Float glass production process is mainly completed in the tin tank, the completion of the necessary conditions for the tin tank must have protective gas (N2 and H2) through. Float glass is produced by adding molten tin in the tank and adding glass to the molten glass. As the density of the molten glass relative to the molten tin is small, the glass will float on the surface of the molten tin solution, Under the influence of the surface pressure, the glass liquid will be opened and flattened on the surface of the molten tin liquid, thereby forming a glass ribbon having a certain width and thickness, and the surface of the glass ribbon is smooth and neat, and this glass ribbon is And the mechanical polished glass comparable, and this glass belt in terms of mechanical properties or from the chemical stability and other aspects, are better than the mechanical polished glass.
But due to the tin oxide is extremely easy to oxidize, resulting in a series of tin defects. Tin oxidation is the main reason for the occurrence of tin permeation on the surface of the float glass. When the glass after tin infiltration is heated, the surface of the glass will form a color, and the surface of the glass will become uneven and opaque. Glass production rate and deep processing, so that the application of glass greatly reduced, which is China's glass products can not be one of the main reasons for the development of fine. At present, there are many researches on the influencing factors of tin permeation on the surface of float glass, but with the improvement and upgrading of modern production technology, the development of the surface of tin has also developed a new development.
1. Influencing factors of tin permeation on the surface of float glass
1.1 The effect of temperature
According to experimental studies, under the same production conditions, the amount of tin and tin bath is proportional to the temperature, with the tin bath temperature increases, the amount of tin will increase. This is because the temperature of the tin bath increases the viscosity of the molten glass, the activity of the tin ions increases, the ion changes and the exchange rate is also accelerated, and the amount of tin infiltrated into the glass increases at a certain time, and the depth of infiltration deepen.
1.2 Influence of thickness
During the infiltration process, the time of infiltration of the glass ribbon and the tin liquid is determined by the thickness of the glass. As the glass becomes thicker, the time for the glass ribbon to stay in the tin bath becomes longer, and the time of ion exchange and exchange reaction Will increase, and the amount of tin ions that penetrate into the glass will increase. According to the experiment, the number of tin ions increases with the thickening of the glass, but it does not affect the diffusion of depth.
1.3 Effects of N2 and H2 on the purity and ratio
Tin liquid is prone to oxidation, resulting in a certain degree of tin defects, in order to prevent the emergence of tin oxidation, the approach is to pass in the tin tank N2 and H2 shielding gas. The addition of hydrogen in the tin bath is intended to consume the oxygen in the tin bath and the amount of trace oxygen is related to the solubility of the tin solution, which is proportional to the solubility of the tin solution, Will also be reduced. The oxygen content in the high and low temperature regions of the tin bath is different, and the oxygen content in the high temperature region is lower than that in the low temperature region. Therefore, in order to ensure the reduction conditions of the middle and low temperature areas of the tin bath, Of the hydrogen content. Therefore, in the actual production and life, in order to produce a higher quality glass, control the content of hydrogen is the key. Among them, the content of tin under the float glass is affected by the purity and water content of the protective gas. The lower the purity of the shielding gas, the greater the chance of the tin tank being polluted.
1.4 The effect of groove pressure
In order to maintain the purity of the tin bath atmosphere, you need to adjust the size of tin slot pressure. In order to prevent the entry of external air and restore the atmosphere, usually to enhance the tin tank and the external pressure difference. When the tank pressure is reduced, the external air and other impurities in the gas is easy to enter the tin tank, the destruction of the tin tank internal conditions, so that tin tank pollution, resulting in an increase in the amount of tin. Therefore, in order to reduce the amount of tin on the surface of float glass, increasing the pressure is one of the most effective means. In actual production, it is often used to change the amount of protective gas and adjust the outlet of the curtain height to control the pressure inside the tin tank.
1.5 Effects of basic chemical composition of glass
The basic chemical composition of the float glass also affects the amount of tin on the glass surface. Among them, the content of iron in the float glass is the most important influencing factor. According to a large number of experiments show that the content of iron and the amount of tin is inversely proportional to the amount of tin will increase with the increase in iron elements, so the increase in iron in the glass is an effective solution to reduce the amount of tin.
1.6 trace oxygen and water vapor and other oxidizing gas concentration
The oxidation of the oxidizing gas is easy to oxidize the tin liquid, but it is difficult to prevent the entry of oxidizing gases such as trace amounts of oxygen and water vapor in the production of glass. The main reason for the tinning phenomenon is due to tin oxidation, although tin and glass do not melt together, but tin ions will easily penetrate into the glass surface. The relationship between trace oxygen, hydrogen and trace water in the tin bath can be observed by the dew point in the tin bath. The relationship between the three is dynamic and balanced, that is, by reducing the amount of trace oxygen in the tin bath It is feasible to reduce the dew point in the tin bath. In the other conditions do not change the case, reduce the dew point can effectively reduce the amount of tin.
1.7 Effect of Oxygen Combustion Process
The oxygen-burning furnace contains up to 90% hydrogen and more than 50% water vapor. The glass liquid reacts with the water molecules under high temperature, so that the water content in the glass is much higher The traditional float in the production of glass. The viscosity of the glass is influenced by the action of water molecules, so that the finished glass and the traditional float glass produced by the furnace for burning the whole oxygen are not the same. The experimental results show that the amount of tin in the whole process is higher than that of the general float glass, which is mainly because the water content in the whole oxygen combustion is higher than that of the ordinary float glass.