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The current work presents an optimization approach for improving stainless steel's performance and environmental impact. A Taguchi‐based grey relational analysis is used to determine the optimal alloy design of six stainless steels (304, 316L, 904L, 2304, 2205, 2507). The alloy design of a multivariable system (C, Mn, Cr, Ni, N, Mo, and Cu) is initially formulated based on the Taguchi orthogonal array. It combines the multiperformances (pitting corrosion resistance, proof strength, tensile strength, and greenhouse gas emissions) to determine a numerical score and suggests the optimal combination of alloy contents. The results are further analyzed using a range analysis to detect the significance of each alloy parameter and its level. The results show that nitrogen plays the most important role in determining the stainless steel's combined performance. Besides, the optimum alloy design consists of a high content of nitrogen, chromium, molybdenum, and copper combined with a low content of nickel. The study has a focus on proposing the systematic approach, Taguchi‐based grey relational analysis, to optimize the stainless steel's different mechanical properties with respect to environmental impact. [ABSTRACT FROM AUTHOR]

Producing sustainable anode materials for lithium-ion batteries (LIBs) through catalytic graphitization of renewable biomass has gained significant attention. However, the technology is in its early stages due to the bio-graphite's comparatively low electrochemical performance in LIBs. This study aims to develop a process for producing LIB anode materials using a hybrid catalyst to enhance battery performance, along with readily available market biochar as the raw material. Results indicate that a trimetallic hybrid catalyst (Ni, Fe, and Mn in a 1:1:1 ratio) is superior to single or bimetallic catalysts in converting biochar to bio-graphite. The bio-graphite produced under this catalyst exhibits an 89.28% degree of graphitization and a 73.95% conversion rate. High-resolution transmission electron microscopy (HRTEM) reveals the dissolution–precipitation mechanism involved in catalytic graphitization. Electrochemical performance evaluation showed that the trimetallic hybrid catalyst yielded bio-graphite with better electrochemical performances than those obtained through single or bimetallic hybrid catalysts, including a good reversible capacity of about 293 mAh g−1 at a current density of 20 mA/g and a stable cycle performance with a capacity retention of over 98% after 100 cycles. This study proves the synergistic efficacy of different metals in catalytic graphitization, impacting both graphite crystalline structure and electrochemical performance. [ABSTRACT FROM AUTHOR]

This work presents a process model developed based on mass and energy conservation to assess high carbon ferrochrome production from cradle to gate through four supply routes: (1) a conventional submerged arc furnace (SAF), (2) a closed submerged arc furnace with preheating (CSAF+PH), (3) a closed submerged arc furnace with 60% prereduction (CSAF+PR60%) and (4) a direct-current arc furnace (DCAF). The energy requirements are between 40 and 59 GJ/t FeCr (74–111 GJ/t Cr), and the greenhouse gas (GHG) emissions range between 1.8 and 5.5 tCO2-eq/t FeCr (3.3–10.3 tCO2-eq/t Cr). The upgrading of coal-powered SAF process to a closed furnace CSAF+PH and CSAF+PR60% contributes to an emission reduction of 23% and 18%, respectively. Moreover, the use of hydro-powered electricity leads to a further emission reduction of 68% and 47%, respectively. For CSAF+PR process, the GHG emissions can be reduced by 14% when increasing the pre-reduction ratio from 30% to 80% and decreased by 10% when charging hotter feed from 100 °C to 1000 °C. The proposed process model is feasible in generating site-specific inventory data and allowing for parameter studies as well as supporting companies to improve the transparency of the environmental performance in the FeCr value chain. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) serve as the most promising next-generation commercial batteries besides lithium-ion batteries (LIBs). Hard carbon (HC) from renewable biomass resources is the most commonly used anode material in SIBs. In this contribution, we present a review of the latest progress in the conversion of waste biomass to HC materials, and highlight their application in SIBs. Specifically, the following topics are discussed in the review: (1) the mechanism of sodium-ion storage in HC, (2) the HC precursor's sources, (3) the processing methods and conditions of the HCs production, (4) the impact of the biomass types and carbonization temperature on the carbon structure, and (5) the effect of various carbon structures on electrochemical performance. Data from various publications have been analyzed to uncover the relationship between the processing conditions of biomass and the resulting structure of the final HC product, as well as its electrochemical performance. Our results indicate the existence of an ideal temperature range (around 1200 to 1400 °C) that enhances the formation of graphitic domains in the final HC anode and reduces the formation of open pores from the biomass precursor. This results in HC anodes with high storage capacity (>300 mAh/g) and high initial coulombic efficiency (ICE) (>80%). [ABSTRACT FROM AUTHOR]

The iron and steelmaking industry faces the dilemma of the need to decrease their greenhouse gas emissions to align with decarbonization goals, while at the same time fulfill the increasing steel demand from the growing population. Replacing fossil coal and coke with biomass-based carbon materials reduces the net carbon dioxide emissions. However, there is currently a shortage of charcoal to fully cover the demand from the iron and steelmaking industry to achieve the emission-reduction goals. Moreover, the transportation and energy sectors can compete for biofuel usage in the next few decades. Simultaneously, our society faces challenges of accumulation of wastes, especially wet organic wastes that are currently not reused and recycled to their full potentials. Here, hydrothermal carbonization is a technology which can convert organic feedstocks with high moisture contents to solid fuels (hydrochar, one type of biochar) as an alternative renewable carbon material. This work studied the differences between a hydrochar, produced from lemon peels (Lemon Hydrochar), and two types of charcoals (with and without densification) and an Anthracite coal. Characterizations such as chemical and ash compositions, thermogravimetric analyses in nitrogen and carbon dioxide atmospheres, scanning electron microscope analyses of carbon surface morphologies, and pyrolysis up to 1200 °C were performed. The main conclusions from this study are the following: (1) hydrochar has a lower thermal stability and a higher reactivity compared to charcoal and Anthracite; (2) densification resulted in a reduction of the moisture pickup and CO2 reactivity of charcoal; (3) pyrolysis of Lemon Hydrochar resulted in the formation of a large amount of tar (17 wt%) and gas (39 wt%), leading to its low fixed carbon content (27 wt%); (4) a pyrolyzed hydrochar (up to 1200 °C) has a comparable higher heating value to those of charcoal and Anthracite, but its phosphorous, ash, and alkalis contents increased significantly; (5) based on the preliminary assessment, hydrochar should be blended with charcoal or Anthracite, or be upgraded through slow pyrolysis to fulfill the basic functions of carbon in the high-temperature metallurgical processes. [ABSTRACT FROM AUTHOR]

