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- Mills, K.C., et al.
(author)
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Looking into continuous casting mould
- 2014
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In: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 41:4, s. 242-249
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Journal article (peer-reviewed)abstract
- When you look into the continuous casting mould you can see very little. Consequently, steelmakers have had to rely on plant trials, simulation experiments and physical property measurements on fluxes and steels to gain an understanding of the mechanisms responsible for process problems and product defects. However, in recent years, mathematical modelling has advanced to the stage where they can provide us with great insight into these mechanisms. As a nonmathematical modeller, I was initially sceptical of some of the predictions of the mathematical models. However, I have been completely won over by the ability of these models to simulate accurately the mechanisms responsible for various defects, such as slag entrapment, oscillation mark formation, etc. Mathematical modelling literally allows us to 'see' what is happening in the mould. It is a remarkable tool. © 2014 Institute of Materials.
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| 2. |
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| 3. |
- Lee, P.D., et al.
(author)
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Review: The "butterfly effect" in continuous casting
- 2012
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In: Ironmaking and Steelmaking. ; , s. 244-253
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Conference paper (peer-reviewed)abstract
- The continuous casting (CC) mould may appear very peaceful when viewed from above, but the powder bed hides relentless fluctuations in the following phenomena: metal flow, thermal gradients, chemical reactions and multiple phase transformations. When observed separately, some of these phenomena seem to have a 'simple behaviour', which may appear easy to control through the main casting parameters (e.g. casting speed, pouring temperature and powder type) and associated control systems (e.g. mould level control, automatic powder feeding and mould oscillation). However, when combined, these phenomena exhibit periodic fluctuations in behaviour, which is both difficult to predict and control. For instance, the combination of casting speed, submerged entry nozzle design and slab size can cause the metal flow pattern to shift from double roll to single roll and back, which can cause unstable fluctuations in metal level, standing waves, etc. In this respect, the CC process closely resembles a meteorological system where both variations and local fluctuations in temperature, humidity, pressure, etc., can result in effects that are difficult to predict in the long term. This is equivalent to the famous Lorenz premise: 'Does the flap of a butterfly's wings in Brazil set off a tornado in Texas?' In this paper, we give some examples of the 'butterfly effect' in CC discussed below by using a mathematical model able to predict the slab solidification inside the mould in which various factors affecting the process stability are analysed and the probable sources of fluctuation are identified. © 2012 Institute of Materials, Minerals and Mining.
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| 4. |
- Ramirez Lopez, Pavel Ernesto, et al.
(author)
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A unified mechanism for the formation of oscillation marks
- 2012
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In: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 43:1, s. 109-122
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Journal article (peer-reviewed)abstract
- Oscillation marks (OMs) are regular, transverse indentations formed on the surface of continuously cast (CC) steel products. OMs are widely considered defects because these are associated with segregation and transverse cracking. A variety of mechanisms for their formation has been proposed (e.g., overflow, folding, and meniscus freezing), whereas different mark types have also been described (e.g., folded, hooks, and depressions). The current work uses numerical modeling to formulate a unified theory for the onset of OMs. The initial formation mechanism is demonstrated to be caused by fluctuations in the metal and slag flow near the meniscus, which in turn causes thermal fluctuations and successive thickening and thinning of the shell, matching the thermal fluctuations observed experimentally in a mold simulator. This multiphysics modeling of the transient shell growth and explicit prediction of OMs morphology was possible for the first time through a model for heat transfer, fluid flow, and solidification coupled with mold oscillation, including the slag phase. Strategies for reducing OMs in the industrial practice fit with the proposed mechanism. Furthermore, the model provides quantitative results regarding the influence of slag infiltration on shell solidification and OM morphology. Control of the precise moment when infiltration occurs during the cycle could lead to enhanced mold powder consumption and decreased OM depth, thereby reducing the probability for transverse cracking and related casting problems. © The Minerals, Metals & Materials Society and ASM International 2011.
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