ABSTRACT. Automated inclusion analysis is a highly valuable tool for developing and monitoring clean steel practices. The chemical composition and concentrations of non-metallic inclusions in steel are sensitive to reactions between steel, slag, and refractory, and to process upsets like reoxidation. However, the ability to obtain quantitative inclusion information is constrained by the physics of imaging and microanalysis: many of the inclusions are similar in size to the electron interaction volume. Monte Carlo simulation of the interaction between electrons and steel samples is a valuable tool in understanding what can be measured, and how detection of inclusions is affected by image and threshold settings. In this paper, the effect of inclusion size and accelerating voltage on the brightness of manganese sulfide inclusions in steel is examined in some detail, as an example.

ABSTRACT. In the transition to a sustainable society an increased metal demand is expected. Even though the recycling rate of steel is high the demand for primary iron sources is expected to increase in connection to the green transition. Currently several projects are aiming at producing fossil-free iron by hydrogen reduction, both in direct reduction shaft furnaces and fluidized bed systems. Both processes requiring some level of agglomeration of magnetite based-iron ore concentrates as well as specific agglomerate properties. To obtain fossil-free iron the induration needs to be fossil-free, and today most of the external heat needed for induration is generated by fossil-based fuels. The production of hydrogen will generate a vast amount of oxygen that could be used in the production of iron ore agglomerates based on magnetite concentrate. The rate of the exothermic oxidation reaction is expected to be affected by the oxygen level in the gas used during induration and thus a high oxygen content could lead to a temperature increase in a pellet bed lowering the need for external fuel. It has been systematically explored in this work to provide thorough understanding which can assists in designing an optimal thermal and gaseous profiles in induration.

ABSTRACT. For sustainable iron making, the situation is becoming more and more challenging owing to the faster depletion of high-grade iron ore, increased fines generation due to mechanized mining, wide variations in chemistry and mineral characteristics, high content of gangue minerals and loss-on-ignition (LOI), and poor liberation characteristics of iron minerals. To counter the challenges of iron ores and making good quality of agglomerates, the focus has shifted to blending of low-grade iron ores with high-grade, beneficiation of lean iron ores, development of new technologies, and adopting the best available practices for agglomeration. Through conventional beneficiation, the iron ore fines having 55-57% Fe is being processed to achieve the concentrate of 60-62% Fe with 80-82% weight recovery. Further, low grade iron ores of 45-58% Fe with high gangue minerals have been treated at laboratory and pilot scale level to achieve the iron concentrate of 60-64% Fe with acceptable silica and alumina content for pellet making. The impact of iron concentrate quality, i.e., high LOI, moisture, high blain number, and pelletizing parameters on the pellet properties have been studied.

ABSTRACT. Carbon in hematite ore pellet provides in-situ heat and improves diffusion bonding as well as slag bonding. Coke or anthracite coal is generally used as the carbon source in hematite ore pelletizing. However, there are many waste materials wherein carbon is available such as blast furnace flue dust contains 35-40% C and Jhamacoal contains around 70-75% C. Both the above materials have no metallurgical use. The present study explores the possibility of using these two materials as carbon sources in place of coke/anthracite. The process parameters have been optimized to develop pellets with these carbon sources and the properties have been compared with coke added pellets. While the coke added pellets show 1.5% C as optimum, BFD and Jhama coal pellets show better pellet properties even at a 1%C level. Comparing all properties like CCS, reducibility, reduction degradation and swelling index, better performance has been found in BFD and Jhama coal pellets than coke added pellets. The use of these two materials also decreases induration temperature up to 50-75 °C. Thus, this study establishes the use of BFD and Jhama coal as alternative carbon sources in hematite ore pelletizing.

ABSTRACT. Induration of magnetite pellets comprises of oxidation phenomena at lower temperatures and sintering at relatively higher temperatures. Owing to incomplete or partial oxidation, the magnetite pellet may comprise of phases such as oxidized magnetite (hematite) as well as non-oxidized magnetite at any instant, and differ in their rate of sintering (reflected by shrinkage). Therefore, it is crucial to understand the probable factors which can influence the intrinsic sintering characteristics. The effect of temperature on rate of sintering has been presented elsewhere, while the influence of load or pressure imposed on the pellet is discussed here. Optical and push-rod dilatometers have been used to capture and evaluate the intrinsic sintering behavior of oxidized as well as non-oxidized magnetite pellets, where they are exposed to three levels of load – 0, 5 and 20 g at different temperatures. It was found that the rate of sintering varies with the load imposed on the pellets, and thus can affect the overall sintering kinetics. Such findings can further be incorporated into the Single Pellet Induration Model (SPIM) to simulate the induration behavior of single pellet at any position within the packed bed of pellets, where it is subjected to certain amount of load imposed by the weight of pellets above it.

ABSTRACT. With the scarcity of high-grade lump iron ore, the generation of a significant quantity of low-grade iron ore fines, and a huge amount of fines generation during mining, the development of blast furnace grade iron ore pellets is inevitable. In the present investigation, polyvinyl alcohol is used as a binder for iron ore pelletization. Iron ore pellets were prepared with different dosages of PVA and green pellet properties like green compressive strength, drop number and dry compressive strength were evaluated. The optimum binder percentage was determined based on standard green properties as per the requirement of pellet. Subsequently the stability of binder was evaluated by heating the pellet at different heating temperatures. The strength of pellets initially decreased but consequently its strength increased after heating at high temperatures. This phenomenon was observed firstly owing to loss of binder from pellet structure thereupon its strength increased by the formation of solid bridges in between the hematite particles to impart better bonding. Some of the physical properties of the pellet (i.e., shock temperature, apparent porosity) were also determined.

