Technology Of Making Float Glass

Melting technology of float glass

The melting process of float glass is a process in which qualified mixtures are heated at high temperature to form uniform, pure, transparent and forming liquid glass, which is one of the main processes in the manufacturing process of float glass.

The melting speed and the rationality of melting have a great influence on the output, quality, qualified rate, production cost, fuel consumption and tank furnace life of glass.

Float glass forming technology

The molten glass in the tank kiln flows into the tin tank along the flow channel at a temperature of about 1100C. Because the density of the glass is only about 1x3 of the density of the liquid tin, it floats on the tin surface to complete the levelling process of the glass, and then gradually cools down and cools into a plate under the action of external force.

When the glass belt is cooled to 600-620 ℃, it is lifted by the transition table, and under the action of the tractive force of the conveying wheel, it leaves the tin trough and enters the annealing kiln to relieve the stress, then it is inspected by quality, cut vertically and horizontally, and packed into storage.

In order to prevent the oxidation of tin liquid at high temperatures, weak reductive protective gas is usually introduced to improve the quality of glass.

There are two kinds of forces in the forming of glass tape, namely, surface tension and self-gravity, the former prevents the liquid glass from spreading infinitely and has a great influence on the finish of the glass surface, while the latter promotes the glass to spread out. When the surface tension is balanced with its own gravity, the natural thickness of the glass strip floating on the tin surface is obtained.

Annealing Technology of float Glass

The reduction or elimination of the residual internal stress in the glass is only possible when the glass is reheated to begin plastic deformation. The temperature range of glass during this plastic deformation is called the annealing temperature range of glass.

The maximum annealing temperature refers to holding 2min at this temperature, and the stress can be eliminated by 95%, which generally corresponds to the transition temperature of glass; the lowest annealing temperature refers to holding 2min at this temperature, and the stress can be eliminated by 5%, which generally corresponds to the strain temperature of the glass.

These two temperatures constitute the annealing temperature range of the glass.

The processing system of annealing is the annealing zone. Glass annealing zone is for glass annealing in the annealing furnace, according to different conditions and requirements, so that the zone can be controlled, in order to improve the quality of glass annealing. In fact, the glass annealing process is also a cooling process, but the cooling rate should be controlled according to the different thicknesses and requirements of the glass, so that the residual internal stress in the annealed glass can meet the requirements; at the same time, the temporary stress produced by the glass during annealing should not be too large, otherwise it will cause the glass to burst in the annealing furnace. Therefore, according to the annealing process, the glass can be divided into the heating precooling zone (also known as the pre-annealing zone), an important cooling zone (also known as the annealing zone), a cooling zone (also known as the post-annealing zone) and rapid cooling zone. The rapid cooling zone is divided into a direct hot air cooling zone and a direct cold air cooling zone.

The technological principle of cold end

The cold end equipment mainly performs all kinds of inspection, cutting and breaking, surface protection, stacking and packing of the annealed glass plate in the production process, as well as the transportation of these processes.

The process principle of cold end

According to the function and working sequence of the cold end equipment, it can be roughly divided into three main sections.

• Glass ribbon detection and pretreatment section.

• cutting the breaking section.

• slicing, stacking and packing section.

The function and structure of cold-end equipment.

The cold end of the float glass production line is composed of the following major professional machinery and equipment.

• The conveying equipment of glass plate, such as all kinds of conveying wheels, belts, negative pressure suckers, air cushions, slicing equipment, etc.

• The cutting and breaking devices of glass plates, such as emergency crosscutting machines, longitudinal cutting machines, transverse cutting machines, transverse breaking devices, edge breaking devices, longitudinal breaking and slicing devices, falling devices of the waste plates, etc.

• The various quality testing devices, such as online stress, plate thickness, plate edge position tracking detection, spot defect detection device, etc.

• The various surface protection devices set up to protect the surface of high-quality float glass, such as the device for spraying anti-mildew liquid to prevent mildew, the electrostatic paper spreader and powder spraying device to prevent abrasion on the glass surface, and the use of air cushion transportation, etc.

• The various types of glass plate stacking and packing equipment, such as horizontal and vertical stacking units for large, medium and small pieces, etc.

• The tangent lines of large and medium films on or outside the branch line, such as longitudinal and horizontal cutting tables, longitudinal and horizontal breaking devices, plate falling devices, and reversible stacking and taking machines of large and medium pieces, etc.

• The electronic computer-distributed control system is used to control the cold-end equipment.

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