Seznam abstraktů 2019: SEKCE A - POKROKOVÁ VÝROBA ŽELEZA, OCELI A LITINY
Datum: 22.5.2019
The residence time for individual tundish configuration is one of the most important factors of the tundish metallurgy. In the T-type tundishes, it is difficult to set a tundish furniture in order to obtain similar residence time for every strand. The tundish furniture is obviously designed for correct set ladle shroud position and angle. In this paper is quantified the ladle shroud deviation angle from vertical axis on residence time of three strand tundish of ŽP, a.s. using water model in scale 1:2. In the continuous casting machine in Železiarne Podbrezová, a.s., the manual ladle shroud mounting on ladle is used. Generally, the misalignment of the shroud has a negative effect on the flow of the steel in the tundish. This fact may negatively affect the cleanliness of the cast steel but also wearing of the exposed places of the tundish lining. The results are also evaluated by using sophisticated statistical methods.
Computational thermodynamics is a powerful tool widely applied in materials science, e.g. for alloy design. However, for applications in process metallurgy the use of computational thermodynamics is still rather limited. A thermodynamic database, TCOX, has been developed for calculating thermochemical interaction between liquid steel and slag. With the TCOX database an attempt is made to develop an internally consistent database for oxygen-containing systems. Today the TCOX database includes the major alloying elements (Fe, C, Co, Cr, Cu, Mn, Mo, Nb, Ni, V and W) as well as the important slag elements (Ca, Mg, Si, Al, F, O, P and S). Gd, La, Y and Zr are also included to be able to make calculations for yttria stabilized zirconia. In the near future, Ti and the alkali metals will also be included in the database.
In addition, a graphical interface for steel/slag calculations is developed which is easy to use and suitable for the steel industry. Such an interface, together with the TCOX database, could be a useful tool for controlling complex metallurgical processes, for example desulphurization, dephosphorization or ladle refining, and in the development of new steel grades.
Model alloys based on Fe-C-Ni and Fe-C-Cr with graded carbon, chromium and nickel content were studied. Two devices with various arrangements and principle of measurement were used and solidus, peritectic transformation and liquidus temperatures were precisely determined for prepared model alloys. DTA method with simultaneous thermal analyser Setaram SETSYS 18TM and dilatometry with NETZSCH DIL 402 Expedis Supreme (NanoEye) dilatometer were performed. Phase transition temperatures were studied during crossing from solid to liquid phase. Differences between experimental and theoretical temperatures in order of dozens of degrees of centigrade were observed, especially for solidus and peritectic transformation temperatures.
The potential use of artificial neural networks to determine the solidus temperature for steel based on composition has been investigated. Input data consist of solidus composition and temperatures both from literature and both from measurements. The primary performance testing of the model was then performed for steel grades measured. Several types of network topologies have been designed and trained and the best model selected. Testing was done on previously unseen data measured by differential thermal analysis method as on new input data. The used method is described. Obtained results are then compared to those measured and calculated by commonly used software among the academic and commercial community like IDS and Thermo-Calc. Performance of these three modelling approaches is discussed by means of selected statistic tools.
During the sintering of iron ore in the sintering process, nitrogen oxides (NOx) are produced and discharged with the process off-gas. The reported concentrations of nitrogen oxides expressed as NO2 in sintering off-gas are typically in the range of 300-500 mg/Nm³. However, also concentrations up to 1000 mg/Nm³ have been reported. NOx emissions from combustion can originate from three different formation mechanisms: thermal NOx, prompt NOx and fuel NOx. It has been established that in the sintering process the most significant source of NOx emissions is the fuel NOx. According to literature, only a few iron ore sinter plants operate a DeNOx system for the reduction of the NOx emissions (Secondary measures). However, there is plenty of ongoing research in primary measures for the reduction of the NOx emissions from the sintering process. These measures include the recirculation of the process off-gas, pre-treatment of the coke breeze used as fuel, replacement of the coke breeze by other fuels and the addition of various compounds to the sinter feed for the reduction of the NOx formation. In this study, the data available in the literature about the primary measures for the reduction of the NOx emissions from iron ore sinter plants are summarized, compared and discussed.
The aim of this work is to understand how to manage biomass, either as a stand-alone fuel or in interaction with fossil fuel, and to help define optimal granulometry and fuel mix. A higher proportion of fine-grained particles in sawdust can lead to complications in agglomeration mixture. This work describes the process of absorptivity of oak and pine pellets with water of 25 °C, water of 60 °C, soapy water and industrial surfactant. The decisive factors influencing the absorption were the surface tension of the liquids, the type and granulometry of the materials. It has been confirmed that the use of liquids with a lower surface tension or surfactant value has resulted in higher material absorption values. The absorption values obtained are a basic data base that can be further studied and further developed. Based on the data obtained, it is possible to consider the appropriate granulometry of alternative fuels and the hypotheses to verify the fuels together with the iron ores and slag additives by pregranulation.
