Steel Production Technology Research Articles

Analysis of Thermophysical Properties of Electro Slag Remelting and Evaluation of Metallographic Cleanliness of Steel.

Improving the competitiveness of steel companies is linked to sustainable, quality-compliant steel production. Therefore, new steel production technologies contributing to increased cleanliness of steel are continuously being developed and optimized. One way to achieve a high steel quality is to use electro slag remelting (ESR) technology. In this paper, the principle of ESR technology and the importance of fused slags for optimizing the process are outlined. The aim of this work was to analyze the main thermophysical properties of steel and fused slags used in the ESR process. Determination of the properties of steel and slags was performed using the FactSage calculation software, which involved the calculation of the liquid and solid temperature of steel and slags, the calculation and construction of quaternary diagrams, and the calculation of viscosity. The resulting quaternary diagrams revealed the substantial influence of chemical composition on melting temperatures of slags. In order to validate the acquired results, a CrNiMoV-type steel was subjected to investigation of its metallographic cleanliness and evaluation of its mechanical properties; the ESR process was shown to significantly improve the cleanliness of the steel and improve the mechanical properties of the steel compared to its cleanliness and quality when produced via vacuum degassing (VD) technology. During the ESR process, the average size of non-metallic inclusions was reduced from 20 μm to 10 μm, and the maximum size of non-metallic inclusions was reduced from 50 μm to 28 μm. The mechanical properties of the steel produced using ESR technology were impacted as follows: the ductility increased by 10%, contraction increased by 18%, notched toughness at 20 °C increased by 46%, and at -40 °C (respectively -50 °C) it increased by 30%.

Термомеханическая прокатка при производстве обсадных труб (обзор исследований)

Introduction. The modern oil and gas industry requires the development of high strength materials for well casing. Changes in rolled steel production technologies are one of the urgent tasks. Reducing the cost of high quality steel well casing is becoming a major challenge for the oil and gas industry. Multiphase microstructures containing acicular ferrite or an acicular ferrite-dominated phase exhibit good complex properties in HSLA steels. This paper focuses on the results obtained using modern methods of thermomechanical rolling. Results and discussion. This work analyzes the characteristics of thermomechanical rolling technologies and its impact on the microstructure of rolled steel for well casing. It is shown that predicting mechanical properties based on the microstructural characteristics of steel is complicated due to the large number of parameters involved. This requires an optimal microstructure of the steel. A satisfactory microstructure depends on several factors, such as chemical composition, hot work processing, and accelerated cooling. Alloying elements have a complex effect on the properties of steel, and alloying additives are usually introduced into the steel composition. From a metallurgical point of view, the choice of alloying elements and the metallurgical process can greatly influence the resulting microstructure. Conclusion. This review reports the most representative study regarding thermomechanical rolling technologies and microstructural factors in well casing steels. It includes a summary of the most important process variables, material properties, regulatory guidelines, and microstructural and mechanical properties of the metal for well casing production. This review is intended to benefit readers from a variety of backgrounds, from non-metal forming or materials scientists to various industrial application specialists and researchers.

Improvements in steel production technology for main pipelines

Improvements in steel production technology for main pipelines

Low-cost technological methods aimed at improving steel production technology in order to reduce costs and improve the quality of metal products

Low-cost technological methods aimed at improving steel production technology in order to reduce costs and improve the quality of metal products

Взаимосвязь микроструктуры с ударной вязкостью металлов сварного шва трубных высокопрочных низколегированных сталей (обзор исследований)