ABSTRACT. This work deals with advanced modeling and experimental methods to study the evolution of non-metallic inclusions during liquid steel processing. The modeling approach assumes the rate of inclusion modification is due to mass transfer-controlled reactions at the slag/metal interface. These models employ computational thermodynamics software for equilibrium calculations. The talk will focus on the effects of thermodynamic modeling on these predictions. The advanced experimental approach of interest here is the use of computer vision and machine learning methods to accurately and rapidly classify inclusions by chemical composition using the results of automated scanning electron microscopy and energy dispersive spectroscopy.

ABSTRACT. Fatigue life of bearing steels predominantly depends on steel cleanliness which requires controlled steel making practise. Formation of CAMS (CaO - Al2O3 – MgO - SiO2) type after refining process is detrimental to fatigue life of bearings. Strong de-oxidation through aluminium addition at tapping and weak de-oxidation through ferro-silicon addition at tapping both resulted in CAMS type during subsequent processing in rolled product due to steel-slag interaction. Industrial trials were conducted to study the evolution mechanism of inclusions during secondary refining processes under different de-oxidation practices to understand and control the hard alumina formation in steels. The inclusion compositions evolution was evaluated for various trial heats with different de-oxidation practice at different stages of steel processing using scanning electron microscopy. The evolution route of the high carbon chromium bearing steels deoxidised through aluminium and silicon are Al2O3  CaO - Al2O3– SiO2 – MgO and CaO - Al2O3 – SiO2  CaO - Al2O3 – SiO2 – MgO respectively. Process optimisation trials were carried out to control the Al2O3 content in inclusions so as to enable formation of liquid inclusions through modified de-oxidation recipe. Better castability with lower clogging tendency were observed with the modified deoxidation practice which is attributed to formation of liquid CAMS inclusions with lower Al levels in final inclusions.

ABSTRACT. High carbon eutectoid grade steel is widely used for tire cord application and requires low grain boundary carbides, low alumina and titanium nitride inclusions to avoid filament breaks during final wire drawing. Titanium nitride and alumina inclusions are non-deformable and have extremely high strength and could cause delamination and filament breaks during wire drawing. Cementite network at grain boundaries has been identified as a source of embrittlement in high carbon steels. Alumina and titanium nitride inclusions in high carbon eutectoid grade wire rods were therefore controlled in this study by the optimization of ladle slag chemistry, ferroalloy addition practice, argon bottom purging of ladle. Titanium nitride inclusions precipitate in steel during solidification even with low titanium and nitrogen content due to the effect of elemental segregation. This elemental segregation in billet was controlled by optimizing the continuous caster EMS parameters. Liquid steel super heat is controlled below 40 °C and continuous caster secondary cooling parameters were modified to reduce billet centerline carbon segregation and subsequent grain boundary carbide network in wire rods. Billet reheating temperature, stelmore conveyor laying head temperature and cooling pattern on stelmore conveyor at wire rod mill were also optimized to reduce the severity of grain boundary carbide network in wire rods.

ABSTRACT. Originated more than three decades ago, continuous improved , Calcium Treatment of liquid steel has become necessary with the increase in continuous casting ratio and is a well-established method to transform oxide and sulphide inclusions in steel to less harmful inclusions for improved steel properties. Deoxidation , desulphurization and inclusion modification are some of the essential features in secondary steel refining through injection of calcium alloy in the form of a cored wire. Amongst all the processes in secondary metallurgy, calcium treatment is certainly the most difficult due to its low density, low melting and boiling temperature and higher vapour pressure. A failure in calcium treatment may have catastrophic consequences. These problems have led to the development of special addition technique like cored wire injection. Minex Metallurgical Company Limited, started journey almost four decades back pioneer in “Cored Wire Injection System” as well as “Cored Wire Manufacturing Technology”. Developed different types of cored wire in addition to traditional CaSi cored wire and CALLOCK Pure Ca wire to stabilized improved recovery of Ca. In order to succeed right & efficient calcium treatment, continuous improvements are being pursued on both aspects: calcium based wire as well as injection conditions of the wire. Theoretical aspects of calcium treatments as well as salient features of plant scale trials have been presented in this paper.

ABSTRACT. Better understanding of the agglomeration behavior of non-metallic inclusions in the steelmaking process is of vital importance to control the cleanliness of the steel product. Less inclusions in the steel ingot are always desired by the steelmakers to reduce the risk of engineering problem, e.g. nozzle clogging and improve the final product’s mechanical properties. On the other hand, non-agglomerated inclusions with fine size can be utilized in different processes to optimize the microstructure and improve the final property. Both aspects correspond to the concept of ‘Inclusion Engineering’. In this work, the inclusion motion and agglomeration behaviors at the interfaces between steel/gas and steel/slag are overviewed, and former results in the open literature including the in-situ characterization as well as theoretical development are summarized. The authors’ work is also mentioned. Furthermore, previous results of the behaviors of the inclusion agglomeration at the bulk of the steels are also mentioned in comparison to the agglomeration behaviors of inclusions at the interfaces. Mechanisms of the attraction force between inclusions at these two cases are critically discussed. This work aims to provide an overview of the agglomeration behaviors of inclusions at different stages and provide a way forward to the future research of this important phenomenon contributing to ‘Inclusion Engineering’ in steels.

