Seznam abstraktů 2019: POSTEROVÁ SEKCE A

Production of innovative types of steel and other metallic materials requires the composition to contain, in addition to iron, other chemical elements that influence desired properties of the alloy. Alloy additions are mainly introduced due to the use of appropriate ferroalloys in the production process. The paper presents effects of complex ultrapure FeSiCr alloy production process.

Current computational IT techniques allow to compute large complex multi-physical models and come up with a real-time solution. Due to this fact, a thermo-mechanical model for continuous steel casting can be created and used as a real-time crack prediction tool. Thermal and mechanical crack conditions must be evaluated to conclude whether the cast strand is of a sufficient quality suitable for its immediate next processing such as rolling. The previously developed solidification model BrDSM will be coupled with a newly developed mechanical stress-strain model. The crack criteria mentioned in this paper can be used as an optimization tool for the quality prediction of steel. Thus, this approach can be applied for the increase of the steel production due to the fast assessment of the strand quality based on the evaluation of critical crack conditions, which assure high quality steel. In the paper, the use of crack criteria as a quality predictor is outlined and the idea of the coupling between thermal and mechanical models is presented. The functionality of these models will be verified with data obtained from experimental measurements at a steel plant.

Low carbon steels are used in variety of structural states. One of the most used is fine grained dual or multi-phase structure with prevailing ferrite. Martensite/austenite islands forms rest of the structure. At least two of the phases - pearlite, bainite, martensite and rest austenite - occur in multi-phase steels. Main strengthening mechanisms are grain refinement and the hard phase content. The mostly ferritic soft matrix ensures sufficient plasticity. The constraining phenomena is cohesion of soft ferrite and the hard phase for the steel performance. Voids open upon deformation at the boundary between these constituents and lead to fracture. The difference in strength can be reduced by softening of the hard phase or by strengthening the ferrite. Copper alloying has possibility to do ferrite strengthening by precipitation. The experimental steel was subjected to controlled rolling to achieve dual- or multi-phase structure. Deformation in intercritical region resulted in fine ferritic matrix. Samples were subsequently quenched in water to transform remaining austenite into hard martensite or bainite. The delay between rolling and quenching gave opportunity for Cu to precipitate in freshly-formed ferrite and strengthen it. This approach leaves opportunity to gain precipitation strengthening in soft phase with no loss in hard phase strength. This is different from conventional quenching and tempering approach. The tempering acts also as precipitation hardening, but the tempering decreases strength of martensite in far higher rate than Cu precipitation can strengthen the ferritic matrix.

The steel casting temperature is defined as liquidus temperature plus the superheat temperature. In practice, it is the temperature measured in the tundish during the continuous casting of steel. Together with the casting speed and water settings in the secondary cooling, they are key process parameters of continuous steel casting, and have a decisive impact on the quality of cast strands. An increase in the casting speed causes an increase in the strand temperature during continuous casting [1-4]. The paper analyses the impact of two casting speeds on the cast billet surface temperature for the selected strands of a continuous steel casting machine. The experiments were carried out in the industrial conditions at ArcelorMittal Poland S.A. Dąbrowa Górnicza at a six-strand machine for billet casting. When casting a sequence comprising five heats of a high carbon steel grade, dimensions 160x160 mm, the temperature was continuously measured with two optical pyrometers. One measurement point was located within the secondary cooling chamber, whereas the other one was immediately after the exit of the strand from the chamber. Additionally, during casting, the temperature was measured on the selected caster strands with a thermographic camera. This paper will present conclusions on the performed measurements of the cast strand surface temperature. Determining a reliable and accurate impact of the superheat temperature on the strand surface temperature was possible thanks to the capacity of the steel ladle, which exceeded 300 t.

In small companies, the machining chips of their production are sometimes not processed. Therefore, their use is discussed in the article. Geopolymers are generally known as materials in which machining waste can be incorporated and they have been used for processing in geopolymer composites. The article is about geosilicate composites made from Baucis Lk filled with steel chips from machining of steel, basalt fibers, sand and SiO2. Furthermore, the paper describes the mechanical properties of these composites. At the same time, the paper describes composites and their mechanical tests filled with steel balls, sand, basalt fibers and SiO2.

The article presents a method of description the Al2O3 oxide layers structure observed by scanning microscopy. Unusual geometrical features of the structure enforce the use of non-standard techniques for their description. The authors propose the use the descriptors based on skeleton analysis and compare their effectiveness with morphological methods used in standard stereological descriptions of material structures. The analysis was carried out on a series of photographs presenting the top layers received at 303K and curry density 2A/dm2 and 4A/dm2.

