Steel Purity Research Articles

Effect of Cs2O-containing refining slag on the purity of ultra-clean steel for ultra-fine saw wire

The influence of Cs2O-containing refining slag on the purity of steel for ultra-fine saw wire has been studied in this article. The result indicated that a small amount of Cs2O can significantly improve the capability of low-basicity refining slag to purify molten steel. In detail, the number and size of inclusions decreased dramatically when Cs2O was added to the refining slag. Additionally, the composition of most inclusions is controlled within the low melting point region. However, it will reduce the capability of low-basicity refining slag to purify molten steel if the content of Cs2O exceeds 10 wt%. Cs2O changes the ability of low-basicity refining slag to remove inclusions by changing the slag's viscosity and microstructure. The viscosity of refining slag increased gradually with the mass fraction of Cs2O in the slag increasing, and the disparity of viscosity values between different experimental groups increased sharply with temperature decreasing. Furthermore, the viscosity curve of Cs2O-containing slag developed a turning point, that is, the speed of viscosity increasing raised sharply at the turning point, while this phenomenon cannot be found in a normal experiment group without Cs2O. The detection results of the Raman spectrum show that the three-dimensional network of slag increased greatly with the content of Cs2O in the slag increasing gradually.

Root cause analysis of coining tool failure with proposed solution to extend its service life

The article deals with a root cause analysis of coining tool failure after its untimely discarding and the design to extend its service life by innovating the manufacturing process. The analysis was performed on the coining die which had to be put out of service due to the insufficient quality of minted stainless coins. The purity of steel and the microstructure of the material of the semi-finished goods were evaluated. Furthermore, an analysis of the coining die failure under the surface and in the core was performed as well as the state of the chromium layer failure on the coining die relief. Based on the results of the analysis, a new experimental coining die was designed and produced according to an innovative manufacturing process. The pressing of the relief was carried out in a vacuum furnace and relief was coated with a TiAlN by the PVD method. New processes introduced in the production of coining die prevented the failure of die punches, extended the time of operation, thereby increasing quality of the coin production.

Investigating the origins of the 'double rise' shape in hydrogen permeation transients on pure iron

This study delves into the underlying causes of the atypical 'double rise' shape observed in hydrogen permeation rising transients on pure iron and low alloy steels. Electrochemical permeation experiments on pure iron reveal a fast initial rise, a short pseudo-plateau, and a slow second rise. Similar patterns emerge in the decaying transients. The micro-porosity present in material appears to act as reversible traps, affecting hydrogen diffusion. Surface damage, confirmed by SEM analysis, exacerbates the issue. Utilizing numerical simulations, an FEM model effectively replicates the 'double rise' behavior, attributed to limited recombination/dissociation kinetics at bulk-cavity interfaces. Overall, micro-porosity is identified as the primary factor behind this unique permeation curve shape.

Evaluation of hydrogen interactions with defects induced by deformation in the duplex stainless steel microstructure: An internal friction study

Despite their good corrosion resistance and optimal mechanical properties, duplex stainless steels are affected by hydrogen embrittlement. Therefore, understanding the hydrogen-defect interactions in these steels is crucial. This study uses internal friction to evaluate the interactions of hydrogen with microstructural defects. Analysis of the internal friction spectra of the steels subjected to straining and hydrogen charging, together with thorough microstructural characterization, gives new insights in hydrogen interactions with defects present in the different phases, i.e. ferrite (body centered cubic) and austenite (face centered cubic).While no significant effect of tensile deformation can be observed by thermal desorption spectroscopy, the internal friction spectra show a clear influence of the presence of defects. Detailed analysis of these spectra reveals the interactions in the austenite as dominant, while no indications for hydrogen-dislocation interactions in ferrite are observed. This can be related to limited trapping in ferrite due to the austenite sink action or to limited dislocation formation in ferrite. Indications for hydrogen interactions with dislocations in the austenite are found, possibly suggesting enhanced dislocation mobility when surrounded by hydrogen. Moreover, a pronounced influence of hydrogen charging on the vacancy cluster related peaks is observed, indicating strong interactions between hydrogen and vacancy clusters in austenite. This can be put in contrast to behavior of pure ferritic steels, where dislocations provided the strongest hydrogen interactions. As these specific defects are of primary interest in the hydrogen embrittlement mechanisms, internal friction is concluded to provide important unique insights in hydrogen-defect interactions, even for complicated multiphase microstructures.

