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Session Chairperson: Kurt Ehrke, Aluminium Essen GmbH, Sulterkamp 71, D-45356 Essen, Germany
REFRACTORY SOLUTIONS DESIGNED TO OVERCOME CORUNDUM GROWTH IN ALUMINIUM FURNACES: Duncan Jones, Morganite Thermal Ceramics Ltd., Liverpool Road, Neston, South Wirral, L64 3RE, England
Corundum is an extremely hard, high temperature form of aluminium oxide. Its formation in aluminium melting furnaces and metal treatment units can lead to a reduction in operating efficiency and premature failure of the furnace lining. The formation of corundum is known to be dependent on several factors, including furnace atmosphere, operating temperature, alloy composition and refractory type. The paper describes solutions to this phenomenon identifying its cause and effect whilst highlighting refractory design criteria. Results from an extensive testing programme, classifying resistance to corundum growth against various qualities of refractory product are discussed.
USE OF SMALL DIAMETER IMMERSION HEATERS IN MOLTEN ALUMINUM: Mark Palmer, Pyrotek Inc., E.9503 Montgomery Avenue, Spokane, WA; Andre Teytu, Atherm, Rue de Moirind 13, 38420 Domene, France
Small diameter electric immersion heaters offer unique benefits when used in molten aluminum heating applications. The 1" diameter heaters allow greater flexibility in vessel design than traditional immersion heating systems. The electric heating elements are inside a Sialon sheath, which is non-wedded by molten aluminum and offers long life. Since the development of these heaters, they are being used in many different types of molten aluminium holding vessels. Pechiney Aluminium Engineering utilizes these small heaters in Alpur degassing vessels and the Pechiney Deep Bed Filter Heaters are also used in die casting holding furnaces for both primary and supplemental heating applications. The net result of using the small immersion heaters is high metal heat-up rates, compact vessel designs, energy savings, uniform metal temperatures, and user friendly equipment designs. The paper describes the capabilities of the heaters, the design flexibility they allow, and performance results obtained from initial installations.
IMPACT OF GOOD METAL CIRCULATION AND FURNACE OPERATION FOR INCREASED PERFORMANCES FOR SIDEWELL FURNACES: G. Riverin, W. Stevens, Arvida Research and Development Centre, Alcan International Limited, 1955 Mellon Blvd., Jonquière, Québec, Canada G7S 4K8; D. Bristol, Alcan Rolled Products Company, P.O.Box 837, Greensboro, 30642; Y. Kocaefe, Université du Québec à Chicoutimi 555, Boul. de l´Université E, Chicoutimi, Quebec, Canada G7H 2B1
Sidewell furnaces have long been operated for scrap melting, including UBC. The paper discusses important criteria for the optimum energy and melt rate performances for these types of furnaces. Intensive work has been done in several Alcan recycling installations in order to increase these furnace performances. Several operating parameters are outlined combined with the importance of melt stirring in the main hearth and in the sidewell. Mathematical and physical modeling provided key elements responsible for better furnace operation. The impact and advantages of the improved melt stirring and furnace operation are explained and discussed in detail.
CAST HOUSE WATER TREATMENT WITH AEC TECHNOLOGY: Ed Grodecki, Betz Water Management Group, 4150 Washington Road, Bldg.2, Suite 206, McMurray, PA 15317
Cast house water treatment programs typically use organic phosphates to control both corrosion and deposition. These materials can break down or revert into inorganic phosphates in the presence of heat, long retention times and oxidizing biocides. The consequence of this reversion is the loss of calcium carbonate deposit control and an increase in the potential for forming inorganic phosphate deposits. Both situations would result in poor heat removal at the critical heat transfer surfaces. With the advent of the AEC molecule, cast house water treatment technology has taken a new step in controlling corrosion and scaling. The AEC molecule does not contain phosphate and does not break down in the presence of oxidizing biocides. It also has good thermal stability and does not degrade over time. Used in place of an organic phosphate, AEC will provide excellent calcium carbonate scale control without the risk of phosphate deposition. This paper studies a case history of one such application on a billet caster.
MOLTEN ALUMINUM PLUS WATER--A DIFFERENT POINT OF VIEW: George J. Binczewski, S C Systems, PO Box 6154, Moraga, CA 94570
For forty years, the Aluminum Industry has conducted and sponsored investigations directed at establishing a better understanding of the safety aspects associated with the sometimes explosive occurrence which may happen when there is a physical contact between molten aluminim and water. Industry concern has resulted in a poling of resources among companies, associations, and technical organizations. There has been a substantial funding of investigative projects conducted by capable research organizations employing sophisticated techniques. While useful information has been gained and translated into operational procedures, the basic cause remains elusive. A completely different, and additional, investigative approach is suggested based on cumulative experience and observation of daily occurrences. This can provide the informational basis to alleviate the safety and liability concerns associated with direct contact between molten aluminum and water.