The pressure on the steel industry to reduce its carbon footprint has led to discussions to replace coke as the main reductant for iron ore and turn to natural gas, bio-syngas or hydrogen. Such a major transition from the blast furnace-basic oxygen furnace route, to the direct reduction-electric arc furnace route, for steel production would drastically increase the demand for both suitable iron ore pellets and high-quality scrap. The value for an EAF plant to reduce the SiO2 content in DRI by 2 percentage points and the dirt content of scrap by 0.3 percentage points Si was estimated by using the optimization and calculation tool RAWMATMIX®. Three plant types were studied: (i) an integrated plant using internal scrap, (ii) a plant using equal amounts of scrap and DRI and (iii) a plant using a smaller fraction of DRI in relation to the scrap amount. Also, the slag volume for each plant type was studied. Finally, the cost for upgrading was estimated based on using mainly heuristic values. A conservative estimation of the benefit of decreasing the silica content in DRI from 4 to 2% is 20 USD/t DRI or 15 USD/t DR pellets and a conservative figure for the benefit of decreasing the dirt in scrap by 0.3 percentage points Si is 9 USD/t scrap. An estimate on the costs for the necessary ore beneficiation is 2.5 USD/t pellet concentrate and for a scrap upgrade, it is 1-2 USD/t scrap. [ABSTRACT FROM AUTHOR]

Typical non-metallic inclusions in two industrial low-carbon steels for oil pipelines were investigated as three-dimensional objects on film filters after electrolytic extraction and filtration of metal samples. A method of soft chemical extraction using a 10%AA electrolyte was used to study the initial corrosion process in the steel matrix surrounding various non-metallic inclusions. To determine and compare "corrosive" inclusions and their influence on the initial stages of corrosion of the adjacent layer of the steel matrix, quantitative parameters (such as the diameter of the corrosion crater (Dcr) and pit (Dpit), and the relative dissolution coefficient of the metal matrix (KD) around various inclusions) were determined after chemical extraction. It was found that CaO-Al2O3-MgO oxides and TiN inclusions did not cause an initial corrosion of the steel matrix surrounding these inclusions. However, tensile stresses in the steel matrix occurred around CaS inclusions (or complex inclusions containing a CaS phase), which contributed to the initiation of corrosion around these inclusions. [ABSTRACT FROM AUTHOR]

Several stainless-steel slags have been successfully employed in previous studies as substitutes for lime in the treatment of industrial acidic wastewaters. This study deepens the knowledge of such application, by analyzing the neutralizing capacity of different slags related to their mineral compositions. To do so, firstly the chemical and mineral compositions of all the slag samples are assessed. Then, 0.5 g, 1 g, 2 g of each slag and 0.25 g and 0.5 g of lime are used to neutralize 100 g of 0.1 M HCl or HNO3 solutions. After the has neutralization occurred, the solid residues are extracted and analyzed using XRD spectroscopy. Then, the solubility of the minerals is assessed and ranked, by comparing the XRD spectra of the residues with the obtained pH values. The results show that minerals such as dicalcium silicate and bredigite are highly soluble in the selected experimental conditions, while minerals such as merwinite and åkermanite, only partially. Moreover, Al-rich slags seem to perform poorly due to the formation of hydroxides, which generate extra protons. However, when the weight of slag is adequately adjusted, Al-rich slags can increase the pH values to higher levels compared to the other studied slags. [ABSTRACT FROM AUTHOR]

Laboratory experiment and thermodynamic calculation for the Ti-containing 24 mass pct Cr ferritic stainless steel with a CaO-SiO2-Al2O3-MgO system slag were performed to investigate the effect of slag addition on the inclusion characteristics in molten steel. The morphology, composition, and size evolution of inclusions in steel samples were analyzed in three-dimensional by the electrolytic extraction method and in two-dimensional by the automatic analysis method. The results showed that the Ti content significantly decreased after the slag addition. However, the change of the Si content showed an opposite tendency. The decrease of the Ti content in steel was due to the reduction of SiO2 and Al2O3 in the slag by dissolved Ti in steel. An increase of the TiO2 content in the slag can decrease the Ti loss in steel based on the slag-steel kinetic analysis. The total O content in the steel melt decreased from 62 to 26 ppm, and the steel cleanliness was improved, since the number density of inclusions decreased after the slag refining. The results of a kinetic analysis showed that the rate-determining step of the oxidation of Ti in the steel and the reduction of SiO2 in the slag were the mass transfer on the slag side. In addition, high Ti2O3-containing inclusions were found to be transformed to Cr2O3-Ti2O3-Al2O3 and Cr2O3-Ti2O3-SiO2 system inclusions after the slag addition. The Al2O3 contents in inclusions increased while the Ti2O3 contents decreased with time. However, there were some amount of high melting point inclusions with high Al2O3 content, which were not what we expected. When plotted on logarcxithmic scales, the mole ratio X Al 2 O 3 / (X Ti 2 O 3 · X Cr 2 O 3 ) values of the inclusions were expressed as a linear function of the a Al 2 / (a Ti 2 · a Cr 2 · a O 3) values of the steel melts with a slope of unity, which was theoretically expected. [ABSTRACT FROM AUTHOR]