Optimasi Sudut Baji, Kecepatan Pemakanan & Rpm Terhadap Kekasaran Permukaan Material SCM 440 Dengan Metode Respon Surface (RSM)

The development of manufacturing technology has developed so rapidly. In this study, SCM 440 steel material was used, which is an alloy steel of chromium molybdenum. This steel has the advantages of stable composition,low harmful elements,high steel purity. Surface roughness is important, surface roughness is defined as the irregularity of surface configuration in an object resulting from a finishing process. This study aims to determine the influence of process variables on the surface roughness rate of SCM 440 material by varying the total cutting angles of 700,750 and 800 then variations in feeding speed of 0.08mm, 0.09mm, and 0.10mm and spindle speed or RPM, namely 160,220, and 280 puts / min in the RSM method. The Rspon Surface method is a set of mathematical and statistical techniques that are useful for analyzing problems where several independent variables affect the response variable and determine the optimal value of the process variable. From the results of the study, the value of the Second order yˆ = + 0.092224 X1² + 0.208515 X2² - 0.03661 X3² was obtained. With stationary point value X0 = ( total Cut angle ) = - 0.382409, X0 = (feeding) = 0.161715, X0 = (RPM) = 0.578250. and found the optimal values of Wedge Angle (78.212), Feeding Speed (0.095 mm) and RPM (278.29 put/min). Then it can be analyzed the optimal value that is different from the value of the RSM method framework and if the values are the same then the research fails.

Using calcium-containing injection wire filled with electrolytic calcium in steel ladle treatment

Aluminum is one of the most common deoxidizers; when it is used in the melt, refractory inclusions of alumina are formed. The presence of these non-metallic inclusions negatively affects the purity of liquid steel, mechanical properties, makes casting difficult due to tightening of the steel-pouring fittings. The modification of alumina inclusions with calcium promotes the formation of liquid calcium aluminates, which leads to an acceleration of their removal from the metal due to a higher ascent rate. Having a high affinity for sulfur, calcium reduces its harmful effect by binding it with the formation of calcium sulfides, reducing the anisotropy of steel properties during further rolling. For steel treatment with calcium, injection wires with a calcium-containing filler are used. As a filler can be used: electrolytic calcium, silicocalcium, aluminum-tremic calcium, or ferrocalcium. The paper describes results of the tests carried out on a calcium-containing wire filled with electrolytic calcium and silicocalcium. It is shown that the consumption of calcium when using silicocalcium wire is on average 35 % higher in comparison with calcium injection wire filled with electrolytic calcium. The calcium recovery rate for different steel grades was evaluated using calcium-containing wires of different designs and filler. In this work, the steel pourability was analyzed. As a determining parameter, dependence of change in position of the tundish stopper rod on calcium content in the metal was considered in the sample from CCM. It was established that a wire filled with electrolytic calcium shows a more effective result in comparison with a silicocalcium wire.

Effect of Salt Tracer Dosages on the Mixing Process in the Water Model of a Single Snorkel Refining Furnace

The improvement in mixing conditions in a vacuum refining unit plays an important role in enhancing the purity and decarburization of molten steel. Mixing time is an important index to evaluate the operation efficiency of a metallurgical reactor. However, in water models, the effect of salt tracer dosages on the measured mixing time in a vacuum reactor is not clear. In this study, a water model of a Single Snorkel Refining Furnace (SSRF) was established to study the effect of salt solution tracer dosages on the mixing time of monitor points. The experimental results show that, in some areas at the top of the ladle, the mixing time decreases first and then increases when increasing the tracer dosage. Numerical simulation results show that, when the tracer dosage increases, the tracer flows downwards at a higher pace from the vacuum chamber to the bottom of the ladle. This may compensate for the injection time interval of large dosage cases. However, the mass fraction of the KCl tracer at the right side of the bottom is the highest, which indicates that there may be a dead zone. For the dimensionless concentration time curves and a 99% mixing time, at the top of the vacuum chamber, the curve shifts to the right side and the mixing time decreases gradually with the increase in tracer dosage. At the bottom of the ladle, with the increase in tracer dosage, the peak value of the dimensionless concentration time curve is increased slightly. The mixing time of the bottom of the ladle decreases significantly with the increase in tracer dosage. However, in the dead zone, the mixing time will increase when the tracer dosage is large. At the top of the ladle, the effect of the tracer dosage is not obvious. The mixing time of the top of the ladle decreases first and then increases when increasing the tracer dosage. In addition, the mixing time of the top of the ladle is the shortest, which means that sampling at the top of the ladle in industrial production cannot represent the entire mixing state in the ladle.