This work shows the numerical simulation results of liquid steel flow in three strand tundish designed for the continuous bloom casting process. The authors proposed the modification of ladle shroud by expanding-compressing-expanding system at the end of ladle shroud. The considered ladle shroud modification consisted on the decrease momentum of the liquid steel feeding stream. The aim of the research was checked the influence of ladle shroud immersion depth in liquid steel on hydrodynamic structures in the three strand tundish based on the E and F-type residence time distribution curves. Furthermore, the flow and temperature fields of liquid steel were considered too. The research results allowed to assess the appropriate the modified ladle shroud depth in a liquid steel according to the amount of active and stagnant liquid steel flow volume. The transition zone during the sequential casting process was established for every research cases. Also, the factor of asymmetrical liquid steel flow in the tundish was checked based on the residence time distribution curves. The computer calculations were performed in the Ansys-Fluent computer program.
During High Carbon Ferromanganese production, the understanding of phases formation is of vital importance since they determine the quality of the overall operations in the furnace. This is also strongly dependent on the chemical composition of the feed. As opposed to other manganese ores that are acidic, South Africa has a basic manganese ore. The formation of phases during HCFeMn from still needs more investigation since it has been found that some theories do not explain what is observed in the South African manganese industry. The current work compared the phases that formed in the prereduction zone when carbon was used as opposed to carbon monoxide being blown into the furnace. Manganese ore from Nchwaning was used in the current work. Coke containing 86 % fixed carbon and a bottle containing CO with 98 % purity were used. The basicity was adjusted to 1 through addition of silica. The ore and the flux were crushed and milled together for better homogenization of the feed. XRD, XRF and SEM were used to characterize the feed and the products. The working temperatures were from 1200oC to 1300oC with 50oC increment. Graphite crucible was used for the experiments. To ensure that products analysed were not from the interaction with the crucible, only samples from the centre of the crucible were considered. Experiments were conducted in an alumina tube furnace for two hours after reaching the aimed temperature. Although carbon monoxide was blown into the furnace at a rate to ensure more reducing conditions that would presumably prevail same than when using carbon, results show similarities in the phase composition but the MnO content differed considerably.
The present work describes the investigations of rare-earth metals effect on the metallurgical quality of ingots and finished rolled products. Experimental lab steel meltings of high strength strips steel were performed using various modifiers containing rare earth metals, experiments to simulate the process of controlled rolling were performed, mechanical tests of samples of rolled metal were performed. At all stages of the work, metallographic studies of the metal structure were carried out, including the evaluation of the cast and deformed structure. Electron micro probe analysis (EMPA) of non-metallic inclusions and the metal matrix were perfomed.
The influence of modifying additives on the morphology of the dendritic structure of steel is fixed: modifier additives contribute to the formation of an equiaxed (spherulite) dendritic structure in contrast to the tree dendritic structure. The influence of modifying additives on the structure of cast grain is established: the size of cast grain is reduced by an average of 200 microns, the transcrystallization zone is reduced. The results of the metallographic study of the deformed structure of ingots without modifiers and in their presence indicate that the final structure of the hot-rolled sheet in addition to rolling modes is determined by the structure of the metal in the cast state. Samples of ingots having, due to modification, more dispersed cast and dendritic structure, after controlled rolling are characterized by a higher grain number, a smaller volume fraction and the size of the areas of bainite rack morphology, thus providing a highly dispersed morphologically similar structure of the strip. According to the results of the study, it was found that for experiments in industrial conditions it is recommended to use as modifiers RZNTB, the composition of which is as follows: Ce=15.7 %; La=7.3 %; Nd=6.5 %; Pr=1.8%; Ca=3 %; Al=32 %; Ti=5.9 %, Nb=6.6 %, Fe=5.9 %, Ni=15.3 %.
One model alloy based on Fe-C-Cr and one model alloy based on Fe-C-Ni were studied. Fe-C-Cr based alloy contained carbon of 0.34 wt. % and chromium of 0.92 wt. %. Fe-C-Ni based alloy contained carbon of 0.38 wt. % and nickel of 1.08 wt. %. Temperatures of phase transformations (temperature of the solidus, liquidus and peritectic transformation) were studied in the high-temperature area by a heating rate of 1, 2, 5, 10 and 20 °C/min., the influence of heating rate was investigated. The influence of the sample mass was also studied by the heating rate of 10 °C/min. Samples with mass 50, 100, 190, 280 and 370 mg were studied. Samples with the mass 190 mg were studied by various heating rates. The Setaram Setsys 18TM device was used for experiments with the use of the DTA method. No influence of the heating rate was detected for the temperature of solidus for both alloys. The most significant influence of heating rate was observed for the temperature of liquidus (temperature difference 6 - 8 °C). More noticeable impact of heating rate on the temperature of peritectic transformation shift was observed by Fe-C-Cr based alloy investigation. The influence of sample mass is negligible regarding the temperature of solidus and significant in case of liquids (for both alloys) and peritectic transformation (for Fe-C-Cr alloy) temperature.
