Advances in Molten Slags, Fluxes, and Salts: Proceedings of the 10th International Conference on Molten Slags, Fluxes and Salts 2016

The high temperature environment of steelmaking process, offers sustainable pathways for utilizing chemical reactions to re-purpose waste materials as resources. The use of waste polymeric materials in steelmaking is not only a solution for end-of-life products, which currently impose a serious burden on overstretched landfills but it also results in reduction of resource consumption and energy saving. This paper presents industrial plant results on the effect of the utilization of waste polymeric materials in steelmaking on coke and energy consumption.The foaming slag phenomenon is an important criterion through which the effect of waste polymeric materials on EAF performance could be studied. The stability of foaming behaviour mainly depends upon physical properties of slag and also the size of gas bubbles which are generated during the process of reduction. The understanding of the relationship between these parameters and foaming is also presented in this paper.

Since the use of metallurgical slags is of great importance due to its versatile functions at high temperatures, comprehensive information is required to optimize the processes in iron and steelmaking processes. Primary silica-based slag composition can drastically deviate from expected norms by the significant amounts of additional constituents during processes. Accordingly, the comprehensive change in the slag composition and viscosity has a dramatic impact on the physico-chemical properties of the slags. In the current lecture, special focus will be put on the future technology relating the optimization of metallurgical slag composition and viscosity to cope with the situation with low quality of materials introduced into the metallurgical processes.

Refractory metals like Mo and V are alloyed in the special steels like heat-resisting, tool, ship and pipe steels for the improvement of their physical and mechanical properties. Most of refractory metals are refined as by-products in the other metals production processes. Recently, it becomes difficult to open new mines up for the environmental pollution issues, and as the results, it pays attention to recover them from industrial wastes as Mo and V resources instead of new mines development, because these wastes contain higher MoS₂ in spent lubricant, MoO₃ in oil refining catalysis and V₂O₅ in an domestic heavy oil combustion ash than the natural minerals containing them. In the present work, it was tried that these refractory metals was recovered as Fe-alloys because more than 80% of refractory metals are used as steel alloying elements and the energy consumption for reduction and production to Fe-alloys are less than that of pure refractory metals production.At first, the recover principal of Fe-Mo alloy from spent lubricant, in which Mo existed as MoS₂, was experimentally established via their oxidizing roast and reduction processes at 1773K based on the knowledge of Cu process metallurgy. The spent lubricant mixed with CaCO₃, Fe₃O₄ and C was reduced in a C_gr. crucible at 1773K. The mixed sample melted completely and separated into slag and metal phases.In the second step, the recovery of Fe-V alloy from V₂O₅ in the combustion ash of Orinoco tar was tried. The ash mixed with CaO and C was reduced in a C_gr. crucible at 1773K. The mixed sample melted completely and separated into slag and metal containing vanadium carbide. V was not almost observed in slag phase, and it meant that most of V in ash was recovered as vanadium carbides into the metal phase. The metal was Fe-Ni alloy. In the present work, Fe-Ni-V-C quo-ternary isothermal section phase diagram was experimentally assembled at 1773K.As the result, 53.3mass%Fe-42.2mass%Mo-4.3mass%C alloy from spent lubricant and 37.4mass%Fe-46.4mass%Ni-12.3mass%Si-2.1mass%C alloy — VxCy mixture from Orinoco tar combustion ash by the reduction with carbonaceous materials were successfully recovered in the present work.

Quartz (SiO₂) is the main silicon source for production of metallurgical grade silicon in submerged arc furnaces. During heating in the furnace, quartz will first transform to other SiO₂ polymorphs, then soften and melt. Volume changes during heating and melting are expected to affect for the rate of reactions with SiO₂ and gas flow. Industrial quartz sources are investigated here with heating rates relevant for industrial furnaces. A method to study softening and melting of quartz at conditions relevant for Si-production was developed. Both volume expansion and melting properties vary considerably between quartz sources. Theoretical volume expansion is 22 % and melting temperature 1726 °C. Volume increase up to 40 %, softening temperatures in the range 1675 °C to 1800 °C, and melting temperatures in the range 1790 °C to 1900 °C were recorded.

