The Science of Melt Refining: An LMD Symposium in Honor of Christian Simensen and Thorvald Abel Engh: TAE/CJS Honorary Symposium I: Inclusion Removal
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: John Grandfield, Grandfield Technology Pty Ltd; Anne Kvithyld, SINTEF
Tuesday 8:30 AM
February 28, 2017
Location: San Diego Convention Ctr
Session Chair: Mark Badowski, Hydro
8:30 AM Introductory Comments
The Contributions of Thorvald Engh and Christian Simensen to the Science of Melt Refining: John Grandfield1; Anne Kvithyld2; 1Grandfield Technology Pty Ltd; 2SINTEF
Christian Simensen and Thorvald Abel Engh have made a sustained contribution to the general field of melt refining in aluminium but also to other materials including steel, magnesium and silicon. Both have been ambassadors for Norway spending extended periods in England, Australia, USA, Sweden and Japan. They have supervised many PhD students and collaborated extensively with industry and other researchers. Topics covered include: modelling, degassing, filtration, dissolved impurity removal including hydrogen sodium and iron in aluminium, analytical techniques for characterizing microstructures and inclusions, inclusion detection, melt oxidation and alloying.
The Fundamentals of Forming Microbubbles in Liquid Metal Systems: Roderick Guthrie1; Mihaiela Isac1; 1McGill University
Gases are now widely used for stirring purposes in liquid metals, given the inventions of the porous plug, as well as other submerged gas injection methods, such as through nozzles, or tuyeres. Nonetheless, we know that any small bubbles forming at the exit pores of porous plugs, will normally rapidly coalesce into much larger bubbles. So, the question of how to form, and maintain, microbubbles in liquid metal systems still remains something of a question. It is nevertheless possible, but only under well-defined conditions. Given that such micro-bubbles can be very helpful in promoting mass transfer reactions (e.g. hydrogen degassing of liquid aluminum), and efficiently removing micro-inclusions (e.g. from liquid steel or aluminium), this is an important topic that needs to be properly addressed. We demonstrate the necessary conditions for the formation of microbubbles, and for their continued existence, by way of a typical ladle-tundish metallurgy example.
A Holistic Approach to Molten Metal Cleanliness: D. Corleen Chesonis1; 1Metal Quality Solutions, LLC
Metal cleanliness is an important aspect of ingot quality, with requirements that vary according to the final product. Too often, filters are treated as the only option to improve metal cleanliness. All of the molten aluminum filters used in industry today act by removing a percentage of the incoming inclusions. The cleanliness of the metal coming into the filter is thus critical to the final ingot quality. This means that final ingot quality is impacted by charge makeup, melting practices, furnace treatment, and in-line degassing as well as filter performance. Each of these individual steps must be considered to provide the metal cleanliness required for a particular product at the lowest cost. This paper will provide an overview of how various steps in the casting process affect metal cleanliness and will examine several examples of how they might be combined into an economical process.
10:15 AM Break
Results of Trials with a Multi Stage Filtration System Employing a Cyclone: John Courtenay1; Marcel Rosefort2; 1MQP Limited; 2Trimet Aluminium SE
The development of a multi stage filter comprising a ceramic foam filter applied in a first chamber operating in cake mode; grain refiner added in a second chamber and a cyclone deployed in a final chamber was presented at TMS 2014. The first industrial prototype was installed at Trimet Aluminium at Essen in Germany on a sow casting station and demonstrated that liquid metal could pass through the cyclone successfully without splash or turbulence. In 2016 new trials were undertaken on the Research Casting pit casting from a 5t tilting furnace. A satisfactory start up was achieved and steady state flow at a rate of 4-8t/hr was maintained over 60 minutes. Three pairs of before and after filter Podfa samples were collected to assess metal cleanliness and the analysis of these results is presented.
Developments in Inclusion Removal Technology: John Grandfield1; 1Grandfield Technology Pty Ltd
This paper reviews the past, present and possible future of molten aluminium inclusion removal technology. Filtration technology is far from a stagnant field. Methods used to remove inclusions from the melt are selected on the basis of the product requirements, operating and capital costs of the method, ease of use and reliability of the method. The basic principles of inclusion removal for settling, floatation and filtration are reviewed along with an overview of current typical practice. New developments such as cyclones, MHD priming, vacuum assisted filtration and combo filters are described. Some ideas that have fallen by the wayside like “sticky” filters and use of Lorentz forces to increase filter efficiency are re-examined. The potential for new filter structures utilising 3D printing methods to achieve high efficiency at low head loss is highlighted.