How is the glass produced?

1. Ingredients: According to the designed material list, weigh various raw materials and mix them evenly in the mixer. The main raw materials for glass include quartz sand, limestone, feldspar, soda ash, boric acid, etc.

2. Melting: The prepared raw materials are heated at high temperatures to form a uniform and bubble free glass liquid. This is a very complex physical and chemical reaction process. There are two main types of kilns: one is a crucible kiln, where glass materials are stored inside the crucible and heated outside the crucible; Another type is the pool kiln, where the glass material is melted in the kiln and heated by firing at the top to heat the glass liquid. The melting temperature of most glass ranges from 1300 to 1600 ℃. Most of them use flame heating, while a few use electric current heating, known as electric melting furnaces. Now, the pool kiln has been continuously produced, with small tanks reaching several meters and large tanks reaching over 400 meters.

3.Forming: It is the process of transforming a molten glass liquid into a solid product with a fixed shape. Forming must be carried out within a certain temperature range, which is a cooling process. Glass first transitions from a viscous liquid state to a plastic state, and then to a brittle solid state. The molding methods can be divided into two categories: manual molding and mechanical molding.

A. Artificial molding.

(1) Blowing, using nickel chromium alloy to blow pipes, selecting a set of glass in the mold, and blowing while flipping. Mainly used for forming glass bubbles, bottles, balls (for scratching glasses and lenses), etc.

(2) Drawing, after blowing into small bubbles, another worker sticks it with a top plate, and two people blow and pull at the same time, mainly used to make glass tubes or rods.

(3) Pressing, pick a ball of glass, cut it with scissors to make it fall into the concave mold, and then press it with a convex mold. Mainly used for forming cups, plates, etc.

(4) Free form, pick up materials and use tools such as pliers, scissors, and tweezers to directly make handicrafts.

B. Mechanical forming. Due to the high labor intensity, high temperature, and poor conditions of manual molding, most of it has been replaced by mechanical molding, except for free molding. In addition to pressing, blow molding, and drawing, mechanical forming also includes

(1) Rolling method is used to produce thick flat glass, engraved glass, laminated glass, etc.

(2) Casting method for producing optical glass.

(3) Centrifugal casting method is used to manufacture large-diameter glass tubes, vessels, and large capacity reaction pots. This involves injecting molten glass into a high-speed rotating mold, where centrifugal force causes the glass to adhere tightly to the mold wall and continue to rotate until the glass hardens.

(4) Sintering method is used to produce foam glass. It adds foaming agent to glass powder and heats it in a covered metal mold. During the heating process, a large number of closed cell bubbles are formed in the glass, making it a very good insulation and sound insulation material. In addition, there are other forming methods for flat glass, such as vertical guidance method, flat drawing method, float method, etc. Floatation is a method of allowing glass to float on the surface of molten metal (tin) to form flat glass, with the main advantages of high glass quality (flat, smooth), fast pulling speed, and large output.

4. Annealing: Glass undergoes drastic temperature and shape changes during the molding process, leaving thermal stress on the glass. This thermal stress will reduce the strength and thermal stability of glass products. If cooled directly, it is likely to self rupture (commonly known as glass cold explosion) during the cooling process or during storage, transportation, and use in the future. In order to eliminate the phenomenon of cold explosion, glass products must undergo annealing treatment after forming. Annealing is a process of holding or slowly cooling within a certain temperature range for a period of time to eliminate or reduce the thermal stress in the glass to the allowable value.

 

In addition, some glass products can be hardened to increase their strength. Including: physical strengthening (quenching), used for thicker glass, tabletop glass, car windshields, etc; Chemical hardening (ion exchange), used for watch case glass, aviation glass, etc. The principle of hardening is to generate compressive stress on the surface of glass to increase its strength.