Refractory linings in pyrometallurgical furnaces are attacked by various process phases (e.g. metal, slag, gas). However, refractories are the barrier between these phases and the environment: refractory damages and consequent furnace failure can cause severe damages including potential danger for workers/operators. Hence, refractory corrosion and attack of molten phases require attention to study the mechanisms and effects on refractory performance and lifetime. This is of special importance in ferroalloys production, where temperatures are generally even higher than in base metal processes and the corrosion effects therefore more pronounced.To understand the nature of the reactions involved in refractory corrosion, it is crucial to have an understanding of the chemical equilibria and the thermodynamics of the reactions.The present work studies the high-temperature interactions between refractories and molten slags, comprising theoretical thermodynamic analysis (FactSage™) and experimental work (hot-stage microscopy) to better understand the corrosion mechanisms and draw implications for improving the refractory performance and lifetime.The results will provide a framework for investigating refractory corrosion processes and trigger research efforts in the area of thermodynamic applications, optimizations and simulations in high-temperature processes.

The high temperature reduction behavior of manganese ore was investigated with the aim of utilizing ore as a more economical manganese source in the steelmaking process. The melting temperature and phase change behaviors of raw and sintered manganese ores were measured by high temperature X-ray diffraction and DTA in the temperature range from 303K to 1773K under atmospheric and vacuum conditions. The melting temperatures of the raw and sintered manganese ores were 1688K and 1732K, respectively. The main manganese compounds in the raw and sintered manganese ores were CaMn₆SiO₁₂ and MnO, Mn₃O₄ respectively. Under a vacuum (0.13kPa), both the raw and sintered manganese ores were reduced to MnO above 1473K, whereas under the atmospheric condition (101.3kPa), the manganese ores were reduced to Mn₃O₄ rather than MnO. The obtained results were discussed from a thermodynamic viewpoint.

The extraction of chromium from chromite ore is based on the oxidative alkali roasting of the mineral forming water-soluble alkali chromates. Previous investigations reported the formation of a molten Na₂CO₃-Na₂CrO₄ binary mixture during roasting of chromite with sodium carbonate. The physical properties of the Na₂CO₃-Na₂CrO₄ liquid phase, which are dependent on temperature, charge and gangue composition, play an important role in the oxidation reaction and may limit the chromium recovery by hindering the oxygen transport to the reaction interface.This investigation focuses on the alkali roasting of chromite ore at 1000°C using NaOH and KOH, and subsequent water leaching. The influence of the alkali ratio on the chromium extraction yield is analysed, and the results obtained with both hydroxides are compared. The formation of molten salt phase under different roasting conditions and its effect on chromium recovery is studied by means of sample characterization and phase diagram analysis.

Ferronickel production process takes place in two basic stages. The first stage is calcination and preliminary reduction of minerals. These minerals contain significant amounts of iron, which must be partially reduced. The second stage is the final reduction and fusion process of the calcined product. This stage takes place at temperatures of 1600°C, in order to obtain ferronickel. The main objective is to treat nickeliferous laterites with the CaO addition, in order to decrease energy consumptions and the fusion temperature. The mineral composition was 1.78% nickel. The CaO additions were from 3% to 20%. The basicity indexes varied with respect to the CaO amount from 0.55 to 0.81. The fusion temperatures of mineral change between 1496.5 and 1462.9 °C. Metal recoveries (FeNi) change from 15.5 %to 19.3 %. It can be concluded that the addition of CaO is important to lower the melting points in obtaining ferronickel.

The Furnace Method for the production of low carbon ferrochrome has been found to offer significant savings in energy and raw material consumptions, compared to the Mixing Method processes. The operating conditions for the Furnace Method differ significantly from those of the Mixing Method processes. This paper describes the characterisation of the slag operating regime for the Furnace Method in order to minimise risks during implementation.The slag liquidus temperature, as well as its chemical and thermal compatibility with different refractory systems was evaluated to identify the preferred fluxing agent, basicity ((CaO+MgO)/SiO₂) range and refractory system. A lime fluxed slag was found to provide the best combination of liquidus temperature and alloy product quality, while being compatible with a magnesia refractory at an operating temperature of 1750°C.Slag chemistry variations throughout batches pose a risk to the integrity of the refractory lining. The impact that these variations have on the process chemistry was quantified in order to arrive at a feeding methodology for the process.