A Web-Based Metallographic Atlas for Teaching Materials Science

The COVID-19 pandemic has forced many higher education institutions to offer their courses online, which is quite challenging when implementing laboratory sessions. Here we describe a web-based teaching resource consisting of a metallographic atlas with more than 200 micrographs corresponding to pure metals, binary alloys, steels, cast irons, and light alloys. The atlas is designed for majors and graduate level students in materials science disciplines, and it focuses on the interpretation of optical micrographs. The web page metrics, the impact on academic scores, and the results of an anonymous and voluntary survey indicate a very positive response to this online teaching resource material.

Application of Graphite Electrode Plasma Heating Technology in Continuous Casting.

In this study, the industrial, experimental effect of a plasma heating system in the form of graphite electrode in the tundish of double-strand slab caster was evaluated for the first time. The system uses three graphite electrodes, two of which are cathodes and one of which is an anode, to form a conductive loop through molten steel in the tundish. The system is built on an old two-strand slab caster and is installed on the premise that the original ladle tundish equipment remains unchanged. The normal working power of the system is up to 1500 kW, and the heating rate of molten steel in the tundish can reach 1.0 °C/min under conditions of 5 t/min total steel throughput and a tundish capacity of 50 t. After the system was put into operation, the purity of molten steel undergoing heating was investigated. The sample analysis of low carbon steel and ultra-low carbon steel before and after heating showed that the contents of N and O in the steel did not increase, while the size of the oxide inclusions near the heating point increased but showed little change in terms of the overall quantity. This process benefited from the addition of inert gas during the heating process to control the atmosphere in the heating area, which prevents reoxidation. The sample analysis also showed that there is no obvious carbon absorption phenomenon after heating, and the fluctuation in C content is within 0.0001%, which is consistent with the general production results. By using this system, the temperature of molten steel in the steelmaking process can be reduced by 10~15 °C, allowing continuous low superheat casting to be supported, which is helpful for reducing production costs and improving the solidified structure inside the slab. The results of the study show that the plasma heating technology can be applied to the continuous casting of low carbon–nitrogen steel slabs, which shows the benefits of reducing emissions and improving production efficiency.

НАНОСТРУКТУРУВАННЯКРИСТАЛІЧНИХ МАТЕРІАЛІВ ТА НАПИЛЕНИХ ПОКРИТТІВ ПЕРЕДРЕКРИСТАЛІЗАЦІЙНОЮ ТЕРМІЧНОЮ ОБРОБКОЮ

Modern production requires the improvement and creation of materials with unique properties, and their use in structures is determined by the ratio between strength and plasticity, therefore metal materials are characterized by the most attractive ratio from the point of view of practical expediency. The increase in strength properties is ensured mainly due to the purposeful formation of a crushed structure.Analysis of the latest research and publications showed that methods of thermomechanical processing of materials re-main promising for the formation of ultra-and nanostructures in metallic materials.The purpose of the work is to establish the patterns of changes in the structure and properties of crystalline materials after deformation and pre-recrystallization heat treatment.The work presents methods for determining the strength properties of metal materials and determining the size of their structural elements.The article highlights the feasibility of using pre-recrystallization heat treatment of previously deformed technically pure iron (GOST 3836-83), carbon steels 20, 45 (GOST 1050-88) and U8 (GOST 1435-88), alloy steels 40X (GOST 2591-2006), 12X13 and 12X18N9T (GOST 2590-2006) to increase their hardness due to the formation of a thermally stable polygonization substructure, mostly on of a nanoscale. It is shown that an increase in the content of carbon and chromium in steels during short-term exposure at a temperature that corresponds to the temperature threshold of recrystallization of the mentioned steels leads to a decrease in the increase in their hardness. Combined deformation, which consists of dynamic deformation by 30% followed by static deformation by 30%, provides an opportunity to increase the exposure time for technically pure iron, carbon and alloy steels up to 60 minutes due to the formation of a thermally stable polygonization substructure in the process of their pre-recrystallization heat treatment. It was established that the increase in hardness of technically pure iron, steel 20and 45 decreases with an increase in the amount of carbon, and the increase in hardness of chromium-alloyed steels increases with an increase in the amount of chromium. The optimal mode of pre-recrystallization heat treatment of a heat-protective plasma coating with ZrO2+ 7% Y2O3was determined, which provides an increase in hardness by 13% and a decrease in the thermal conductivity of the ceramic layer by 15% compared to the state after sputtering due to substructural changes.

