The current nature of steel design and production is a response to meet increasingly demanding applications but without much consideration of end-of-life scenarios. The scrap handling infrastructure, particularly the characterization and sorting, is unable to match the complexity of scrapped products. This is manifested in problems of intermixing and contamination in the scrap flows, especially for obsolete scrap. Also, the segmentation of scrap classes in standards with respect to chemical compositions is based on tolerance ranges. Thus, variation in scrap composition exists even within the same scrap type. This study applies the concept of expected value of perfect information (EPVI) to the context of steel recycling. More specifically, it sets out to examine the difference between having partial and full information on scrap composition by using a raw material optimization software. Three different scenarios with different constraints were used to appraise this difference in terms of production and excess costs. With access to perfect information, production costs decreased by 8–10%, and excess costs became negligible. Overall, comparing the respective results gave meaningful insights on the value of reestablishing the compositional information of scrap at the end of its use phase. Furthermore, the results provided relevant findings and contribute to the ongoing discussions on the seemingly disparate prioritization of economic and environmental incentives with respect to the recycling of steel.

A novel horizontal stirring has been introduced to investigate the effect of such a stirring on the ladle profile during the combined stirring process at the refining stage. The multiphaseInterFoam solver has been updated to consider the induction forces imposed on the liquid bath by the magnetic stirrer.During the combined stirring stage, the gas plume is affected by the rotational movement. The gas plume seems to be intact in the lower one-third of the domain, then breaks into clusters in the upper section while the rotational movement of clusters dissipates a large portion of upward momentum of the bubbles. This prevents large openings in the slag layer and respectively, prevents the exposure of steel. It also disperses the bubbles to various sections of the ladle. Hence, such a novel stirring strategy seems to have the potential of improving the cleanness of the liquid steel during the ladle refining process.

A two-dimensional CFD model was developed to simulate the fluid flow and temperature distribution in an AOD nozzle using a mixture of oxygen and nitrogen as the fluid phase, aiming at predicting how the outlet gas properties are influenced by the inlet pressure, inner nozzle length/diameter and process gas composition. The proposed mathematical model assumes a steady, non-isothermal flow condition, using the realizable k- e turbulence model to describe the gas phase. A mesh sensitivity analysis was performed where predictions were compared to experimental data. The results show that the gas properties are mainly dependent on the inlet pressure, nozzle length/diameter and heating condition but less dependent on the composition of the gas mixture. This fundamental model can be applied to provide a process specified boundary condition for gas blowing when simulating a multiphase flow in a full- scale AOD converter.

Ceramic foam filters (CFFs) are used to remove inclusions and/or solid particles from molten metal. In general, the molten metal poured on the top of a CFF should reach a certain height to form the pressure (metal head) required to prime the filter. For estimating the required metal head and obtaining the permeability coefficients of the CFFs, permeability experiments are essential. Recently, electromagnetic priming and filtration of molten aluminum with low and high grades of CFF, i.e., 30, 50 and 80 pore per inch (PPI) CFFs, have been introduced. Since then, there has been interest in exploring the possibility of obtaining further inclusion entrapment and aluminum refinement by using electromagnetic force to prime and filter with stacked CFFs. The successful execution of such trials requires a profound understanding concerning the permeability parameters of the stacked filters. Such data were deemed not to exist prior to this study. As a result, this study presents experimental findings of permeability measurements for stacks of three 30, three 50 and three 80 PPI commercial alumina CFFs from different industrial batches and compares the findings to numerically modelled data as well as previous research works. Both experimental and numerical findings showed a good agreement with previous results. The deviation between the experimentally and numerically obtained data lies in the range of 0.4 to 6.3%.

Metallurgical converters such as the argon–oxygen decarburization (AOD) converter generally utilize gas blowing for the mixing and refinement of liquid steel. Due to the harsh environment of the complex and opaque system, it is common practice to study the stirring of the process through physical and numerical models. Effective mixing in the bath has an important role in refinement such as decarburization and has been vividly studied before. However, high‐temperature chemical reactions that also play a major role are sparsely investigated. With the help of modeling, a computational fluid dynamics model coupled with chemical reactions is developed, allowing the study of both dynamic fluid transport and chemical reactions. Herein, the chemical reactions for a single gas bubble in the AOD are investigated. The study shows that a 60 mm oxygen gas bubble rapidly reacts with the melt and is saturated with carbon in 0.2–0.25 s at low‐pressure levels. The saturation time is affected by the pressure and the composition of the injected gas bubble. The impact of ferrostatic pressure on the reactions is more significant at larger depth differences.