3:40 pm BREAK
THIN GAUGE TWIN-ROLL CASTING, PROCESS CAPABILITIES AND PRODUCT QUALITY: O. Daaland, M.L.Nedreberg, A.B.Espedaal, Enge Alwestad, Hydro Aluminium a.s, R&D Materials Technology, N-4265 Håvik, Norway
Traditionally industrial twin roll casters have been operated at gauges 6-7 mm, depending on the type of caster and the final product requirements. Over the past few years it has become apparent that a significant increase in productivity can be achieved when the casting gauge is reduced. Hydro Aluminium embarked on an extensive R & D thin gauge casting program in the beginning of the 1990's, and this paper presents results of a five year lasting project (joint program between Hydro Aluminium and Lauener Engineering). Based on over 400 casting trials the major benefits and limitations of casting at reduced gauge and increased speed are outlined. Important aspects for product quality are discussed including: cooling rates and dendrite structure, microstructural characteristics (as-cast grain structure and texture), segregation behaviour, surface quality and mechanical properties after thermomechanical processing. Results for casting of several alloys (including the 5xxx and 8xxx-system) are given. Additionally, numerical modelling results of the strip casting process are included.
PECHINEY JUMBO 3CMTM--START-UP OF THE NEUF-BRISACH THIN STRIP CASTER: Pierre-Yves Menet, Pechiney Rhenalu Neuf-Brisach, Z.I.Biesheim, BP 49, F-68600 Neuf-Brisach, France; Robert Cayol, Pechiney Aluminium Engineering, Centr'Alp-725 rue Aristide Bergès, F-38340 Voreppe, France; Jacques Moriceau, Pechiney Rhenalu Melting and Casting Direction of Technology, Centr'Alp-725 rue Aristide Bergès, F-38340 Voreppe, France
Following extensive research and development work at the Pechiney Research Center in Voreppe, a new Jumbo 3CMTM thin strip caster has been installed at the Pechiney Rhenalu Neuf-Brisach plant. First of its generation, it is capable of casting a 2m wide strip under a maximum load of 2900 tons. This paper reviews the various features of the equipment which make possible the casting of thin strip of aluminum alloys covering a wide range of applications, from foil stock to can stock. Initially scheduled for start-up in June '96, the equipment was started on time. Performances concerning the installation itself and the casting of several alloys are given. A video of the installation and an actual casting will be shown during the Cast-Shop session.
AN UPDATE ON DOWN-GAUGING THE FATA-HUNTER SPEEDCASTERTM AT NORANDAL, HUNTINGTON (TN): R. Beals, B. Taraglio, C. Romanowski, FATA Hunter Inc., 6147 River Crest Drive, Riverside, CA 92507
The first of a new generation of Thin-Gauge/High-Speed FATA Hunter machines is now in operation at Norandal's Huntington (TN) facility. Following the late February 1996 start-up of the machine, a down-gauging program was commenced which combined normal 5 mm gauge production with a series of pilot production trials at progressively lighter gauges. This paper overviews this start-up program and compares the production rates and metallurgical characteristics of the thin-gauge cast material with conventional-gauge, twin-roll cast strip. In addition, a brief video tape of the FATA Hunter 86" wide SpeedCasterTM in operation will be presented.
MAGNETIC EDGE DAMS IN A TWIN ROLL ALUMINIUM CASTER: Craig Anderson, Peter Davidson, Engineering Department, Cambridge University, Cambridge CB2 1P2, United Kingdom
In the twin roll casting process, molten aluminium is fed between two cooled rotating rollers where it cools, solidifies and is carried by roller rotation to the nip, where it is compressed to a single sheet and expelled. To prevent aluminium escaping laterally, from the roller edges, dams are required. Physical edge dams are subject to erosion from the rollers and molten metal and require maintenance and replacement. Hence there is a strong economic case for using magnetic edge dams, where the interaction of a magnetic field and a current provide sufficient repulsive force to contain the molten aluminium, which do not physically touch either the rollers or molten metal and require little or no maintenance. This paper discusses the theory behind high frequency magnetic edge dams and describes the design and construction of a practical system. Laboratory testing of the magnetic edge dam system is shown to give good agreement with theory and the installation and operation of the system on an experimental twin roll caster is described.
DECOATING TECHNOLOGY FOR THE ALUMINIUM INDUSTRY: O.H. Perry, Stein Atkinson Stordy Ltd., Midland House, Ounsdale Road, Wombourne, Wolverhampton WV5 8BY, England
The technology for recycling aluminium scrap has evolved over a number of years through five major changes as follows: direct charging, side bay melter with puddlers, rotary furnaces, shredding and flat belt delacquering machines, shredding and rotary kilns, today it is now possible to fully decoat any aluminium material which can be shredded. With the invention of IDEX® rotary kiln systems all materials from UBC, extrusions, coated foils, through to 6 micron aseptic foils can be successfully reclaimed and either remelted or processed with minimal metal loss. During 1996 three systems have been commissioned in the Americas for decoating materials which contain 3 to 80% VOC by weight and ranging from 4 to 7 tonnes per hour. This paper discusses the changing technology and the current "state of the art" in rotary kiln technology.
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