ABSTRACT. Electrical steel sheets used as the main material for magnetic iron cores in electric motors are manufactured by adding silicon and aluminum higher than conventional carbon steels. However, previous studies mainly focused on the high-Si, low-Al(<0.5%) systems, and the effect of slag on the inclusion formation behavior immediately after the Al or Si alloy was added is scarcely found. Therefore, in the present study, the formation behavior of non-metallic inclusions was investigated when Si was added to molten steel equilibrated with CaO-Al2O3-FetO-SiO2-MgO slag and when Al was added thereafter. When 4% Si is added, Al2O3 in the slag is reduced and Al pick-up occurs to molten steel, and hence the inclusions are transformed from silica- to alumina-rich system. Then, Mg pickup from the slag is caused by Si to convert the alumina inclusions into the MgO-Al2O3 spinel system. When 1.5% Al is added 30 minutes after Si addition, a higher fraction of spinel and some monoxide(MgO) inclusions are generated due to Mg pick up by Al. Area fraction and number density of inclusions increases after Al addition, because an additional deoxidation driving force is generated due to the lower equilibrium [O] level by Al. Consequently, it has been confirmed that the composition, area, and number of inclusions changes according to the addition of Al after the addition of Si.

ABSTRACT. As AI is the all-pervasive technology of the day causing disruptions in all domains including process industries, integrated steel plant is not an exception but rather a fertile space for piloting AI solutions and leveraging the same for impactful business results. Tata Steel has undertaken a journey in digital transformation wherein intelligent automation is being incorporated at all facets of the business from manufacturing to sales. This is primarily driven by Infusion of technologies like IoT, RPA, AI/ML/DS though inhouse efforts as well as technology partnerships. In this lecture, the speaker would like to give a glimpse of the few notable use cases developed and deployed within TSL India. Will try to cover examples through the value chain from raw material to finishing. Covers Data Science based process monitoring, Deep Learning bases Visual Analytics, Hybrid solutions using both AI and first principle modelling etc.

ABSTRACT. In Hot Strip Mill, the roughing mill exit temperature (RMET) is an essential input for calculating mill set-up. Any deviation in RMET would lead to either poor surface quality or unstable rolling. To achieve the desired RMET, slabs should be discharged from the reheating furnace at a precise soaking temperature. In reheating furnace, there are five zones, namely, recuperative, preheating, heating, pre-soaking and soaking. This article describes about a forecasting model aims to predict RMET value of a slab as it moves through pre-soaking and soaking zones. The forecasted RMET value is compared with the target temperature and if any deviation is found, the necessary correction can be achieved during its journey in the reheating furnace. The employed algorithm - Long Short Term Memory (LSTM) – takes thermal profiles of a given slab till its journey up to the heating zone and the actual RMET values of the previously discharged slabs gone through the roughing mill as inputs and forecasts the RMET temperature. Six months data has been used for developing the model. The root mean square error of the model is 13.92o C and 11.06 o C for furnaces 1 and 2 respectively. The model is integrated with the furnace Level-2 system. With this work, over or under heating of slabs has been eliminated significantly.

ABSTRACT. Optimizing process efficiency of blast furnace is important to increase its productivity and to reduce hot metal cost. Due to COVID pandemic in 2020, FBF was running under throttled production run. Post ramping of production, peripheral temperatures in lower belly and bosh region were running relatively low and furnace was operating at relatively higher fuel rate. To determine the factors affecting fuel rate of the furnace, a machine learning model was developed to ascertain the factors. In addition, K-means clustering method was used to determine optimum range of process parameters for reducing fuel rate and to increase peripheral temperatures. After adapting the recommendations provided by the machine learning model and K-means clustering, fuel rate was reduced by 14 kg/thm and peripheral temperatures had improved.

ABSTRACT. High strength low alloy steels achieve their enhanced properties by a combination of microalloying and controlled thermomechanical processing. An integrated microstructure based in-silico framework has been developed to enable design of hot-rolled Nb,Ti microalloyed steels. The integrated model suite captures the precipitation kinetics of Nb,Ti (C,N) and their impact on austenite recrystallization and phase transformation of ferrite in a hot strip mill. It comprises of a cellular automata model for austenite recrystallization, phase field model for austenite to ferrite phase transformation and FEM based micromechanics model for predicting the mechanical properties of the final microstructure. A multi-component equilibrium precipitate model is utilized to compute the precipitation kinetics of (Nb,Ti )(C,N) and their influence on the evolving microstructure across the processes. The effect of different process parameters on the precipitate kinetics and corresponding microstructure evolution will be presented.

ABSTRACT. Continuous casting is a critical link in the steel making value chain. Longitudinal cracks, defects on slab surface, would severely affect the end-product quality. Moulds are embedded with thermocouples to detect solidification abnormalities. When a crack moves in the downward direction along the mould, a characteristic ‘V’ type of signature in the time-temperature trend can be noticed. However, real time detection of cracks from this data has resulted inferior accuracy. Most of the times, cracks passes through the gaps between two thermocouple segments and hence would not get detected. In this investigation, machine learning models for predicting cracks have been developed. The inputs to the model consist of process parameters such as casting speed, super heat, heat fluxes, mould level fluctuations, Manganese to Sulphur ratio etc. Since cracks are observed in less than 1% of the total slabs produced, preparing a data frame for model building will create a highly imbalanced data set. Hence various imbalanced-learning methods such as under and over sampling of majority and minority classes, combination of both and balanced bagging classifier have been explored. Among all, balanced bagging classifier has provided the best results. On the final data set, XGBoost algorithm has been employed. The true positive is 83% and false negative is 11%. Model has been successfully implemented for real time prediction.

ABSTRACT. Optical fiber technologies offer many exciting possibilities for performing distributed temperature, strain, chemistry, and gap measurements in the harsh environments found in steel manufacturing. This presentation will highlight several promising fiber optic sensing technologies that are being employed to meet these measurement challenges and will review the status of five research programs that are employing these technologies: (1) Liquid core detection in continuous casting using silica FBG strain sensors, (2) Distributed temperature measurement for high spatial resolution thermal mapping of molds, refractory linings and EAF components using Rayleigh scattering with single mode silica fibers, (3) distributed temperature measurements at temperatures of up to 1800 C using multimode sapphire fiber FBG technology, (4) Analysis of mold flux chemistry and structure at 1400 C using a remote fiber optics Raman probe, and (5) temperature insensitive distributed gap measurement using fiber optic based extrinsic Fabry-Perot interferometry.

