Lead glass ultrathin forming technology
Narrow slit pull-down method is a process between overflow method and float method. The flatness of the board is slightly poor, and it is not yet possible to produce large-format ultra-thin glass. Its birth promotes the development and leap of glass industry. The development of this technology has become increasingly mature and perfect, and it is a reliable plate forming process. China's existing float production lines have reached more than 200. According to the chemical composition and technological characteristics of lead glass, the existing ultra-thin float production technology in our country, the current market demand and capital situation, the forming method more suitable for ultra-thin lead glass should adopt micro float production technology, our country should pay close attention to the development of technology and equipment in order to obtain thickness 1. High precision ultra-thin glass products below 5mm.
For the process parameters of micro float production, the glass pool kiln with melting capacity of 15-35 t can be selected according to the process parameters of lead glass temperature-compatibility. According to the temperature-compatibility curve of glass, select exclusion 103. The corresponding temperature near 8dPa · S is used as the feeding temperature. Its feeding temperature is 1320-1280 ℃, and it enters the tin trough through lip bricks, which are naturally diluted and cooled slowly, in the range of 105-107dPa · S, the corresponding temperature range is 1050-850 ℃. In this temperature area, 9-13 pairs of edge pulling machines are arranged to overcome the shrinkage effect of glass surface tension, gradually pull the glass tape into a thickness of 1.0-1.5mm, and control the speed and angle of the edge pulling machine drive motor during the drawing process. The Edge pulling machine is the main control method during the drawing process of float forming process. By adjusting the gear linear velocity V at the rod end of the edge pulling machine and the angle a with the forward direction of the glass belt, the generated outward pulling speed is Vsina, which can overcome the shrinkage of the glass belt caused by glass detergent surface tension. It is limited to make the thickness of the glass strip thinner under the pulling action of a pair of edge pulling machines. To make the glass thinner effectively, select multiple pairs of edge pulling machines to work together, to overcome the viscous resistance and gravity, friction force and surface tension generated by glass detergent high degree of rejection, as well as the force balance system formed by the pulling force and main drive traction force generated by the edge pulling machine, so as to ensure the smooth float forming, equal-value thinning technology should be adopted in production step by step. It can obviously improve the thickness and thickness difference of glass mainly by controlling the spacing, angle and temperature system in the tin tank of the edge pulling machine.
In addition, by reducing the influence of temperature difference in the cross section of the tin bath at the same time, the appearance of glass ribs is reduced, and the dimensional accuracy of the thickness difference of the glass plate is controlled. The situation of tin liquid flow in the tin tank is relatively complicated, so it becomes particularly important to adjust and stabilize the tin liquid flow in the tin tank. The control device of liquid tin flow is divided into passive and active. The active type mainly adopts linear motor, which can conveniently control the direction and speed of liquid tin flow. The electromagnetic force generated by the linear motor pushes the movement of the tin liquid. Changing the output power of the linear motor can control the direction and speed of the flow of the tin liquid. Using linear Madar in the thin area and contraction area of the tin trough can effectively solve the generation of optical distortion defects on the lower surface of the glass strip. At the same time, linear motor can also be beneficial to reduce the fluctuation of glass thickness caused by uneven temperature caused by hot and cold flow mixing of tin in tin bath. A pair of linear motors are set in each of the thin area and the contraction area. The passive control device of tin liquid flow mainly relies on the retaining wall. By adopting the retaining wall in the polishing area, the thickness fluctuation of the ultra-thin float lead glass can be significantly reduced, and the stability of the glass ribbon can be significantly improved at the same time, the number of retaining walls depends on the size of the pool kiln and the length of the polishing area. The retaining wall should be made of metal tungsten and graphite, which can effectively resist the high temperature environment in the tin tank. There is obvious horizontal and vertical temperature difference in the tin bath of the tin bath. The tin bath is not only a forming equipment, but also a very important thermal equipment. Therefore, the equipment must have heat loss, as a result, the temperature of the tin groove edge is lower than that of the center, which may exist even in the flattening area. Therefore, the actual flattening is difficult to meet higher requirements. In view of this situation, 3 to 9 groups of retaining walls are artificially set. The retaining wall should have the function of angle adjustment, basically forming an angle of 15 to 90 degrees with the movement direction of the glass belt, and controlling it to spread and unfold too fast.
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