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Flushing blast furnace by manganese ore was one of the important methods to recover the hearth inactivity caused by hearth accumulation. In this work, the properties and mechanism of the slag with different MnO content were researched, including the viscosity and critical temperature measured by rotating cylinder method, the mineral phase and microstructure confirmed by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and fourier transform infrared spectrometer (FTIR). The experiment results showed that during the process of flushing blast furnace, the appropriate and optimal MnO in the slag was 1,5 to 2,0 mas .%, the mechanism of flushing by MnO was that the tephroite whose melting point is low forms, the depolymerization of [SiO4]-tetrahedral structure caused by MnO addition also plays an important role in reducing the viscosity of the slag.

The longitudinal wedge mill (LWM) of a new design is proposed in this article. By using the MSC.SuperForge software product which designed for the stress-strained state of the billet when rolling strips from steel S235JR on the LWM. The STD 812 plastometer analyzed the influence of temperature-deformation processing modes on the microstructure of S235JR steel which rolled on LWM, the conditions for the formation of a fine-grained structure were noted. The rational modes of hot and cold rolling and their effect on the anisotropy of sheet metals from steel S235JR have been defined. It was proved in our work that compared with cold rolling, during hot rolling of sheet billets in the sheet plane it does not appear the significant anisotropy of mechanical properties.

The paper presents the results of corrosion resistance of Cu/Co multilayer systems fabricated by using the electrolytic method. The systems obtained were composed of layers differing in number and thickness, which was determined by observing the cross-sections of the samples using scanning electron microscopy (SEM). The measurements of multilayer system corrosion properties carried out in 3,5 % NaCl solution showed different corrosion resistance depending on system thickness. The microscopic observations revealed the effect of the aggressive environment on the Cu/Co multilayer systems manufactured, adopting various forms of corrosion degradation.

This article presents the results of hydrometallurgical studies of gold-bearing ore. The experiments were carried out on 2 parallel weighed portions with the analysis of products by assay (cake) and atomic absorption (solution) analyzes of gold. To determine the technological properties, tests were carried out on the direct and sorption cyanidation of ore samples using different material sizes, the concentration of the complexing agent in the solution and the preliminary treatment of the pulp with lime. The study of the sorption activity of the ore, as well as the dynamics of gold dissolution was carried out.

The regularities of non-uniform plastic deformation evolving on the Lüders bands are studied in a low carbon steel – austenite stainless steel bimetal via a digital image speckle method. The local strain distributions in the bimetal low-carbon steel base layer at the yield point stage are presented by the two strain localization bands that are similar to the Lüders bands. Analogous distributions arise at the yield point from the bimetal austenite stainless steel clad layer in the form of two strain localization fronts that are identical to the Portevin-Le Chatelier bands. Finally, the generation of strain localization bands is described in the context of a solid-state wedging model.

The publication consists on the situation in Polish steel industry in crises. The aim of the publication is to compare the volume of steel production in Poland in the periods of two crises that is the financial crisis from US in 2007-2009 and the COVID-19 crisis. In the quantitative analysis such data are compared: manufacture of crude steel and finished steel products, consumption of steel products, foreign trade in steel products. The changes in the steel production, consumption and foreign trade in two analyzed crises are helping to assess the depth of the crisis in steel industry.

The main aim of the paper is to characterize the proposed model of risk management system. Threats identification and risk assessment of the systemic character result in taking action directed on risk elimination, minimization or financing. Concept of the risk management system includes the following anti-risk activities concerning: knowledge, operating, experience and improvement. Those risk actions guarantee effective manner of risk management, which is of particular meaning due to the difficult situation of the European Union’s steel industry facing geopolitical, economic and environmental challenges. The model in question can be treated as a guidelines for proceeding in case of prevention and response to the potential, both strategic and operational, metallurgical risk.