Investigation results for segregation in terms of chemical compositions of various ordinary and refined ultra-low carbon FeSi75 ferrosilicon fractions have been presented. The subject of investigations was ferrosilicon obtained under industrial conditions after mechanical shredding and separation on 10-60 mm, 3-10 mm and 0-3 mm sieves. In addition, specimens of the individual ferrosilicon fractions were sieved on sets of laboratory sieves and fractions with limited granulometric compositions were separated. The investigations have confirmed a high level of elemental segregation in individual fractions, which is related to ingot solidification, a high-temperature range between liquidus and solidus of silicon-based alloys, movement of the solidification front towards zones with decreasing melting points and self-decomposition of silicon-based alloys. The most distinctive differences in chemical compositions between ordinary and refined ferrosilicons refer to light elements with a high affinity for oxygen: Al, Ca, which is associated with their oxidation during ferrosilicon transfer from the tapping ladle into the refining ladle. It has been confirmed that the mechanism of carbon removal during ferrosilicon refining occurs through floatation of SiC carbide inclusions in liquid metal bath mediated by CaO, Al2O3 oxides.

Modern devices for continuous casting (cc.) of steel - despite the shape of cross-section of cast billets, are equipped with electromagnetic systems for stirring liquid core inner the solidifying steel shell. Depending on the grade of cast steels, requirements for isotropy of chemical composition and properties along transverse and longitudinal cross-section of cc. billets, there are applied various schemes in placing systems inducing motions (rotation) of the liquid core. Based on the analysis of samples after etching, being cut out as continuous casting billets with square cross-sections, the following was stated: the surface of the equiaxed crystal zone, values of overheating and the total surface - on which internal structural defects can be observed in continuous casting of billets.

Design and construction issues of blowing systems, lances and nozzles for high-temperature reactors is a hot issue, which addresses not only metallurgy but also other industrial sectors. In general, the problems of design and construction solutions are mainly oriented on issues of reducing the consumption of materials and energy, which ultimately affect the investment and operating costs of the aggregates. Among the most watched indicators can be included, for example, a reduction of the blowing media consumption while reducing the energy intensity of the technical production process and increasing the degree of its use. According to the nature of the distribution in individual determinating quantities, we can, when e.g. considering a metallurgical heat aggregate, determine the dynamic effect of a outlet flow on the working space (a bath), a change in the blown gas concentration and the best position of the lance with a view to increase its lifespan while reducing wear on the lining of the respective heat aggregate. Using the outlet flows from the lances we can analyse the parameters significantly affecting the design of the lance and nozzles intended for the given purpose. These are, for example, the interaction of outlet flows in multi-nozzle lances, the length of the supersonic flow core, the angle of outlet flows extension depending on the geometry of the nozzles, the effect of the nozzles shape on the outlet flow parameters and shaping of nozzles. Knowledge of the basic properties of the outlet flow field from the lances and nozzles helps designers and engineers to meet demanding requirements for the blowing systems. This paper presents the distribution and structure of free streams from lances including their selected characteristics.

During the casting of heavier ingots, internal porosity occurs during solidification due to shrinkage of the cast metal. Porosity, or non-metal-filled areas, is up to several centimeters inside large ingots. The present work deals with the study of physical-metallurgical parameters of casting a large circular ingot, leading to the elimination of porosity. Which was done using the numerical software Magma 5.4. In order to find the most suitable casting conditions, the planned experiment method called DoE was also partially used. Particular attention was paid to casting speed with investigation and finding the most suitable casting temperature. For the basic variant cast in the Magma software, an initial investigation of the temperature field and voltage state during the ingot cooling in the numerical software Forge NxT 2.1 was performed.

The research work is a part of a larger study on identifying distribution of microparticles in the model liquid, which flows through a model of the tundish. Model (physical) testing is aimed at qualitative (based on visualization of the process) and quantitative assessments (performed by using the Abakus® Mobil Fluid laser microparticle counter). The article presents methodology on preparing microparticles for research tests and research test findings performed by using a laser microparticle counter. These tests were aimed at developing correct methodology for collecting samples in the tundish model, as well as, for their analysis by using a measuring instrument - a laser particle counter.

Rheological properties (dynamic viscosity, flow curves) of selected Fe-C-O-Cr alloys were experimentally investigated with the use of a high-temperature rotating viscometer Anton Paar FRS 1600. The viscosity of concerned alloys was measured during cooling at a rate of 2.5 °C/min. The maximum temperature achieved within experiments was 1,550 °C. The flow curves were recorded at this temperature to assess flow properties. According to their shape, all alloys exhibited non-Newtonian behaviour. At the temperature of 1,550 °C, the alloys behaved as shear thickening fluids. Given that viscosity depends mainly on the change in temperature and chemical composition, these aspects were considered in this work. Two series of model Fe-C-O-Cr alloys, which differed in chromium (0.924 wt.% - 4.795 wt.%) and carbon (0.042 wt.% - 1.378 wt.%) content, were selected to examine the influence of these elements. In the given concentration ranges, only slight dependence of viscosity on chromium and carbon content was found. Further, the viscosity increased exponentially with decreasing temperature at measured temperature intervals of 1,550 °C - 1,450 °C (1,350 °C).