ABSTRACT. Transverse corner cracks are one of the most common defects formed during casting of micro-alloyed steels slabs in conventional casting process. Such cracks result in poor surface quality and may require rework in the form of scarfing. These activities are time consuming, cause production loss and poor customer satisfaction. If cracks are undetected before hot rolling or not properly removed by scarfing, they may result into material rejection and yield loss. The present work focuses on the study of cracking phenomena occurring during the casting process by combining the effect of process parameters and material behaviour. Oxide scale formed on slab surface during casting affects the efficiency of secondary cooling. Due to non-uniform cooling pattern on slab surface, it may lead to transverse corner crack formation. Additionally, mechanical stress generated during slab bending and unbending along with unfavourable temperature (in the low ductility zone) can also contribute to this defect formation. Constant and high casting speed with soft cooling is found to be helpful in reducing this defect. Crack susceptibility was investigated through hot ductility tests and it was found out that the temperature range between 700 to 900°C is more susceptible to cracking. The chemistry was redesigned to improve hot ductility through ferrite potential beyond normal peritectic regime.

ABSTRACT. The development of Continuous Temperature measurements at continuous casting machines in India is discussed as there is an increasing need to accurately control the parameters associated with casting liquid steel in a continuous casting machine. One of the main parameters is superheat, which is defined as the elevated temperature of the liquid steel above its liquidus. Accurate measurement of this elevated temperature is required to reliably control the casting speed of the machine. and in order to reflect the conditions in the Continuous Casting mould, which is where the liquid steel actually freezes at the start of the solid product forming process. A sensor mounted close to this and continuously monitoring the temperature is the superior solution. In order to complete the superheat picture, an accurate assessment of the liquidus must be provided in conjunction with continuous temperature. Heraeus Electro-Nite (HEN) have developed CasTemp Superheat package as a means for enhancing the visualisation of dynamic Superheat during casting, and ultimately helping to improve the control of casting through optimal use of the features included in the package. An overview and early adoption of the system is given highlighting the potential benefits for controlling superheat thereby reducing energy requirements and improving the associated process control parameters.

ABSTRACT. In the continuous casting process of steel, the inelastic strains, generated in the solidification front, are largely responsible for a crack generation. A non-homogeneous temperature field in casting due to improper secondary cooling can have a detrimental impact on the distribution of inelastic strains at the solidifying shell distorting the shape of the cast product. The internal cracks in the cast products are primarily generated in the solidification front where the strains are more due to improper cooling and lack of proper support to the solidifying shell. In this article, a coupled fluid, thermal and mechanical model has been developed to estimate the thermal profile and the inelastic strains, generated in the solidification front, during casting steel mini slabs of section size 300mm × 150mm, in the secondary cooling zones. The effect of these strains has been studied in the formation of cracks and deformation of solidifying shells. A modified secondary cooling strategy has been developed and validated to reduce the bulging and cracks in cast products.

ABSTRACT. As opposed to conventional thick slab casting, thin slab casters run at higher casting speeds and directly enter hot rolling. In such manufacturing setup, the steel surface quality assumes lot of importance. Defects such as cracks which manifest on the surface severely impact the quality and integrity of the slab. Longitudinal facial cracks (LFCs) are one such defect that led to downgrading of products. Investigation of LFCs in thin slab casters showed the locations of cracks around the edges of the funnel mould. The funnel mould in thin slab casters is specially designed to accommodate the submerged entry nozzle. The unique funnel shape results in shell deformation during casting solidification into the rectangular slab cross-section. This deformation of initial shell may result in hot tearing and cracks may propagate to the surface resulting in LFCs. In the present work, a coupled fluid flow, heat transfer and thermo-mechanical model is developed to predict the fluid flow, solidification, and stresses in the solidifying shell in the mould region of thin slab caster. High stress regions are observed along the funnel edges. Such stresses coupled with the weak unstable shell may result in serious defects during casting.

ABSTRACT. Refractory lining in the Blast Furnace hearth is always under severe thermo-chemical stress on account of the high temperatures of liquid metal and slag as well as the corrosive nature of the slag pool. The wear status of these linings is monitored indirectly through the temperatures of thermocouples embedded at different depths in the hearth bed as well as wall. While these temperatures give indication of the erosion or skull build up inside the hearth on a real-time basis, it is highly imperative to have a quantitative estimation of remaining thickness of original lining as well as built up skull. To derive the refractory thickness from thermocouple readings, an inverse heat transfer problem is solved using numerical methods. While a two-dimensional heat conduction is considered in the hearth pad and its vicinity, a simpler one-dimensional model was employed in the wall since heat conduction is predominantly radial there. A realistic profile of thermal conductivity was taken considering brick and skull properties through the thickness. Historic thermocouple data since start of furnace campaign was fed into the model and the estimated remnant thickness at different points in time was compared with measured refractory thickness (through NDT methods) which were in good agreement. The model is currently deployed in one of the Blast Furnaces of Tata Steel India and runs daily.

ABSTRACT. Complex, multiphase flow inside an iron-making blast furnace relies on the permeability of the coke bed, which is adversely affected by the accumulation of unburnt coal and coke powder resulting from Pulverised Coal Injection (PCI). Achievement of a stable operation at a high PCI rate necessitates a deeper understanding of gas, liquid and powder distribution, raceway shape and size, and powder and liquid accumulation characteristics due to a reduction in permeability.

A computational study of a laterally injected gas-powder flow into a two-dimensional packed bed in the presence of a raceway and cohesive zone is undertaken. The gas and powder phases are modelled as a two-fluid system. The packed coke bed is replicated by the Discrete Element Method (DEM) and a Discrete Liquid Flow (DLF) model to replicate the percolation of molten iron as droplets and rivulets. Based on experimental data, a correlation is used to predict the static portion of the accumulated powder and liquid.