In this work, a time-dependent thermodynamic AOD process model, TimeAOD3™, is proposed to be used as a prediction model at practice to reach the desired nitrogen level to lower the cost and carbon footprint. The model is developed from an existing model and integrated with Thermo-Calc®. The modelling results suggest a fairly good prediction when compared with production-scale heats. The relative error of dissolved nitrogen content during and after decarburisation is −0.05 < RE < 1.36 and −0.23 < RE < 0.29, respectively. Besides, most modelled dissolved N% are higher than the measurement during decarburisation. This is probably owing to the formation of high turbulence flow and CO gas bubble which can flush the dissolved nitrogen out of the bath at practice. Moreover, dissolved C%, Cr% in bath and Cr2O3%, CaO%, MgO% in slag, as well as bath temperature are also compared and studied.

Recycling plays a vital role in preserving resources like steel and consequently in a circular economy. Scrap dealers and steel mills, the main business units in this system, often encounter opposing financial and sustainability incentives in using scrap as feedstock because regular sorting and scrap-preparation infrastructure cannot deal with the increasing complexity of steel scrap. Mismatches between the inputs and the target composition of the recycled steel result in trade-offs that favor the economics at the expense of resource efficiency. By examining literature and interviewing several actors, different scrap characteristics were identified as dimensions of scrap quality. Quality is typically associated with chemical composition, which is important, but this study aims to elaborate the concept of quality further and to connect it to the realities of scrapyard operations. Industry actors have different definitions for desired content, physical condition, shape and size, and homogeneity, based on their needs. Very few studies examine these details. Additionally, the relationship of quality and the level of information about the characteristics of the material was established. Having more definitive information on scrap increases opportunities for resource-efficient actions. This work offers an alternative perspective on how to address issues pertinent to recycling.

The characteristics of elongated MnS have a critical effect on fatigue anisotropy and all mechanical anisotropies. A comparative investigation of nonmetallic inclusions in both stainless steels and tool steels has been carried out in this study. The inclusion characteristics were investigated using electrolytic extraction (EE) followed by scanning electron microscopy combined with energy-dispersive spectroscopy (SEM-EDS). Overall, three types of MnS inclusions (type I (regular), type II (irregular) and type III (Rod)) were found in tool steels in as-cast samples, which had not been heat-treated. Furthermore, three types of MnS inclusions (Rod-like sulfide (RS), Plate-like sulfide (PS) and Oxysulfide (OS)) were found in samples taken after rolling. Based on the breakability of the elongated MnS, three types of inclusions, Type UU, UB and BB, where U represents the undamaged or unbroken edge of an inclusion and B represents the fragment or broken edge of an inclusion, were studied in both stainless steels and tool steels both before and after additional heat treatment. The effect of heat treatment and dissolving the metal layer during the EE process is also discussed. The results show that both processes have a limited effect on the breakability of inclusions in steels with carbon contents <0.42 mass%.

Small‐scale physical models are commonly used to investigate gas‐stirred processes in steelmaking practice. The argon oxygen decarburization (AOD) converter is among various processes widely used in the metallurgy field and utilizes side blowing of oxygen and inert gas for mixing in the bath. Herein, the effect of the converter inclination on mixing time and jet‐penetration length with a side‐blown physical model is investigated. Scaling with the modified Froude number is applied on data from a real industrial AOD converter to achieve a system with reasonable gas flow rates. During the experiments, water is used to simulate liquid steel and air is blown through side‐mounted nozzles for stirring. A NaCl tracer is added and subsequent conductivity measurements are used to measure mixing time. Overall, the penetration length is shown to be independent of inclination angle. The mixing time is found to be influenced by the change of bath height to diameter ratio, change of geometry in the bath volume, gas flow rate, and the intensified wave motion at the interface caused by the inclination of the vessel. The mixing time increase with 14% when 14° angle is applied.