Increasing the Image Sharpness of Light Microscope Images Using Deep Learning

Abstract Image-based qualitative and quantitative structural analyses using high-resolution light microscopy are integral parts of the materialographic work on materials and components. Vibrations or defocusing often result in blurred image areas, especially in large-scale micrographs and at high magnifications. As the robustness of the image-processing analysis methods is highly dependent on the image grade, the image quality directly affects the quantitative structural analysis. We present a deep learning model which, when using appropriate training data, is capable of increasing the image sharpness of light microscope images. We show that a sharpness correction for blurred images can successfully be performed using deep learning, taking the examples of steels with a bainitic microstructure, non-metallic inclusions in the context of steel purity degree analyses, aluminumsilicon cast alloys, sintered magnets, and lithium-ion batteries. We furthermore examine whether geometric accuracy is ensured in the artificially resharpened images.

Improvement in Galvanic Corrosion Resistance between AA5083 and Pure Fe or Stainless Steels in Diluted Synthetic Seawater Due to Anodizing

Because of worldwide emission gas control, the weight reduction for automobiles has been widely required. Multi-material structures for automobiles, in which several materials like steels and aluminum alloys are utilized, are effective methods as techniques to reduce the weight; however, the galvanic corrosion becomes a serious problem for the joints between steels and aluminum alloys. In our previous research [1], galvanic corrosion damages on pure aluminum coupled to pure iron or stainless steel were prevented by anodizing because the anodic oxide film on pure aluminum becomes thicker with increasing anodizing time and voltage. For aluminum alloys, intermetallic particles on aluminum alloys become the initiation sites of localized corrosion; therefore, anodizing behavior on intermetallic particles should be important for preventing the galvanic corrosion damage on aluminum alloys. In this research, anodizing conditions were determined to prevent the localized corrosion generation on AA5083 when pure iron or stainless steels were coupled to AA5083. Pure iron, type 304 stainless steel, type 430 stainless steel, and AA5083 (Al-Mg alloy) were prepared as specimens in this research. Diluted synthetic seawater (200 mg/L Cl-, pH 8.2) was used as the electrolyte for electrochemical measurements. The electrode area was ca. 10 mm2. Ag/AgCl (3.33 M KCl) was used as the reference electrode. Galvanic currents and electrode potentials of aluminum alloy electrode were measured via a zero resistance ammeter. The distance between steel and aluminum alloy electrodes was kept at 10 mm. Additionally, anodizing was treated to AA5083 in various anodizing voltage and time conditions. The galvanic currents and electrode potentials of AA5083 coupled to pure iron were measured. The galvanic currents were anodic currents during the measurements, and the small oscillations of galvanic currents and electrode potentials were generated. After the measurements, many pits and filiform corrosion were observed on AA5083. The localized corrosion was induced by ennoblement of the electrode potentials of AA5083.[1] Takumi Kosaba, Izumi Muto, Yu Sugawara: Effect of anodizing on galvanic corrosion resistance of Al coupled to Fe or type 430 stainless steel in diluted synthetic seawater, Corros. Sci., 179 (2021), 109145.

A comparative study on the grain boundary internal friction peak of pure iron

The high-temperature relaxation behavior of single-crystal and polycrystalline iron is systematically investigated using the internal friction (IF) technique. A relaxation peak located at ∼0.45Tm (Tm, the melting temperature) is observed in the IF spectrum of polycrystalline iron as reported in conventional studies, but it is absent for single-crystal iron, implying that the appearance of this peak is related to grain boundaries, which provides a direct and important evidence for the origin of the peak located at ∼0.45Tm from grain boundary relaxation. At the same time, parameters of grain boundary relaxation of polycrystalline iron are carefully evaluated combined with a coupling model. This study will provide an important reference for the study of defect relaxation behavior in pure iron and ferrite steels.