The aim of the research was to analyze the influence of the flow behavior of liquid steel in a three-strand, asymmetric tundish when not all outlet openings are working. This problem was solved through physical modeling. The tests were carried out with the use of the water model of the continuous casting (CC) machine equipped with an asymmetrical, three-strand tundish model, made on a reducing scale. Modelling research concerned casting 110 x 110 mm square ingots. The obtained results of visualization tests and resistance time distribution (RTD) characteristics (F type) allowed to determine the method of mixing the steel (changes in mixing intensity were estimated) for the analyzed experimental variants.

The present work is aimed at studying the macroscopic localization of plastic strain in low-carbon steel AISI A283 Grade C. The evolution of macroscopically localized plastic strain at various stages of strain hardening is visualized via a Digital image speckle correlation (DISC) method. The processing of stress-strain curves of the steel samples enabled one to distinguish the following stages of strain hardening: the yield point, the parabolic hardening, and the pre-failure. The inspection of local strain distributions reveals that the parabolic work hardening is presented by a system of stationary plastic strain centers placed at equal distances. To perform a comprehensive analysis of local elongations from the parabolic work hardening toward the pre-failure stage, the total elongation components were measured at the strain centers. The average total elongation is found to be almost constant at the parabolic work hardening, but abruptly increases when approaching the pre-failure stage. The plastic strain instability is highlighted, as well, by the rising total elongation (amplitude) at the strain sites.

The publication presents the key trends in production, employment and productivity in Polish steel industry. Analysis was realized on the base of statistical data in the period from 2004 to 2019. The publication presents the results of statistical analysis and the dependences between analyzed trends. The end of analyses is 2019 year, so the actual situation in Polish steel industry is presented in the publication.

The thermal capacities of nanodimensional (nanocluster) cobalte (nickelite) - cuprate-manganites of lanthanum and sodium of LaNa2CoCuMnO6, LaNa2NiCuMnO6 were investigated with the calorimetry method on the IT-S-400 device in the temperature interval of 298,15 - 673 K. Based on the experimental data the equations of temperature dependence of thermal capacity of the studied compounds were set up. The temperature dependences of thermodynamic functions were estimated with using of measured values of thermal capacity and calculated value of standard entropy.

A complete thermodynamic modeling of chemical transformations during carbothermic reduction of barium and boron from oxides has been performed. It was shown that during the processing of charge with a high BaO: BaO:B2O3(3:1), barium carbide (BaC2), iron boride (FeB), and barium hexaboride (BaB6) are present as phase components in the smelting products, with the former predominantly noticeable. The data obtained allow us to conclude that it is possible to produce a new ferroalloy containing boron and barium.

Based on the measurement of viscosities and critical temperatures of CaO-MgO-SiO2- Al2O3-B2O3 slag system with various B2O3 contents, the slag with higher than 15 mas. % Al2O3 content has the lowest critical temperature and the widest solid-liquid coexisting region at about 2,0 mas. % B2O3. Furthermore, the X-ray diffractometer (XRD) result verified that bechilites whose melting point are low forms. Raman spectra revealed that the effect of network forming on viscosity is smaller than the effect of bechilites, which leads to the slag viscosity decrease with B2O3 addition. Base on the above research, so ludwigite can meet the requirements of a BF welding flux to decrease the critical temperature and improve the fluidity of the high Al2O3 slag.

The article deals with studying the properties of refractory masses made by two-stage pressing under industrial conditions in order to increase strength and slag resistance of chamotte bricks due to increasing density by ensuring uniform porosity throughout the volume of the product. Changing porosity when firing is less significant than changing porosity when pressing, therefore, the structure of the product is corrected by the initial mass of components.

Experimental research with synthetic mixtures imitating typical ferroalloy slags is described in the paper. Samples imitating slags of high-carbon ferrochrome, ferrotitanium and high-carbon ferromanganese were made of analytical grade reagents by mixing and melting in a resistance furnace. Slag viscosity was measured with electric vibratory viscometer in the temperature range of 0 – 1 800 °C. Based on research results it is recommended to use higher basicity slags together with specific additions (fluxes) reducing slag’s viscosity and melting point.