Introduction. The modern pipeline industry requires the development of materials of high strength and toughness for the production of steels for oil and gas pipelines. Changes in steel production and rolling technologies have become a challenge for welding consumables and joining technologies. This is more critical for strength levels above 830 MPa, where there are no specific regulations for the approval of welding consumables. Research methods. The failure of stainless steel pipeline welds is becoming a serious problem in the pipeline industry. Multiphase microstructures containing acicular ferrite or an acicular ferrite-dominated phase exhibit good complex properties in HSLA steels. This paper focuses on the results obtained using modern methods of scanning electron microscopy for microstructural analysis, backscattered electrons (BSE) for electron channel contrast imaging (ECCI) and orientation microscopy based on electron backscatter diffraction (ORM), as well as characteristic X-rays for compositional analysis using energy-dispersive X-ray spectroscopy (XEDS) and secondary electrons (SE) for observing surface morphology. Results and discussion. This paper analyzes the characteristics of the microstructure of the weld and its relationship with impact toughness. It is shown that predicting impact toughness based on the microstructural characteristics of steel weld metals is complicated due to the large number of parameters involved. This requires an optimal microstructure of the steel. Satisfactory microstructure depends on several factors, such as chemical composition, hot work processing, and accelerated cooling. Alloying elements have a complex effect on the properties of steel, and alloying additives commonly added to the steel composition include Mn, Mo, Ti, Nb and V. From a metallurgical point of view, the choice of alloying elements and the metallurgical process can greatly influence the resulting microstructure. A longer cooling time tend to improve the toughness and reduce the mechanical strength of weld deposits on high-strength steels. Welding thermal cycles cause significant changes in the mechanical properties of the base material. The analysis showed that impact toughness strongly depends on the microstructure of the multi-pass weld of the material under study, which contains several sources of heterogeneity, such as interdendritic segregation, and the effective grain size can also be a significant factor explaining large deviations in local impact toughness values. Acicular ferrite nucleated in intragranular inclusions has been shown to produce a fine-grained interlocking arrangement of ferrite plates providing high tensile strength and excellent toughness, and is therefore a desirable microstructural constituent in C-Mn steel weld metals. At the same time, discussion regarding the relationship between acicular ferrite and toughness is very complex and still open at present. Relating impact toughness to acicular ferrite, taking into account the top bead, is not a reliable procedure, even for single-pass deposit welding. Impact strength depends on several factors, and the strong effect of acicular ferrite is generally recognized due to its fine-grained interlocking structure, which prevents the propagation of brittle cracks by cleavage. The large-angle boundaries and high dislocation density of acicular ferrite provide high strength and toughness. However, for the same amount of acicular ferrite, different viscosity values may be observed depending on the content of microalloying elements in the steel. An analysis of the results of various studies showed that other factors also affect the impact strength. For example, microphases present along the Charpy-V notch are critical for the toughness of weld metals. The combination of OM, SEM and EBSD techniques provides an interesting method for metallographic investigation of the refined metal microstructure of stainless steel pipeline welds. Conclusion. This review reports the most representative study regarding the microstructural factor in the weld of pipe steels. It includes a summary of the most important process variables, material properties, regulatory guidelines, and microstructure characteristics and mechanical properties of the joints. This review is intended to benefit readers from a variety of backgrounds, from non-welding or materials scientists to various industrial application specialists and researchers.

Development of a non-destructive depth-selective quantification method for sub-percent carbon contents in steel using negative muon lifetime analysis

The amount of C in steel, which is critical in determining its properties, is strongly influenced by steel production technology. We propose a novel method of quantifying the bulk C content in steel non-destructively using muons. This revolutionary method may be used not only in the quality control of steel in production, but also in analyzing precious steel archaeological artifacts. A negatively charged muon forms an atomic system owing to its negative charge, and is finally absorbed into the nucleus or decays to an electron. The lifetimes of muons differ significantly, depending on whether they are trapped by Fe or C atoms, and identifying the elemental content at the muon stoppage position is possible via muon lifetime measurements. The relationship between the muon capture probabilities of C/Fe and the elemental content of C exhibits a good linearity, and the C content in the steel may be quantitatively determined via muon lifetime measurements. Furthermore, by controlling the incident energies of the muons, they may be stopped in each layer of a stacked sample consisting of three types of steel plates with thicknesses of 0.5 mm, and we successfully determined the C contents in the range 0.20–1.03 wt% depth-selectively, without sample destruction.