Problematic issues of high-carbon electrical steel production

Currently, wire rod for the production of wire from low-, medium- and high-carbon unalloyed and alloyed steels for springs, ropes, metal cord, welding electrodes and copper-plated wire for welding building structures, ship hulls, large-diameter pipes and main gas and oil pipelines is in demand on the world market. for the production of which it is not necessary to carry out softening annealing before drawing the wire rod or on an intermediate size of wire. The most responsible types of wire rod made of high carbon steel are wire rod, intended for the production of metal cord and high-strength reinforcing ropes. The above-mentioned products must have high consumer properties, the level of which largely depends on the formation of the structural state of the metal, including in the process of accelerated cooling from rolling heating. Currently, the volume of wire rod production in the world exceeds 50 million tons, which is explained by the wide range of finished products made from it - ropes, metal cord, springs, needles, strings, nets, fasteners, welding electrodes and other metal products. According to GOST 2590-2006, wire rods are round profiles with a diameter of 9.0 mm and less, round profiles with a diameter of 10.0 mm and more are classified as small-grade rental In foreign and domestic literature, wire rod is sometimes considered to be a round rolled product made of carbon, low- and high-alloy steels, produced on continuous wire mills and wire lines of small- and wire looms, regardless of the diameter, which reaches 26 mm. The main part of the wire rod is directed for further processing at steel wire and hardware enterprises. In recent years, the volume of production of wire rod from continuously cast blanks with a high degree has increased metallurgical purity, including for the production of particularly responsible products. For example, such as a metal cord, which has a high level of endurance, and in terms of strength, this type of product is divided by normative strength into normal (NT 2400 ... 2750 N / mm2), high (HT 2750 ... 3100 N / mm2), super high (ST 3100... 3450 N / mm2) and ultra-high-strength (UT 3450 ... 3750 N / mm2). Considerable attention is paid to the improvement of the high-carbon steel smelting process. Various methods are offered to ensure the purity of steel and the formation of high strength properties. To improve the plasticity of steels, alloying additives with a significant content of carbon and manganese are widely used limited nitrogen content. Processing at the ladle-furnace installation in the process of high-carbon smelting was analyzed steel with improved plasticity for cold deformation.

Oxygen distribution between phases during ladle processing of aluminum killed bof steels

The modern state of secondary metallurgy is characterized by the sustainable development of technologies that ensure high metal quality by reducing the number of non-metallic inclusions, the which is closely related to the oxygen content in steel after smelting. Therefore, the issues of regularities of oxygen distribution between phases at the stage, BOF - CCM. Purpose. The aim of the research was to determine the conditions of redistribution of oxygen dissolved in the metal depending on the stages of steel processing, to determine the degree of approach of deoxidation processes to thermodynamic equilibrium. Methodology. Research was carried out in industrial scale. Steel grades 34Cr and 36CrB were smelted in BOF of 170-t capacity. Processing of crude steel was carried out in a LF unit with further vacuum degassing and wi thout it and transfer of steel to CCM. At each stage of steel treatment, metal and slag samples were taken using an automatic sampler to determine the chemical composition, and the temperature. Oxygen content were monitored using a "Celox" analyzer. Findings. The carried-out studies showed that before the end of metal processing in the ladle, it is possible to detect individual reoxidation processes caused by unwanted ingress of oxygen from the air and from ladle slag oxides. Accor ding to calculations, in the second half of processing in the ladle and during casting, there is a slight deoxidation of steel with aluminum due to a decrease in temperature. Even if during this time due to the exchange reaction between steel and slag, a small amount of Mn and Si is recovered from the ladle slag, while its composition is practically constant throughout the period of steel processing in the ladle, while the metallurgical reactions proceed in the region of thermodynamic equilibrium. Originality. It has been determined that oxygen activity in steel varies unevenly over time and decreases to 3 ppm by the end of treatment in the ladle. While in each case it is in the Fe – a[O] – Al system near the calculated values of thermodynamic equilibrium. Practical value. The use of the obtained regularities makes it possible to obtain the specified content of aluminum in steel for the studied assortment and to predict the burning of deoxidizers and alloying elements, ensuring the reliability of obtaining the required chemical composition of steel with a high degree of purity. Key words: reoxidation, deoxidation, oxygen activity, slag, metal, non-metallic inclusion After blowing end in the converter, the oxygen activity in steel is in the range of 1000-1500 ppm [1-3]. After tapping from the vessel to a teeming ladle, the oxygen content in the metal is reduced by secondary metallurgy processes in order to provide high-quality of continuously cast billets and high purity of steel. At this stage steel reaches necessary temperature and chemical composition. Important for theory and practice are patterns of oxygen distribution between phases at each stage of secondary metallurgy, studied directly under production conditions. This distribution determines the removal efficiency of harmful impurities, non-metallic inclusions and gases from the steel. It is advisable to compare the measured oxygen contents with equilibrium states, which can be easily achievable in practice, and their calculation can be carried by metallurgical scientists.