The steadily growing demand for critical metals and their price increase on the world market makes the mining of marine mineral resources in the not too distant future probable. Therefore, an enormous focus lays currently on the development of a viable process route to extract valuable metals from marine mineral resources such as polymetallic nodules. For a country with few natural resources like Germany, the industrial treatment of marine mineral resources could lead to a significantly decreased dependence on the global natural resource market. The focus during treatment of these nodules lies on the pyrometallurgical extraction of Ni, Cu and Co on one hand as well as the generation of a sellable ferromanganese and/or silicomanganese product on the other. All work is conducted in lab-scale SAF furnaces. The concept approach is zero-waste, which includes careful slag design, so that the produced slags adhere to environmental restrictions.

The current liquidus surface and phase equilibria established in air for fluxed titaniferous magnetite (titanomagnetite) slags conforming to a composition of 37.19% TiO₂, 19.69% SiO₂, 13.12% Al₂O₃, and 30.00% of various ratios of CaO+MgO were reviewed at applicable PO₂ using FactSage simulation and phase composition of a real plant titanomagnetite slag. The testwork included the incorporation into FactSage of a private MgTi₂O₅-Al₂TiO₅ pseudobrookite solution model. The results of the investigation showed that the liquidus surface and Ti3+/ Ti4+ mass fraction ratio increased with decreasing the PO₂, At low PO₂, perovskite crystallizes as a primary phase at high CaO content. The spinel solution, i.e. (Mg)(Al,Ti)O₄, generally crystallizes as the primary phase at high MgO contents, though it is replaced by MgTi₂O₅-Al₂TiO₅ solution at PO₂ of 10–10 atm to 10–15 atm. An intermediate equilibrium phase diagram established at PO₂ of 10–16 atm is proposed. This phase diagram does not show the observed primary phase crystallization competition, however, the phase composition of a real titanomagnetite slag produced by Evraz Highveld Steel and Vanadium Corporation in South Africa does show primary phase crystallization competition between (Mg)(Al,Ti)₂O₄ and MgTi₂O₅-Al₂TiO₅. Smelting involving such slags is likely conducted around the transition PO₂, i.e. PO₂ of about 10–16 atm. Complex modelling with MgTi₂O₅, Al₂TiO₅ and Ti₃O₅ end members and experiments are underway to verify and update the intermediate phase diagram.

This work investigates the effect of slag composition in steel-slag and steel-inclusion reaction kinetics in silicon-manganese killed steels by using FactSage macros to simulate and predict inclusion composition and morphology changes during ladle treatment. Two different conditions of ladle treatment were simulated in regard to alumina and silica content in a basic slag. The simulated changes in inclusion chemical composition and phases, as well as total oxygen and dissolved aluminum in steel were compared. One experimental trial was made to simulate ladle steel-slag and steel-inclusion reactions using an induction furnace to simulate deoxidation and slag addition. The average steel mass transfer coefficient for the experimental setup was calculated from the analyzed aluminium pick-up by steel. Average inclusion composition was measured using Scanning Electron Microscopy and Energy-Dispersive X-Ray Spectroscopy. The chemical compositions of the inclusions and the steel agreed with the FactSage macro simulations.

As Al contents in Advanced High Strength Steels (AHSS) increase, the possibility exists that Al will reduce CaO and MgO from slag or refractory. Excessive Ca or Mg transfer would form solid inclusions that can cause nozzle clogging. This study documents experimental observations of reduction of CaO and MgO from slag and refractory in steels containing 2, 0.5 and 0.1 wt% Al at 1600°C or 1700°C. Mg transfer was observed in all experiments, while Ca transfer was only noticed under certain conditions and less intense when comparing with Mg transfer. These observations were consistent with considering the rate of reaction to be controlled by Mg and Ca transfer from slag/crucible to liquid steel.