A solver is developed, and the results indicate an excellent agreement with the experimental data. The effect of operational parameters such as gas flow rate, liquid flow rate, particle size and density, and powder feed rate and size are analysed and show that the raceway characteristics and the cohesive blocks play a vital role in the distribution and accumulation of powder and liquid.

ABSTRACT. The gas flow patterns in blast furnace are dictated by the profile of coke and ore layers charged, which has a substantial impact on its gas utilization index. To ensure that desirable top burden profiles are maintained, it is critical to keep an eye on charging behaviour. Mechanical probes are used to measure top burden profile, top gas temperature distribution, flow path of falling material trajectories, top gas compositions, and other parameters in the blast furnace. Generally these probes have their limitations in term of availability, usability at different conditions. To address these issues, Tata Steel developed and demonstrated several non-invasive technologies for measuring and visualizing the internal features of blast furnace top. This article describes how contactless measuring sensors such as laser distance meter and microbolometers are combined with an intelligent data processing system to obtain the necessary measurements and visualizations at the blast furnace top. The difficulties in commissioning these systems at the furnace have also been highlighted in this article.

ABSTRACT. Blast furnace (BF) route of iron making dominates the world’s hot metal production. Hot and slag tapped from the BF is collected in the trough. The refractory lined trough is responsible for complete separation of hot metal and slag and transporting hot metal to torpedo. The refractory lining of trough is subjected to continuous erosion in impingement zone and along the flow of hot metal and slag. Erosion of refractory lining impacts the availability of trough and hampers the production. Hence, in this article, a three-dimensional Eulerian multi-fluid VOF model is applied to investigate the complex multiphase flow of hot metal, slag and air in trough. Erosion behavior of refractory lining is predicted by calculating wall shear stress through Newton’s law of viscosity. Impact of interferences among hot metal, slag and air on wall shear stress in specified zone of impingement region is evaluated and compared with literature. Further, cross-sectional profile of trough is modified to decrease the wall shear stress by increasing pool volume, reducing velocity at impingement region without changing the overall length of the trough. Modified design shows drastic reduction in the wall shear stress, which is expected to improve the campaign life of the trough.

ABSTRACT. Gas-solid fluidized bed reactor with a wide particle size distribution (PSD) is extensively used in alternate ironmaking processes such as Finex, Finmet, Iron-Carbide, Circored, and Circofer for DRI production. It is found that wide PSD is better handled in tapered fluidized beds due to the vertical velocity gradient. The hydrodynamics of tapered fluidized beds are studied through experiments as well as using the Eulerian-Eulerian mathematical modeling approach with heterogeneous and homogeneous drag models. It is reported that the bubble-based energy minimization multi-scale (EMMS) heterogeneous drag model can capture the heterogeneity in the bed's flow structure, which is caused by bubbles. However, all the existing EMMS models contain the implicit interdependency between the bubble size and its drag coefficient. Therefore, a modified EMMS drag law is proposed and coupled with the two-fluid kinetic theory of the granular flow model to study the hydrodynamics of tapered fluidized beds using the computational fluid dynamics method. The effect of taper angle and air velocity on the bulk parameters such as bed expansion ratio, bubble fraction, and unfluidized area fraction are studied. The simulation results obtained from modified EMMS law have been compared with Gidaspow law and experiments. It is found that the bulk properties predicted from modified EMMS law are nearer to the experimental findings.

ABSTRACT. Inter-diffusion studies were performed in the (Fe,Mg)O system for studying the interactions between Fe/FeO with MgO-C refractory under flash ironmaking conditions. The respective raw materials (i.e., Fe or FeO) were reacted with MgO-C in a horizontal tubular reactor for specific periods of time and reacted samples were quenched and analysed using SEM-EDX and EPMA. Analyses revealed the formation of magnesiowustite (MgxFe1-x)O solid solution phase at all temperatures and reaction times. Kinetics models were developed for the growth of the magnesiowustite phase for different cases considering the physical situations of the interaction processes with Fe and FeO. Based on the kinetics models and the composition profiles of Fe and Mg determined using EPMA, an average value of the inter-diffusion coefficient (D ̅_(Fe-Mg)) was determined for various temperatures and oxygen partial pressures. An activation energy value of ~ 385 kJ/mole was calculated for D ̅_(Fe-Mg). Next, composition dependent values for the inter-diffusion coefficient (D_(Fe-Mg)) were calculated using the Boltzmann-Matano (BM) method. In was observed that the D_(Fe-Mg) increased monotonically with in the increase in Fe concentration in magnesiowustite. Furthermore, it was observed that, within the range of oxygen partial pressure values used in the experiments, D_(Fe-Mg) increased with oxygen partial pressure. A justification for such observations was given based on the defect chemistry of magnesiowustite.

ABSTRACT. Calcium magnesium aluminate (CMA) has started to be used widely in a range of refractory applications within a decade of its commercial launch in 2011 thanks to its unique multiphase composition with reactive microfine magnesium aluminate (MA) spinel and calcium aluminate. In monolithics and precast shapes, CMA forms hydraulic bond due to its calcium aluminate phases and enhances corrosion resistance against basic oxygen furnace (BOF) slags thanks to its microfine MA spinel distributed throughout the microstructure of the castable. Such compact microstructures do not allow the penetrating slag to bypass microfine spinels, which changes the composition the infiltrated slag making it viscous and less penetrating by picking up Fe and Mn ions in the MA spinel structure. For MgO-C bricks of steel ladles, CMA addition improves performance in both slag and metal zones thanks to the formation of slag coating and sealing of joints providing better protection of bricks together with generation of viscous liquid which releases thermomechanical stress.