On the effect of non-metallic inclusions in production of small diameter wires

Invistigations are directed to detection of the metallurgical reasons of the breakage of alloy steels during production of the small diameter wire. Several batches of the coiled bar(s) of low carbon silicon-manganese steels of the Sv-08G2S and G3Si1 were taken as materials for invistigation. The main influence on the metal breakage during drawing is exerted by its structure and mechanical characteristics, it is known. The initial structure of the coiled bar(s) before drawing to small diameters from the differents smelting within one sort was not differ and represented globular pearlite for Sv-08G2S steel, ferrite and pearlite for G3Si1 steel. The influence of equipment and drawing technology on the wire breakage is minimal, as the processing is performed with the same conditnions. Special attention in the invistigations was paid to the contamination of steel with nonmetallic inclusions during the drawing. Analysis is showed in the wire of low carbon silicon-manganese steels the presence of the point oxides, non-deformable silicates and sulfides, and fragile inclusions, which are located along the rolling direction. The feature of the wire, which has observed the breakage during the production, is the presence of the large quantity of the line inclusions (3...5 points), which are located in some cases over the entire surface of the polished section of the Sv-08G2S steel. The structure of all investigated steels does not differ, the mechanical characteristics of the wire with breakage corresponded to the required standard values. It is shown that contamination of the original wire rod with (more than 2 points) of nonmetallic inclusions are significantly increases the chance of difficulties arising during production of the wire with a diameter of 1,2...0,8 mm and can lead to breaks. The high purity of steel in terms of nonmetallic inclusions guarantees the absence of breakage due to this defect during the production of wire, which contributes to increase of the performance and decrease in the cost of finished products.

Boosted photoinduced cathodic protection performance of ZnIn2S4/TiO2 nanoflowerbush with efficient photoelectric conversion in NaCl solution

Boosting the photoinduced cathodic protection (CP) for metals in NaCl solution is crucial for achieving the application of photoelectrochemical conversion in marine corrosion protection. An environmentally friendly three-dimensional ZnIn2S4/TiO2 nanoflowerbush (NFB) photoelectrode was constructed with sufficient interfacial incorporation based on the ultrafine branched TiO2 nanobush substrate via a facile in situ hydrothermal method. This ZnIn2S4/TiO2 NFB nanoheterojunction composite behaves excellent photoinduced CP performance for metallic materials. This is owing to the optimized construction of photoelectrode with relatively negative band potential, wide solar spectrum response, effective generation and collection of photoinduced electrons. The morphology, distribution and performance of ZnIn2S4 vary with different substrates. The pure ZnIn2S4 powder is nanoflower sphere composed of a lot of thin petals; when ZnIn2S4 grow onto the FTO glass, the ZnIn2S4 petals are distributed vertically on the two-dimensional structure; when ZnIn2S4 grow on the three-dimensional ultrafine branched TiO2 nanobush substrate, a ZnIn2S4/TiO2 NFB architecture with ultrafine TiO2 branchlet cores are formed. This ZnIn2S4/TiO2 NFB photoelectrode can achieve efficient photoinduced CP performance for pure copper and low alloy steels with different negative self-corrosion potentials, such as Cu (−0.18 V), E40 (−0.45 V), Q345 (−0.55 V) and Q235 carbon steel (−0.65 V) under simulated sunlight irradiation in NaCl solution without additional hole scavengers, and the photoinduced CP current densities reach as high as 170, 72, 63 and 44μAcm−2, respectively. The high-efficiency photoinduced CP performance is closely related to the band structure gradient matching between the TiO2 and ZnIn2S4, prompting both the widened absorption of solar spectrum and high-efficiency transfer of the photogenerated electron–hole pairs. Importantly, the negative band potential of ZnIn2S4 endues a lower surface work function which benefits the electron transport to the under-protected metallic materials to achieve photoinduced CP. This photoelectrode exhibits huge photoinduced CP application potential in marine environments.

