The Saratov Institute of Glass has developed a domestic version of the float process using two-stage formation of glass and is one of the leaders of applied research in Russia in the field of production and development of new different types of float glass and products based on this glass.The Saratov Institute of glass was founded in 1960 as a branch of the State Institute of Glass (GIS) and is currently one of the leading applied research centers in Russia successfully functioning in the field of production and development of various new types of float glass and products based on this glass.The Saratov Institute of Glass has developed the domestic float-glass technology involving two-stage glass formation; it has developed heat-absorbing tinted float glass, electrochemically tinted glass, as well as the Ritm and Metelitsa decorative glass. The institute uses it own float-glass line to produce heat-absorbing glass of diverse colors and thickness, as well as decorative glass with corrugated or figured surface.The principle of the float process is the formation of a glass ribbon upon metallic melt in the melt tank, which constitutes an enclosed metallic shell lined by refractory materials and is one of the critical machinery items in the technological line. The requirements on refractories for the melt tank differ from traditional requirements on refractories for glass-melting furnaces or furnaces producing metallic tin, since the former ones operate in contact with tin, tin vapor, and tin oxide in a hydrogen-bearing atmosphere. Research on refractories capable of serving in a melt tank was started in 1965 based on the experience of the metallurgical sector. Several companies, including the East Refractory Institute, studied the behavior of different refractory materials in contact with tin, but none of those was recommend for the melt tank.The target of the Laboratory of Refractories at the Saratov branch of the GIS institute was to provide refractories for the new float-glass process. By the end of 1967 all known refractories had been tested on specially designed test plants.Based on the research performed and the analysis of refractory production in Russia and the industrial experience, the following main criteria for estimating the suitability of refractories for melt tank lining in a float-glass line were formulated:-materials for the tank bottom lining should be durable under long-term service in the interval of 600 -1000°C in a hydrogen-bearing medium in contact with tin and its oxides and should not form reaction products at the refractory -hydrogen or refractory -metal (oxide) contact interface that could impair the quality of glass;-the chemical composition of the refractory (content of Al 2 O 3 , Na 2 O, K 2 O, Fe 2 O 3 , and SiO 2 ) depends of the main requirements on its properties, since they depend on the chemicomineralogical composition and structure of refractory products;-refractory materials should have a structure ensuring minimal permeability for hydrogen, the melt, and metal oxide vapors (the ...
The Semiluki Refractory Works produces refractories according to the technology of concrete and keeps developing compositions and refining the technology for producing large-size products by vibromolding. The Saratov Institute of Glass has performed service testing of concrete samples and determined their physicomechanical characteristics. The testing of samples fired at temperatures not higher than 1000°C has demonstrated their rather high compressive strength (from 40 to 60 N/mm 2 ).The decreasing volume of chamotte refractories produced by ramming in Russia has made it necessary to develop new refractory mixtures suitable for state-of-the-art mechanized molding technologies (vibromolding and vibrocasting) and that impart to the products strength sufficient for transportation and installation without using high-temperature firing and still preserve all refractory service properties. Refractory concretes, which are nonfired composites with refractoriness 1700°C and higher, have been known and used in glass production for over 30 years. Such concrete consists of a refractory filler and a binding material (binder) curing at a normal or increased temperature and having limited shrinkage at service temperatures. The type of the binder is selected based on the properties that the product should posses, i.e., a constant volume and a sufficient strength in the entire temperature interval: from ambient to service temperatures [1]. High-alumina cement with water acting as a dispersion medium can be conveniently used as a binder for refractory concrete. High-alumina cement is classified as a hydrationcuring binder, in which the curing process proceeds with formation of hydrates:Due to the formation of hydrates, the strength of refractory concrete varies depending on heat treatment temperature. Under relatively low curing temperatures (around 300°C) the strength grows, whereas in the interval of 400 -1000°C mainly determined by the dehydration of the binder and the loss of chemically bound water the strength decreases (the strength drop) [2]. As the temperature increases above 1000°C, the process of sintering starts and the strength increases. The strength of refractory concrete depends on the strength of the filler, the binder, the contact phase, and especially on the existence of shrinkage, thermal, and other stresses. Destructive forces in concrete do not always lead to crack formation, since stresses in concrete are nonuniformly distributed and concentrate on components with a high elasticity modulus, i.e., the filling components; consequently, high strength of the filler determines high strength of the concrete. Concrete produced by vibration molding typically has a filler of enhanced coarseness (up to 6 -8 mm). Cracks in fact do not propagate across the product thickness; emerging cracks become arrested on the filler grains. This is a positive property of vibromolded concrete, since in ramming technology, due to the presence of cracks going in different directions, a nonuniform distribution of pores and filler grains...
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