The influence of gas heating on the calculated supersonic parameters of gas-powder flow at slag blower in the converter. Message 1

The article shows that one of the priority tasks in steel production technology is to increase the durability of the lining of oxygen converters. It is shown that the slag blower is a radical way to increase the durability of the lining of oxygen converters. When blowing the melt with oxygen, the MgO content in the slag is 6-8%. To increase the chemical affinity of the slag and the lining, it is proposed to blow the converter slag with jets of nitrogen or powder gas. To achieve optimal chemical affinity of the lining and slag, it is recommended to modify the latter by increasing the content of magnesium oxide in it to 12-14%. Increased durability of the lining makes it possible to solve the problem of replacing wasteful wastes of coal slag and changing environmental concerns on the excess media. It is shown that an attempt to increase the efficiency of modeling very complex processes of interaction of supersonic jets with converter slag has not yet been solved a. A critical analysis of existing methods for constructing mathematical models based on the use of known gas-dynamic laws of interaction of free turbulent jets with the melt is carried out. It has been established that only supersonic jets with their characteristic shock-wave structure always enter the slag melt. An integral method for calculating the parameters of a gas-powder flow in a supersonic nozzle taking into account the powder concentration is presented. It is determined how heating of the gas suspension affects the required pressure in front of the nozzle block, the speed and flow density in the outlet section of the supersonic nozzle. The gas dynamics system is connected to the heat exchange of the flowing gas-dispersed mixture in the Laval expansion nozzles to establish the heating effect in front of the nozzle block of the two-phase gas suspension to a temperature that will ensure The increase in the fluidity of the gas flow is doubled and its kinetic energy is increased threefold. The method of expanding the parameters of the gas-powder flow between the Laval expansion nozzle involves the infusion of 10 physical effects into 14 parameters of the gas-powder flow. It is shown that numerical expansions allow the tuyere body to be used as a heat exchanger for heating the gas suspension, as well as for increasing the pressure of the gas-powder jet that flows from the nozzles

Mitigating emissions in the global steel industry: Representing CCS and hydrogen technologies in integrated assessment modeling

We conduct a techno-economic assessment of two low-emissions steel production technologies and evaluate their deployment in emissions mitigation scenarios utilizing the MIT Economic Projection and Policy Analysis (EPPA) model. Specifically, we assess direct reduced iron-electric arc furnace with carbon capture and storage (DRI-EAF with CCS) and H2-based direct reduced iron-electric arc furnace (H2 DRI-EAF) which utilizes low carbon hydrogen to reduce CO2 emissions. Our techno-economic analysis based on the current state of technologies found that DRI-EAF with CCS increased costs ∼7% relative to the conventional steel technology. H2 DRI-EAF increased costs by ∼18% when utilizing Blue hydrogen and ∼79% when using Green hydrogen. The exact pathways for hydrogen production in different world regions, including the extent of CCS and hydrogen deployment in steelmaking are highly speculative at this point. In illustrative scenarios using EPPA, we find that, using base cost assumptions, switching from BF-BOF to DRI-EAF or scrap EAF can provide significant emissions mitigation within steelmaking. With further reductions in the cost of advanced steelmaking, we find a greater role for DRI-EAF with CCS, whereas reductions in both the cost of advanced steelmaking and hydrogen production lead to a greater role for H2 DRI-EAF. Our findings can be used to help decision-makers assess various decarbonization options and design economically efficient pathways to reduce emissions in the steel industry. Our cost evaluation can also be used to inform other energy-economic and integrated assessment models designed to provide insights about future decarbonization pathways.

Iron ore wires as consumable electrodes for the hydrogen plasma smelting reduction in future green steel production

In this work we investigate the feasibility and optimisation pathways for using oxide-filled consumable electrodes as both ore feeding system and reducing/melting arc carrier in the hydrogen plasma smelting reduction process. Similar in nature to Söderberg-type electrodes, but free of C-containing substances, this approach has the potential advantage of eliminating the carbon emissions stemming from conventional electric arc furnace electrodes while drastically simplifying the ore feeding into the process. Using a commercial welding setup with a 1.2 mm thick oxide-cored steel wire, area investigations indicate that approximately 50% of the introduced iron ore could be reduced to metallic iron at 100 A arc current under an Ar-10% H2 atmosphere independent from deposition time. The reduction efficiency was negatively affected by increasing arc current and it was increased by using the wire as the anode. Based on the performed variation of deposition parameters, microstructural characterisation results, high speed footage and first upscaling trials, the key scientific questions and engineering pathways for technological optmisiation towards future green steel production technology are outlined and discussed.