Inclusion content minimization is key in the production high quality steels. This is typically achieved through approaches ranging from preventing inclusion formation via process control to optimising process conditions to remove any inclusions that form. Inclusion removal from steel is generally through reaction with a slag. The inclusion transfers across the steel-slag interface to dissolve in the slag. This transfer process is primarily a dynamic interfacial tension/wetting driven process. In this study, the dynamic wetting (θ) of a range of slags in the CaO-Al₂O₃-SiO₂-(MgO) system on alumina (Al₂O₃), magnesia spinel (MgAl₂O₄) and calcium aluminate (CaO.Al₂O₃) substrates has been assessed using the sessile drop technique. The reactivity of selected inclusion phases was studied by evaluating the wetting results and characterizing the microstructure of the slag-inclusion interface. It was found the dependence of θ value on the composition was lower for the basic ladle type slags than the acid tundish type slags.

Aluminum deoxidized steel tends to form solid inclusions (alumina, spinel, partially modified calcium aluminates). These solid inclusions are known to present challenges during casting, cause slivers during mechanical working and act as crack initiation sites for mechanical failure. Calcium injection practice has been used by the industry to transform these solid inclusions into liquid inclusions for several decades. There has been a significant amount of study to understand the mechanism of calcium modification of alumina/spinel inclusions. However, there has been little attempt to understand calcium transfer from slag to steel to inclusions that may modify alumina inclusions. In this study, laboratory deoxidation experiments were conducted using an induction furnace, physically simulating a ladle furnace; samples were taken during these experiments to study the extent of calcium transfer through inclusion analysis. This study shows that in the presence of silicon, there can be significant amount of calcium transfer from slag. Also, as the rate of calcium transfer from slag is limited by mass transfer in steel and slag, it is difficult to modify a large concentration of inclusions. However, an appreciable extent of calcium transfer was found in the case of lower concentration of inclusions (less than 150 ppm area fraction).

The evolution mechanisms of Al₂O₃-SiO₂ system inclusion in 13Cr stainless steel with CaO-SiO₂-Al₂O₃ top slag were investigated from thermodynamic ,kinetic as well as experimental work.From theoretical aspect: the stability diagrams of Ca-Si-Al-O and Mg-Al-O were obtained, From experimentally aspect: Increasing Al₂O₃ content in slag would low slag melting temperature and the usage of CaF₂. On the condition of relatively high Al₂O₃ in slag, the top slag would have a good kinetic condition. But excessive high Al₂O₃ in slag would increase total oxygen in stainless steel and cause a more complex series of slag-steel-inclusions reactions. Meanwhile, it is found that high basicity slag has good de-oxidation ability and it also accelerates the transition from high Al₂O₃ inclusions to low melt point CaO-Al₂O₃-SiO₂-MgO system inclusions. But excessive high basicity would have no effect on T.O and leads high content of [Al], [Mg] in liquid iron and which would promote the MgO-Al₂O₃ inclusions.

The sulphide capacities of CaO-MgO-Al₂O₃-SiO₂-CrO_x slags with were measured by gas-slag equilibration method in the temperature range of 1823-1898K to reveal the effect of CrO_x on the sulphide capacities of slags. Both higher basicity and temperature enhanced sulphide capacities. The CrO_x additions in the range of 0–5 mass% increased the sulphide capacity, but, further increase of CrO_x contents to 7 % was found to lower the sulphide capacity. Utilizing the relationship for estimating the ratio of Cr2+/Cr3+put forward by the present authors, the influence of Cr(II) on the sulphide capacities of the slags studied is discussed.

Silicate slags are widely used in many pyrometallurgical processes. The physiochemical properties of the slags, particularly viscosity, are closely related to their internal structures at operating conditions. To fundamentally investigate the correlation between slag structures and viscosities, the glassy samples in SiO₂-CaO, SiO₂-CaO-MgO and SiO₂-CaO-Al₂O₃ systems were prepared by directly quenching to water. The quenched slags that maintain structures at high temperature were analyzed quantitatively by Raman spectrometer. The appropriate conditions of Raman spectroscopy measurements have been evaluated to obtain a better spectra for quantitative analysis. The proportions of four types of Si with different coordination can be clearly revealed from the analyses of the Raman peaks. The viscosities of the slags are correlated with the changes of the characteristic peak positions and areas.

