Search

The main problem in the production of forgings from tool steels, especially thick plates, blocks, pulleys and rods which are used for special machine components for demanding applications, it is the inhomogeneous structure with segregations, cracks in segregations or complex type of non-metallic inclusions MnS and TiCN. These forgings are actually produced from conventional forging ingots. Due to the size of forgings, it would be interesting the production of these forgings from slab ingots. It is possible that the production of forgings from slab ingots (which are distinguished by a characteristic aspect ratio A/B), it would reduce the occurrence of segregations. The paper presents the verification of the production process of slab steel ingots in particular by means of numerical modelling using finite element method. The paper describes the pre-processing, processing and post-processing phases of numerical modelling. The attention was focused on the prediction of behavior of hot metal during the mold filling, on the verification of the final porosity, of the final segregation and on the prediction of risk of cracks depending on the actual geometry of the mold. Web of Science 60 4 2885 2879

The paper deals with evaluation of relevant information about transfer processes taking place in the interface slag – metal and with the assessment of the rate and course of steel desulphurization. The study of mentioned processes took place with the verification of the results obtained by the plant experiments in the homogenization station using 180 t ladle and in the physical model of the ladle in the geometrical scale 1 : 9 supplemented by homogenization nozzle. Plant and physical experiments were based on similar methodology. Samples of metal and slag were taken in regular time intervals for following evaluation of kinetics of the sulphur loss in the metal and appropriate increase of sulphur contain in the slag. Web of Science 54 4 614 611

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 Science 58 1 177 171

This paper deals with an investigation of the development of refractory materials for the fabrication of ceramic filters for the filtration of steel. Ceramic filters are used for increasing the cleanliness of steel and they must meet several strict requirements, such as the ability to remove impurities, a resistance to sudden changes in temperature, a resistance to corrosion and erosion by metal. The use of filters must not lead to an excessive reduction of the steel’s temperature, as this may lead to solidification of steel and thus to filter clogging. That is why a special refractory material has been developed with reduced thermal capacity caused by increased porosity. Tests were made in a laboratory of the Department of Metallurgy at V[B-TUO in order to simulate the industrial conditions of the filtration of steel with a focus on the evaluation of the erosion and corrosion effects and also on a determination of the resistance and service life of ceramic filters. Web of Science 45 6 608 603

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 Science 47 5 575 569

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 Science 46 6 682 677