Effect of the manufacturing parameters of float-glass on its heat-tolerance

Abstract

The results of investigations of the heat-tolerance of 4.0 -12.0 mm thick heat-absorbing float-glass are presented. It is shown that the heat-absorbing glass possesses high heat-tolerance (> 100°C). It is concluded on the basis of the character of the heat-tolerance over the width of the ribbon that the heat-tolerance of float-glass depends on manufacturing processes such as formation and annealing.Glass with high strength is finding increasingly wider applications in construction, in automobile manufacturing, as well as in the manufacture of aviation glass articles with larger size, fewer laminations, and higher weight and optical indices [1].One strength characteristic of glass is its heat-tolerance, i.e., the capability to withstand sharp temperature differentials without breaking. Publications present largely the results of investigations of the heat-tolerance of glass rods, glass filters, and glasses in simple systems of the type "metaphosphate-phosphorus anhydride" which are synthesized under laboratory conditions [2, 3].The investigations of heat-tolerance of industrial sheet glass obtained by vertical drawing [4,5] have shown that the heat-tolerance of the glass depends on its chemical composition, thickness, shape, linear dimensions, as well as the mechanical strength, intensity of the heat action, and other factors.The objective of the present work is to determine the manufacturing factors that affect the heat-tolerance of floatglass.We have investigated the heat-tolerance of heat-absorbing glass, obtained on pilot float-line at the Saratov Institute of Glass.The heat-tolerance was investigated by a method developed on the basis of GOST 11103-85 [6].In practice, glass articles are often exposed to water or air. The most stringent conditions are in the tests performed on glass in water, so that the results of such tests are more indicative and form basis for the method used to determine the heat-tolerance of the glass.The essence of the method used to measure the heat-tolerance consists in determining the stability of the heated samples of glass with respect to a sharp change of the temperature when they are cooled in water.The difference of the glass and water temperatures at which a sample fractures is a measure of the heat-tolerance:where Q is the heat-tolerance,°C; T 2 is the temperature of the heated glass,°C; and, T 1 is the temperature of the water,°C.The following equipment was used in our investigations: an electric muffle furnace, holding frames for glass of different thickness, and a container with cooling water. The tests were performed on 100´100 mm samples cut in a strictly determined order over the entire width of the glass ribbon. To eliminate the effect of factors which are unrelated to the manufacturing technology (mechanical damage, scratches, and others) the samples were taken directly from the floatline. In the process, the manufacturing parameters of the glass production (chemical composition and thickness of the glass, rate of production of the ribbon, and others) and defects which...