Hot blast stove air supply is a continuous process, and the working conditions are very complex. The improper data processing of the traditional Markov prediction will easily lead to the deviation of the results. In this paper, a hybrid intelligent optimization algorithm is used to pre-process the data sources and obtain reasonable data. The experimental results show that the algorithm has good convergence and stability. The improved Markov predicted value is close to the actual value and accords with the target.

Based on the software Visual-Environment, Finite element method (FEM) was performed on the dissimilar butt-joint between Q345 and 2Cr13 steel aiming at the welding residual stress. The main contents in the paper were different current intensity was applied to modeling the welding process of Q345/2Cr13 dissimilar steel and the law of residual stress field were discussed. Based on the result, different current intensities have little effect on the lateral residual stress, while the longitudinal residual stress and the initial and end of the weld have a great influence. The physical properties of the dissimilar plates lead to uneven distribution of residual stress, and the current intensity should be smaller.

This paper reports the study of silicon-doped diamond-like carbon coatings a-C:H:Si prepared by Plasma-Assisted Chemical Vapour Deposition (PACVD) on 100Cr6 steel. Surface morphology and elemental composition were determined with the use of Scanning Electron Microscopy (SEM) / Energy Dispersive Spectroscopy (EDS). Surface topography measurements were performed using Atomic Force Microscopy (AFM). The scratch test assessment of the influence of a-C:H:Si coatings on mechanical properties was based on the measurements of nanohardness and adhesion to the substrate. The results show that silicon-doped diamond-like carbon coatings a-C:H:Si are characterized by a uniform surface structure, high hardness and good adhesion to the substrate.

This paper demonstrates the research results on flotation of the oxidized copper ore with the preliminary sulfidization by a modified reagent. The planning method of an experiment investigated the influence of various factors on flotation process of the oxidized copper ore with a preliminary sulfidization by the modified reagent. Dependence of copper extraction in a flotation concentrate was received from consumptions of sulfidizer and collector, pulp agitation time with a sulfidizing reagent. A mathematical model of process was received.The optimal conditions of flotation providing the copper extraction in flotation concentrate at a level of 85,12 % were determined with this model.

The surface of AISI 316L was treated by shot peening at different shot durations. Shot peening variables in this work are shot durations for 0, 4, 10 and 20 minutes, with compressor pressure at 8 kgf/mm2, steel balls with a diameter of 0,6 mm and shot gun nozzle diameter of 5 mm. The purpose of this research is to investigate the shot peening effect duration on surface roughness, hardness, and fatigue-corrosion characteristic of AISI 316L in 0,9 % NaCl solution. The results show that the duration of shot peening can affect the improvement on surface roughness, hardness, wettability and fatigue-corrosion life of AISI 316L.

In the work there have been calculated the values of enthalpies for a number of ternary compounds and carried out triangulation of the Fe–Al–Si system. The main areas of the compounds crystallization have been determined in relation to industrial compositions of ferrosilicon-aluminum. There has been carried out the analysis of possible causes of some alloy compositions self-grinding and recommended compositions with guaranteed stable physical characteristics.

On the occasion of the 80th birthday of Acad. Ilija Mamuzić for 35 years as Editor-in-chief of the journal Metalurgija, 42 years as the President of the Croatian Metallurgical Society, the goal of this article is to give an overview of his life and achievements. Rarely has an individual not only in Croatia but in the world had influence on his profession as I. Mamuzić his own – metallurgy. He was involved and worked in all metallurgical areas: science, profession, education, organising of Faculty or Institute, Symposiums, editing, popularisation and responsability for the profession and he is an author of the history of metallurgy on the territory of Croatia, during 6000 years. In Croatian Bibliografphy base CROSBI by registration, accepted and on print will be 925 works. By the same conditions in foreign bibliography ORCID 800 works. He participated even in the education of 47 generations students (1963–2010. He received 75 various acknowledgments etc. He is an exceptional personality as individual, scientist, pedagoge, and professional. Ilija Mamuzić has achieved plenty, not because he had or was obliged to, but because he wanted to. He didn’t work to live, but to live to work.