Argon Oxygen Decarburization (AOD) converter slags are known to consist of both liquid and solid phases, but limited information on the slag characteristics has been published in the open literature. Therefore, a new methodology to study the characteristics of slag samples taken from the AOD converter process during production was developed based on petrography. The results show that the preparations of the slag samples using the borax method are suitable to use when determining the chemical composition of AOD slag samples using the X-ray fluorescence (XRF) method. The results also showed that both the light optical microscopy (LOM) method and a method combining scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) can be used to characterize the slag samples and that the correlation between the methods was found to be good. This means that it is possible to use the faster LOM method instead of the more complicated SEM-EDS method to characterize AOD slag samples. Finally, the results show that the difference between calculated values based on stoichiometry and measured data for Ca and Cr in AOD slags are 11.7 mass% and 11.3 mass%, respectively. This is considered to be a good agreement for industrial samples.

The primary energy consumption and greenhouse gas emissions from nickel smelting products have been assessed through case studies using a process model based on mass and energy balance. The required primary energy for producing nickel metal, nickel oxide, ferronickel, and nickel pig iron is 174 GJ/t alloy (174 GJ/t contained Ni), 369 GJ/t alloy (485 GJ/t contained Ni), 110 GJ/t alloy (309 GJ/t contained Ni), and 60 GJ/t alloy (598 GJ/t contained Ni), respectively. Furthermore, the associated GHG emissions are 14 tCO2-eq/t alloy (14 tCO2-eq/t contained Ni), 30 t CO2-eq/t alloy (40 t CO2-eq/t contained Ni), 6 t CO2-eq/t alloy (18 t CO2-eq/t contained Ni), and 7 t CO2-eq/t alloy (69 t CO2-eq/t contained Ni). A possible carbon emission reduction can be observed by comparing ore type, ore grade, and electricity source, as well as allocation strategy. The suggested process model overcomes the limitation of a conventional life cycle assessment study which considers the process as a ‘black box’ and allows for an identification of further possibilities to implement sustainable nickel production.

Molybdenum is mainly used as an alloy material in the iron and steel industry and typically in the form of ferromolybdenum (FeMo). The current study aims to evaluate the energy consumption and greenhouse gas emissions (GHG) of four ferromolybdenum production cases using inventory inputs from a process model based on mass and energy conservations. The total energy required for producing 1 tonne of FeMo can vary between 29.1 GJ/t FeMo and 188.6 GJ/t FeMo. Furthermore, the corresponding GHG emissions differ from 3.16 tCO 2 -eq/t FeMo to 14.79 tCO 2 -eq/t FeMo. The main variances are from the mining and beneficiation stages. The differences in these stages come from the beneficiation degree (ore grade) and the mine type (i.e., co-product from copper mining). Furthermore, the mine type has a larger impact on the total energy consumption and GHG emissions than the beneficiation degree. More specifically, FeMo produced as co-product from copper mining has a lower environmental impact measured as the energy consumption and GHG emission among all the four cases. The inventory, consumed energy or associated GHG emission is independent on the initial ore grade and mine type in the downstream production stages such as roasting and smelting. Also, transport has the least impact on the energy consumption and GHG emission among all production stages.

A non-uniform temperature across the width of martensitic stainless-steel strips is considered to be one of the main reasons why the strip exhibits un-flatness defects during the hardening process. Therefore, the effect of the gas inlet position in this process, on the temperature distribution of the steel strip was investigated numerically. Furthermore, an infrared thermal imaging camera was used to compare the model predictions and the actual process data. The results showed that the temperature difference across the width of the strip decreased by 9% and 14% relative to the calculated temperature and measured values, respectively, when the gas inlet position was changed. This temperature investigation was performed at a position about 63 mm from the bath interface. Moreover, a more symmetrical temperature distribution was observed across the width of the strip. In addition, this study showed that by increasing the amount of the hydrogen flow rate by 2 Nm(3)/h, a 20% reduction of temperature difference across the width of strip was predicted. Meanwhile, the results show that the effect of the strip velocity on the strip temperature is very small.