Physical and chemical calculations of steelmaking processes and predictive models for the production of clean steel

The results of physicochemical calculations of steelmaking processes for the production of clean steels deoxidized with aluminum are presented. The efficiency of the calculations was achieved using as the main scientific idea the position on the leading role of the oxidation potential in the metal – slag – gas system, while controlling the external supply of oxygen from the atmosphere, materials, slag and refractories. The advantage of this idea lies in the fact that thanks to it it provides a quick identification of critical points in developed and existing technologies, and determines effective ways to solve emerging quality problems in clean and ultra-clean steels. An approach is considered to improve the technology of clean steel production, including elements of mathematical and thermodynamic models, as well as algorithmic approaches for building static models using machine learning technology to improve efficiency in steelmaking technologies. For the application of the presented approach it is necessary to prepare the data set before-hand, as well as to carry out the interpretation of the results of machine learning, based on fundamental laws and physical and chemical processes occurring in steelmaking production. As a result of the thermodynamic calculations performed in the STM program, measures were developed for the production of clean steels. On the examples of the production of thin slabs and billets search and confirmation of significant technological parameters in the formation of steel-making defects due to non-metallic inclusions was carried out using methods of in-depth analytics and machine learning

Decarbonisation of the steel industry: theoretical and practical approaches with analysis of the situation in the steel sector in Poland

Climate change and environmental degradation are nowadays the key challenges of the industries in Europe (according to the European Green Deal). The primary goal is to achieve a climate-neutral in Europe by 2050. Technologies with carbon dioxide (CO2) emissions should be completely stopped in the future. The iron and steel industry is among the manufacturing industries with high CO2 emissions in Europe. In Poland, steel mills produce about 9 million tonnes of steel per year (average for 2000-2021). Steel mills in Poland use two steel production technologies, EAF and BOF. The first technology is highly energy intensive, and the second has high emissions of CO2. There will be no BF technology in zero-emission smelters; this technology will be replaced by DRI (i.e., direct iron reduction) installations, and electric furnaces will be powered by renewable energy. The paper consists of two parts: a theoretical section and a practical section. In the first section, the way the steel industry moves towards climate neutrality was presented. The part of the paper was realized based on European documents and a literature review. The second part was an analysis of the CO2 emission in the steel industry in Poland. The analysis was realized based on data from the Polish Steel Association.

Experimental and numerical investigation on fatigue behaviors of Q690D butt welds

With the improvement of steel production technology, different grades of high-strength steel have been developed and widely applied in engineering, however the fatigue properties of high-strength steel need to be further studied. In this research, regarding the fatigue properties of Q690D high strength steel butt welds, experimental investigation and numerical simulation were carried out. Experimental investigations of Q690D high strength steel butt welds were performed, and properties including the basic mechanical behaviors, metallographic structure, fatigue crack growth rate and fatigue performance were obtained. The fatigue test results were compared with fatigue data from existing studies of butt welds and the Eurocode3 fatigue design S-N curve. The fatigue life prediction was performed and the fatigue crack propagation process was simulated based on the platform combining ABAQUS and Franc3D. The results show that the tested butt-welded joints specimen includes more initial defects, its fatigue properties are comparable to those of 355 MPa grade steel butt-welded joints, and the fatigue resistance advantages of high strength steels are not obvious. The simulated results are in good agreement with the fatigue test results, indicating the proposed simulation method is applicable in the fatigue life assessment of engineering structures with known initial defects. The proposed simulation method provided a numerical analysis approach to the fatigue assessment of engineering structures, thereby reducing the cost of fatigue tests and bringing significant economic and social benefits.