EDM is effectively used in many application like aerospace, turbine, medical and etc., due to its non-contact process between work piece and tool. In this study, the important machining process parameters such as peak current, pulse on time, pulse off time and fluid pressure are inspected that incitement to distress the performance of the operation Material removal rate (MRR) and Tool wear rate (TWR). Subsequently tool geometry and materials that are predominantly affect the work piece response factor as Surface roughness (SR). Hence copper electrode with coating of brass material and different tool geometry are also considered. PH15-5 stainless steel precipitated hardening steel was machined up to 5 mm depth with EDM die sinking machine using 27 number of experiments designed.

The paper presents the results of tests carried out on grey cast iron obtained in laboratory conditions. Cast iron EN-GJL-200 was enriched with REM at 0,3 % wt. in relation to the weight of the charge metal. The presence of REM was found only in some elements of the structure, i.e. in ferrite and in precipitations. An 18 % decrease in the coefficient of friction was observed for REM-modified cast iron as compared to the base cast iron.

The Gleeble - 1500D thermal simulator was used to conduct the isothermal compression test of 21 - 4N heat-resistant steel under the T range of 1 273 - 1 453 K and ε̇ of 0,01 – 10 s-1. Using the obtained stress - strain data, various parameters of the modified Zerilli-Armstrong (m – Z - A) model were calculated. The constitutive equations of 21 - 4N heat-resistant steel based on the m – Z - A were established. The m – Z - A model can well describe the rheological behavior of 21 - 4N heat-resistant steel. The simulation process can be completed successfully, indicating that the established models can be used for the simulation study of thermal deformation of 21 - 4N heat-resistant steel and are correct. The results can provide some important basic data for the simulation of 21 - 4N heat resistant steel on plastic deformation process.

The article states new results of the theoretical and applied research on prevention of chatter in stands of continuous cold rolling mills. It was found that chatter occurs under those process conditions, which involve violation of a condition of strip rolling with tension because of ongoing change of the process state, when the process proceeds now with tension and now with pushing because of variation of strip volumes per second in a negative or positive range of values. It is demonstrated that it is possible to influence effectively the difference of strip volumes per second and prevent chatter by decreasing reduction in a stand subject to chattering and simultaneously increasing reduction in adjacent stands, and also by changing the ratio of rolling speeds in these stands of the mill. This has led to development of process conditions for thin steel strip rolling on the 5-stand mill 1700 of PAO Severstal, enabling rolling speed increase and process stabilization.

The object of the research were bends of steam pipelines 10CrMo9-10, in which the highest frequency of failures caused by material cracks occurs. The forecast of pipeline operation time was determined on the basis of results Rm. Applying the principles of statistical inference to forecast the trouble-free operation time of steam pipelines, mathematical models were selected that in a highly statistically significant way most reflect the actual reduction in Rm over time and determine the limit value of material exhaustion to avoid failure.

The problem of natural environment pollution, due to the increase in industrial activity, is of interest to an increasing number of countries around the world. The main purpose of waste policy should be the recycling of valuable raw materials, and thus the protection of the natural environment. The steel industry is an industry in which, alongside of mining and energetics, large amounts of waste are generated. These wastes in the EU are classified as thermal wastes and hazardous wastes. New technologies are being developed in many countries to reduce the amount of waste deposited. This study presents the results of research of iron-containing wastes in terms of their environmental impact in the case of storage, the possibility of iron recycling through the process of reducing iron oxides and the metallisation grades of selected wastes. The conducted research indicates the directions of waste management friendly to the natural environment.