The influence of commercial low carbon ferrochromium (LCFeCr) additions on the inclusion characteristics in Ti-containing ferritic stainless steel was studied by laboratory experiment in this work. The inclusions in steel before and after the FeCr alloy additions were investigated through systematic samplings and microscopy investigations of the liquid steel. Different types of inclusions in the FeCr alloy and steel were detected and the evolution of the inclusion characteristics (e.g., composition, size, morphology, and number density) were investigated. The results showed that the Ti content decreased after the FeCr alloy additions. Furthermore, MnCr2O4 spinel inclusions originating from the FeCr alloys transformed into Ti2O3–Cr2O3-based liquid inclusions and Ti2O3-rich solid inclusions. They were formed due to the reactions between MnCr2O4 and TiN inclusions or dissolved Ti in molten steel. The ratio of Ti/Al in the steel melt has a direct influence on the evolution of inclusions from thermodynamic calculations. The addition of FeCr alloys caused an increased number density of these Ti2O3-containing inclusions and TiN inclusions up to 8 minutes from the time of alloy addition. The increased Cr content from 16 to 24 mass pct due to the FeCr additions can increase the critical N content to form TiN inclusions at a specific Ti content. Overall, this study has contributed to the understanding the behavior of inclusions from LCFeCr alloy during the alloying process in Ti-containing steel. [ABSTRACT FROM AUTHOR]

Ferroalloys are one of the most important raw materials widely used in the steelmaking processes. Depending on the cleanliness of used ferroalloys, they can be an inevitable source of impurities and nonmetallic inclusions (NMIs) in steelmaking products. Herein, the inclusions in five different industrial ferroalloys (FeTi, FeMo, FeW, MnN, and FeCrN) are investigated. This is done using 2D investigations on polished cross sections of ferroalloy samples and using 3D investigations of NMIs on film filters and metal surfaces after electrolytic extraction (EE) using scanning electron microscopy in combination with energy‐dispersive spectroscopy (SEM‐EDS). Moreover, the characteristics of the main types of inclusions presented on film filters and metal surfaces after EE are compared and their possible transformations in Al‐killed steel are evaluated. The results show that the main inclusions are more likely the oxidization products of the reductant and some unreduced ore during the ferroalloy production process. The 3D investigations of inclusions on metal surfaces after extraction are found to be very useful in detection and evaluation of larger‐sized inclusions. Overall, this study helps to better understand the impurities in different ferroalloys and their possible effect on the steel cleanliness. [ABSTRACT FROM AUTHOR]

The characteristics of nonmetallic inclusions (NMIs) in low‐alloyed steel samples taken during ladle treatment before and after Ca treatment are evaluated using the pulse distribution analysis optical emission spectroscopy (PDA/OES) method, INCA‐Feature investigations of inclusions on a polished surface of steel samples, and 3D investigations of NMIs after electrolytic extraction (EE) of steel samples. The investigation results of NMIs using the different methods were compared. The PDA/OES results show a clear tendency of a change in the average composition and quantity of NMIs during ladle treatment, which correlates well with the results obtained from the other two methods. Overall, it is found that the application of the PDA/OES method is appropriate to enable a fast online evaluation of inclusion compositions and their behaviors during steelmaking. This, in turn, provides the means for establishing an online control and correction of technological operations of the ladle treatment to implement necessary modification of NMIs to improve the cleanliness of steels and avoid clogging problems during casting. [ABSTRACT FROM AUTHOR]

High turbulence at the liquid steel−mold flux interface results in mold flux entrapments, which can generate nonmetallic inclusions during the ingot‐casting process. Those nonmetallic inclusions are detrimental to the final steel quality. The teeming process during ingot casting is typically conducted using the uphill teeming method. The authors propose a novel alternative method using a side teeming process, which decreases turbulence at the free surface. To define the optimum operational conditions, a 3D mathematical model is developed to investigate the effect of the filling angle on the motion of the free surface and the resulting shear stresses during the teeming process. The investigated filling angles are 0°, 30°, 45°, 60°, and 90°. The present findings suggest that using the filling angle of 90° between the mold and the runner is an effective way of reducing the number of inclusions due to mold flux entrapments and refractory wear. [ABSTRACT FROM AUTHOR]

Alloy 825 is a nickel-based alloy that is commonly used in applications where both high strength and corrosion resistance are required, such as tanks in the chemical, food and petrochemical industries and oil and gas pipelines. Components made from Alloy 825 are often manufactured using hot deformation. However, there is no systematic study to optimise the processing conditions reported in literature. In this study, a processing map for as-cast Alloy 825 is established to maximise the power dissipation efficiency of hot deformation in the temperature range of 950 to 1250 °C at an interval of 50 °C and strain rate range of 0.01 s - 1 to 10.0 s - 1 to a true strain of 0.7 using a Gleeble-3500 thermomechanical simulator. The processing conditions are also correlated to the Vickers hardness of the final material, which is also characterised using optical microscopy and scanning electron microscopy, including electron backscattered diffraction. The true stress-true strain curves exhibit peak stresses followed by softening due to occurrence of dynamic recrystallization. The activation energy for plastic flow in the temperature range tested is approximately 450 kJ mol - 1 , and the value of the stress exponent in the (hyperbolic sine-based) constitutive equation, n = 5.0 , suggests that the rate-limiting mechanism of deformation is dislocation climb. Increasing deformation temperature led to a lower Vickers hardness in the deformed material, due to increased dynamic recrystallization. Raising the strain rate led to an increase in Vickers hardness in the deformed material due to increased work hardening. The maximum power dissipation efficiency is over 35 % , obtained for deformation in the temperature range 1100-1250 °C and a strain rate of 0.01 s - 1 - 0.1 s - 1 . These are the optimum conditions for hot working. [ABSTRACT FROM AUTHOR]

The flow pattern affects the interaction between the mold flux and liquid steel, especially during the initial entry of liquid steel into the mold. Strong turbulence can cause mold flux entrapments during the ingot casting process. If this happens, nonmetallic inclusions are generated, which decreases the quality of the final product. Herein, the side teeming process is introduced as an alternative to the traditional uphill teeming process to decrease mold flux entrapments. Both physical experiments and mathematical modeling are conducted to study the free surface. Specifically, the Weber number is also evaluated to predict the possibility of mold flux entrapments at the free surface. The results show that a calmer free surface is formed in the side teeming process compared with the uphill teeming process. Also, the results show that the Reynolds stress model is more suitable to predict the free surface compared with the realizable k–ε model. The present findings strongly suggest that an implementation of a side teeming process would be an effective way of reducing the risk for mold flux entrapments. [ABSTRACT FROM AUTHOR]

