Vliv chemického složení oceli na numerickou simulaci plynulého odlévání sochorů

The chemical composition of steels has significant influence on the actual concasting process, and on the accuracy of its numerical simulation and optimization. The chemical composition of steel affects the thermophysical properties (heat conductivity, specific heat capacity and density in the solid and liquid states) often requires more time than the actual numerical calculation of the temperature fields of a continuously cast steel billet. Therefore, an analysis study of these thermophysical properties was conducted. The order of importance within the actual process and the accuracy of simulation were also determined. The order of significance of the chemical composition on thermophysical properties was determined with respect to the metallurgical length. The analysis was performed by means of a so-called calculation experiment, i.e. by means of the original numerical concasting model developed by the authors of this paper. It is convenient to conduct such an analysis in order to facilitate the simulation of each individual case of concasting, thus enhancing the process of optimization.Chemické složení ocelí má významný vliv na reálný proces plynulého odlévání a na přesnost jeho numerické simulace a optimalizace. Chemické složení oceli ovlivňuje termofyzikální vlastnosti (tepelné vodivosti, měrné tepelné kapacity a hustoty v tuhém i tekutém stavu) a jejich prostřednictvím ovlivňuje výpočet teplotního pole plynule odlévaných ocelových sochorů. Proto byla provedena analýza studie těchto termofyzikálních vlastností. Vliv významu chemického složení na termofyzikální vlastnosti byla určena s ohledem na metalurgickou délku. Analýza byla provedena pomocí takzvaných výpočetních experimentů, tj. pomocí originálního numerického modelu teplotního pole, který byl vyvinut autory tohoto příspěvku. Tato analýza usnadní a tím zlepší proces optimalizace plynulého odlévání oceli

Nov način ocenjevanja kemijske mikroheterogenosti kontinuirno ulitih slabov

The paper deals with a new approach to measuring and evaluating the chemical micro-heterogeneity of the elements in solidified poly-component metallic systems. The original approach is based on experimental measurements made on the samples taken from characteristic places in a casting and the subsequent application of an original mathematical model for determining the element-distribution profile, characterizing the most probable distribution of an element concentration in the frame of a dendrite, and an original mathematical model for determining the effective partition coefficients of these elements in the structure of the analyzed alloy. The paper also describes an application of this method in the research of the chemical heterogeneity on a cross-section of a CC steel slab and presents the selected results (indices of the heterogeneity and effective partition coefficients of seven analyzed elements) characterizing the chemical micro-heterogeneity on one-half of the cross-section of this CC steel slab. The following main results were obtained: (i) the dendritic heterogeneity of the accompanying elements and impurities is comparatively high; (ii) all the analyzed elements segregate during the solidification into an inter-dendritic melt, and their partition coefficient is smaller than one; (iii) the effective partition coefficients calculated in this new way inherently include both the effect of segregation in the course of an alloy solidification, and the effect of the homogenization occurring during the solidification as well as during the cooling of an alloy.Web of Science471837

Investigation of a Temperature Field of the Steel Billet 150x150 mm Continuously Cast

The solidification and cooling of a continuously cast billet and the simultaneous heating of the mold is a very complicated problem of three-dimensional (3D) transient heat and mass transfer. The solving ofuch a problem is impossible without numerical models of the temperature field of the concasting itself which it is being processed through the concasting machine (caster). The application of the numerical model requires systematic experimentation and measurement of operational parameters on a real caster as well as in the laboratory. The measurement results, especially temperatures, serve not only for the verification of the exactness of the model, but mainly for optimization of the process procedure. The most important part of the investigation is the measurement of the temperatures in the walls of the mold and the surface of the slab in the zones of secondary and tertiary cooling

Importance of the experimental investigation of a concasting technology

The solidification and cooling of a continuously cast billet, slab cylinder, generally of a concasting and the simultaneous heating of the mold is a very complicated problem of three-dimensional (3D) transient heat and mass transfer. The solving of such a problem is impossible without numerical models of the temperature field of the concasting itself hich it is being processed through the concasting machine (caster). The application of the numerical model requires systematic experimentation and measurement of operational parameters on a real caster as well as in the laboratory. The measurement results, especially temperatures, serve not only for the verification of the exactness of the model, but mainly for optímization of the process procedure: real process input data numerical analyses optimization correction of real process. The most important part of the investigation is the measurement of the temperatures in the walls of the mold and the surface of the slab in the zones of secondary and tertiary cooling

The Influence of Chemical Composition of Steels on the Numerical Simulation of a Continuesly Cast of Billet

The chemical composition of steels has significant influence on the actual concasting process, and on the accuracy of its numerical simulation and optimization. The chemical composition of steel affects the thermophysical properties (heat conductivity, specific heat capacity and density in the solid and liquid states) often requires more time than the actual numerical calculation of the temperature fields of a continuously cast steel billet. Therefore, an analysis study of these thermophysical properties was conducted. The order of importance within the actual process and the accuracy of simulation were also determined. The order of significance of the chemical composition on thermophysical properties was determined with respect to the metallurgical length. The analysis was performed by means of a so-called calculation experiment, i.e. by means of the original numerical concasting model developed by the authors of this paper. It is convenient to conduct such an analysis in order to facilitate the simulation of each individual case of concasting, thus enhancing the process of optimization