Temperature and frequency dependencies of velocities and absorption coefficients of ultrasonic waves were measured on molten 33(mol%)Na₂O-SiO₂ and 33(mol%)K₂O-SiO₂, and compositional dependencies of ultrasonic velocities were summarized using previous data on molten M₂O-SiO₂ (M = Li, Na and K) so as to elucidate the relation between acoustic properties and silicate network structures. The velocities and absorption coefficients of ultrasonic waves are identical irrespective of frequencies above ca. 1400 K for 33Na₂O·67SiO₂ and ca. 1500 K for 33K₂O·67SiO₂, respectively, while frequency dependencies appear below these temperatures. Frequency dependency stems from the structural relaxation of molten silicates. It has also been found that there is an identical linear relation between the ultrasonic velocities and the molar volumes for these alkali silicates. This indicates that the molar volume is one of the most significant factors affecting the ultrasonic velocity value instead of the iconicity of atomic bonding.

Waste Electrical and Electronic Equipment (WEEE) offers a significant resource for precious metals such as gold and silver. To maximize precious metal recoveries and sustainable use their behavior during WEEE smelting with copper as the collector metal needs to be characterized. This study experimentally determines the distributions of gold and silver between metallic copper and FeO_x-SiO₂-Al₂O₃ slag (LCu/s[Me] = [Me]_Copper/[Me]_Slag) in alumina-saturation over the oxygen potential range of 10-5–10-10 atm at 1300 °C. The experiments were conducted employing equilibration / quenching followed by major element analysis by Electron Probe Micro-Analysis (EPMA) and trace element analysis by Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICP-MS) techniques. Our results show silver distribution increased exponentially from 30 to 1000 as a function of decreasing oxygen partial pressure. Gold distribution was 105 at pO₂ = 10-5 atm and >106 at pO₂ = 10-6–10-10 atm.

Waste smartphone, as an important type of secondary resource has high content of rare and precious metals. The traditional mechanical process could easily lead to the dispersion and loss of precious metals. In this research, a smelting method using Al₂O₃-FeO_x-SiO₂ slag system is proposed to recover the valuable metals in smartphone PCBs. Based on the evaluation of liquidus projection calculated and plotted by Factsage software, reasonable smelting temperatures and slag composition ranges were selected, namely 1300℃-1500℃, 10-15wt% Al₂O₃, FeO / SiO₂ ratio of 0.8-1.5. Then several lab experiments were conducted, with Cu-Fe-Sn-Ni alloy obtained. The results show that distribution of valuable metals could be controlled by appropriate oxidation of iron. Rare metals primarily enrich in the alloy, and most of active metals like Fe, Al in slag as oxide. Recovery efficiencies of Cu, Ni, Sn, Au, Ag are more than 95wt%.

Plenty of valuable metals, such as cobalt, nickel, copper, manganese and lithium, are present in spent lithium-ion batteries. A novel smelting reduction process based on MnO-SiO₂-Al₂O₃ slag system for spent lithium ion batteries is developed, using pyrolusite ore as the major flux. And Co-Ni-Cu-Fe alloy and manganese-rich slag contained lithium are obtained. The results show that it is reasonable to control MnO/SiO₂ ratio in the range of 2.05-3.23 (w/w) and Al₂O₃ content in 19.23-26.32wt.%, while the MnO and Li₂O contents in the manganese-rich slag can reach 47.03 wt.% and 2.63 wt.%, respectively. In the following leaching experiments of the manganese-rich slag by sulphuric acid solution, the recovery efficiency of manganese and lithium can reach up to 79.86% and 94.85%, respectively. Compared with the conventional hydro-pyrometallurgical process of spent lithium-ion batteries, the present can preferably recover Mn and Li besides Co, Ni and Cu.

In order to optimize the recycling process, fundamental understanding of the rare earths distribution in the slag and the precipitation behavior of the REE containing compounds during slag solidification are of significant importance. In this work, “in-situ” observations of rare earth containing phase precipitation, and solidification behavior of the CaO-SiO₂-Nd₂O₃ and CaO-SiO₂-Nd₂O₃-P₂O₅ melts were performed using a confocal scanning laser microscope (CSLM) combined with an infrared imaging furnace heating (IIF). The compositions of the precipitates formed during cooling of those slags were examined using EPMA method. The addition of P₂O₅ was found to influence the precipitation behavior and to decrease the liquidus as well as the solidus temperatures of the slags.