Chromium is normally added to liquid alloy in the form of different grades of ferrochromium (FeCr) alloys for the requirement of different alloy grades, such as stainless steels, high Cr cast iron, etc.. In this work, inclusions in two commercially produced alloys, i.e., high-carbon ferrochromium (HCFeCr) and low-carbon ferrochromium (LCFeCr) alloys, were investigated. The FeCr alloy/liquid iron interactions at an early stage were investigated by inserting solid alloy piece into contact with the liquid iron for a predetermined time using the liquid-metal-suction method. After quenching these samples, a diffusion zone between the alloys and the liquid Fe was studied based on the microstructural characterizations. It was observed that Cr-O-(Fe) inclusions were formed in the diffusion zone, FeOx inclusions were formed in the bulk Fe, and an "inclusion-free" zone was detected between them. Moreover, it was found that the HCFeCr was slowly dissolved, but LCFeCr alloy was rapidly melted during the experiment. The dissolution and melting behaviors of these two FeCr alloys were compared and the mechanism of the early-stage dissolution process of FeCr alloys in the liquid Fe was proposed. [ABSTRACT FROM AUTHOR]

A recent three-dimensional (3D) model that revisited earlier theoretical work for longitudinal electromagnetic stirring in the continuous casting of steel blooms is analyzed further to explore how the bloom width interacts with the pole pitch of the stirrer to affect the magnetic flux density. Whereas the first work indicated the presence of a boundary layer in the steel near the interface with the stirrer, with all three components of the magnetic flux density vector being coupled to each other, in the analysis presented here we find that the component along the direction of the travelling wave decouples from those in the other two directions and can even be determined analytically in the form of a series solution. Moreover, it is found that the remaining two components can be found via a two-dimensional computation, but that it is not possible in general to determine these components without taking into account the surrounding air. The validity of the asymptotically reduced model solution is confirmed by comparing it with the results of 3D numerical computations. Moreover, the asymptotic approach provides a way to compute the time-averaged Lorentz force components that requires two orders of magnitude less computational time than the fully 3D approach. [ABSTRACT FROM AUTHOR]

In this numerical study, the variations in the surface area of the cooling channels in a solid oxide fuel cell with different cross sections and multi-walled carbon nanotubes oil/MWCNT nanofluid volume fractions are considered. Rectangular, trapezoidal and elliptical cross sections, and nanofluid volume fractions of 0–6% for the fluid are chosen as the studied parameters as well as the mass flow rates. In this research, a 3D model is developed by the finite volume method using the computational fluid dynamics (CFD). Then, the flow field and the heat transfer rate are predicted. The results show that the dissipated heat in the fuel cell is dependent on the mass flow rate of the fluid. That increased heat increases the heat transfer rate. The presence of the solid particles can also reinforce the heat conduction of the coolant fluid and consequently improve the heat transfer performance. The pumping power is maximum for the highest mass flow rate and the highest solid nanoparticle volume fractions. Additionally, the pumping power is dependent on the route in which the sections with lowest momentum changes and lowest pressure drops have the least amount of the pumping power. The ratio of the dissipated heat by the nanofluid over the base fluid is compared to a pressure drop. The movement of flow with the lower mass flow rates will result in penetrations of the thermal boundary layers into different flow regions, which can increase the optimum temperature in the solid part of the fuel cell. By increasing the mass flow rate of the fluid passing through the channels from 0.002 to 0.004 kg s−1, the maximum temperature is decreased by 6.13, 3.34 and 6.35% for rectangular, trapezoidal and elliptical channels, respectively. [ABSTRACT FROM AUTHOR]

During electric arc furnace (EAF) steelmaking process, burnt lime is charged together with other slag forming materials to attain a specific basicity of the slag and to achieve purification by removing unwanted elements. Herein, fly ash (FA) containing ≈60% CaO generated from pulp/paper mills is tested to partially (15–50%) replace primary lime (PL) in pilot scale EAF trials. The obtained results show good possibilities. It is found that an increased amount of FA instead of PL reduces the required amount of FeSi (up to 3 kg t−1 of scrap) and increases the sulfur content in the final slag. As a result, the amount of required slag/ton of steel can be decreased. However, the phosphorus content in the metal is slightly increased. The replacement ratio of FA will be limited by the acceptable phosphorus level in the final steel, due to higher phosphorus content in FA from pulp and paper mills compared with that in PL. Applications of FA as slag formers can reduce the consumption of natural resources in the metallurgical processes. In addition, it can reduce the amount of wastes from pulp/paper industries sent to landfill, which is important from an environmental point of view. [ABSTRACT FROM AUTHOR]

The IronArc process is a novel approach to ironmaking which aims to reduce the associated CO 2 emissions. By superheating gas using electricity in a plasma generator (PG) the heat required for the process can be supplied without burning of coke. Reduction of hematite and magnetite ores is facilitated by additions of hydrocarbons from liquid natural gas (LNG). The melting and reduction of ore will produce a molten slag containing 90 pct wüstite, which will be corrosive to most refractory materials. A freeze-lining can prevent refractory wear by separating the molten slag from the refractory. This approach is evaluated in CFD simulations by studying the liquid flow and solidification of the slag using the enthalpy–porosity model in two different slag transfer designs. It was found that a fast moving slag causes a high near-wall turbulence, which prevents solidification in the affected areas. The RSM turbulence model was verified against published experimental research on solidification in flows. It was found to accurately predict the freeze-lining thickness when a steady state was reached, but with lacking accuracy for predicting the time required for formation of said freeze-lining. The results were similar when the k - ω SST model was used. A design with a slower flow causes more solidified material on the walls and can protect all areas of the refractory wall from the corrosive slag. A parameter study was done on the effect of viscosity, mushy zone parameter, heat conductivity and mass flow on the amount of solidified material, thickness of solidified material, heat flux, and wall shear stress. In the current geometry, freeze-linings completely protect the refractory for mass flow rates of up to 3 kg s - 1 , and are stable for the expected viscosity (0.05 to 0.3 Pa), heat conductivity (2 W m - 1 K - 1 ) , and used mushy zone parameter (10,000). [ABSTRACT FROM AUTHOR]