Evolution of the Numerical Model Describing the Distribution of Non-Metallic Inclusions in the Tundish

Continuous casting is one of the steel production stages, during which the improvement in the metallurgical purity of steel can be additionally affected by removing nonmetallic inclusions (NMIs). This can be achieved by means of various types of flow controllers, installed in the working space of the tundish. The change in the steel flow structure, caused by those flow controllers, should lead to an intensification of NMIs removal from the liquid metal to the slag. Therefore, it is crucial to understand the behavior of nonmetallic inclusions during the flow of liquid steel through the tundish, and particularly during their distribution. The presented paper reports the results of the modeling studies of NMI distribution in liquid steel, flowing through the tundish. CFD modeling methods—using different models and computation variants—were employed in the study. The obtained CFD results were compared with the results of laboratory tests (using a tundish water model). The results of the performed investigations allow us to compare both methods of modeling; the investigated phenomena were microparticle distribution and mass microparticle concentration in the model fluid. The validation of the CFD results verified the analyzed computation variants. The aim of the research was to determine which numerical model is the best for describing the studied phenomenon. This will be used as the first phase of a larger research program which will provide for a comprehensive study of the distribution of NMIs flowing through tundish steel.

On the issue of complex processing of phosphorous iron ores

The reasons for the complete or partial rejection of the phosphorous iron ores (PIO) usage in ferrous metallurgy contrary to a shortage of iron ore raw materials are considered. Dephosphorization of metal from high-phosphorous cast irons leads to the complication of technology and deterioration of the production economics because of high intensity of the converter smelting and increasing requirements for the purity of steel. Limitation of PIO share in the blast furnace charge and decrease of phosphorus contents in cast irons led to a deterioration of the steel phosphate slag (PS) quality as fertilizers, which results in its disposal to the dump. Information on the opposite foreign practice of obtaining satisfactory phosphate slags is given, which is an increase in cast iron phosphorus contents by addition of ferrophosphorus. The reasons for abandoning this practice are analyzed. The authors studies aimed at increasing of phosphorus concentration in phosphate slags to bring PS conditions up to the requirements for specially produced by the chemical industry fused fertilizing phosphates and/or an intermediate product for the production of yellow phosphorus are described. On the basis of research and a technical and economic assessment, the feasibility of returning to the use of ferrophosphorus after making appropriate adjustments was substantiated. According to the proposed technology, phosphorous ferroalloy is used as a direct reagent in relation to substandard phosphate slags using their physical heat and exothermic reaction. The process is feasible outside the main metallurgical units and does not require the complication of steelmaking technology. It is possible to use ferrophosphorus as a by-product of the phosphorus industry due to its excess in the world market. It could also be obtained by reduction smelting of dump PS or current discharge slag. Phosphorous iron ores deep processing and the associated production of expensive chemical products will rise economic viability of “phosphorus-infected” iron ores usage.

Причины образования трещиноподобных дефектов в толстолистовой стали 09Г2С для резервуарных металлоконструкций

Determination of causes of crack-like defects in the heavy plate steel 09Г2С is a crucial task, the solution of which is aimed at improving the mechanical safety of oil storage steel vertical tanks. In order to determine the causes for the formation of a group of crack-like defects oriented towards rolling, revealed during grinding and magnetic inspection of the tank wall surface near the vertical weld, the analysis of the chemical composition and testing of the mechanical properties of heavy plate steel were carried out, including the determination of the anisotropy of impact toughness in the temperature range from +20 to –75 °С, analysis of metal microstructure in the area of defect formation on transversal sections and rolled surface. Impact bending tests of 09Г2С heavy plate steel after controlled rolling in longitudinal and transverse directions showed no anisotropy of impact toughness, as well as high purity of steel as for sulfur and titanium, which at higher content causes impact toughness anisotropy. The revealed features of metal microstructure near the defects made it possible to conclude that the crack-like defects were formed during the rolling of gas bubbles at the stage of preparing semi-finished rolled products for finishing rolling. One of the possible methods to prevent such defects from getting into finished rolled products is the use of automated systems of visual inspection of rolled products in the manufacturing process.