Seznam abstraktů 2022: POSTEROVÁ SEKCE A

The subject of this paper is the analysis of phase transformation temperatures, specifically liquidus temperature (TL) for steel quality 41CrV. To calculate the temperatures, 66 different variants of the chemical composition of a given steel grade were compiled. The calculations were performed in the CompuTherm thermodynamic database using the Lever microsegregation model. The resulting temperatures are further supplemented by multiple regression analysis, which considers the dependence on the chemical temperature. The results of the regression analysis are used to design a regression equation to calculate the liquidus temperature. It is clear from the obtained results that the chemical composition of the steel has a significant temperature effect on the change in the calculated values.

The article deals with numerical simulations of filling and solidification of ductile iron castings produced in the MOTOR JIKOV Foundry a.s. The simulations we performed in the ProCAST simulation software. The research analyzes the geometry of the gating system consisting of two branches, with a total of 12 castings type YOKE A. Each of the branches contained a different gate shape. The operational partner defined operating conditions. Based on it, casting, solidification and stress states were calculated. An analysis of selected parameters was then performed to verify the influence of individual shapes of gates on the filling and solidification. Some differences in filling and solidification between the individual branches were found. However, these differences are not significant. The findings are discussed in the text of this paper.

Large volumes of slags are formed as by-products during the refinement of pig iron and steel manufacturing. Generally, the steel slag (steel furnace and ladle furnace slags) contains an appreciable amount of magnetic substances such as metallic iron and magnetic iron oxide, and thus, they can be recycled by wet magnetic separation. This work presented here investigates the effect of fine grinding for maximum recovery of iron from the steel furnace slags. Three kinds of slags, namely furnace steel slag (FS) containing 30 wt% of Fe2O3, ladle slag (LS) containing approx. 16 wt% and slag from desulfurization process (DeS) containing approx. 35 wt% of Fe2O3, were crushed, grounded and sieved under 0.045 mm for wet magnetic separation experiments. Results showed that the proposed magnetic separation process allowed to isolate 24, 18 and 42 wt% of magnetic fractions for FS, LS and DeS, respectively. The content of Fe2O3 in magnetic fractions increased from 30 to 44 wt%, from 16 to 46 wt%, and from 35 to 48 wt% of Fe2O3 in the case of the FS, LS and DeS, respectively. The fractions obtained by wet magnetic separation process were subjected to the chemical and phase analysis, the morphology of the particles was studied using scanning electron microscopy.

At present, cast iron foundries are facing increasing competition along with increasing demand for ductile iron. Therefore, there is no other way than to improve the technological processes of casting production and use other possibilities for more efficient management of their quality by means of 3D scanning of dimensional accuracy in critical production nodes.
The paper is based on the gained experience with the study of the potential of the method of non-contact 3D measurement of shape and dimensional accuracy of model devices and castings, which is to be used in optimizing the process parameters of gravity casting of ductile iron castings.
The ROMER Absolute Arm 7525SI portable laser measuring arm is used. The dimensional accuracy of newly manufactured models is monitored. Then, it can be confronted with the original 3D model. Subsequently, the models are scanned over their life cycles to identify critical dimensional deviations. All in connection with the control of dimensional deviations in molds, but especially in castings. The study of dimensional stability of the model, molds, and castings will allow monitoring the actual state in connection with the implementation of our own casting technology. As it turns out, it is possible to identify critical production parameters in terms of compliance with the dimensional accuracy of castings. The entire measuring system is connected to a professional program for measuring, dimensional evaluation according to the GD&T methodology, comparison with 3D objects, fitting, and export to a CAD system as STL 3D objects.

The presented paper deals with a numerical simulation of casting and solidification of a 65-ton ingot made of 25CrMo4 low-alloy chrome-molybdenum steel. The aim was to assess the steel melt flow, the risk of formation of microporosity and segregation according to Niyama or Suzuki criteria respectively, solidification. The numerical simulation was done for parametric analysis of solidification process in casting based on boundary conditions. Correctly set values of casting parameters like casting speed, casting temperature of steel, H/D ingot ratio are the essential precondition to minimize the defects of steel ingots.