The characteristics of different shapes of nonmetallic inclusions (NMIs) are determined using different methods. In this respect, various shapes of NMIs, including spherical, octahedral, elongated, bar‐like, plate‐like, polyhedral, and irregular inclusions, are observed in different steels and ferroalloys. The inclusions are investigated using three methods: 1) 2D investigations on a polished cross section (2D method); 2) 3D investigations on a film filter after electrolytic extraction and filtration (EE method); and 3) 3D investigations on a metal surface after electrolytic extraction (MS method). In addition, scanning electron microscopy (SEM) with an energy‐dispersive spectrometer (EDS) is used for the determination of the chemical composition of inclusions. The advantages and limitations of different methods for investigations of different shaped inclusions are discussed. The results show that the 2D method is less precise to detect the morphology, size, and number of inclusions; however, the EE and MS methods are used to determine a more accurate morphology. Furthermore, the MS method is found to be more advantageous in detecting large‐sized inclusions. This study also shows that the results on both the film filter and metal surface should be grouped together to obtain more comprehensive information of the inclusion characteristics. [ABSTRACT FROM AUTHOR]

In semi-solid metal high pressure die casting and in conventional high pressure die casting, it is common to find a defect band just below the surface of the component. The formation of these bands is not fully understood. However, there are several theories as how they occur, and it has been suggested that segregation is caused by the migration of aluminium-rich externally solidified crystals. In the present work the formation of these bands is investigated theoretically by reviewing suitable potential mechanisms for the migration of such crystals. Two mechanisms are identified as the most probable: Saffman lift force and the Mukai-Lin-Laplace effect. However, it was not possible to identify which of these two mechanisms acted in the case studies. Further testing is required to identify the mechanism that is causing the migration of the aluminium globules and suitable tests are proposed. [ABSTRACT FROM AUTHOR]

Herein, the volume of fluid (VOF) model is applied to simulate the phenomenon caused by the bubble motion from the molten metal into a slag. First, the mathematical model is validated by the experimental data from the literature. Then, the model is used to quantitatively predict the process of a single argon bubble passage from the liquid steel into the liquid slag. Finally, a parametric study is conducted to determine how the bubble diameter and the interfacial tension influence the bubble movement. The simulation results show that the bubble passing patterns at the steel–slag interface are oscillation‐pass, oscillations‐breakup, oscillations‐pass, pass, and pass‐breakup for the 3, 5, 7, 10, and 15 (20) mm bubbles, respectively. For a 5 mm bubble, it is found that an increase in the interfacial tension from 0.04 to 0.8 N m−1 results in a delayed bubble passage time. The results also show that the bubble experiences an oscillations‐breakup process if the interfacial tension value is up to 1.15 N m−1. However, a higher interfacial tension value (1.8 N m−1) can make the bubble pass again but with a longer passage time. [ABSTRACT FROM AUTHOR]

The generation of nonmetallic inclusions due to mold flux entrapment is detrimental for the final steel quality in the uphill teeming process. Herein, physical and mathematical modeling using a full‐scale mold is conducted to investigate the change of the hump height and the surface height at the free surface during filling. Moreover, the Weber number is also studied to analyze the tendency of mold flux entrapment at the free surface. The results show that the Reynolds stress model can predict the hump height more accurately compared with the k − ε‐based turbulence models. In addition, the result shows that a lower filling rate can result in a lower hump height as well as less fluctuations of the hump and surface heights. Furthermore, the Weber number for the low flow rate case is lower than 12.3, which indicates a small or no risk for mold flux entrapment. The present findings suggest that a reduction in velocity in the mold entrance region are an effective means of reducing the risk of mold flux entrapment. [ABSTRACT FROM AUTHOR]

This article seeks to demonstrate a direct and simplified correlation between the measurement of the wettability and the agglomeration potency of the inclusion particles in liquid ferrous alloy. The established methodology has been validated by the agreement between the calculated coagulation coefficient of Al2O3 particles and the experimental data in the open literature. Subsequently, the coagulation coefficient of Al2O3, MgO, and Ti2O3 particles in ferrous alloy melts was evaluated quantitatively by the proposed method using the actual experimental data of contact angle and surface tension. Meanwhile, the effect of the matrix composition has been investigated by comparing the Hamaker constant and coagulation coefficient between Ti2O3/pure iron and Ti2O3/low-carbon steel systems. It is noted that the change of coagulation coefficient associated with the contact angle is caused by the formation of a new phase at the oxide/metal interface at the high temperature. The present work aims to provide a deep understanding of the connection between inclusion motion behavior in the liquid alloy and the high temperature interfacial phenomenon. [ABSTRACT FROM AUTHOR]

Samples taken from laboratory-produced 3rd generation advanced high-strength steels, solidified at a low cooling rate, have been investigated to study the characteristics of non-metallic inclusions. Two steels, containing 2 and 5 pct Mn content, were produced for this purpose. A higher number of total inclusions were observed in 5 pct Mn steel. The four main types of inclusions observed were Al2O3, AlN, MnS, and AlSiMn-oxide. These classes were divided into subclasses according to variations in their chemistry. The major subclasses of AlN inclusions are either plate-like or regular in shape and have different size distributions. Thermodynamic calculations suggest that plate-like AlN inclusions are formed at the initial stage of solidification, while faceted/regular-shaped inclusions are precipitated toward the end of solidification. Moreover, it was found that the size of nitride inclusions is related to their N content. This phenomenon is discussed from the viewpoint of nucleation theory. [ABSTRACT FROM AUTHOR]