Blister copper smelting in a flash furnace results in the generation of slag with a Cu content greater than 15 percent. In the process of reduction in an electric furnace, coke or coke breeze is used as a carbon-bearing material. The presented work shows the results of studies on the reduction of the slag with a carbon flotoconcentrate as a substitute for coke breeze. The microstructure, chemical composition and phase composition of slag samples were analyzed. Based on the results of chemical composition of the Cu-Pb-Fe alloy and the post-reduction slag, it was shown that carbon flotoconcentrate might be considered as an alternative for currently used reducers.

Book of abstracts of the 14th International Symposium of Croatian Metallurgical Society - SHMD '2020, Materials and metallurgy held in Šibenik, Croatia, June 21-26, 2020. Abstracts are organized in four sections: Materials - section A; Process metallurgy - Section B; Plastic processing - Section C and Metallurgy and related topics - Section D.

This research focuses on improving the hardness and wear resistance of ZrSiO4- SnO2/Cu10Sn composite. In this investigation, the SnO2 tailing sand dominated by ZrSiO4 and SnO2 was used for the reinforcement. The Cu10Sn composites with 0, 5, 10, 15 and 20 weight % SnO2 tailing sand were produced using double action warm compaction followed by sintering. The results show that the highest hardness value and the lowest wear rate of the composites were achieved by adding 15 weight % of SnO2 tailing sand. Moreover, the wear rate of Cu10Sn matrix composite exhibits a decrease significantly with an increase in the amount of SnO2 tailing sand due to the presence of hard particles.

A magnesite-based desulfurizer was used for removing sulfur from hot metal by means of high temperature electrolysis technique. Through carrying out orthogonal factorial experiments it was found that the effect of the electric current on desulfurization is more significant than that of temperature. Results of single-tailed test show that when the temperature is constant, the desulfurization rate first increases with the increase of the current to a maximum value, and then, after dropping to the lowest level, gradually increases again as the current further increases. Finally, an optimum experimental condition is obtained as temperature of 1 400 °C and current of 1 A, achieving a desulfurization rate of 47,6 wt./% /min, which corresponds to a desulfurization efficiency of 62,6 %.

AISI 316L is one kind of implant materials due to its excellent mechanical properties and corrosion resistance. However, some of their mechanical and surface properties must be improved to a higher level of cobalt-based alloys and titanium properties. Shot peening is a surface treatment that improves properties on material surface. In this research, the effects of shot peening duration (0, 2, 4, 10, 20 and 30 min) on surface hardness, roughness, wettability, and corrosion in 0,9 % sodium chloride were investigated and discussed. According to the experimental results, it was found that shot peening increases both surface roughness and surface hardness compared to untreated sample. Furthermore, shot peening can reduce contact angle and corrosion rate after 2 minutes.

In this paper, the macroscopic observation and chemical composition analysis of the third crankshaft journal have been carried out. Moreover, macroscopic observation, chemical composition analysis and metallographic analysis were carried out, and were compared with the journal with cracks and without cracks. Based on the experimental results and the causes of crankshaft neck cracks, it can be concluded that the crack form of crankshaft goes along with the grain brittle direction.

This article presents a new methodof obtaining the sheet steel with ultrafine-grained structure. The ultrafinegrained structure is obtained by implementing severe plastic deformation developed by a spiral roller. This paper investigates the stress-strain state (SSS) of the workpiece during rolling in a spiral roller and a longitudinal wedge mill (LWM). A rational technology of rolling aluminum alloy 1050 was developed and tested under the laboratory conditions. It was proved that the system achieves an equilibrium state by diffusion along the grain boundaries accelerated by the flow of vacancies formed during the deformation. It has been established that rolling aluminum alloy 1050in the spiral rollers and LWM leads to an increase in the strength and plastic properties of the sheet metal.

