Seznam abstraktů 2023: SEKCE A - POKROKOVÁ VÝROBA ŽELEZA, OCELI A LITINY

The purpose of the research in hot metal desulfurization process is to identify the main process parameters affecting the final effect of desulfurization. Therefore, the measurable effect of the actions taken should be the improvement of the quality of control. One of the important elements of the project was the physical modelling of the phenomenon of mixing the metal bath during desulfurization. For this purpose, a physical model of an industrial stand was built on a scale of 1: 10, in which measurements were carried out for various variants of the process implementation - parameters such as the flow of gas transporting reactants, the height of the lance position and its internal diameter were regulated. On the basis of the obtained results, the real impact of the method of supplying the desulfurizing agent on the time of complete mixing of the metal bath was assessed. The conducted research became the basis for developing a model of mixing hot metal during desulfurization. Thanks to the availability of both technical and process data of the metallurgical reactor as well as qualitative data of hot metal, it is possible to develop a comprehensive model of desulfurization. The proposed model was based on the tank theory. In the future, this solution will make it possible to simulate the desulfurization process, taking into account all relevant parameters, during the process in a time shorter than the real desulfurization time.

Small punch test is an advantageous method for evaluation of mechanical properties of components especially in cases, where it is technically difficult or even impossible to obtain enough bulk material for standard tests. Therefore, the method is very well applicable in power industry, for example in residual lifetime assessment of critical parts of components and structures after long-term operation. The testing material is sampled using special sampling device that ensures no component damage and the amount of material being sampled is so small that no component repair is necessary after sampling. Small punch testing is viable not only for evaluation of mechanical properties, but also microstructural and chemical analyses can be performed from the obtained sample and complex actual material characteristics of components can be assessed. MATERIAL AND METALLURGICAL RESEARCH, Ltd., has more than 20 years of experience with small punch testing in industrial applications and several examples of its application for analysis of material properties and residual lifetime assessment are presented in this paper.

Considerable amounts of dust are generated as by-product in steel production in an electric arc furnace (EAF). Dry off-gas de-dusting systems, usually dust filters are used to collect these dusts from the off-gas. In the design and operation of storage and transport equipment for the collected dusts the flow properties of the dusts play an important role. The properties relevant for particle flow - angle of internal friction, flowability, wall friction angle, bulk density, particle size, angle of repose and time consolidation - of EAF filter dusts originating from seven steel mills were investigated. The results showed significant differences between the EAF dusts from different steel mills. The relations between the various parameters are shown and consequences for the design of EAF dust silos and conveyors are discussed.

The influence of sulfur on both slag and melt is very important in steelmaking. This is especially true for high-sulfur machining steels. Machinability is achieved by alloying high sulfur contents, above 300 ppm. These are steels that form small chips and shavings during mechanical processing by cutting, which is more appropriate and favorable for both the workpiece and the processing tool and machine. However, the secondary steelmaking slag is typically designed for desulfurization. This means that the sulfur content rapidly falls after sulfur additions. This is especially true for high machinability stainless steel grades where S contents can exceed 1000 ppm. This causes the sulfur wire yield to vary greatly in each charge, making the process unreliable. Some aspects of understanding the interaction between the steel melt and slag and the effect on casting are presented in this work. Based on industrial charges, we analyzed the yield of sulfur additions and the influencing factors on the efficiency of the sulfur addition. Melt and slag samples were analyzed. Slag entrapment during ingot casting was linked to the high sulfur contents, and laboratory experiments were conducted to estimate the changes in the slag due to the high sulfur content.

Recycled Al-Si alloys are an important raw material for sustainable and green production due to their low energy consumption. However, various impurity elements, such as Bi, coming from the scraps or recycling process can deteriorate the mechanical properties of the final product. After the limitation of Pb-containing products due to their toxicity by the European Union, Bi content in secondary Al-Si alloys has continuously increased. Bi can interact with other alloying elements affecting the final microstructure and consequently the tensile properties. On the other hand, several investigations about the effect of lanthanide addition into the Al-Si alloys have been performed in recent years. Some lanthanide elements can refine the primary α-Al and modify/refine the eutectic Si crystals. The aim of this work is to study the influence of Bi as a trace element over Gd-containing Al-7Si-0.3Mg alloys. Alloys containing 200 ppm Bi as impurity have been treated by Gd. Two-thermocouple thermal analysis and microstructural investigations were performed to investigate the changes in the solidification sequence and microstructure of the alloys. The results demonstrated that Gd is ineffective on the refinement of α-Al dendrites while it decreases the growth temperature of eutectic reaction and refines the eutectic Si crystals of the Al-7Si-0.3Mg alloy. Unlike traditional eutectic Si modifiers, such as Na and Sr, the efficiency of Gd addition on the eutectic was not influenced by Bi impurity. No Bi/Gd interaction was detected. Additionally, SEM investigations showed that Bi-rich phases are located in the growth front of the GdAl2Si2 phases.