The concepts of oxide metallurgy and inclusion engineering can be utilized to improve the properties of low-alloy steels. These concepts aim at controlling the formation of intragranular ferrite (IGF), often a desirable microstructure providing good mechanical properties without the need for expensive alloying elements. IGF formation is stimulated to occur at non-metallic inclusions and form an arrangement of fine, interlocking ferrite grains. A method that has contributed significantly to investigations in this field lately is high-temperature confocal laser scanning microscopy (HT-CLSM). HT-CLSM is suited for in situ studies of inclusion behavior in liquid steel and phase transformations in solid-state steel, where in particular, displacive phase transformations can be studied, since they provide sufficient topographic contrast. The purpose of the present report is to provide a brief review of the state of the art of HT-CLSM and its application for in situ observations of ferrite formation in inclusion-engineered steels. The scientific literature in this field is surveyed and supplemented by new work to reveal the capability of HT-CLSM as well as to discuss the effect of factors such as cooling rate and parent grain size on IGF formation and growth kinetics. The report concludes with an outlook on the opportunities and challenges of HT-CLSM for applications in oxide metallurgy. [ABSTRACT FROM AUTHOR]

IronArc is a newly developed technology for pig iron production with the aim to reduce the CO2 emission and energy consumption, compared to a conventional blast furnace route. In order to understand the fluid flow and stirring in the IronArc reactor, water modeling experiments are performed. Specifically, a down scaled acrylic plastic model of the IronArc pilot plant reactor is used to investigate the mixing phenomena and gas penetration depth in the liquid bath. The mixing time is determined by measuring the conductivity in the bath, after a sodium chloride solution is added. Moreover, the penetration depth is determined by analyzing the pictures obtained during the experimental process by using both a video camera and a high speed camera. The results show that the bath movements are strong and that a circular movement of the surface is present. The mixing in the model for the flow rate of 282 NL min−1 is fast. Specifically, the average mixing times are 7.6 and 10.2 s for a 95% and a 99% homogenization degree, respectively. This is 15% and 18% (per degree of homogenization) faster compared to the case when using 3 gas inlets and the same flow rate. [ABSTRACT FROM AUTHOR]

A water/oil physical model is built up to investigate the slag behavior under the side gas‐blowing condition of an AOD process. The critical side‐blowing air flow rates for the top oil entrainment and emulsification are investigated. In addition, the oil entrainment with the existence of solid particles is studied. Specifically, the influences of the tuyere size, oil viscosity, oil thickness, and volume fraction of solid particles in oil on the mixing phenomena are studied. It is found that oil viscosity is an important factor for the initial oil entrainment and emulsification. Oil thickness only has a slight influence on these phenomena. The critical air flow rate for both initial oil entrainment and emulsification increases slightly with an increased tuyere size from 2.0 to 3.2 mm. Empirical equations have been proposed to predict the critical air flow rate for the initial oil entrainment and emulsification. Furthermore, solid particles in oil are found to increase the critical air flow rate for an initial entrainment. This may be due to the increase of oil viscosity when solid particles exist in oil. In addition, a new model is developed to predict the oil viscosity when solid particles exist inside it. [ABSTRACT FROM AUTHOR]

It is well known that inclusions affect the properties of alloys. Therefore, the importance of understanding what inclusions exist and how they behave cannot be overstated. This study has examined the behavior of Al2O3-MgO particles and clusters in the melt during the ladle treatment of Alloy 825, who is a Ni-based Alloy. The effect of different stirring directions of electromagnetic stirring in combination with gas stirring is discussed based on three-dimensional investigations of the clustered particles. More specifically, the composition, size, and number of particles and clusters are determined after electrolytic extraction of metal samples by using SEM in combination with EDS. The results show that the agglomeration of Al2O3-MgO particles in the melt is faster for an upward induction stirring combined with a gas stirring in comparison to a downward stirring combined with a gas stirring. However, the total removal of clusters from the melt is more effective when using a downward induction stirring compared to when using an upward induction stirring, especially for large size clusters (>11.2 μm). The effect of the different stirring modes on the behavior of the Al2O3-MgO particles and clusters in the melt for the ladle treatment experiments agree with the theoretical predictions based on Stokes', Brownian, and Turbulent collisions. [ABSTRACT FROM AUTHOR]

During reduction in a blast furnace (BF), the iron ore pellets undergo structural changes, which facilitate dust generation due to the mechanical wear/disintegration of the pellets. The generated dust decreases the permeability and productivity of the BF process. Thus, this study investigates the mechanical wear of iron ore pellets reduced at 500 °C (P500) and 850 °C (P850) and compares the results to the wear of unreduced pellets (P25). Moreover, the dust generated during the wear experiments is also characterized. It is found that pellets reduced at 500 °C exhibit a ≈16-35% higher wear rate than reference unreduced pellets. For the pellets reduced at 850 °C, the mechanical wear is inhibited by a formation of a metallic layer at the outer surface of the pellets. Further, the dust generated due to mechanical wear of reduced pellets contain 3-6 times higher amount of coarse particles (>20 μm) as compared to the dust from unreduced pellets. The obtained results are explained on the basis of the structural changes, which take place during the reduction of pellets. [ABSTRACT FROM AUTHOR]

It is well known that inclusions affect the properties of the steel and other alloys. The importance of understanding the behavior of the inclusions during production can never be overstated. This study has examined the main types of big size (>10 μm) inclusions that exist in Ni-based Alloy at the end of ladle treatment and after casting during industrial production of Ni based Alloys 825. Sources, mechanisms of formation and behavior of different type large size inclusions in Alloy 825 are discussed based on 2 and 3D investigations of inclusion characteristics (such as, morphology, composition, size, and number) and thermodynamic considerations. The large size inclusions found can be divided in spherical (Type I and II) inclusions and in clusters (Type III-V). Type I-A inclusions (Al2O3-CaO-MgO) originate from the slag. Type I-B inclusions and Type II inclusions consist of CaO-Al2O3-MgO and Al2O3-TiO2-CaO, respectively. Both types originate from the FeTi70R alloy. Type III clusters (Al2O3-MgO-CaO) are formed during an Al deoxidation of the Ni-based alloy. Type IV clusters (Al2O3-TiO2-CaO) formed from small inclusions, which are precipitated in local zones which contain high Ti and Al levels. These clusters are transformed to Type III clusters over time in the ladle. Finally, Type V clusters are typical TiN clusters. [ABSTRACT FROM AUTHOR]