Modifying liquids with nanoparticles is widely recognized as a practical approach for improving their heat transfer characteristics without significantly increasing viscosity. This work examines the effect of adding hematite and acid-leached blast furnace sludge particles on the rheological and thermal properties of deionized water. The investigated fluids were prepared by dispersing a certain amount of hematite and leached blast furnace sludge particles in distilled water using a sonicator. The modifier content in the liquid varied up to 5 wt%. Pristine iron oxides with particle sizes of approximately 5 micrometers and 50 nanometers were used as model systems. Leached sludge particles were deagglomerated for an extended period prior to measurement. The rheological behavior of the fluids was studied using an FRS 1600 furnace rheometer system designed for viscosity measurement from 1 mPa·s, and the specific heat capacity of hematite and leached blast furnace sludge was obtained by SENSYS EVO TG-DSC thermogravimetric analyzer equipped with 3D-sensor technology. Furthermore, the characterization of the prepared liquids was also supported by the results of SEM analysis. The results of this study provide the foundation for the use of leached blast furnace sludge as a potential heat transfer fluid.

The search for possibilities of slags utilisation, produced by various metallurgical plants, is relevant mainly due to its connection with circular economy and environmental protection. Using slags in construction or other fields of the industry is closely related to their properties and behaviour in contact with water. In the presented study, slags of different technological origins were studied: blast furnace slags (non-granulated and granulated), ladle slags, and steelmaking slags. Fresh samples of slags (max. 5 days old) and stored slags in landfills were taken from each type of slag. After sampling, the samples were adjusted to the same grain size ( 0.1 m) and their chemical and phase composition were determined. At the same time, aqueous leachates were prepared under defined conditions with different solid to liquid phase ratios. The conductivity and pH value of water leachates were measured. The concentrations of Ca, Al, Na, K, and Mg were determined using atomic absorption and emission spectrometry. The determined values were analysed in relation to the phase and chemical composition of individual solid slag. The kinetic study performed on the selected slags showed that the contact time of the slag with water may not always lead to the release of a larger amount of cations into the leachate.

Even in the production of steel, the quality of the final product depends on the quality of the raw material used for its processing. One of the raw materials that is put into steelmaking furnaces is also steel scrap. The purity of steel scrap is one of the main indicators of its quality, which in turn affects the quality of the final product leaving the steelmaking furnace, i.e. the quality of the liquid steel melt. Various technologies are currently used for the preparation and treatment of steel scrap used as charges for steelmaking furnaces. Baling technology is one of the most widely used technologies for scrap treatment nowadays. However, this technology has its pros and cons. The presented article will inform readers about the main characteristics of this technology, including a description of the three most widely used axial baling presses, used for the production of the biggest and heaviest faggots that serve as a charge for steel furnaces.

The article will deal with the determination of austenite decomposition temperatures using the available SW FactSage. The determination of austenite decomposition temperatures is one of the basic information that can provide the technologist and subsequently help change the properties of steel during steel processing. Austenite is one of the interstitial carbon solutions. Austenite is characterized by a cubic area-centered lattice and its structure is formed by regular grains. Various phases or structural components may form during cooling of austenite. Depending on the cooling of the steel, perlite, bainite and martensite may be formed. During the cooling of the steel, the area-centered lattice changes to a spatially centered iron lattice alfa. The aim of the presented work will be to determine the decomposition temperatures of austenite in 41Cr4 steel.

The paper compares classical models for determining the thermophysical properties of steels based primarily on empirical equations derived using linear regression methods with models created using machine learning methods. The selected investigated quantities include phase transformation temperatures, specific heat capacity, coefficient of thermal expansion. The results of both approaches are verified on the measured data by methods of thermal analysis such as differential scanning calorimetry, differential thermal analysis and dilatometry. The methods are evaluated both in terms of the accuracy of predictions and in terms of the adequacy of use for a specific purpose, or in terms of the complexity of creating and using the model.

Presented paper deals with the technology of production of ductile iron on industrial scale. Particularly, the material in question is EN-GJS-400-18-LT, which is suitable for castings intended for extreme conditions. Drawing on previous works, most attention has been paid to the implementation of the cored wire technology for modification and primary inoculation. Two technological options were compared, namely modification and primary inoculation by the pour method in the ladle and modification and primary inoculation by the cored wire using a twin-core feeder. Test samples within the inlet system of the moulds were cast during the pouring process to analyse the chemical composition, evaluate the microstructure and perform mechanical tests without interfering with the casting itself. The chemical composition was determined by optical emission spectrometry and combustion analysis. Metallographic analysis and microstructure evaluation were performed by optical microscopy and image analysis. Mechanical properties testing was focused on tensile test, impact test and hardness test. It was demonstrated that the foundry is capable of producing ductile iron of the required quality with the adoption of modern cored wire technology.

