Iran Float (IFG), the first Kava glass float production line, was established in 2000. The factory is located in the Kaveh industrial city, 120 kilometers from Tehran. The use of the latest technology in the glass industry has become one of the leading manufacturers of glass floats in the Middle East.
The advantages of the following automatic quality control systems in the production of each glass cup as well as our final discharge and rebooting system have significantly contributed to the production of various types of float glasses that can be used in glass automobile factories.
- Tensile measuring system
- Thickness measurement system
- Zebra control system
- Troubleshooting system
- Coding system
What is a glass of float and how is it made?
Since the introduction of the Float Glass in 1959 by Pilkington, the slow-float process has been widely replaced by flat glass processes. Today there are about 180 float designs with a production capacity of about 40 million tons per year. This corresponds to about 35% of the world’s total glass production.
Flat glass resulting from the float method has advantages in comparison with the older production processes of flat glass, which include:
– The float can produce high quality flat glass in the thickness range of 0.5 to 25 mm in width with a strip width of more than 3 m.
The production of float glass production makes it possible to produce high production unlike previous processes.
– The float process is continuous and allows for the possibility of automation to a large extent.
-The light quality of the float glass surface is comparable to that of a polished polished plate.
-According to the continuous progress and improvements made in the last 35 years, the float process is safer and safer than other glass production processes.
History of floating glass production:
Continuing the process of flat glass production, which began in the early 20th century, has gone through a thriving path. In this way, three methods of stretching, rolling and floating, began almost their experimental stages simultaneously. The first two methods quickly acquired their commercial value and were used in mass production of flat glass. However, the failure of these methods to produce flat glass without distortion, without severe fluctuations in thickness, and also a lot of troubles, and the glass sculpted rolled up, eventually attracted the attention of glass makers to the advantages of the floating method.
The flashing of the floating method was made by an Italian named “Lombardo”, which in 1900 invented a method for producing flat dielectric plates using liquids such as wax or paraffin on liquid mercury. Immediately in 1920, William Hill recorded a new method for flat glass production based on the Lombardo method.
In this method, he dipped the glass melt on another molten surface of the metal and then, by drawing the molten glass on the metal surface of the melt bath, it was made as a flat sheet. Initial experiments were carried out in 1920 at the Gregton factory of the American company (Pitsburg Plat Glass PPG). In this factory, it was tried to flatten the glass by floating glass melt on molten antimony. But the experiment was stopped because of failure in the preparation and construction of a pond body that could hold molten antimony.
The success of a floating experimental unit in 1950 was given to the British company “Pilkington Brothers”. In this method, the first successful commercial unit in 1959 in the United Kingdom was to produce molten glass after melting and decontamination, using homogeneous mechanical stirrers, at a temperature of 1050 ° C, and through an integrated refractory bricks The name of the bricks edge (Spout) enters the molten tin bath.
The amount of molten inlet to the bath is controlled by a tweel. The molten glass in the tin bath, floating on the tin mold, results in a balance between the surface tensile forces completely flat, flat and without distortion. The thickness of the glass strip inside the tin bath is made by applying a special temperature curve using roller cogs located on the sides and graphite belts.
General description of the float process:
In this method, the glass is melting in a melting furnace at a temperature of about 1550 ° C without dagghus. Therefore, the rotational movement of the glass strips does not occur, and this also has a beneficial effect on the optical properties of the flat glass.
The glass melt falls into the float through the canal, in which the amount of fall is controlled by a vertical brick block (Tweel). The glass is melting at a temperature of about 1050 degrees centigrade from a fioskast edge rock on a molten tin bath, which is the heart of the floating part of the planet, and expands into a film of constant thickness.
The film extends in the longitudinal direction in strips more than 3 m wide and cools to 1050 to 600 degrees Celsius. At this temperature, the glass strip has the integrity and stiffness that can be removed from the tin bath and reach the desensitization channel. At 150 m in length of the decontamination grill, which occurs when the glass hardens, the glass bottle is cooled down to prevent residual stresses. After the stripping furnace, the glass strip continuously passes through the optical inspection to identify the defects of the glass and eventually the glass strip is cut.