On transition to hydrogen metallurgy

The article shows that climate change is not only warming, but also extraordinary natural phenomena (droughts, floods, storms, tornadoes etc), which lead to significant economic damage. Climate warming is caused by increasing concentrations of greenhouse gases in the earth's atmosphere. The main task is to reduce carbon dioxide emissions. An analysis has been carried out of international documents such as the Kyoto Protocol, the Paris Climate Agreement, aimed at reducing greenhouse gas emissions into the atmosphere. It is shown that a significant amount of CO2 enters the atmosphere during the production of pig iron and steel, the data on the amount of carbon dioxide emissions from steel smelting in Ukraine and at «Azovsteel» iron and steel works have been provided. The article contains a critical analysis of the existing steel production technology, which is highly efficient but requires significant capital investment, fuel and energy resources, the source of which is the product of heat treatment of hard coal – coke, its carbon in the form of CO2 entering the atmosphere. Numerous proposed methods of steel production without the use of this coke are considered. One of the directions was the production of sponge iron without melting, another direction of coke-free metallurgy was high-temperature processes of obtaining liquid metal, that are carried out in one stage. The theoretically required amount of reducing agent at of iron with carbon monoxide and hydrogen has been determined. Methods of producing renewable gas by conversion of natural gas and gasification of coal are considered. The plans of the Metinvest Group management to develop a long-term technological strategy for metallurgical production taking into account environmental requirements are presented

Methods and installations for utilization of fine screenings of ferroalloys

To date, the production of such ferroalloys as ferrosilicon, ferromanganese, ferosilicomanganese, high-carbon ferrochrome amounts to thousands of tons per year. Preparation of the ferroalloy for sale involves crushing the ferroalloy ingot to the commercial fraction, as a result of which there are dust-like screenings, which are further stored in warehouses and harm the environment. The existing sieving is a finished product, which in composition is close to the final fraction, the size of which is 10-250 mm. To apply sieving in steel production technology, it must be re-melted and cast into an ingot. The resulting ingot is repeatedly crushed until a commercial fraction is obtained. The main problem is the remelting of the dropout, since various difficulties arise due to its size and electrophysical properties. This article presents methods and installations for remelting sieving ferroalloys of various brands, as well as their comparison, disadvantages and advantages. The article describes plasma, induction crucible, as well as dual DC and AC installations designed for remelting sieving of various ferroalloys with a fraction less than 10 mm. The disadvantages and advantages of each method and remelting installation are described. Various experimental data obtained during the melting of ferroalloys sieving in the described installations are presented. Based on the data described in the article, as well as relying on other conclusions, in conclusion, a method of remelting with the removal of ferroalloys was proposed, including the advantages of existing ones, as well as excluding their disadvantages.

Deoxidation capacity of aluminum in ferromanganese carbon-containing melts

Deoxidation (reduction of oxygen concentration dissolved in liquid metal) is an integral part of steel production technology. For obtaining deeply deoxidized metal, mainly aluminum is used at metallurgical enterprises. It should be taken into account that alloying elements of steels and alloys under certain conditions can act as deoxidizing elements, contributing to the complex nature of the deoxidation process. Almost all steels contain manganese in one concentration or another. The study of interaction processes in the Fe – Mn – Al – O – C system at steelmaking temperatures is of applied importance. In this paper, a thermodynamic analysis of the deoxidation ability of aluminum in oxygen-containing iron-manganese melts was carried out. At the same time, influence of carbon on course of the deoxidation process was taken into account. In the study, it is effective to use a technique for constructing the solubility surface of components in metal (SSCM) – a diagram that connects the compositions of liquid metal with the compositions of conjugated non-metallic phases. In the course of this work, oxygen solubility isotherms in the Fe – Mn – O system were calculated for the temperature range of 1550 – 1650 °C. For the Fe – Mn – Al – O – C (1600 °C) system, composite sections of the SSCM were constructed at fixed carbon concentrations in steel [C] = 0; 0.1; 0.4; 0.8 and 1.2 % (hereafter by weight). It is shown that with the simultaneous presence of manganese and aluminum in an oxygen–containing iron-based melt (at industrially significant concentrations [Al] = 0.001 – 0.010 % and [Mn] – less than 1.0 %), aluminum in the liquid metal will act as a deoxidizing agent, and corundum inclusions will be formed as interaction products. Complex deoxidation by aluminum and manganese with the formation of spinel is typical only for manganese-alloyed steels, where the concentration of manganese is more than 1.5 %.