In the twin-roll casting process, how to accurately control the molten metal pool level is a key problem to produce high quality strip. In this paper, the mathematical model about the pool level control is set up based on the process characteristics. Meanwhile, the limitations of the traditional PID control strategy are analyzed owing to the real-time change of the roll gap and roll speed. Furthermore, the neural network is applied to adaptively optimize the PID control parameters and the simulations show the neural network PID strategy can precisely control the molten metal pool level in twin-roll casting process under the condition of multiple factors interfering.

The activities of FeO, V2O3 and MnO in quaternary systems V2O3-FeO-SiO2-MnO have been investigated. Investigation of thermodynamic data of this slag system, aims extracting vanadium, from the waste and obtaining Mn-V alloy with potential industrial application. The oxygen potential in the systems was determined by the Electromotive force (EMF) method. The solid electrolyte was ZrO2 (CaO), and the reference electrode - a mixture of Mo/MoO2 was used as a galvanic cell. The Gibbs free energy and the activity were calculated based on experimentally obtained oxygen potential. On the basis thermodynamics of the calculations, the experimental results revealed the possibility of obtaining a complex alloy from the manganese concentrate and the vanadium waste catalyst.

A procedure was developed to calculate the position of lines of monovariant phase equilibria for crystallization areas of congruently melting compounds through the dissociation degree of a chemical compound.The relevant mathematical apparatus was recommended to describe analyticallythe lines and surfaces of crystallization phases using the Bjerrum-Guggenheim coefficient. The iron-silicon phase diagram demonstrated that the osmotic coefficient of Bjerrum-Guggenheim (its linear dependence) can be as an assessment criterion of the composition of melts.

In this paper, the temperature field and heat transfer stress mathematical model of the unidirectional solidification ingot of the traditional water-cooled chassis and the improved water-cooled chassis are established, and the numerical simulation calculation of 45 tons unidirectional solidification ingot is carried out by using the finite element simulation analysis method. The results show that adding proper forced cooling conditions to the bottom of ingot is beneficial to the balanced advance of the solidification front of molten steel. The improvement of the bottom forced cooling scheme obviously shortens the solidification time of the ingot. The water cooling at the bottom of the ingot is adapted to the air gap distribution to achieve uniform air gap distribution. The ingot solidifies evenly in the longitudinal direction to avoid bottom warpage.

Reasonably determination of the rolling temperature of the cross wedge rolling (CWR) is the key to o btain the qualified surface of the aluminum alloy shaft parts. In this paper, the 6 082 aluminum alloy shaft parts with different section shrinkage rate between 43,75 % and 64 % are taken as examples. The thermal-deformation coupling finite element model (FEM) is established to analyze the effect of the process parameters on the temperature field. The influence law of the temperature field on the surface quality in CWR process is obtained and verified by experiment. The results provide theoretical and experimental basis for temperature selection and surface quality improvement.

Untreated alloy in cast-samples showed that hardness increases with increased pouring temperatures, while for samples after heat treatment (T4 and T6), the hardness value decreased with increased pouring temperatures. Tensile strength generally increases with heat treatment T4 and T6, but the influence of the temperature on the pouring tensile strength values initially presents high then decreases, then increases again. Impact energy increases after heat treatment T4 and T6. The distribution of precipitates in grain structure results in improved material properties such as hardness, tensile strength, and impact strength compared to when precipitates gathered at the grain boundary.

The paper presents results of the analysis of selected indicators used to assess the efficiency of blast furnace operation: running time operation, plan fulfilment, unit daily production of pig iron and the influence of these parameters on monthly pig iron production and intensity of coke combustion. The study was carried out in cooperation with a Blast-Furnace Department of a Polish steelworks and was based on the results coming from this Department. The analysis covers the period of one calendar year.

