Sponsored by: LMD Aluminum Committee
Program Organizer: Julian V. Copenhaver, Technical/Quality Manager, NSA A Division of Southwire, PO Box 500, Hawesville, KY 42348
Wednesday, PM Room: A10
February 7, 1996 Location: Anaheim Convention Center
Session Chairperson: Dr. Wolfgang Schneider, VAW Aluminium AG, George-Von-Boeselager-Strasse, 25D-53117 Bonn, Germany
2:00 pm
REAL-TIME VIDEO MONITORING OF INGOT CASTING: Ray T. Richter, P. R. Adomaitis, G. J. Hildeman, Alcoa Company of America, Alcoa Technical Center, Alcoa Center, PA 15069
During start-up and steady-state casting of ingots, a number of effects related to ingot casting variables can be observed on the surface of an ingot. For example, the amount of curl at the bottom of the ingot, surface laps, liquation, cracks, and folds, as well as extreme events such as "bleed-outs" when molten metal melts through the shell of the ingot crater, are significant surface effects which could be viewed. Unfortunately, observation of these surface effects is difficult since the as-cast surface is hidden below the casting table, and direct visual observations of ingot surfaces are limited due to the proximity of the molds, cooling water sprays, and the ability of casting operators to safety view ingot surface details at close range. The purpose of this paper is to describe a unique video monitoring capability which is being used at Alcoa's Advanced Vertical Casting facility, to observe in real-time, surface effects of an ingot during casting. A description of the development of the video monitoring system, including camera, lighting, and video recording capability will be presented. Examples of various surface conditions on direct chill (DC) and electromagnetic cast (EMC) ingots will also be discussed.
2:20 pm
A PRACTICAL MODEL FOR DETERMINING HEAT LOSS IN A MOLTEN METAL DISTRIBUTION SYSTEM: J. Martin Ekenes, Casting Consultant, North 3418 Arden Road, Otis Orchards, WA 99027
The casting of aluminum ingots for wrought and other applications necessitates transferring molten metal from furnace to mold. This is ordinarily accomplished via refractory-lined troughs. In a multi-strand casting system, substantial heat losses can occur even between casting positions. In order to conserve energy and minimize process and product variability, it is desirable to minimize heat losses at each stage of molten metal transport. Troughing design plays an important role in minimizing these losses. This paper describes a practical model for determining heat losses in multi-strand casting systems. Predicted results are presented for various trough designs and compared with operating data.
2:40 pm
NON-CONTACT LEVEL CONTROL CASTING OF AA5182: Dr. Bjorn Rune Henriksen, I. J. Thorvaldsen, J. Hayes, Elkem Aluminium Mosjoen, PO Box 566, N-8651 Mosjoen, Norway
Elkem Aluminium Mosjoen has developed a non-contact metal level control system using lasers. The goal was to control the metal level in each mould within +/-2 mm. The metal level is continuously monitored and controlled during casting. Typically, the metal level varies within +/-0.1 mm and +/-0.25 mm at maximum. The system has the ability to cast with low metal level in order to improve surface quality, and hence reduce the edge cracking of ingots during hot rolling. The automatic start-up of the casting improves the safety of the operators. The total cost of the project was approximately $400,000.
3:00 pm
CHANGING AN INGOT PROFILE BY COMPRESSING THE MOLD TO A DIFFERENT DIMENSION: Brad S. Whiteleather Krumme, Senior Casting Metallurgist, Ravenswood Aluminum Corporation, PO Box 98, Ravenswood, WV 26164
For the past few years, RAC has had a problem with a high number of rescalps on our 24" x 55" ingot size. It was discovered that our molds were designed to cast at faster speeds than where we are currently casting. Instead of our ingots have a nice flat profile (24" thick), this design problem is giving us an ingot which is 1/4" bigger in the center than on the sides. We are in the process of having some of our molds compressed to a smaller dimension in order to get a flatter ingot profile and reduce the rescalp problem. This paper will compare the ingot profile before and after the molds were compressed and the impact on rescalp rates.
3:20 pm
QUANTITATIVE EVALUATION OF INGOT BUTT COOLING CONDITIONS REQUIRED FOR THE OPTIMIZATION OF D.C. SHEET INGOT START-UP PRACTICES: A CASE STUDY: Yves Caron, André Larouche, Alcan International Limited, Arvida Research and Development Centre, 1955 Mellon Boulevard, PO Box 1250, Jonquière, Québec, Canada G7S 4K8
During a cast start-up, the ingot butt is subjected to severe quench conditions resulting from direct water cooling. These quench conditions, which were determined through experience acquired by technical and production personnel, are based on safety and the production of a defect-free ingot butt. In spite of the precautions taken to ensure a flawless cast start-up, unforeseen defects may occur. The effectiveness of the corrective measures to be brought to the casting practice, therefore, greatly depends on our understanding of the phenomenon in question. This paper presents an experimental approach to understand the formation of unusual subsurface ingot butt defects observed on can body stock. It describes the quantitative technique developed to evaluate ingot butt cooling conditions during cast start-ups as well as their correlations to the subsurface defect observed. Finally, it describes how quantification of the ingot cooling conditions is essential in implementing the appropriate corrective actions required to eliminate the defect.
