RU2166482C2 - Method of manufacturing sheet glass - Google Patents

Abstract

FIELD: manufacture of glass for architectural and building purposes, industrial and optical glass. SUBSTANCE: firing of glass is carried out completely or partially within viscosity range of 10¹²-10¹⁸ in bath of melted metal. Operation of rapid and accelerated cooling are carried out on gas-air cushion and roller conveyer rolls. EFFECT: more efficient manufacturing method.

Description

 The invention relates to methods for the production of flat glass using molten metal for molding the glass surface and can be used both for the production of glass for architectural and construction purposes, and for the production of technical and optical glass.

 1. The prior art.

Currently, the production of flat glass includes the operations of pouring glass into a bath to a molten metal, forming a plane-parallel ribbon of glass of a given thickness in the bath with simultaneous cooling to ≈ 600 ^o C, annealing of the glass ribbon (including the one responsible) in a tunnel oven on a roller conveyor from rolls [1, 2, 3]
The disadvantage of this production method is that responsible annealing of the glass tape is carried out on a roller table from the rolls after the molded tape exits the bath with molten metal. Rolls, as a rule, are made of metal, their thermal characteristics differ significantly from the characteristics of the gas space of the furnace above the glass ribbon.

 Therefore, the intensity of heat removal from the lower and upper surfaces of the glass is different, which significantly reduces the quality of annealing, especially in the case of the production of optical glass, where there are especially stringent requirements for the quality of annealing.

It becomes even more difficult to anneal glass in a tunnel rolling table in the case of producing refractory optical glasses such as barite crowns, heavy and superheavy crowns, in which the upper annealing temperature is 100-150 ^o C higher than the upper annealing temperature of most technical glasses and can reach 660 ^o C / 4/.

 These disadvantages are eliminated by the fact that the most critical part of the glass annealing is carried out in a molten metal bath.

 2. The invention.

The proposed method for the production of flat glass includes pouring heated glass melt into a bath with molten metal, forming a plane-parallel glass ribbon with predetermined geometric parameters, and cooling the ribbon to the upper annealing T ^o . A distinctive feature of the proposed technical solution is that responsible annealing (in whole or in part) is carried out in the melt pool, and the operation of rapid and accelerated cooling on a gas-air cushion and roller conveyor shafts.

 As is known, the technological operation of glass annealing consists of the following parts: responsible annealing, rapid cooling operation, and accelerated cooling operation. The most important is the first operation, which does not allow significant temperature drops across the width and thickness of the glass tape.

 The molten metal bath is an ideal space for annealing glass, since it allows you to maintain almost the same temperature across the width and thickness of the tape. This is ensured by the nature of the support (molten metal), which has high thermal conductivity, averaging the temperature of the metal and glass.

Optical glasses TK-14 and STK-3, the so-called heavy crowns, have a critical annealing range of 660-590 ^o C and a dilatometric softening point of more than 700 ^o C. For comparison, the widely used "long" glasses have a critical annealing range of 580-460 ^o C and softening point ≈ 595 ^o C.

The molten bath covers a temperature range from 1000 to 600 ^o C. Thus, the formation of heavy crowns ends in the first half of the bath (1000-790 ^o C), and the annealing temperature range falls into the second part of the bath.

In accordance with the invention, after molding, the temperature in the bath in the area of the 4th zone is reduced to 660 ^o C (the upper temperature of the glass annealing TK-14) at a speed of 20-100 ^o / min and then cooled to 590 ^o C in section 5, 6 and 7th zones of the bath at a speed of 10-18 ^o / min. Lowering the temperature is achieved by reducing the loads on the respective heaters, which saves on energy costs.

In addition, the glass, having undergone a critical annealing operation, allows subsequent cooling at very high speeds (60 ^o / min or more) in subsequent operations, which is reflected in a decrease in the length of the cooling unit after the melt bath, and a reduction in the total line length.

 3. Information confirming the possibility of carrying out the invention.

The proposed method is tested on a pilot production line on a superheavy crown (STK-3). The critical annealing interval corresponded to a viscosity range of 10 ¹² - 10 ¹⁸ Pa • C and covered temperatures of 680-590 ^o C. The dilatometric softening point determined on a DKV-5A dilatometer was 705 ^o C. To test the method, a ladle with molten glass was introduced in 1- the main zone of the molten metal bath and was poured onto molten metal at 1000 ^° C. The glass was blown into a flat sample, which was glued to the board of a moving glass ribbon and passed through all zones of the bath.

Then the sample was prepared and the end stresses in it were measured. They amounted to 10-12 kg / cm ² (1.0-1.2 MPa) when converted to 1 mm of glass thickness, which indicates that the sample underwent annealing operation.

The greatest effect from the application of this invention should be expected from the production of glasses belonging to the class of even shorter glasses, for example, with a very short annealing interval (less than 70 ^o C) [4].

 According to the proposed method, it is possible to produce “long” glasses, but for this it is necessary to lengthen the molten bath by about 1/4 so that the zone of critical annealing is located in it.

Sources of information
1. SU 141822, 11.24.60.

2. SU 1046195, 01/13/66
3.SU 2079195, 08/18/75
4. Physicochemical principles of the production of optical glass, Sat. under the editorship of L.I. Demkina, L .: Chemistry, 1976, p. 440.

Claims (1)

Method for the production of flat glass, including pouring heated glass melt into a bath with a molten metal, forming a plane-parallel glass ribbon with predetermined geometric parameters, cooling the ribbon to the upper annealing temperature and glass annealing, characterized in that the critical annealing is in the viscosity range 10 ¹² - 10 ¹⁸ Pa • With fully or partially carried out in the melt pool, and the operation of rapid and accelerated cooling on the gas cushion and rolls of the roller table.