ABSTRACT. Magnesium is used in co-injection process of Hot Metal Desulphurization along with Calcium Carbide or Lime based reagent. The fire hazards associated with Magnesium together with dependence on a single country for sourcing the same and high price volatility necessitated an alternative reagent. Disruption in Supply Chain due to COVID-19 pandemic reminded the urgent need for an alternative reagent. However, higher efficiency of Magnesium in removing sulphur has always posed a challenge to find a suitable substitute. JAMIPOL took up this challenge and developed an alternative reagent to minimise / eliminate use of Magnesium in Hot Metal Desulphurization. This reagent has been developed through intensive research for developing the recipe followed by laboratory experiments and pilot scale industrial trials at LD2 shop of Tata Steel Ltd. This new reagent would make the Hot Metal Desulphurization safer and sustainable. There by enabling steel plants to mitigate risk of fire hazards and supply chain disruption.

ABSTRACT. The dissolution behaviour of directly reduced iron (DRI) in liquid iron and followed refining of melt in an induction furnace are studied. It has been observed that DRI pellets dissolve slower than DRI lumps in an induction furnace. The dissolution of the DRI pellet happens with a change in the melt composition. In general, an Indian induction furnace adopts the feed materials of 70-80% DRI and 30-20 % cast iron scrap to produce the steel. However, the phosphorus content in the steel, produced through the induction furnace route is in the range of 0.085 to 0.1 % while sulphur is around 0.06-0.1 %. However, the induction furnace steelmaking route has its limitations for the refining of liquid metal. To overcome the above-mentioned problems, the refining method is developed for both sulphur and phosphorous removal during steelmaking in an induction furnace with basic lining along with suitable synthetic slag addition. It has been found that phosphorus and sulphur content in steel is reduced to 0.03-0.04 % each with the addition of a developed flux of 3-5 wt % of the liquid steel. Therefore, refining of the steel in an induction furnace is achieved with the addition of synthetic slag for DRI and cast iron scrap as feed materials.

ABSTRACT. Modern day steelmakers encounter unique challenges in the pursuit of achieving the twin objectives of productivity and simultaneously meeting the metallurgical quality requirements from their discerning customers. The need for higher sequence length though a single tundish often imposes severe restrictions due to operational limitations like SEN clogging caused by deposition of alumina inclusions. Contemporary tundish covering fluxes like synthetic slag and similar products try to address this problem only partially as excess absorption of alumina by the flux leads to radical changes in its composition, leading to significant reduction in its absorption capacity and increase in viscosity.

BaSi 1, an active tundish flux developed by Allied Metallurgical Products, provides a lasting solution to the above problem. It is granular in nature and carbon-free, with a low melting point to facilitate quick formation of an active slag. Alumina absorption of 20-25% have been reported by some steel majors, after extensive evaluation.

ABSTRACT. The physicochemical properties of molten slag are highly important to understand and to control the complicated phenomena occurred in steel refining processes. For example, the MgAl2O4 spinel is one of the harmful inclusions in various kinds of steels. The probability of spinel inclusion has been known to be strongly affected by slag chemistry and deoxidation practices. Moreover, the thermophysical properties of slags such as viscosity should also be carefully controlled to suppress the formation of this harmful inclusion at the ladle refining stage. Alternatively, tundish metallurgy has been issued because it is the final reactor for controlling the steel cleanliness in view of the reoxidation phenomenon of molten steel. The reoxidation is experienced by the contamination of molten steel not only due to air entrapment but also due to slag-metal reaction. There is less investigations for the latter compared to the former. Consequently, in this paper, the recent issues for the physicochemical properties of slag will be discussed in terms of clean steel production technologies.

ABSTRACT. Steel industries consists of several interconnected units operating at a massive scale exchanging material, energy and information amongst themselves. With the advancement in sensing, automation and control, each of these units and steel plant as a whole generate a huge amount of data. Using this data, though the steel plants extract strategic insights and develop operating regimes which can improve their process performance and product quality, there exists a large scope in utilizing these data for even newer analysis. In this context, opportunities exist especially with the availability of novel machine learning techniques and artificial intelligence. In this panel discussion, we have panelists from the steel industry as well as from the data analytics sector who will interact with each other to explore the possibilities.

ABSTRACT. The current study investigates hydrogen reduction of low-grade banded iron ores (~35% Fe). Gaseous hydrogen reduction is conducted under isothermal conditions in a custom-made tubular furnace, followed by magnetic separation. Effects of time and temperature were studied on process responses of the degree of reduction, metallization, and magnetic characteristics. Completely selective reduction of hematite was attained for 60 min at 600 °C, whereas prolonged reduction was futile for reduction degree but facilitated the separation of quartz impurities from the ferrite. Reduction of hematite initiates above 300°C and the reduction rate synergized with time and temperature, improving reduction and metallization degree. The association of impurities with hematite does not affect the reduction rate; however, it hinders the separation of quartz from ferrite and deteriorates the product quality. The reduction carried at the highest parameter levels: 900 °C, 60 min yielded ferrite concentrate possessing saturation magnetization of 150 emu/g (75% FeM) with 100 % degree of reduction/metallization and ~43% yield. The non-magnetic fraction contains ~95% silica with saturation magnetization values of 2-4 emu/g. The reduction of hematite results in the formation of microcracks and porous morphology in the ferrite matrix. The reduction sequence comprises Fe2O3 → Fe3O4 → Fe and does not include wustite or fayalite phases in the reduced product.