The article deals with the investigation into steel flow characteristics using three different shapes of impact pads in a 6-strands tundish.
The key purpose of the investigation presented in this article was to improve flow characteristics and steel temperature distribution across the whole tundish space with the aim of preventing erosion of the lining in the upper section of the inflow area. Simulations were realized for various types and shapes of impact pads. The steel flow in the tundish was evaluated using vectors, contours, streamlines, RTD curves, and the values of minimum and maximum residence times.
The results indicated that the application of different shapes of impact pads may improve the flow characteristics in terms of homogenizing residence times for the individual outlets and adjusting the proportions of the mixing zones, which has a significant effect on thermal and chemical homogenization, the capacity to refine steel, i.e. purify it from non-metallic inclusions and erosion of the tundish refractory lining.

The presented research was focused to optimize the conditions in a T-shaped three-strand tundish to minimize the intermix zone during steel casting. The intermix zone occurs when different steel grades are cast in a single sequence without interruptions or restarts, resulting in mixing of old and new steel grades in the tundish and the continuous cast billet. To achieve maximum steel casting efficiency, the conditions of the tundish were optimized to minimize the intermix zone. The study is focused on investigating the starting height of the steel level in the tundish before opening the pouring ladle and the duration of the steel level in the tundish after opening the pouring ladle for a specific time period. The SimCont physical model was utilized to realize the research.

In this work, was studied the possibility of producing nickel-free stainless ODS steel using liquid metallurgy. In order to investigate the injection of dispersed yttrium oxide into steel, 5 different methods under induction vacuum melting conditions were tested. The aim of the study was to approbate the possibility of mechanical introduction of yttrium oxide powder into the martensitic-ferritic matrix of AISI 410 steel by two methods, or the possibility of oxidation of yttrium metal by 3 methods (from iron oxide, from residual oxygen in the furnace chamber, from injected oxygen into the furnace chamber). As a result of the performed work, the highest yttrium concentration of 0.0552 ppm from the oxidation of metallic yttrium during the reduction of iron oxide was recorded.

During High Carbon ferromanganese production, the slag formation plays an important role on the overall process. Though the slag formation starts in the prereduction zone, silica may be reduced depending on the reducing conditions. Stronger reducing conditions lead to some silicon reporting to the metal. The influence of Al2O3/SiO2 ratio on the slag in the reduction zone was investigated. The variation of A/S ratio was obtained by adding silica while alumina was kept unchanged. For better homogenization the ore, flux and coke were mixed and milled to -75 microns for 15 minutes. Bench tests scale were conducted using an alumina tube furnace that was programmed at different temperatures. A graphite crucible placed into a silica crucible; the crucible was placed in the hot zone of the furnace. To create more reducing conditions, carbon monoxide was blown into the furnace at a flow of 0.5L/min. Argon was blown into the furnace from room temperature to 600oC then switched off to allow only carbon to react with the oxide ore. The furnace was kept for two hours at the aimed temperature and switched off until the furnace reached 600oC then argon was blown into the furnace down to room temperature. XRD, XRF, SEM and EPMA were used for characterization. An alumina tube furnace was used for the experiments. The temperatures used were 1400, 1450 and 1475oC. The influence of the A/S ratio on phases that formed and the impact on the slag formation in the reduction zone were assessed.

The process of obtaining ferrovanadium by the electro-aluminothermic process has been studied. This process involves reducing vanadium oxide with aluminum in a slag layer in an electric furnace, using iron additions to achieve a desired alloy composition and lime to flux alumina. The electro-aluminothermic process is more controllable than the aluminothermic process. The chemical composition and viscosity of the slag play a critical role in the smelting results, which can be optimized by adjusting the charge composition and temperature. Is also important to achieve as complete separation of metal and slag as possible. By changing the composition of the charge, the electro-aluminothermic process allows producing ferroalloys ranging from 40% to 80% vanadium. An essential advantage of this process is relatively low equipment investment, simple raw material preparation requirements, and high product quality. Waste-free production can be implemented based on this process.

The identification of the wear mechanism of the refractory lining of the basic oxygen furnace is a prerequisite for the optimization of the steelmaking process. Knowledge of the way in which a given factor acts on the amortization of the refractory lining is closely related to the development of technological procedures serving to limit their influence. The results of the analysis of the mechanism by which the thickness of basic oxygen furnace refractory lining is reduced during the campaign can be applied to the development of new refractories with more suitable chemical composition and physical properties. In this respect, the determination of a balanced consumption of gunning materials is also very important, since the expenditure on repair mixtures has a major portion of the total financial cost of the campaign. By determining the optimum consumption of gunning materials, it is possible to define the duration of the basic oxygen converter campaign during which the entire steelmaking process is financially viable for the producer. On the basis of the literature, the mechanism of wear of refractory lining has been developed. Temperatures from 1300 °C to 1700 °C, which can occur during the steelmaking process in the basic oxygen vessel, were considered. The wear process was divided into logical steps. In each step, the most probable course of the sub-processes and the products of the chemical reactions are described based on thermodynamic data.