In this study, the composition, size, and number of large non-metallic inclusions (>20 μm) are investigated in a commercial refined FeTi70R alloy, which is used for deoxidation and alloying of different industrial high-quality steels. It is found that this ferroalloy contains different complex oxide inclusions, which sizes vary from 20 to 260 μm. These different complex inclusions contain mostly CaO, SiO2, and TiO x. When adding FeTi70R alloy in the steel during the final stage of ladle treatment, these large size inclusions can significantly decrease the cleanliness and mechanical properties of steel. Therefore, the evolution and behavior of these inclusions after addition of this ferroalloy into the liquid iron or Fe-40Ni-20Cr steel are investigated in laboratory experiments. In addition, the results from the laboratory scale experiments are compared to results obtained from industrial heats using Alloy 825. A consideration of the evolution mechanism of large inclusions after an addition of a FeTi70R alloy helps to understand their behavior in the melt. It also helps to estimate their possible harmful effects on the quality of this steel grade during commercial production. [ABSTRACT FROM AUTHOR]

The effect of different stirring conditions during ladle treatment on the steel cleanliness was studied in the steel plant of SSAB Special Steels in Oxelösund, Sweden. The cleanliness was examined with regards to the contents of sulfur, nitrogen, and large inclusion (>10mm). The results showed that vacuum degassing increased the amount of inclusions larger than 10 mm and that subsequent induction stirring suggested a possible positive effect on the inclusion removal. A shortening of the vacuum degassing time from 24 to 15 min did not affect the nitrogen or sulphur refining. Overall, all heats reached the desired composition and cleanliness levels regardless of the treatment time. [ABSTRACT FROM AUTHOR]

Clusters of Al2O3 inclusions in a liquid stainless steel (18/8) and in a clogged ZrO2 nozzle after casting were studied during a pilot plant trial. Samples were taken from the melt at different holding times after an addition of 0.1 mass% Al. The characteristics (composition, size, number, and morphology) of clusters and clustered inclusions in the steel samples and in the clogged nozzle were investigated after electrolytic extraction and etching by using SEM. It was found that the Al2O3 inclusions in the clusters are transformed from a spherical into irregular and regular (with sharp edges) shape during the holding time. Most of the inclusions in the clusters (>80%) after a 6 min holding time are regular inclusions, which have sharp edges and flat faces. The size of the inclusions in clusters in the melt increased on average from 1.0 μm at a 1 min to 5.2 μm at a 12 min holding time. While the sizes of different types of inclusions in the clogged nozzle correspond to those present in the liquid steel at respective time, the frequency of spherical inclusions in the clogged nozzle is about 2-4 times larger (particularly near the nozzle wall) compared to that in the melt. Growth and transformation of Al2O3 clusters in the liquid steel at different holding times after an addition of Al and during casting were considered based on the obtained results. [ABSTRACT FROM AUTHOR]

In the preceding work, the inclusion behavior in a submerged entry nozzle (SEN) and mold induced by using a swirl flow has been investigated. The results showed that a swirl flow can effectively promote the inclusions removal to the meniscus as well as reduce the inclusions entrapment at the solidified shell wall. Moreover, that the swirl flow was generated by using a full type electromagnetic swirl flow generator (EMSFG). In the present work, a kind of a half type EMSFG was investigated, since it is easier to implement in a production scale. The influence of the stirrer on the fluid flow, heat transfer, and inclusion behavior in the SEN and mold was studied. Furthermore, a comparison between these two types of EMSFG from the aspects of flow field, temperature field, and inclusion behavior was done. In addition, the effect of different magnetomotive forces, inclusion sizes, densities as well as boundary conditions on the inclusion behavior was studied. The results show that the effect of a half type EMSFG (88000 AT) on the molten steel is very close to a full type case (44000 AT). More specifically, the flow pattern, temperature distribution as well as inclusion behavior in the SEN and mold look very similar. Also, it was found that from the viewpoints of the inclusions separation to the mold meniscus and the inclusions trapping at the solidified shell wall, better results could be obtained for a 'Trap' boundary condition when using half type EMSFGs. [ABSTRACT FROM AUTHOR]

In this study, a side tuyere was introduced to investigate how it is possible to lower the mixing time and to avoid problems of a reduced stirring when using the application of slag splashing process in the combined top and bottom blown converter. Both physical and mathematical models were applied to study the flow in the bath. Specifically, the effects of a side-blowing gas jet on the bath stirring intensity was studied. The results indicate that the mixing time for a side blown converter is decreased profoundly compared to a conventional combined top and bottom blown converter. Overall, the mathematical model showed similar trends and a good agreement with that of the physical modeling data. Furthermore, the shear stress at the wall in the top-bottom-side (TBS) converter was considered, since the furnace lining is important when side blowing is used in the converter. It was found that the side wall shear stress is increased by introducing side blowing, especially in the region near the side blowing plume. Three side tuyeres with different locations in the same level did not show any obvious effects on the mixing of the bath, but showed apparent differences in the shear stress and the oscillation of the bath. Overall, the results showed that the mathematical model can be used to design the configuration of the metallurgical vessels when it is necessary to consider the oscillation and the shear stress of the bath. [ABSTRACT FROM AUTHOR]

