stress in the glass surface layer to increase its strength.
Post time: Oct-16-2020