Blast furnace gas, which is created as a by-product during the ironmaking, belongs to the less valuable fuels due to its low heating value. Due to BF gas parameters (high amount of gas and high content of CO), it is used as an energy source for the preparation of preheated air in the stoves or for the heating of industrial furnaces. In addition to low heating value, BF gas contains a large amount of dust. In order to prohibit reduction of the heating value of the gas, the gas must be cleaned by a gas cleaning system. Gas cleaning includes two phases: dry cleaning including dust catcher or cyclone and wet cleaning including scrubber, Venturi tubes and water separator (demister, droplet separator). The water separator is a cylindrical vessel with a diameter of 4 to 6 m and a total height of 25 m. During the gas flow in the separator, the water droplets and dust particles are trapped and deposited on the walls, and subsequently carried away in the form of sludge at the bottom of the separator. The main problem with gas cleaning in the separator is the location (shape, dimensions) of the inlet and outlet of gas to and from the separator. In order to achieve the maximum gas cleaning efficiency, a primary simulation of the gas flow through the separator was performed by numerical modelling in the CFD program ANSYS Fluent. In the following stages, optimization of the internal arrangement of the separator will be carried out.

Quantitative methods for determining the contamination of non-metallic inclusions (NMI) steel can be divided into metallographic, physicochemical or chemical. The quality control of steel in the metallurgical industry mostly uses a method in which their microstructure is observed on undigested destruction. In this way, the initial morphological characteristics of the NMI are revealed and their quantity, size and distribution can be estimated.
Presented work is a part of a larger project investigation on the distribution of non-metallic inclusions in liquid steel, carried out using both: physical and numerical modelling research techniques. Therefore, before performing the model investigations, determinations were made, including the disclosure of the inclusions morphology occurring in the steels along with their diameters.

In industrial practice, the charge is heated before plastic working and often reaches the furnace as "cold". This means that after leaving COS, for various reasons, it is not heated immediately, but stored instead. This not only causes the cooling of the charge, but also its oxidation in the atmosphere of the surrounding air. The paper presents the research methodology and discusses the results of adhesion measurements for the pre-oxidisedsteel charge.

In precise casting, the important parameters of multi-layered ceramic forms are their thickness and porosity. Defects, e.g. in the form of cracks, are determined visually. However, the remaining defects of the molds are not revealed before liquid metal pouring, which means that many defects may occur in the castings. The only way to determine the quality of molds in their volume seems to be non-destructive testing. One of the investigations is active thermovision, which involves observing temperature changes of the excited object using an external heat source.
The paper presents the results of thermovision tests of a ceramic form with the use of various heat sources used for its heating. A research stand equipped with a FLIR thermal imaging camera, heater, radiators and a laboratory dryer was used for the research. The results were developed using the dedicated FLIR Reaserch IR software. The presented results in the form of thermograms show the temperature differences of individual mold elements, which may indicate their differences in thickness and porosity. Thermovision can thus be used to eliminate defective forms from further stages of production, which translates into lower costs and higher quality of products.

The vast majority of metals and alloys used in technical practice are produced from a liquid state - a liquid metal. A most important phase transformation at steelmaking process is crystallization of steel (phase transformation of liquid steel from liquid to solid state) and process of own solidification of steel. This paper deals with study of phase transformations in steel during its solidification process. Specifically, it is focused on possibility of experimental refinement of liquidus (TL) and solidus (TS) temperatures of real industrially produced steel grades cast into mould by the direct thermal analysis method. Experimental study of steel solidification process is one of the ways to eliminate their possible impacts on quality of cast steel during solidification and to achieve required properties of steel without any additional treatment. Dozens of ingot steel grades by direct thermal analysis method on Netzsch STA 449 F3 Jupiter experimental system were analysed. A series of methodological experiments on pure nickel standard metal in order to generate a methodology of direct thermal analysis methods to study real steel grades and identification of the influence of selected experimental conditions were performed. Practical implementation of the Design of Experiment method (DOE) to system of evaluation of correctness of measured data was also realized. Comparison of the results of the parallel methods used for TL and TS identification was also performed. A result of the whole process of refinement of TL and TS temperatures represents a final recommendation of one proper TL and TS temperature of each studied steel grade.