3:40 pm BREAK
3:50 pm
3-D MODELING OF THE START-UP PHASE OF DC CASTING OF SHEET INGOTS: G.-U. Grün, Dr. Wolfgang Schneider, V.A.W. aluminium AG, Georg-von-Boeselager-Strasse 25, D-53117 Bonn, Germany
Three-dimensional transient simulations of the coupled fluid flow and heat transfer problem during the filling of the mold and the beginning of starting block movement have been used to investigate the influence of distributors and start-up programs on temperature and solidification front. As butt curl and possible hot tearing of the ingot are critically controlled by the temperature development of the metal in the mold, and the temperature itself depends on mold filling and start-up strategy, quality is strongly connected to appropriate metal distribution conditions in this early start-up phase. The calculated filling behavior and temperatures are discussed in dependency of parameters like distributor geometry or ingot size. The simulations support the development of adjusted metal distribution systems.
4:10 pm
3-D SOLIDIFICATION ANALYSIS OF THE INITIAL STATE OF D.C. CASTING PROCESS: Yoshio Watanabe, Norifumi Hayashi, Teruo Uno, Sumitomo Light Metal Ind., Ltd., Technical Research Laboratory, Process Technology Department, 1-12, 3-chome, Chitose, Minato-Ku, Nagoya, 455, Japan
The computer simulation program which considered motion of the ingots was developed to solve thermal problem associated with the initial non-steady state of D.C. casting process. Boundary conditions were investigated by casting tests of pure Al slabs. Heat transfer coefficient between ingots and cooling water (H), which was important to simulate the initial state, was affected by boiling phenomena and depended on surface temperature of the ingots. However, temperature dependency of H in the region where cooling was impinged on the ingot surface differed from that below the region. It became clear that H should be defined as different functions of temperature in two regions. Sump profiles which were calculated with H proposed in this study airly agreed with measured profiles in both the initial and steady states. The agreement between calculation and measurement under the different casting conditions was also confirmed.
4:30 pm
INGOT BUTT CURL CONTROL OF ALUMINUM INGOTS THROUGH THE USE OF SHIM MATERIAL: Brad S. Whiteleather Krumme, Senior Casting Metallurgist, Ravenswood Aluminum Corporation, PO Box 98, Ravenswood, WV 26164
RAC has experienced a reduction in butt curl by as much as three inches through the use of shim tape. A factor that affects butt curl is how the shim material is applied. For example, the amount of butt curl is significantly less if shim tape is applied to all four faces of the molds as compared to only two faces of the mold. This paper will compare the amount of butt curl versus (1) different types of shim material and (2) application (four faces versus two faces) of the shim material.
4:50 pm
RECENT DEVELOPMENT IN LARGE FORMAT MAGNESIUM CASTING: Bjørn Kittilsen, Norsk Hydro a.s., Research Centre Porsgrunn, PO Box 2560, N-3901 Porsgrunn, Norway; Peter M.D. Pinfold, Hydro Magnesium Marketing, 5, Place Ville Marie, Suite 1537, Montréal, Québec, Canada H3B 2G2
Safety concerns from customers led to a decision to replace magnesium sows in the mid-eighties. The introduction of DC-cast T-bars and cylinders overcame these safety concerns, but DC-casting imposed productivity limitations in the magnesium foundry, as casts were limited to one or two strands only. The transition to today's multi-strand, hot-top, level pour, DC-casting technology, which addresses these productivity needs and also produces an improved product surface, is documented. This technology, when combined with efficient particle refining, offers a wide range of cavity free products, with high degree of internal cleanliness, than was the case with sows.
5:10 pm
DEVELOPING OF MATHEMATICAL MODEL FOR CASTING 2024-2025 ALLOY BILLETS: A. Zorrilla, Hector Medina, CVGVENALUM, Gerencia de Tecnologia de Producción, Ciudad Guayana Estado Bolivar, Apdo. 312
Actually, the 2024-2025 alloys have a high demand on the world market for
automobile and aircraft's aluminum parts. Venalum has developed process
parameters for producing 2024-2025 alloy billets in a conventional vertical
casting process. In order to obtain the casting parameters the ternary diagrams
Al-Cu-Mn and Al-Cu-Mg were studied to know eutectic temperatures and
solidification phases. Also the solidification isotherms were obtained for
horizontal casting to observe the thermal profile of these alloys. Using a
mathematical finite difference model, the theoretical casting parameters were
established as a reference to melting at experimental level in the D.C.
process.
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