The dimension quality of the strip within the hardening process is an essential parameter, which great attention needs to be paid. The flatness of the final product is influenced by the temperature distribution of the strip, specifically across the width direction. Therefore, based on physical theories, a numerical model was established. The temperature of the strip for the section before the martensitic transformation was objected in the predicted model by using a steady state approach. In addition an infrared thermal imaging camera was applied in the real process in order to validate the results and to improve the boundary conditions of the numerical model. The results revealed that the temperature of strip decreased up to 250 °C within the area between the furnace and the quenching bath. This, in turn, resulted in significant temperature difference across the width of the strip. This difference can be up to 69 °C and 41 °C according to the numerical results and thermal imaging data, respectively. Overall, this study gave a better insight into the cooling step in the hardening process. In addition, this investigation can be used to improve the hardening process as well as an input for future thermal stress investigations.

The aim of this paper is to investigate the role of supply chain collaboration between buyers and suppliers in the reverse flow of a system of circular supply chains. The empirical context is Swedi ...

There is no known example of an AOD converter with oblong cross sections in the literature. Changing the geometry of the converter vessel, from the traditional circular cross sections, to increase converter volume could potentially influence the performance of the converter and in particular the decarburisation rate. To study the feasibility of implementing an oblong converter, physical modelling was used to study the fluid flow of the proposed converter configuration, geometry and number of tuyeres, and the potential influence on the decarburisation rate. Two water models were employed using water containing NaOH and gas injected through six or eight tuyeres as fluids. In the model, CO2 gas was injected and the reaction of CO2 and NaOH was indirectly measured by detecting the pH value of the water. The mixing time is considered to be a good indicator of the decarburisation as kinetics will be diffusion controlled in the latter period of the process. The following three configurations were studied: (i) a circular converter with six tuyeres, (ii) an oblong converter with six tuyeres, and (iii) an oblong converter with eight tuyeres. The mixing time can be used to evaluate the different converter configurations. The average CO2 concentrations based on several experiments, differed by less than 5% between the circular and oblong models after 165 s of injection of air and CO2. The results also showed that no difference in mixing time could be found when using 6 and 8 tuyeres, respectively in the oblong model, where the CO2 concentrations differed by less than 2% after 165 s of injection time of air and CO2. Based on the findings, it has been observed that the influence of converter geometry on mixing time is small, it was concluded that decarburisation rate is likely to be the same irrespectively of converter geometry.

It is beneficial that the slag composition can be known as early as possible in the EAF process, so that actions and decisions can be taken promptly for an efficient process control of EAF. However, this is still a challenge today, because no steel companies have yet incorporated direct slag composition data in an online process control system for the EAF process. Therefore, this work is part of an attempt to obtain a better understanding of change of the slag components, based on measurements in a lab-scale EAF. The ultimate goal of the work is to make it possible to measure the slag composition online with optical emission spectrometry (OES) in a full-scale EAF.

Over the last few decades, a number of CFD models have been dedicated to increasing the understanding of the decarburization processes in steelmaking. However, these processes are highly complex with large variations in time and length, and this makes the systems extremely demanding to simulate. Several reports have been published where parts of the processes have been investigated numerically, but to date no models have been presented that can handle the entire complexity of the processes. Here, a review of the research performed on the subject from 1998 to 2016 is given. A table summarizing the models used and the key focus of the studies is given, and it can be concluded that the effort put in so far to investigate the decarburization in steelmaking is substantial, but not complete. The currently available numerical models give an insight into process parameters such as reactions, mixing time, temperature distribution and thermal losses, off-gas post combustion and de-dusting, and also nozzle configuration. With the recent developments in numerical modeling and the increase in hardware capability, the future of simulation and modeling of the decarburization processes in steelmaking seems bright.

The possibilities of obtaining a good process control in order to reach a good cleanliness of the steel were studied based on plant trials. Steel and slag samples were taken from two steel grades with a slightly different composition, but with similar processing conditions. Thereafter, the chemical compositions of the steel and slag samples were determined. The results show that the sum of the FeO and MnO was found to be a clear indicator for when reoxidation had taken place. No conclusive indicator was found to predict the extent of slag carry-over from the electric arc furnace. However, most of the variation in deoxidation seem to originate from the accuracy of the slag raking. Steel grades with low amounts of deoxidisers such as C and Si naturally were found to result in higher oxygen contents at the start of deoxidation. Furthermore, calculations of oxygen activities in the steel melt were made and the results were compared to measurements with varying results. Overall, the results indicate that calculation of oxygen activities with multivalence slag species such as Fe and Cr requires additional measurements to obtain accurate results.

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.