Refractories: Something Old and Something New
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The earliest refractories for containing melts were quarried from natural deposits of limestone and dolomite. Today thèse two carbonate rocks serve important rôles in the production of métal contact refractories. Early refractories for glass melting on the other hand were manufactured from clays and claystones. Thèse ma tenais are also still used extensively for the batch melting of glasses that are hand formed or blown into art and tableware. Glass contact refractories for the continuous (tank) melting of glass are often fired, cast into large shapes, and arranged in a soldier course which constitutes the sidewalls of the glass tank. In this brief exposition of refractories technology and allied research, the articles by B. Brezny, T.F. Vazza and T.A. Leitzel, and by T.S. Busby cover materials development, sélection, and properties of the Systems which hâve evolved for the efficient melting of steels and glasses. As such they relate to extrêmes of technological flux in the processes for the manufacture of steel and glass, respectively. The continuous melting of large volumes of commercial glasses has been carried out in tanks equipped with reverberators for at least 70 years. The basic design of the overall System and of many of the glass fabrication machines for pressing, rolling, and blowing the glass has been constant since World War I. Only the introduction of the float glass method, the famous Pilkington process, for the production of flat glass, has interrupted the slow quiet progress in the technology of continuous glass making. The introduction of fused zirconia-alumina-silica in the 1950s was a watershed materials development which enabled glass melting campaigns
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to increase from a single year to as long as eight years. On the other hand steelmaking technology and related refractories developments hâve been undergoing drastic change throughout the 1970s and 1980s during which the center of gravity of the U.S. industry has shifted from Pittsburgh, Pennsylvariia to Chicago, Illinois. The introduction of ôxygen blowing, first in the open-hearths in the 1950s, and later as the basis for the basic ôxygen process (BOP) enabled a number of new process steps to be strung beyond the melter itself.
The need for very clean métal with constant chemistry is driving the current processing révolution. Today's goals are to produce cleaner steels in order to facilitate fabrication while diminishing levels of reject product in the steelmaker's and the fabricator's shops. Tomorrow's goals are focused around net shape forming technologies which will potentially eliminate the rolling mills. Pilot and full-scale opérations can cast the melt into thin strip and sheet or, in some cases, spray the molten steel onto a quenching drum. Thèse often novel fabrication methods require very clean arid consistent molten steels which must be melted and handled in relatively pure refractory containment and flow control Systems.
The process Systems beyond the melter increasingly include a ladle station, with or without the ability to
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