Glass is tempered out of the tempering furnace, this everyone knows, so what is his process? The production process of glass includes: batching, melting, forming, annealing and other basic processes, as described in detail below:
1. Ingredients, according to the designed material list, weigh all kinds of raw materials in a mixing machine mixed evenly. The main raw materials of glass are: quartz sand, limestone, feldspar, soda ash, boric acid, etc.
2. Melting, the prepared raw materials are heated at high temperature to form a uniform bubble-free glass liquid. This is a very complex physical and chemical reaction process. The melting of glass is carried out in the melting kiln. There are two main types of melting kilns: one is the crucible kiln, the glass material is held in the crucible and heated outside the crucible. Small crucible kilns only place one crucible, and large ones can have up to 20 crucible. Crucible kiln is gap production, and now only optical glass and color glass are produced by crucible kiln. The other is the pond kiln, the glass material is melted in the pond, and the open flame is heated on the surface of the glass liquid. The melting temperature of glass is mostly 1300~1600゜C. Most of them are heated by flame, and a small amount are heated by current, which is called electric melting kiln. Now, the pond kiln is continuous production, the small pond kiln can be a few meters, the large can be as large as 400 meters.
3. Forming is to transform the molten glass liquid into a solid product with a fixed shape. Glass first changes from a viscous liquid to a plastic state and then to a brittle solid. Forming methods can be divided into two categories: artificial forming and mechanical forming.
A. Artificial form.
(1) Blowing, with a nickel chromium alloy blow pipe, pick a ball of glass in the mold while blowing. Mainly used to form glass bubbles, bottles, balls (for glasses) and so on.
(2) Drawing, after blowing into a small bubble, another worker sticks with the top plate, and the two people blow while pulling is mainly used to make glass tubes or rods.
(3) Pressing, pick a group of glass, cut it with scissors so that it falls into the concave die, and then press it with a punch. Mainly used to form cups, plates and so on.
(4) Free forming, after picking materials with pliers, scissors, tweezers and other tools directly into crafts.
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 in addition to free forming. Mechanical forming in addition to pressing, blowing, drawing, there are
(1) Calendering method, used to produce thick flat glass, carved glass, wire glass, etc.
(2) Casting method, production of optical glass.
(3) Centrifugal casting method is used to manufacture large-diameter glass tubes, utensils and large-capacity reaction POTS. This is the injection of glass melt into a high-speed rotating mold, due to centrifugal force to hold the glass against the mold wall, the rotation continues until the glass hardens.
(4) sintering method for the production of foam glass. It is a blowing agent added to the glass powder, heated in the metal mold with a lid, and the glass forms a lot of closed bubbles during the heating process, which is a good insulation and sound insulation material.
In addition, the forming of flat glass has vertical drawing method, flat drawing method and float method. Float method is to let the glass flow float on the surface of molten metal (tin) to form flat glass, its main advantages are high quality glass (flat, smooth), fast drawing speed, large output.
4. Annealed, the glass underwent intense temperature changes and shape changes during forming, which left thermal stress in the glass. This thermal stress will reduce the strength and thermal stability of glass products. If it is cooled directly, it is likely to break itself during the cooling process or later during storage, transportation and use (commonly known as cold explosion of glass). In order to eliminate the phenomenon of cold explosion, glass products must be annealed after forming. Annealing is the holding or slow cooling of heat within a certain temperature range for a period of time to eliminate or reduce the thermal stress in the glass to a allowable value.
In addition, some glass products can be hardened in order to increase their strength. Including: physical hardening (hardening), used for thicker glasses, desktop glass, car windshield, etc.; And chemical hardening (ion exchange), used for watch glass, aviation glass, etc. The principle of hardening is to create compressive stress on the glass surface layer to increase its strength.
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