The recovery of rare earth elements from metallurgical slags containing rare earths is an important topic. The crystallization behavior of CaO-SiO₂-CaF₂-CeO₂ system with CeO₂ content range from 12 to 16 mass pct and a constant CaO/SiO₂ ratio of 1 has been examined by using a confocal laser scanning microscope (CLSM). Diagram of continuous cooling transformation and that of isothermal (time temperature) transformation for the slag have been constructed to characterize the solidification behavior of the slag with cooling rates between 3.125 and 100 K/minutes and temperature between 1373 and 1598 K. Depending on the CeO₂ content in the slag, the primary crystalline phase of CaO-SiO₂-CaF₂-CeO₂ system precipitates with elongated needle-like or short and rod-like crystals. The XRD analyses of crystalline phase of solidified slags confirm that the primary crystalline phase is a rare earth-rich phase Ca₂Ce₈O₂(SiO₄)₆, which contains no fluoride.

Crystallization behavior of blast furnace slag is of great interest for generating value-added products from slag, such as cement feedstock, where the slag structure determines the material quality. Aided with a Hot Thermocouple Device, the kinetics of crystallization of CaO-SiO₂-Al₂O₃-MgO slags was determined. The rate of nucleation and growth of crystals were measured for a range of slag basicities, temperatures, and hold times.

Formation of freeze-linings from aggressive process slags is used in industrial pyrometallurgical processes to protect the furnace wall. In this laboratory study, the formation of freeze-linings from fayalite-based (FeO-SiO₂-Al₂O₃-CaO) slags was investigated. This was performed with a gas-cooled probe at 1200 °C under protective atmosphere. The microstructure of the freeze-linings formed on the samples was characterized using scanning electron microscopy (SEM). The influence of cooling rate, slag agitation and slag composition on the freeze-lining formation was studied by varying the gas-flow rate, rotating the crucible and changing the CaO and Al₂O₃ contents in the fayalite-based slag, respectively. The results indicate that fayalite (Fe₂SiO₄) precipitated from the slag and grew into large columnar crystals along the heat gradient from the cooled probe to the bath slag. The thickness of the freeze-lining increased with increasing cooling rate, while an increase in the slag agitation and the CaO and Al₂O₃ contents in the slag decreased the thickness of the freeze-lining. These macroscopical observations are discussed with respect to the microstructural evolution in the formed freeze-lining samples.

A metallurgical analysis of longitudinal cracks in a medium carbon grade of steel, produced through Thin Slab Casting and Rolling (TSCR) process is presented in this paper. Using characterization techniques, it was established that the defect originated from the funnel mold of thin slab caster. Temperature profiles of thermocouples in caster mold were employed to evaluate the heat transfer characteristics during primary solidification. The profiles helped to assess the performance of a standard mold flux used for casting this grade and hypothesize a possible mechanism of defect evolution. Slightly changed characteristics of the mold flux addressed the defect by promoting a stable and uniform heat transfer. This drastically lowered defect occurrence and rejections due to longitudinal cracks in this grade.

Mold flux plays key roles during the continuous casting process of molten steel, which accounts for the quality of final slabs. With the development of Advanced High Strength Steels (AHSS), certain amounts of Al have been added into steels that would introduce severe slag/metal interaction problems during process of continuous casting. In this article, through the studies of SHTT, IET and SEM, the melting range of mold flux was increased and the heat transfer rate was inhibited under the coordination effect of the combination of BaO and B₂O₃. It was found the case with BaO substituting for CaO to replace B₂O₃ shows the highest general heat transfer rate and lowest melting temperature. The results of slag/steel reaction experiments show that the degree of slag/steel reaction increases with the addition of C/A ratio. The latest developments for this new mold flux system were summarized with the aim to offer technical guidance for the design of new generation mold flux system for the casting of AHSS.