ABSTRACT. Reducibility and reduction kinetics of hardened pellets prepared from a novel, lean-grade multimetallic magnetite ore (MMO) was investigated in the present study. This lean-grade ore contains a significant amount of chromium and nickel, which can lead to a reduction in the cost of steelmaking. The hardened pellets were reduced at 900-1150° C for 30-120 minutes in a bed of high ash coke. The optimum reducibility and metallisation of 76 % and 88% were obtained at 1100 °C at a holding time of 120 minutes. The kinetic model “(1-(2/3) α-(1-α)2/3 = kt” was found to be the best fit for the reduction of pellets. Activation energy calculated for the pellets was 176.46 kJ/mole. Pellets reduced with high ash coke fines at 1100 °C for 120 minutes, and above are thus found necessary to achieve the desired metallization of greater than 85%.

ABSTRACT. Present work evaluated a sustainable approach of using relatively coarser iron ore particles with a suitable binder for ironmaking. Idea was to decrease the energy consumption in milling of the iron ore, and decrease slag volume during steelmaking by selecting a suitable binder. Iron ore fines in the range of −0.25 + 0.05 mm were classified into three size ranges (SR1(−0.25 + 0.1), SR2(−0.1 + 0.05) and SR3(−0.05) mm). Spherical iron ore pellets were prepared using lime as binder for basicity of 0, 1 and 2 respectively. Reduction of iron ore pellets with coal fines as a reductant was performed in the temperature range of 900 to 1200 °C for the duration of 30 to 120 min. The direct reduction kinetics of the iron ore pellets was studied. Various diffusion and chemical reaction control models were employed to fit the experimental data. Equation [(1-f)^(-1/3) -1]2 =kt was found to fit the best. It was found that activation energy increases from 44.3 to 74.76 kJ/mol as the particle size of iron ore decreases from 0.25 to 0.05 mm and basicity increases from 0 to 2. It showed that the pellet with coarser iron ore particle of 0.25 mm with 0 basicity was most reducible having an activation energy of 44.3 kJ/mol.

ABSTRACT. Wide spread process modelling of steelmaking and casting processes has been reported during the last half a century. Transient, multiphase turbulent flow models are now frequent and applied extensively to numerically simulate metal, slag and gas flows in steelmaking and casting operations resulting in significant improvements in our understanding of underlying process dynamics.

Review and analysis on the modelling of key steelmaking and casting processes are briefly presented in this work primary to highlight the state of the art and way forward. In such context, it is generally observed that assumptions and idealisations, typical of process modelling in the eighties, still continue to apply. Similarly, despite many improvements in modelling, features of a chemically reacting flows, integral to steelmaking, are rarely included in modelling of steelmaking. Most notably however, rigorous validation of mathematical models with experimental data has become progressively more passive. In iron and steelmaking research, more than fifty years have elapsed in developing many process models and parallel testing of these against laboratory scale units, including water models. While efforts must continue to include more complex physics into existing models to empower these further, the need for experimental measurements, as well as plant scale trials, should not be undermined. This is important as un-due extrapolation of untested models to actual process analysis, design and optimization are rarely helpful.

ABSTRACT. Many studies have been reported on argon gas bubbling through porous plugs to rinse inclusions from a steel melt. Unfortunately, these techniques cannot remove inclusions below ~50 microns within liquid steel flowing through a tundish, as their buoyant rising velocities are too low, while bubble sizes forming at the surfaces of porous plugs are too large (~ 10-40mm diam.), and their velocities, too high to allow for meaningful interactions. Rather, one has relied on tundish “furniture”, to help remove inclusions in the 50-120 µm range, larger ones floating out by themselves. The present work demonstrates how microbubbles can be generated in all liquid metals and should be effective in capturing all non-wetting inclusions within a batch reactor system. The technique is to use high-speed rotational shearing, at very low argon flow rates. Microbubbles thus formed, would help in floating out the smaller (< 50 µm), as well as the larger inclusions to the surface, by attaching the non-wetting inclusions to their surfaces. The sizes of argon microbubbles generated were investigated by “flash-freezing” a sample of melt, “Cerrolow 136”, onto a cold copper bar dipped into the melt, then rapidly withdrawing it. Microbubbles captured in the surface of the frozen melt on the copper bar, were in the correct size range of 400-600µm, required for removing sub-50µm inclusions.

ABSTRACT. A three-dimensional transient model of in-mold electromagnetic stirring (EMS) in bloom continuous casting (CC) mold has been developed. Time-varying electromagnetic field (EMF) has been coupled with fluid flow, solidification and inclusion tracking model to investigate the effect of EMS on solidification and non-metallic inclusion behavior. The realizable k-ε turbulence model and the enthalpy-porosity approach have been used to investigate the fluid flow and the solidification of liquid steel in the mold. The behavior of non-metallic inclusions is analyzed using the stochastic tracking model. EMS inhibits initial solid shell formation at the mold wall and turns the liquid core at the strand's center into a liquid-solid interface mush. Analysis has also been done on the impact of inclusion size and density on the removal rate of non-metallic inclusions. The findings indicate that inclusion and solidification behavior is significantly influenced by in-mold EMS.

ABSTRACT. Over the past 5 decades, CFD modeling of gas-stirred baths has come a long way, from quasi-single phase approaches to sophisticated multiphase treatments such as interface capturing, population balance, discrete particle mapping, and coalescence-breakup dynamics. Through analysis of new and existing results, both physical and numerical, we examine the underlying concepts which can guide the development of realistic models. Towards this, we examine the critical factors required to correctly configure the superficially different, but practically equivalent, Eulerian and Lagrangian treatments of the dispersed phase, as well as the important but underexamined role of sharp interface treatment when modeling VOF based large continuous interfaces. Together, these exercises illustrate the role of qualitative inferences in placing the tendencies of an approximate model in context of the actual system, in order to improve both realism and robustness, which are easily lost if one looks only at grossly quantification through slag eye or mixing time.