The float bath has a length of about 40-50 meters and a depth of approximately 6-7 cm and a variable width of 4-7 meters. The bath is made up of a metal shell, which is covered with special bluish bricks. Half of the double-glazed bath and thermal elements are embedded inside the wall. The control of temperature, pressure, atmosphere and especially the condition of the molten bar is done automatically and computerized.
In fact, the float bath (tin bath) is made up of a “refractory and graphite” veneer for tin storage and a room as non leaking gas that is used to hold the recovery atmosphere of “10% hydrogen gas and 90% nitrogen gas” It is used to prevent oxidation of tin. In the float process, the fact is that in the case of two non-intermixing liquids, a lower density liquid is spread over a heavier liquid in the form of a film. A completely flattened, lightweight, lightweight fluid is affected by specific gravity and surface energy.
In order to realize the process of float, it was sought after liquid that could be dumped on that melt so that it could produce a completely flat and uniform surface. This liquid should meet the following essential requirements:
-Dansyth should be greater than the glass density gr / cm 3 5/2 is.
– The melting point should be less than 600 ° C.
The liquid vapor pressure of about 1050 ° C is low.
– The glass should not react with the chemical melt.
Ga, In are basically suitable for use in a float bath according to their physical properties. The liquid peak was chosen to be the cheapest in the middle of the metals. It also has the lowest reaction with glass melting at 1050 ° C and has the lowest vapor pressure.
Float Glass Problems:
One of the problems with this method is that the edge of the suspended wall “Tweel” lies inside the melt, which causes the appearance of impurities and melt pollution, which later, after some time trying to solve this problem by covering the edge of the suspended wall of the platinum, eventually the edge of it They removed the melt. One of the most important and important problems was the complexity of the production of thin glass.
The initial work showed that the development and distribution of melt on tin occurs until the molten sheet reaches a balance thickness of about 6 millimeters. Initial experiments were carried out to change the thickness of the glass produced by raising and lowering the speed of the end rollers, but the experience showed that if the speed of the end roller was reduced to reduce the thickness of the glass, the glass sheet’s width would be greatly reduced. For example, in changing the thickness of this method, from 6 to 4 mm, the width of the sheet ranged from 2.5 m to 75 centimeters. Therefore, it was clear from the outset that a significant change in the process of floating glass production was required to control the thickness. To control the thickness of the glass compound was also worked, but the result was not so satisfactory.
The experiments showed that changing the thickness by changing the composition that changes the balance between the surface elastic forces does not have a regulating power of between 6 and 7 mm. After a lot of efforts, changing the temperature curve in the tin bath and the simultaneous operation of temperature change and the movement of the cushioned pliers were very successful for controlling the thickness.
In this method, the melt temperature of about 1050 ° C (viscosity 10 4 centipoises) into the tin bath. The temperature of the bath is gradually reduced and at a temperature of about 700 degrees centigrade, the pair of rollers takes the sides of the glass. This way the glass width stays constant. After fixing the width and overcoming the surface tension, the temperature of the bath is increased again and the temperature of the glass strip reaches about 850 ° C. At this stage, the speed of the roller is increased and the thickness is controlled and adjusted. In this way, it is possible to produce glasses thinner than 6 mm or thicker than float.
To produce glasses that are thicker than equilibrium thickness, the melt movement in the tin bath is controlled by barriers or graphite bars and prevents it from spreading through the bath. In this method, the thickness of the laminate depends on the amount and speed of glass stretching in the bath. To prevent the negative effects of graphite barriers on glass edges, they try to minimize the length of these obstacles. In 1969, glass production of a thickness of 15 mm was made possible by this method.
The third major problem with the float method was the chemical dilemma of this method. The presence of the least impurities in the tin bath, in particular the presence of oxygen and sulfur in the bath room, even add up to one million in tin, and produce compounds such as SnO and SnS that evaporate and migrate to cooler areas of the bath on a melt glass sheet They burn dew and create gluing patches on the surface of the glass sheet. In addition, because the tin oxide solubility is low, if tin oxide occurs, this oxide floats like a floating spot on the melt surface of the tin and damages the bottom of the glass and continues to penetrate into the molecular structure of the glass. And when the glass bends in the heat treatment furnaces, for example in the production of glasses of the automobile, it creates a dimming on the surface of the glass. Reducing these impurities and controlling their circulation in the furnace and bathroom are important success stories of the float method.