In order to find countermeasures against degradation of mold flux properties in high Al steel continuous casting, it is important to understand the reaction between Al-containing steel and CaO-SiO₂–based molten flux. In the present authors’ research group, the reaction rate and mechanism governing the reaction have been experimentally investigated. Based on those observed mechanism, a slag-metal reaction model was developed in order to interpret the reaction and to predict similar reactions between high Al steel and mold flux used for continuous casting process. The model considers both thermodynamic and kinetic information, as well as rate-controlling step observed in the authors’ previous investigation. Thermodynamic information for chemical reaction was interpreted by ChemApp coupled with FactSage thermodynamic database. This is connected to mass flux equations for all relevant components in the system. Flux viscosity change and its effect on the mass flux are also taken into account. The reaction model developed in the present study showed good reproduction of the experimental data. Some possible applications are also shown.

Study of mold fluxes for continuous casting of high-aluminum steel has attracted increasing attention due to severe reaction between aluminum in liquid steel and silica in the flux which results in changes in composition, properties and performance of the flux and adversely affects slab quality. This research began with sampling during the casting process of high-Al nonmagnetic steel 20Mn23AlV to evaluate potential problems. A mold flux was developed in which SiO₂ was partially replaced with Al₂O₃. Different compositions including CaO/Al₂O₃, fluoride-free and low-fluoride lime-alumina-based fluxes were evaluated with respect to their influence on flux viscosity, crystallization and subsequent effects on steel quality. It was concluded that mold flux with CaO/Al₂O₃ ratio in the range 1.1 to 1.6 and characterized by low viscosity, low initial crystallization temperature and good heat transfer properties was appropriate for casting of high-aluminum steel. A viscosity model with high reliability in predicting the viscosity of mold flux containing high Al₂O₃ was also established.

The reaction between [Al] and SiO₂ sharply converted the original CaO-SiO₂-based flux into CaO-SiO₂-Al₂O₃-based flux during the continuous casting of high-Al steels, promoting the crystallization and deteriorating the mold lubrication. Therefore, study on the structure and crystallization behavior of CaO-SiO₂-based and CaO-SiO₂-Al₂O₃-based flux is important to solve this problem. The structure and crystallization behavior were investigated by Raman spectra and the single hot thermocouple technique. The results show that the [AlO₄]5- entered the silicate network (CaO-SiO₂-based) and the melt converted into the aluminosilicates structure (CaO-SiO₂-Al₂O₃-based), the formation of Al-O-Al linkages and Si-O-Al linkages increased the instability of network structure. From the time temperature transformation diagrams, the strong crystallization tendency and the variety of crystals are mainly the properties of slag film in the CaO-SiO₂-Al₂O₃-based flux. Hence, the improvement of the structural stability and suppression the crystallization tendency of the CaO-SiO₂-Al₂O₃-based flux are key to design a high-Al steel mold flux.

The influence of the CaO/SiO₂ ratio on flux viscosity at 1300°C, break temperature and crystallization was investigated.The thermo-chemical software FactSage was used for the calculation of the viscosity, the equilibrium phase content and the liquidus temperature. Based on these results, two sample series with 8.8 wt% TiO₂, 5 wt% B₂O₃ and CaO/SiO₂ ratios from 0.8–1.2 were manufactured. Series M1 contained Li₂O which was replaced by a higher content of Na₂O for F-free mixtures in series M2. The viscosity and break temperature were determined through rotational viscometry, the crystallization temperature and crystalline fraction by a so called Furnace Crystallization Test, a macro style differential thermal analysis which enables a mineralogical investigation of the samples afterwards.The experiments exhibited that the break temperature, the liquidus temperature and the crystalline fraction rose with increasing C/S ratio while the viscosity decreased for both sequences.

The thermal resistance between the cast strand and the copper mold in continuous casting is dominated by the conduction resistance through the partially solidified mold flux layer and the contact resistance between the solidified mold flux and the mold. In the cold-finger approach, a freeze layer of mold flux is grown on a water-cooled probe immersed in molten flux. In principle, the thickness of the solid layer and the steady-state heat flux can be used to estimate conductivity and contact resistance. Lower-basicity fluxes generally give somewhat lower heat fluxes under these conditions and result in formation of glassy films. Glassy films are generally significantly thinner than crystalline films, because of the higher thermal conductivity of crystalline films. A potential approach to estimate thermal conductivity and contact resistance from transient changes in solid film thickness and heat flux is outlined.