ABSTRACT. This study was carried out to understand the evolution behavior of inclusion composition in Al-killed steel during LF-RH process. The investigation result of case-hardening steel exhibited that inclusion compositions during LF-RH process can be explained by three factors: composition change, removal, and generation. In the case of high-Al steel, the CaO content of inclusions kept quite low throughout the LF-RH process. The low CaO content resulted from two reasons: the high stability of Al2O3 phase and the high removability of inclusions from steel melt. In addition, high-S steel was also examined to clarify the behavior of CaS phase during LF-RH process. It was confirmed that the stability of CaS phase corresponded well with the variation of S activity in steel melt. In summary, composition change, removal, and generation of inclusions should be considered to control the inclusion compositions in Al-killed steel. The components of steel melt, namely Al and S, can play important roles to determine the evolution behavior of inclusion compositions during LF-RH process.

ABSTRACT. The effect of slag composition on the refining and reoxidation behavior of Si-killed 316L stainless steel during ladle and tundish processes were investigated in an induction furnace equipped with a MgO crucible under high purity Ar atmosphere at 1873 K and 1773 K, respectively. For the ladle refining process, the total oxygen (T.O.) content decreased with increasing the Vee ratio (CaO/SiO2=C/S) of the CaO-SiO2-Al2O3-MgO-CaF2 ladle refining slag, but the effect of CaF2 content on the T.O. can be neglected at high C/S condition. The CaO-SiO2-Al2O3-MgO system liquid inclusions transformed from MnO-SiO2-Cr2O3 system liquid inclusions can be found as the C/S is less than 1.3, and the formation of spinel and MgO inclusions were observed under conditions of the C/S=1.7 to 2.3, respectively. For the tundish metallurgy process, the liquid and SiO2-rich Mn-Si-O system inclusions were found as the liquid steel reacted with rice husk ash (RHA) and RHA-CaO-SiO2. The liquid Mn-Si-Al-O system inclusions were observed as reacted with RHA-CaO-Al2O3 flux. The number density of inclusions increased, decreased, and remained constant with the reaction time when the liquid steel reacted with RHA, RHA-CaO-Al2O3, and RHA-CaO-SiO2 fluxes, respectively. The results indicated that the reoxidation of the liquid steel is aggravated as the RHA was used, whereas the RHA-CaO-Al2O3 can facilitate the removal of the inclusions during the tundish metallurgy process

ABSTRACT. Nanometer-sized precipitates in steels are often the most important microstructural constituents determining the mechanical and thermophysical properties. Small amounts of elements are employed to promote a finer austenite grain size during hot rolling, because a finer grain size can help to achieve steel with higher strength. A comprehensive characterization of the various precipitates is thus very helpful. In this talk, we present a electron microscopy workflow solution for characterization of steel from the micro to the nano scale, using Thermo Fisher Scientific instruments. We look at complex inclusions using a new EDS-based Thermo Scientific™ ChemiSEM technology. The “always on” EDS mapping makes the identification of complex oxides simpler and faster. An automated TEM sample preparation using the Thermo Scientific Helios™ 5 UX DualBeam to prepare electron beam transparent lamella. Thin lamellas was investigated on the Thermo Scientific Talos F200X G2 S/TEM and EDS mapping was used to search for small precipitates. We present a high throughput workflow for steel precipitate analysis that doesn’t just focus on generating higher quality results, but also provides automated data acquisition and powerful image processing of the results to provide quantitative data on precipitate numbers, size, shape and composition. Speed, reliability and ease of use are critical for new tools in a successful industrial lab setting such as steel.

ABSTRACT. Commercial ferroalloys are used in the manufacturing of a Fe-Cr-Ni-Mn-Co system alloy due to their price advantage and the productivity of the manufacturing process. However, elemental impurities such as sulfur in ferroalloys can undermine the mechanical properties of HEAs. Therefore, the desulfurization behavior of a Fe-Cr-Ni-Mn-Co system alloy using the CaO-MgO-Al2O3 (CAM) slagging method with alumina or magnesia refractories and ferroalloys raw material feedstock was investigated in an induction melting furnace at 1773 K to determine how to control the cleanness of the alloy. The resulting desulfurization ratios of the alloy were approx. 47% when refined by the CaAl2O4-MgAl2O4 (CA-MA)-saturated slag in an Al2O3 refractory, whereas 94% when refined by the CaO-MgO (C-M)-saturated slag in a MgO refractory. The oxide inclusions MnAl2O4 and MgAl2O4 can steadily exist in the alloy melted in Al2O3 and MgO crucibles with CaO-MgO-Al2O3 slag saturated CA-MA and C-M content, respectively, 1773 K. The alloy melted in the MgO crucible had a higher cleanness compared with that melted in the Al2O3 crucible, indicating that the MgO crucible with CaO-MgO-Al2O3 slag saturated C-M content is suitable for refining the Fe-Cr-Ni-Mn-Co system alloy.

ABSTRACT. The characteristics of non-metallic inclusions including 2D and 3D morphology and size distribution in Fe-22Mn-xAl(0.5, 5, 10)-0.6C low-density steel were investigated. The transportation of Ca and Mg and the evolution behavior of inclusions between the reactions of refining slag/ molten steel/MgO crucible were studied. The results showed that the increase of Al content during the smelting process caused the overall size of AlN inclusions to increase. The nucleation core of composite inclusions was transformed from Al2O3-MnS to AlN-MnS. For the steel-slag reactions, the transfer amount of Ca and Mg elements from refining slag to molten steel increased rapidly after 30 min. The interfacial layer of MgAl2O4 formed at the interface of molten steel/crucible. The uniform CaAl2O4 interface layer formed at the molten steel/crucible interface. Erosion of the MgO crucible caused MgO particles to enter the transient refining slag due to the reaction between high Al molten steel and slag.