Research and development of the solidification of slab ingots from special tool steels

The paper describes the research and development of casting and solidification of slab ingots from special tool steels by means of numerical modelling using the finite element method. The pre-processing, processing and post-processing phases of numerical modelling are outlined. Also, problems with determining the thermophysical properties of materials and heat transfer between the individual parts of the casting system are discussed. Based on the type of grade of tool steel, the risk of final porosity is predicted. The results allowed to improve the production technology of slab ingots, and also to verify the ratio, the chamfer and the external/internal shape of the wall of the new designed slab ingots.Web of Science6231458145

Numerical modelling of macrosegregation in heavy steel ingot

The paper presents new knowledge and experience from numerical modelling of macrosegregation in heavy steel ingot using ProCAST software. The main aim of numerical modelling realized under the conditions of the Department of Metallurgy and Foundry and Regional Materials Science and Technology Centre at VSB-TU Ostrava is the optimization of the production of heavy steel ingots produced in V´ITKOVICE HEAVY MACHINERY a.s. Input parameters of computation were determined by the real conditions of parallel experimental casting of a 90-ton steel ingot. The input data were also verified by thermal analysis and thermography measurement. The numerical results of macrosegregation were compared with the chemical analysis evaluated in a real ingot section. According to the comparison, attention will be focused next on determination of the effect of boundary conditions of filling and solidification of the ingot on the size of macrosegregation.Web of Science58117717

Postavitev numeriřne simulacije polnjenja in strjevanja velikih jeklenih ingotov na podlagi realnih razmer pri ulivanju

The paper is devoted to new experiences with the setting of a numerical simulation of filling and solidification of a 90-ton steel ingot in the ProCAST simulation programme. The aim of the numerical modelling realized under the conditions of the Department of Metallurgy and Regional Materials Science and Technology Centre (RMSTC) at VSB-TU Ostrava is the verification and optimization of the production technology for the heavy-steel ingots produced in VÍTKOVICE HEAVY MACHINERY a.s. The input parameters of the computation were determined with the real conditions of casting a 90-ton steel ingot. The ingot geometry was created in the CAD system SolidWorks. Before the computational grid generation of finite elements in the Visual-Mesh module, the geometry was subjected to an analysis of the topology. The material properties of the individual components of the ingot-casting system were defined with the Computherm calculating module selecting the materials from its own database of ProCast. In addition, the thermodynamic properties were determined by using the datasheets of the refractory materials of the manufacturer, and finally checked with the equations generally used to determine liquidus and solidus temperatures, density and enthalpy, etc. The boundary conditions and the heat transfer were also defined. In parallel with the numerical simulation, the operational experimental casting of a 90-ton ingot was carried out. To obtain more complete information about the temperature fields of the ingot-casting system and of the data about the values of the heat flow, the process of filling and solidification was monitored by using thermal imaging cameras. The conclusion summarizes the main knowledge obtained on the basis of the primary results of the computation and gives a guideline for further research.Web of Science46440239

Evaluation of influence of briquetted synthetic slags on slag regime and process of steel desulphurization

This paper presents the industrial results of evaluation of efficiency of synthetic slags during the treatment of steel at the equipment of the secondary metallurgy under conditions of the steel plant VÍTKOVICE HEAVY MACHINERY a.s. The aim of the heats was to assess the influence of the briquetted and sintered synthetic slags based on Al2O3 aiming the course of the steel desulphurization and slag regime during the production and treatment of steel grade 42CrMo4 with the technology EAF→LF→ VD. Within the plant experiments, basic parameters influencing the steel desulphurization and slag regime were monitored: desulphurization degree, basicity, content of easily reducible oxides, proportion of CaO/Al2O3 and Mannesmann’s index. Obtained results allowed to compare the steel desulphurization and to evaluate the slag regime. It was proved that the synthetic slag presenting the briquetted mixture of secondary corundum raw materials can adequately replace the synthetic slag created from the sintered mixture of natural raw materials.W pracy tej przedstawiono przemysłowe wyniki oceny efektywności zastosowania żużli syntetycznych podczas obróbki pozapiecowej stali w zakładzie VÍTKOVlCE HEAVY MACHINERY a.s. Celem badań był a ocena wpływu brykietówanych i spiekanych żużli syntetycznych opartych na AI2O3 - na przebieg odsiarczania stali i żużla podczas produkcji i obróbki stali 42CrMo4. zgodnie z technologią EAF → LF → VD. Podczas eksperymentów w zakładzie, monitorowano podstawowe parametry wpływające na odsiarczania stali i żużla: stopień odsiarczania, zasadowość, zawartość tlenków łatwo redukowałnych, stosunek CaO/Al2O3 oraz indeks Mannesniann’a. Uzyskane wyniki pozwoliły na porównanie stopnia odsiarczania stali w kontekście zastosowanych żużli. Wykazano, że syntetyczny żużel składający się z brykietowanej mieszaniny wtórnego korundu, może zastąpić syntetyczny żużel otrzymywany ze spieku mieszaniny surowców naturalnych.Web of Science59281380