Význam termofyzikálních vlastností ocelí pro numerickou simulaci procesu kontinuálního lití

The thermophysical properties of steels have significant influence on the actual concasting process, and on the accuracy of its numerical simulation and optimization. The determination of these properties (heat conductivity, specific heat capacity and density in the solid and liquid states) often requires more time than the actual numerical calculation of the temperature fields of a continuously cast steel billet, cylinder or slab (generally a concasting). The influence of individual properties should be neither under- nor over-estimated. Therefore, an analysis/parametric study of these thermophysical properties was conducted. The order of importance within the actual process and the accuracy of simulation and optimization were also determined. Individual properties, which, in some cases, were obtained from tables, and in others experimentally, were substituted by an approximation using orthogonal polynomials. The accuracy of each polynomial is dependent on the precision of individual values. The order of significance of individual thermophysical properties was determined with respect to the metallurgical length. The analysis was performed by means of a so-called calculation experiment, i.e. by means of the original and universal numerical concasting model developed by the authors of this paper. It is convenient to conduct such an analysis in order to facilitate the simulation of each individual case of concasting, thus enhancing the process of optimization.Termofyzikální vlastnosti ocelí mají významný vliv na reálný proces kontinuálního lití a na přesnost jeho numerické simulace a optimalizace. Určení těchto vlastností (tepelná vodivost, měrná tepelná kapacita a hustota v tuhé a kapalné fázi) často vyžaduje více času než vlastní numerický výpočet teplotních polí plynule odlitého ocelového sochoru, válce nebo bramy (obecně předlitku). Vliv individuálních vlastností by neměl být podceňován ani přeceňován. Proto byla uskutečněna analyza/parametrická studie těchto termofyzikálních vlastností. Bylo rovněž určeno pořadí významu v průběhu skutečného procesu a přesnost simulace a optimalizace. Individuální vlastnosti, které v některých případech byly získány z tabulek, v jiných experimentálně, byly nahrazeny aproximací za použití ortogonálních polynomů. Přesnost každého polynomu je závislá na přesnosti jednotlivých vlastností. Pořadí významu jednotlivých termofyzikálních vlastností byla stanovena vzhledem k metalurgické délce. Analyza byla prováděna pomocí t.zv. výpočtového experimentu, t.j. pomocí originálního a univerzálního numerického modelu plynulého odlévání vyvinutého autory tohoto článku. Je potřebné provádět takovou analyzu pro usnadnění simulace každého konkretního případu plynulého lití a tak zlepšit proces optimalizace

Numerična in eksperimentalna analiza kemijske heterogenosti strjevanja litega težko gnetljivega železnega valja

The quality of the working rollers used for rolling rails is determined by the chemical and structural compositions of the material of the rollers and the production technology. It is necessary to cast rollers with significantly improved utility properties, i.e., mainly a high wear resistance and optimal mechanical and structural properties. It is, therefore, necessary to find and ensure the optimal relationships between the matrix structure and the resulting values of the mechanical properties of the rollers in order to maximize their life time. The requirements introduced here cannot be ensured without a knowledge of the kinetics of the solidification. Therefore, numerical and experimental investigations of the temperature field of the solidifying roller were conducted. The kinetics of the solidification has a measurable and non-negligible influence on the chemical and structural heterogeneity of the investigated type of ductile cast-iron. Linking to the results of the model of the temperature field of the cast rollers, an original methodology was developed for the measurement of chemical micro-heterogeneity. The structure of this cast-iron is created by a large amount of the transition form of graphite and a small amount of globular graphite, and also the lamellar graphite and cementite, whereas the structure of the metal matrix is perlitic. The volume amounts of the structural components were determined using a quantitative metallographic analysis, according to which the places for the analysis of the element composition using X-ray energy-dispersive spectral micro-analysis were selected. The chemical and structural heterogeneity of the cast roller is, therefore, a significant function of the method of melting, modification and inoculation and the successive procedures of risering, casting and crystallization after cooling.Web of Science46439238

Analysis of the Influence of Boundary Condition on Simulation Accuracy of Solidification Thermokinetics Model

For a sample steel casting of a cylindrical shape that was cast in a metallic cylindrical mould, the analysis of influence and importance of the main boundary condition on the simulation accuracy of the temperature field in the system of casting-mould-environment was performed. For this system, the influence of the boundary condition on the frame of the mould, on the bottom of the mould, on the top of the casting, and on the casting-mould interface was analysed. As a comparing quantity for accuracy, the time-dependent temperature field (by means of isotherms) of the casting and of the mould and the total solidification time were selected. When the simulation considers the boundary conditions of one of these boundaries of the system, the heat transfer coefficient on the remaining three boundaries of the system is equal zero. The resultant heat flow along the axis is zero always. The conclusions can be used for fine-tuning of solidification models as well as for other applications; e.g. analysis and solution of inverse heat transfer problems