In this work, the placement of an electromagnetic swirl flow generator (EMSFG) around a submerged entry nozzle (SEN) was proposed as a method for generating a rotating electromagnetic field in a continuous casting (CC) process of steel. First, two kinds of a full type EMSFG and a half type EMSFG were designed based on mathematical modeling. Then, distributions of magnetic flux intensity in an EMSFG as well as distributions of Lorentz force in molten steel were simulated. It was found that the EMSFG structure and electromagnetic parameters have an important effect on magnetic flux intensity and Lorentz force distributions. For both a full type and a half type EMSFG, the magnetic flux intensity and Lorentz force increases as the magnetomotive force increases. Especially, for a full type EMSFG, the magnetic flux intensity is distributed evenly in molten steel. Moreover, the Lorentz force increases along a radial direction in the molten steel in the SEN. However, for a half type EMSFG, the magnetic flux intensity and Lorentz force decreases gradually towards the region without an EMSFG. Consequently, a full type EMSFG with a 44 000 AT magnetomotive force and a 50 Hz frequency is more suitable to apply in the operation of an EMSFG under actual production conditions. [ABSTRACT FROM AUTHOR]

Previous studies have verified that a swirl flow generated in a submerged entry nozzle (SEN) can effectively improve a flow pattern and a heat transfer in a continuous casting (CC) process. In order to obtain a further in-depth understanding with respect to the effect of a swirl flow on a CC process, the inclusion behavior in a SEN and a mold was studied in the present work. The flow field and the temperature field of molten steel as well as the inclusion behavior in a SEN and a square bloom mold were simulated under the influence of a rotating electromagnetic field (swirl generator). Also, the influence of different inclusion parameters such as the densities, sizes, and boundary conditions, on the inclusion behavior was studied. The results show that a flow pattern in a SEN can be characterized into three distinct flow regions: an accelerating flow of molten steel from an electromagnetic swirl flow generator (EMSFG) inlet to an EMSFG center, a decelerating flow of molten steel from an EMSFG center to an EMSFG outlet, and a recirculation flow of molten steel from an EMSFG outlet to an SEN outlet. In addition, it was found that light Al2O3 inclusion moves towards the rotational center by a centrifugal force, and that a swirl flow prevents nozzle clogging. Moreover, it was also found that the inclusion separation to a mold meniscus increased and that the inclusions trapped into a solidified shell wall decreased when using a swirl flow. [ABSTRACT FROM AUTHOR]

This study focuses on the oxidation of water atomized metal powders. Pilot plant experiments were performed using liquid iron alloyed with manganese and carbon. The powder particle shape and the oxides were determined using optical and scanning electron microscopy with energy dispersive X-ray microanalysis. The oxygen in the atomized powders was mainly present as thin surface oxide layers, which were determined to increase from 10 to 40-60 nm, at increased particle sizes from 10 to 750 μm. In addition, manganese oxides were observed to be unevenly distributed at the surface of several particles for iron powders alloyed with 0.3 mass% Mn. Experimental data indicated that between 10 and 20% of the manganese was present as oxides in the powders. However, equilibrium calculations predicted a strong driving force for oxidation of manganese. More specifically, it was estimated that only 4% of the initial manganese content remained in the final atomized powders. [ABSTRACT FROM AUTHOR]

In order to develop efficient visible light-driven photocatalysts for environmental applications, novel g-C3N4/nanocage ZnS composites have been successfully fabricated via an anion exchange route using ZIF-8 as a self-sacrificing template. The as-prepared g-C3N4/ZnS composites were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy and photoluminescence. In addition, the photocatalytic oxidation of organic contaminants in aqueous solution was investigated with the g-C3N4/ZnS composite system under visible light irradiation by using rhodamine B as a model compound. The results indicate that the g-C3N4/ZnS composite photocatalysts show higher photocatalytic activity than the single component (pure g-C3N4 or ZnS). More specifically, the optimum photocatalytic activity of the g-C3N4/ZnS composite was achieved with a weight ratio of 6 :1, which is as high as 37.8 and 2.8 times those of individual ZnS and g-C3N4 under visible light irradiation. The enhanced photocatalytic activity of g-C3N4/ZnS is mainly attributed to an efficient electron-hole separation at the interface of the two semiconductors, as determined by photoluminescence spectroscopy. Moreover, it is observed that 'O2- is the main active species in the photocatalytic oxidation of RhB solution using a g-C3N4/nanocage ZnS composite. [ABSTRACT FROM AUTHOR]

As the requirements on material properties increase, there has been a demand on an additional knowledge on the effect of impurities in the ferroalloys on the properties. Thus, the number, morphology, size, and composition of inclusions in four different ferroalloys (FeTi, FeNb, FeSi, and SiMn) were investigated. This was done in three dimensions (3D) by using scanning electron microscopy in combination with energy dispersive spectroscopy after electrolytic extraction of the ferroalloy samples. The non-metallic and metallic inclusions were successfully analyzed on the surface of film filter. Thereafter, the particle size distribution was plotted for most of the non-metallic inclusions. The non-metallic inclusions were found to be REM oxides in FeTi, FeSi, and SiMn, Al2O3, Ti-Nb-S-O oxides in FeNb and silicon oxides in SiMn. Moreover, the intermetallic inclusions were found to be a Ti-Fe phase in FeTi, Ca-Si, and Fe-Si-Ti phases in FeSi and a Mn-Si phase in SiMn. In addition, the almost pure single metallic phases were found to be Ti in FeTi, Nb in FeNb, and Si in FeSi. [ABSTRACT FROM AUTHOR]

A mathematical model of gas injection in the AOD converter process has been developed by augmentation of an earlier developed three-dimensional two-phase model to the slag phase and an industrial relevant geometry including six nozzles. The model is based on fundamental transport equations and includes separate solution of the steel and the gas phases and their coupling by friction as well as the slag phase. The 3D 3-phase (steel, slag, and gas) AOD model has been used to predict fluid flow, turbulence, and bubble characteristics as well as fluid-slag dispersion. In addition, two different gas flow rates have been simulated which resulted in quite different flow pattern. This new findings opens up for future investigations of gas-metal reactions in the AOD converter, which are of key interest from an industrial point of view. [ABSTRACT FROM AUTHOR]