Determination of the solidus and liquidus temperatures of the real-steel grades with dynamic thermal-analysis methods

The knowledge of the solidus and liquidus temperatures of the real-steel grades is one of the most important technological factors – especially when dealing with the processes of casting and solidification. These temperatures are critical parameters for proper settings of the models (physical or numerical) or in the final stage of an applied research of a real process. A correct setting of a production technology is significantly affecting the final quality of the as-cast steel (billets or ingots). Therefore, this paper is devoted to discussing the findings obtained during a utilization of dynamic thermal-analysis methods to identify the solidus and liquidus temperatures applicable to commercially produced steels. The results obtained with a differential thermal analysis (DTA) for three steel grades and with 3D differential scanning calorimetry (3D DSC) for two steel grades are compared with the results of the selected equations commonly used for liquidus and/or solidus temperature calculations. The calculations obtained with the Computherm SW for the discussed steels were also realized. It can be stated that the equilibrium liquidus and solidus temperatures obtained with the above-mentioned methods for each steel grade differ. The differences between the calculated results, the thermodynamic calculations and thermal-analysis results are very unpredictable and vary individually for different steels. These differences are not marginal (tens of Celsius degrees). So, it is sometimes suitable to combine several methods for a proper determination of the liquidus and solidus temperatures for a correct setting of a steel-making process or its modelling. The best solution for a technological process is to obtain the liquidus and solidus temperatures for a concrete-steel grade from a given steelmaking practice – a thermal analysis of a concrete-steel grade is a possible way.Web of Science47557556

The electrochemical and statistical evaluation of isolation of mellitin and apamin from honey bee (Apis Mellifera) venom.

We present in this manuscript for the first time the electrochemical and statistical evaluation of FPLC isolation of mellitin and apamin from honey bee (Apis mellifera) venom. Venoms are extremely complex blends of diverse substances that target a myriad of receptors or ion channels. Therefore, toxins, isolated from venomous organisms can be a valuable tool with diverse biological applications. In this study we decided to optimize the purification of honey bee venom by using fast protein liquid chromatography, to obtain biologically active peptide - melittin (2846.46 Da). Due to a presence of other compounds with similar molecular weight (apamin 2027.34 Da), we optimized a differential pulse voltammetry method with adsorptive transfer technique (AdT DPV), utilizing Brdicka supporting electrolyte for measurements. Typical voltammograms - fingerprints for each substance were obtained and numerical projections of voltammograms were employed to propose an artificial neural network. Our suggested neural network can simply predict the content of each peptide in fraction with following performance: 100 % for training and 100 % for testing

Evaluation of steel desulphurization in the ladle during the utilization of briquetting fluxing agents for slags

This paper presents the experience obtained from plant experiments specialized in the usage of three types of fluxing agents for slags based on Al2O3. Proper experiments took place during the steel treatment by secondary metallurgy. The objective of the plant experiments was to assess the degree of steel desulphurization and its course. An assessment of the steel desulphurization with the help of basic parameters, such as the degree of desulphurization, the basicity, the content of easily reducible oxides, the proportion of CaO/Al2O3 and Mannesmann’s index was made. At the same time the behaviour of the fluxing agents and the development of their dissolution in steelmaking slags were assessed.Web of Science46668267

Experimental verification of hematite ingot mould heat capacity and its direct utilisation in simulation of casting process

Heat capacity of alloys (metals) is one of the crucial thermophysical parameters used for process behaviour prediction in many applications. Heat capacity is an input variable for many thermodynamical (e.g. Thermocalc, Pandat, MTData, …) and kinetic programs (e.g. IDS-Solidification analysis package, …). The dependences of heat capacity on common variables (temperature, pressure, ...) are also commonly used as the input data in software packages (e.g. ProCast, Magmasoft, ANSYS Fluent, …) that are applicable in the field of applied research for simulations of technological processes. It follows from the above that the heat capacities of materials, alloys in our case, play a very important role in the field of basic and applied research. Generally speaking, experimental data can be found in the literature, but corresponding (needed) data for the given alloy can very seldom be found or can differ from the tabulated ones. The knowledge of proper values of heat capacities of alloys at the corresponding temperature can be substantially used for addition to and thus towards the precision of the existing database and simulation software. This study presents the values of C p measured for the hematite ingot mould and comparison of the measured data with the C p values obtained using the software CompuTherm with respect to simulation of technological casting process.Web of Science112148047

A signal strength fluctuation prediction model based on the random forest algorithm

This article describes the effect of the weather on radio wave propagation in a mobile telecommunication network. The research is focused on urban and countryside environments where a correlation between the received signal power level and weather conditions is found using the Random Forest algorithm as a signal level approximator. The results achieved in this paper clearly indicate that it is possible to predict the behaviour of the received power level in relationship to atmospheric phenomena.Web of Science20512612