The hot ductility behaviour of a Ti-Nb micro alloyed steel was investigated to evaluate the probability of surface crack formation during the continuous casting process, by performing hot tensile tests. The testing temperatures are ranging from 1100 °C to 700 °C. The effects of testing temperature range and deformation rate on hot ductility were investigated. The results show that this steel exhibits poor ductility over almost the whole testing temperature range. The ductility starts to decrease at 1000 °C in the single phase γ-region, characterized by grain boundary sliding and surface cracks, reaches a minimum in the two-phase α-γ-region at 750 °C and slightly increases with decreasing testing temperature. Furthermore, low deformation rates severely decrease the ductility behaviour. Microstructural examinations and supplementary thermo-kinetic computer simulations revealed distinct Ti-Nb precipitation throughout the microstructure being responsible for the deteriorated materials hot ductility.
Datum: 23.5.2019
The use of technological packages and consequently following our technologic & continuous casting principle, we achieve the shortest start-up times in the industry 4.0. Our modular solution approach ideally meets all technological requirements and customer demands, for both new and existing casters and for the production of carbon, stainless and special AHSS (Advanced High-Strength Steels) steel grades. The ever-greater demands for quality and the ongoing development of steel grades mean that the quality level at every stage of the casting process will continue to grow in importance in the future. As our example the CastFlex Oscillation (CFO) technology represents in 2019, the latest generation of Ind. 4.0, oscillation systems and saves money in operation compared to other systems [1]. The hydraulic oscillation drive system enables the dynamic adjustment of frequency, stroke, and wave form during casting for optimized negative strip time. The wear-free leaf-spring oscillator guidance system guarantees the highest guidance accuracy, outstanding operational safety, and low maintenance costs. The design allows a quick coupling of all media supplies to the mold and automatically completes the alignment of the mold and oscillator. By our metallurgical experience and technical expertise to supply cutting-edge technology for maximized bloom caster performance, production and upgrading.
The continuous steel casting (CSC) technology has resulted in an increase in steelworks productivity and made it possible to cast billets of a favourable internal structure. Developing and improving the CSC technology for alloy addition feeding to liquid steel for increasing the purity level or correcting of chemical composition grade seems to be quite an interesting approach for advanced steelmaking process. In the tundish, the chemical homogenisation process is controlled by the feed stream and flow control devices. This paper presents the results of investigation describing the process of liquid steel chemical homogenisation in the six strand billets tundish with stopper rod system. The alloy was fed to liquid steel by pulse-step method. Computer simulations of liquid steel flow and alloy addition mixing were performed using the commercial program Ansys-Fluent. Four tundish variants without and with flow control devices were considered. Additionally computer simulations for four different alloy feeding positions and two type of alloys in the form of nickel and aluminium were performed. Information about the dynamics of steel alloying process was obtained on the basis of fields of liquid steel flow and alloy addition distribution characteristics. For all simulations cases the mixing time was calculated.
This paper deals with an experimental determination of surface tension, densities and wetting angles, which were considered for spreading on an alumina substrate, of selected Fe-C-O-X (X = Cr, Ni) alloys. The concerned physico-chemical quantities were determined by a sessile drop method in the temperature interval between liquidus temperature of the given alloy and temperature of 1,600 °C during heating with a rate of 5 °C·min-1. Several Fe-C-O-Cr and Fe-C-O-Ni model alloys differed in carbon (0.043 - 1.378 wt.%) and nickel (1.084 - 4.478 wt.%) content in order to assess the effect of these elements. From the dependence of surface tension on temperature, it was found that the surface tension of given alloys increases slightly with increasing temperature, i.e. that the temperature coefficient of surface tension dσ/dT was positive. Similar course was ascribed regarding wetting angles dependence on temperature. Further, the influence of carbon and nickel on surface properties was proved by statistical analysis carried out in the R environment for statistical computing and visualization.
Continuous steel reheating furnaces belong to high-energy consumption units and an optimization of their operation can thus bring significant economic and ecological benefits. Numerical modelling is one of the tools for an optimization of a design, process parameters and operation control of the furnaces. A 3D zonal model of a continuous gas burners heated walking-beam furnace is introduced in this contribution. A solution of heat transfer process in the furnace is based on a Hottel zonal method and compartment based discretization. The solution includes convective and radiative heat transfer in the furnace including a participation of a semi-transparent gaseous furnace atmosphere. A method of direct measurement of a charge heating in a continuous walking beam furnace is presented. The method is based on a thermal-box barrier device, which allows temperature measurement of a tested beam during its entire passage throughout the furnace. Results obtained by the numerical simulation and the measurement are compared and a good agreement is confirmed. It is demonstrated that the presented zonal model is an effective tool, which can bring accurate enough results at a very acceptable time.
Currently, there is increasing pressure to reduce waste generation and to use it as a secondary raw material. In the framework of this work, there are presented beginning parts of the project plan called "Research of processing of metallurgical waste, materials and by-products from metallurgical and related operations number CZ.02.1.01/0.0/0.0/17_049/0008426“. The authors deal with the problems including the basic description of processes leading to the reduction of non-ferrous metals in metallurgical wastes. Including a rough draft of the prepared laboratory, which will be used for metallurgical waste treatment, especially in reducing the proportion of non-ferrous metals.