These days, ensuring the high quality of thin products (0,6 – 2,0 mm) is the most promising direction for the development of hot-rolled strip production. Hot-rolled strips can be used in place of a more expensive cold-rolled strip. The effect of cooling modes on quality of hot-rolled metal was observed heating at different temperature, the degree of deformation was observed after cooling by water-air mixture. It was observed that the micro hardness of the samples decreases and the amount of structurally free ferrite increases by decreasing the cooling time and increasing the temperature.

Analysis of technological solutions on complex processing Ekibastuz coals ashes displays efficiency of complex alkaline technologies. However their significant drawback is the necessity to utilize big volumes of alkaline-silicic solutions. This research demonstrates possibility of their rational utilization by using natural raw diatomites to obtain formed and pelleted foamed glass widely used in construction industry as a heat-insulating material. Based on the data from scientific literature and their own research the authors suggest an improved scheme of complex processing Ekibastuz coals ashes.

Titanium sponge process flowchart includes the following main operations: concentrates reduction melting (example for concentrate from the Obukhovskoe field, the Republic of Kazakhstan), chlorination of obtained titanium slug, refining of industrial tetrachloride and ma gnesium-thermic reduction of titanium tetrachloride purified from any impurities. This paper presents the results of material flows balance studies and quality analysis of the technological products. It is shown that stillage bottoms pulp feed on the melt mirror of potassium chloride electrolyte with a speed less than 2,5 t/h excludes the temperature overshoot within 570 - 620 °C of titanium tetrachloride vapors sublimation. Chlorinator melt bubbling in the process initial period with dried air (nitrogen) can significantly improve the quality of titanium products.

The paper presents the results of a thermodynamic diagram study of oxide smelting products from the processing of chromite and titanium raw materials in order to determine their most technologically advanced compositions, allowing for rational use of raw materials and energy resources. The reliability of the effectiveness of these developments was confirmed by tests carried out on a pilot industrial and industrial scale.

Based on the analysis of the fracture of a certain type of QT800-2 nodular cast iron crankshaft, the cause analysis of the fracture crankshaft is discussed based on macroscopic inspection, metallographic analysis and mechanical properties test. The results show that the shrinkage and surface cracks in the casting process are the main factors leading to the fracture of the crankshaft, and the process improvement measures for the manufacturing process of QT800-2 nodular cast iron crankshaft are put forward.

Thermal compression test temperature ranged from 800 to 1 200 °C, the strain rate ranged from 0,01 to 10 s-1, and the deformation degree was 60 % of engineering strain, the deformation behavior of 42CrMo gear steel was studied. As the deformation temperature increases and the strain rate decreases, the stress decreases significantly. By polynomial fitting the relationship between strain(0,05 – 0,9, at intervals of 0,05) and material constants, the straincompensationed Arrhenius constitutive equation for 42CrMo gear steel is established. The correlation coefficient between the experimental data and the predicted data reached 0,9925. This shows that the Arhenius constitutive equation has high accuracy in predicting steel 42CrMo for gear.

In this paper a new method is proposed for solving an optimal control problem using the complex model of a reheating furnace that was used to get reference values for the optimal zone temperatures. Validation before using a complex simulation model in optimal control procedure showed that the model worked well for the prediction of thermal behavior. The aim of optimal furnace temperature control is the minimisation of fuel consumption and the minimum deviation between desired and final steel block temperature profiles. The optimisation procedure and some results are described.

The analysis of steel production volume in relation to the level of capacity utilization in Polish steel industry is the content of this publication. This publication is based on numerical data on the volume of steel production and the degree of capacity utilization. The time range of the analysis covered the period from 2000-2018, and the data presented concerned annual periods. The analysis of steel production volume in the context of the degree of capacity utilization (production capacity) is an important part of the productivity assessment. The choice of the steel industry as a research object was dictated by the importance of steel production volume for the development of steel users’ markets. The main purpose of the work was to reveal the connections between the volume of steel production and the level of steel production capacity involved in Polish steel industry.