Numerické modely tuhnutí a jejich použití v technologii kovů a keramiky

Numerical models of solidification and their application in metal and ceramic technology

kniha odborná

en

Solidification (crystallization) phenomena play a major role in such diverse operations as casting, crystal growth, and welding. Solidification proceeds at various rates, which are sometimes far from equilibrium. Thus, the casting microstructure obtained is generally not homogeneous and gives rise to variations in composition with position at both small and large scales, which is known as segregation. Solute segregation is important because it leads to non-equilibrium phases, cracks, and other problems, which lower the mechanical properties of the final product. Segregation is classified, according to its scale, as macro-segregation or micro-segregation. Macro-segregation prediction is very complex. Among many other things, it depends on an accurate prediction of micro-segregation. Micro-segregation refers to a composition variation within the columnar or equiaxed dendritic solidification structure, which has a length scale of the order of only few micrometers. It is usual to characterize the extent of micro-segregation using a ranking scheme of randomly sampled electron micro-analysis data. Thermodynamic quantities are often calculated from measurements of the as-cast segregation profile, in particular, the partition coefficient. These thermodynamic quantities are used for alloy development programs and in casting process models both as input properties and for validation. A well-founded technique is thus imperative for evaluating compositional data from X-ray microanalysis. Commercially available softwares are not able to predict the chemical heterogeneity of continuously cast material components of multi-component alloys. This publication shows the application of the commercial and the two original models of the simulation of temperature field castings and continuously cast slabs in various applications metallurgical and ceramic technology. The third applied original model is the model of chemical heterogeneity of elements, allowing the description and measurement of the dendritic main elements and impurities in solidifying castings.

Procesy tuhnutí (krystalizace) hrají důležitou roli v takových různých operacích jako je odlévání, růst krystalů a svařování. Tuhnutí probíhá za různých podmínek, které jsou někdy daleko od rovnovážných stavů. To znamená, že získaná mikrostruktura obecně není homogenní a způsobuje rozdíly složení v závislosti na poloze v malém i velkém měřítku, označovaném jako segregace. Tato segregace je významná, neboť má za následek vznik nerovnovážných fází, prasklin a dalších problémů, které snižují mechanické vlastnosti konečného produktu. Segregace je klasifikována podle jejího rozsahu jako makro-segregace nebo mikro-segregace. Předpověď makro-segregace je velmi složitá. Mimo mnoha jiných věcí záleží na přesné predikci mikro-segregace. Komerčně dostupné software nejsou schopné předvídat chemické heterogenity plynule litých materiálových složek vícesložkových slitin. Předložená publikace ukazuje několik příkladů aplikací komerčního a dvou originálních modelů simulace teplotního pole odlitků a kontinuálně odlévaných předlitků v oblasti metalurgické a keramické technologie. Třetím aplikovaným originálním modelem je model chemické heterogenity prvků, umožňující popis a měření dendritické segregace hlavních prvků a nečistot v tuhnoucích odlitcích.

Solidification (crystallization) phenomena play a major role in such diverse operations as casting, crystal growth, and welding. Solidification proceeds at various rates, which are sometimes far from equilibrium. Thus, the casting microstructure obtained is generally not homogeneous and gives rise to variations in composition with position at both small and large scales, which is known as segregation. Solute segregation is important because it leads to non-equilibrium phases, cracks, and other problems, which lower the mechanical properties of the final product. Segregation is classified, according to its scale, as macro-segregation or micro-segregation. Macro-segregation prediction is very complex. Among many other things, it depends on an accurate prediction of micro-segregation. Micro-segregation refers to a composition variation within the columnar or equiaxed dendritic solidification structure, which has a length scale of the order of only few micrometers. It is usual to characterize the extent of micro-segregation using a ranking scheme of randomly sampled electron micro-analysis data. Thermodynamic quantities are often calculated from measurements of the as-cast segregation profile, in particular, the partition coefficient. These thermodynamic quantities are used for alloy development programs and in casting process models both as input properties and for validation. A well-founded technique is thus imperative for evaluating compositional data from X-ray microanalysis. Commercially available softwares are not able to predict the chemical heterogeneity of continuously cast material components of multi-component alloys. This publication shows the application of the commercial and the two original models of the simulation of temperature field castings and continuously cast slabs in various applications metallurgical and ceramic technology. The third applied original model is the model of chemical heterogeneity of elements, allowing the description and measurement of the dendritic main elements and impurities in solidifying castings.

kovové a keramické materiály, tuhnutí, krystalizace, teplotní pole, numerické modely , model chemické heterogeneity prvků

metal and ceramic materials, solidification, crystallization, temperature field, numerical models, the model of chemical heterogeneity of elements

15.11.2016

Brno University of Technology, VŠB Technical University of Ostrava

Litera Brno

978-80-214-5377-7

Numerical models of solidification and their application in metal and ceramic technology

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