Prospects for the development of hydrogen technologies in the domestic metallurgy

The inevitability of the development of carbon-free steel production technologies in the domestic metallurgy is due not only under the pressure of environmental requirements for decarbonization, but also by the need to bring steelmaking technologies in line with the level of modern science. The electronic theory of oxidation/reduction can serve as a scientific basis for new technologies for the reduction of metals. From the standpoint of this theory, the final stage of the electrochemical process of reducing metals with any reducing agent, including hydrogen, is the electrolysis of oxides with the release of metal and gaseous oxygen under the action of an electron flow generated in the fuel cell during the combustion of the reducing agent due to the oxygen of the oxides. Comparison of two technology options ‒ iron reduction by “green” hydrogen or direct electrolysis of ore oxides using electricity from the electrical network shows a multiple advantage of electrolysis in terms of energy costs. It is concluded that the priority in the development strategy of the industry should not be given to the production and use of “green” hydrogen, but to the electrolysis of ore. The use of hydrogen as a reducing agent can be justified in the selective extraction of iron from complex ores in units such as plasma shaft furnaces, plasma reactors or fluidized bed furnace, in which, along with reduction, nitriding would also take place to convert soft iron into steel. In Russia, there is already an opportunity to master the production of steel using “green” or “turquoise” hydrogen. It is most rational to start the introduction of hydrogen reduction of iron on the basis of the deposits of titanomagnetites of the Kola Peninsula using the excess capacity of the Kola NPP to produce hydrogen

ФОРМУВАННЯ МІЖНАРОДНОЇ СТРАТЕГІЇ РОЗВИТКУ РИНКУ СТАЛІ

The article examines the structure of strategic consumers of the metallurgical industry. The most important industries in the structure of consumption of the metallurgical sector are: industrial and civil construction, machine building (mechanical equipment and automobile industry). The integrated types of steel production are identified: based on blast furnace (BF) and basic oxygen furnace (BOF) and electric arc furnace (EAF) steel production technology type. The structural components of the operating cycle of the main types of steel production (iron ore, coal, limestone, scrap, energy), as well as the components of commercial products (main industrial products and related products): steel, sludge, dust, blast furnace gas, converter gas, recovered steam are defined, energy. The cost norms of the material and energy supply sector of the metallurgical sector and the results of metallurgical production in average quantitative terms are substantiated. The trend of global steel production was analyzed and analytical indicators of dynamics were determined (average absolute growth, growth rate, growth rate). In order to ensure further analytical forecasting of industrial product markets, the selection of an approximating curve was made using the method of trend formation. Based on the obtained logarithmic curve, a smoothed estimate of the trend was made and a forecast of world steel production for the period 2023–2027 is formed. The forecast volumes of the metallurgical industry supply markets (iron ore market (iron ore and agglomerate); limestone market, scrap market, energy market), as well as the greening market (recovered steam, converter gas, blast furnace gas) and related products (slag, dust) are determined for the period 2022–2027 The forecast indicators of the growth of markets for industrial products of the metallurgical sector are substantiated. The main principles of the international strategy for the development of the steel market are determined: efficiency and sustainability of development, designing the product life cycle, stimulating the reuse of industrial products; maximum use of scrap, acceleration of decarbonization processes and transition to green steel production, effective and efficient processing of by-products. Proposed areas of the international steel development strategy: ensuring sustainable growth; promoting the development of security markets; development of effective use of related products.

Numerical studies of the kinetics of steel desulfurization with pneumatic stirring

Analysis of recent research and publications. In the conditions of mini-mills, the removal of sulfur in a number of cases is the limiting link in the production of steel. The kinetics of desulfurization is determined by the specific stirring power of the steel melting bath. The influence of the geometry of the bath on the efficiency of pneumatic mixing and desulfurization of steel at a fixed mass has not been sufficiently studied. Purpose and method. The purpose of the work is increasing the energy efficiency of steel production in the conditions of a mini-mill due to the minimization of steel desulfurization time. The method consists of numerical modeling of the desulfurization kinetics taking into account the geometric parameters of the steel melting bath and regime parameters of pneumatic mixing. Novelty and scientific significance of research. In the context of the kinetics of steel desulphurization, an understanding of the energy component of the process was developed through the specific power of pneumatic mixing of the liquid bath Nmix. The finiteness of the isothermal expansion model of the rising gas bubble for determining Nmix in industrial conditions through argon flow rate is shown. A mathematical model for estimating Nmix when purging the bath with argon in jet-bubble mode through the averaged speed of liquid steel movement and Archimedes’ force as a function of the gas content ratio in the two-phase region is proposed. The model allows optimizing argon flow rate according to the criterion of the maximum specific power of pneumatic mixing. This mode ensures the minimum duration of steel desulfurization for the given slag parameters and geometry of the steel melting bath-bottom porous plug system. Practical value. Determining the optimal flow rate of argon to ensure the maximum specific power of pneumatic mixing of a steel melting bath of a certain geometry and mass in the context of minimizing the duration of desulfurization contributes to increasing the energy efficiency of the steel production technology in the conditions of mini-mill operation.