Sulfur and oxygen contamination cycle in tin bath:
Although all possible studies indicated that tin is the best and most suitable substrate for flotation of the glass bar, the chemical properties of this element are intense combinations with oxygen and sulfur, which is aggravated in high temperature, gradually increasing the glass production process of its own problems Will create. Oxygen and sulfur in two different chemical cycles cause the glass surface to be contaminated, as well as the destruction of the thermal elements of the tin bath.
Sulfur contamination cycle begins with the formation of tin sulfur (Stanovian) in molten tin. This sulfur is rapidly steamed at 1050-150 ° C and removed from the tin environment. The Sulfur Stanovar steam emits into the cooler parts of the tin bath in the atmosphere of the tin bath atmosphere and acts on the surface of the ceiling of the bath and its thermal elements, and then, during the incomplete process of reduction, tin-sulfur is tin-plated and eventually a mixture of tin and tin-metal sulfur. The shape of small and stable patches (drops varying from 100 to 1000 microns) dip on the surface of the glass. The presence of 10 ppm of sulfur in the bath atmosphere results in the formation of 100 milligrams of tin sulfur per cubic meter of bath space at 10,000-1050 degrees Celsius. The role of sulfur in comparison with oxygen is much higher in the formation of surface spots, and it is necessary to provide the necessary cost for the presence and presence of this element in the tin bath. Various methods have been tested to control the sulfur pollution cycle. Considering that the ceiling of the site of tin sulfur accumulation is the basis of the primary methods of cleaning the roof of the bath using air blowing or heating the roof area and accelerating the process of reducing drainage in a short time period, which is usually unpowerable when cleaning the glass ceiling, Was used . Now a more radical approach has been taken in this regard. In fact, the experience of past years in controlling the reduction of sodium sulfate, which was mostly carried out in European countries to reduce environmental pollution, showed that this decrease has been effective in reducing the sulfur cycle. For this reason, nowadays, to control this contamination cycle, the introduction of sulfur into the tin bath is avoided through the atmosphere of the furnace or the glass of the glass, reducing the consumption of sulfur particles. Oxygen contamination cycle begins with the combination of oxygen and tin and the formation of tin oxide (Stanovian).
A fraction of tin oxide is evaporated and partly soluble in tin molten. The SnO steam is in the cooler areas on the glass surface of the plant and causes the formation of permanent patches on the surface of the glass. The tin oxide of the solution after reaching the saturation limit of tin molten and floating on the molten surface of the tin, as a gaseous oxide, contaminates and lowers the bottom of the glass bar. From the very beginning of this technology to reduce the problem of oxygen pollution, the only practical way of preventing the entry of oxygen into the bathroom was identified. In this regard, while controlling the atmosphere of the bath using hydrogen and nitrogen, more precise methods for sealing and preventing diffusion penetration Oxygen was taken into the bath. There is about 10% hydrogen in the tin bath atmosphere, if oxygen is absorbed into the bath and the formation of H 2 moleculesO, the cycle stops oxygen contamination. However, the issue of oxygen and sulfur pollution is not a major problem in the production of float glass, and its control and limitation methods are fully flooded.
But contamination of the glass strip to tin or tin oxide is still an interesting topic to follow in the industry. Current studies have shown that there are more than 30% tin oxide in the first 100-angstrom composition of the glass surface. In some cases, surface contamination, although it may not be apparent, but later in the glass work, especially in complementary processes, such as breaking glass or bending for building or automotive applications, will cause dimming on the surface of the glass.
The invention of the floating process for the continuous production of strips of flat glass with two parallel surfaces, without distortion and without fluctuations in thickness, has brought treasure trove of a variety of scientific and technological discoveries to engineers and scientists. Scholars have made great efforts to explain the various aspects of this amazing process using physical laws.
Achieving the rules governing the formation of glass strips in this process has now created a newer arena in the development and innovation of this technology, and the development and completion of this technology has accelerated in recent years and is far from its original form. A new generation of float glass production units is now emerging.