The practice of using electroslag remelting for processing spent non-compact tools from high-speed grade steel is considered. The advantage of the remelting process according to the two-circuit scheme for that purpose is demonstrated. The electroslag remelting process according to that scheme with a T-type mold has been developed and investigated at experimental melts. Spent drills and cutters welded into solid electrodes were remelted with obtaining a high-quality ingot and preserving the chemical composition. The outer diameter of the electrodes was up to 200 mm with the forming part of the mold 180 mm. It was found that the use of a T-type current-supply mold allows remelting with reduced power on up to 25%, and obtaining a high-quality ingot without surface defects at the same time. The dependence of the remelting rate on the filling coefficient as well as the possibility of conducting remelting exclusively on the current-supply section of the mold without loss of productivity has been established.

This paper describes the numerical modelling of solidification of ductile iron castings intended for the shipbuilding industry. Numerical simulations we performed in the computer software MAGMASOFT®. The purpose of numerical simulations was to predict solidification under defined casting conditions to verify whether the proposed production technology is adequate. Attention was focused mainly on the porosity occurrence in the casting, which is determined at a stated location using an ultrasonic test. Variants with different types of chills were simulated to determine their effect on the size of porosity. The results of these variants are presented in this paper. The variant with the best results was then recommended for production under operating conditions.

Metallurgical slag is a waste product of metallurgical processes and an important raw material, for example, in the construction industry or road building. The use of slag depends, among other things, on its chemical composition. Sulphur is an undesirable element in most metallurgical products. This paper deals with determining sulphur content in different types of metallurgical slags by two different methods - X-ray fluorescence spectrometry and combustion elemental analysis. Using standards, it statistically compares the results of the two methods, evaluates the repeatability of the measurements, and assesses the amount of sulphur in different types of slags.

Steels dusts from electrostatic processes, which are currently a problem in the ecological sense, is a rich but problematic carrier of many elements such as Fe, Zn, Mn, Cr. The existing recycling technologies, unfortunately, do not allow for their full recovery. The authors of the work decided to investigate the possibility of reducing the amount of waste to be deposited to the necessary minimum in the process of steel dust recycling.
The paper presents the possibilities of using a metallic alloy, which was one of the products obtained as a result of the processing of steel dust in a resistance-arc furnace. The main objective of the dust processing research was the management and selective recovery. The products of the process were zinc oxide, slag and iron alloy. Iron recovery from dust was determined at the level of 98%. The resulting iron alloy contained alloying elements such as manganese, chromium, and silicon in amounts enabling it to be used in the steel production process. The material can be used for the production of, for example, cast steel resistant to erosive and tribological wear.

The article presents the technology of manufacturing of precursors (special kind of filling mould material) for possibility to create a complex internal structure of the metallic foam casting. Due to the purpose for which the precursors are used, they must meet specific criteria. The material of the precursors must be sufficiently refractory to come into contact with the liquid metal, and the individual particles must also resist the movement of the melt within the mould. At the same time, however, in the context of this metal foam technology, it is essential that the precursors exhibit excellent collapsibility after casting - i.e. that they are easily removable from the resulting complex casting. Therefore, one of the conventionally used core mixtures appears to be the ideal material for the production of precursors. In this paper, the technology for the production of spherical precursors from a furan self-hardening mixture is described and verified. The motivation for the choice of material and all the sub-steps of the process - moulding into the core, tumbling, including the necessary accompanying tests of the mechanical properties of the core mixture being verified - are described.

The program Bi-Growth were used for simulating the formation of non-metallic inclusions (REM-O-S), and their growth. In the process of refining, the non-metallic inclusions are heterogeneous and create a mixture of different oxides or oxides and sulfides. These compounds are a consequence of the introduction of metals and ferroalloys in the form of complex deoxidants. The current work proposes a solution to the bi-growth of oxide and sulfide precipitates by focusing on the formation of precipitates after introducing REM to steel. Because high mixing energies are used during refining, the role of reactant diffusion into the reaction zone was neglected, and the system was treated as perfectly homogeneous in terms of chemical composition. Each precipitate was assumed to grow only on its surface, e.g REMxOy. In this case, the particle growth rate was found to depend solely on the concentration of all three components (REM,O,s).