On modelling conjugated heat transfer in the thin slab CC mold and solid shell formation under the applied EMBr

Continuous casting (CC) became one of the dominant steel production technologies throughout last decades. Better quality, energy savings and high production rates are the main aims of the research especially in the field of the thin slab casting (TSC). The electromagnetic brake (EMBr) is applied to control the highly turbulent flow after the fresh melt is fed through the ports of a submerged entry nozzle (SEN). The numerical modelling is a perfect tool to investigate the multiphase phenomena of the turbulent flow in the CC mold, heat transfer and solidification coupled with the effects of the magnetohydrodynamics (MHD). Traditionally the heat transfer in the CC mold during the numerical simulations is predefined by the heat flux profile which could be taken from the plant measurements, published data, or is described by the semi-empirical formulas. In all these cases the heat extraction in the CC mold cavity is strictly predefined and is not significantly influenced by the transient flow behavior. Moreover, the heat flux, used in a simulation, is frequently measured for the different flow pattern inside the mold. That is especially important when the EMBr effects on the solid shell formation are investigated. Thereby, the presented study considers the coupled heat transfer in the water-cooled copper mold, including the averaged thermal resistance between the slab and mold, implemented using OpenFOAM® open-source CFD software. The melt flow, the temperature field, and the induced electric current density are compared between the traditional approach (the applied heat flux) and the modelled heat transfer in the TSC mold. Different scenarios are studied without and with the applied magnetic field.

Assessment of a multistep revamping methodology for cleaner steel production

A novel revamping methodology is proposed to achieve the decarbonization of currently operating integrated steel mills (step 0) without reducing steel production levels. Such a method encompasses four successive steps involving cleaner and more energy efficient technological pathways for steel production.The decarbonization strategy is reported: step 1, partial replacement of coke with recycled plastic in a conventional Blast Furnace – Basic Oxygen Furnace (BF-BOF) plant; step 2, implementation of a Direct Reduction-Electric Arc Furnace (DR-EAF) line combined with the BF-BOF plant; step 3, complete shut-down of the BF-BOF line and full operation of two DR-EAF lines fed by CH4; step 4, installation of an alkaline electrolyzer and use of 100% green H2 as a reducing agent in the DR plants.The gradual replacement of the integrated steel mill with DR-EAF lines causes a progressive drop in CO2 emissions, ranging from 8.5 Mt/y at step 0 to a minimum of 0.68 Mt/y at step 4 (92% decrease).Coke replacement with recycled plastic in the blast furnace in step 1 leads to a slight decrease in CO2 emissions without altering the structural layout of the plant. In step 2, the combined operation of BF-BOF and DR-EAF lines determines a 39% decrease in CO2 emission compared to the initial configuration, while keeping total steel production constant. Step 3 involves two DR-EAF lines fed by CH4 and reduces the CO2 emissions by 75% compared to the initial configuration. The operation of two DR-EAF lines increases the electricity consumption, especially when 100% green H2 is involved as a reducing agent in step 4. By increasing the scrap mass fraction in the EAFs of step 4, both electricity and H2 demands of the DR plant are expected to decrease, while the CO2 emission levels remain almost unchanged, leading to about 92% total CO2 emissions reduction compared to the initial configuration (provided that green electricity is used). By assuming an initial 10% scrap mass fraction at the EAFs inlet of step 4, the demand of green hydrogen is significant, thus requiring the installation of a 1.42 GW electrolyzer. The capital expenditure (CAPEX) estimated upon completion of the revamping methodology amounts to approximately 2.97 B€. The transition towards a full decarbonization of steel production technologies is demonstrated to be technically feasible, though strictly dependent upon the large availability of low emissions electric power and scrap material.