Mold fluxes are used in continuous casting of steel to control heat transfer from the steel shell to the copper mold based on their structure and properties. Structures observed in mold flux film samples extracted from conventional and thin slab continuous casters at the end of a cast were examined using cathodoluminescence (CL) imaging in conjunction with XRD and SEM/EDS analysis. Glassy and crystalline structures in the flux films varied greatly depending on sampling location in the mold, distance from the mold wall and the mold flux being examined. Temperature data collected from thermocouple arrays in a thin slab funnel mold indicated sawtooth temperature fluctuations in the lower area of the funnel region, presumably due to cyclic fracture and regrowth of the mold flux crystalline layer in that region of the mold. The temperature observations correlate well with the structures observed in the flux film samples from the region. CL microscopy clearly distinguishes glassy regions from regions with devitrified and dendritic crystal growth, as well as continuous and fractured crystallite layers and cuspidine and nepheline phases that are present. The technique also highlights small variations in Mn oxide content in the glassy region of the flux that results from exchange reactions with the steel, making flow lines in the previously liquid portion of the flux film clearly visible. The benefits of applying cathodoluminescence imaging to the analysis of mold flux films in continuous casting are discussed.

Effects of CaF₂ additions to mould fluxes have been investigated from the perspective of radiative heat transfer reduction to design mould flux for mild cooling. Glassy and crystallised mould flux samples were prepared so that the basicity of CaO/SiO₂ was 1 and the Fe₂O₃ concentration was 1mass%, whereas the concentration of fluorine ranged between 2 and 14mass%. The samples were analysed by SEM-EDS and XRD. The apparent reflectivities and transmissivities were measured using two types of spectrophotometer with an integrating sphere. The replacement of CaO by CaF₂ gives no effect on the optical characteristics of the glassy samples, not leading to radiative heat transfer reduction. In contrast, the replacement affects the optical characteristics of the crystallised samples and also the radiative heat transfer, which appear due to changes in the crystalline phases produced and the degree of crystallinity rather than the interaction between iron and fluoride irons.

Most of the commercial mould fluxes contain fluorides which bring about serious environmental problems. The major challenge in the application of fluorine-free mould fluxes is to control the heat transfer from the strand to copper mould which is closely related to crystallisation behaviour. In this study, the effects of Na₂O on the crystallisation behaviour and heat transfer of CaO-SiO₂-Na₂O-B₂O₃-TiO₂-Al₂O₃-MgO-Li₂O mould fluxes were investigated using single /double hot thermocouple technique (SHTT/DHTT) and infrared emitter technique (IET), respectively. Continuous cooling transformation (CCT) and time-temperature transformation (TTT) diagrams constructed using SHTT showed that the increase of Na₂O concentration led to higher critical cooling rate and shorter incubation time. The crystallisation behaviour in a thermal gradient was examined using DHTT. The heat flux measured by IET showed that the increase of Na₂O concentration decreased the heat flux when Na₂O was lower than 9 mass% but the further increase of Na₂O raised the heat flux. The relationship between flux crystallisation and heat transfer was also discussed.

Carbon is easily picked up on the slab surface from the mold flux in the ultra low carbon steel (ULCS). We were trying to find ways to prevent the C-pickup in ULCS. Naturally, we were interested in the C-pickup with slag pool thickness. When the slag pool thickness was increased up to about 30mm, C-pickup on the slab was dramatically decreased and the deviation in the width direction of the C-pickup was also decreased. However, even if the slag pool thickness was thicker, C-pickup was increased when slag bear was formed. More details will be discussed in the paper.

When casting peritectic steel grades, control of heat transfer from the steel shell is critical for minimising surface defects. Cuspidine (3CaO.2SiO₂.CaF₂) is the preferred crystal phase to control horizontal heat flux, due to its high crystallisation temperature and low incubation time. However, the presence of fluoride creates environmental and operational problems. Research into fluoride-free mould powder for peritectic steel grades has still to yield a fully effective substitute.This research has investigated whether horizontal heat flux in the mould can be controlled by manipulating the interface between the copper mould plate and the slag film. Calculations estimate that the removal of fluoride will decrease the total thermal resistance between the mould and strand by 28%. Results show that interfacial thermal resistance can be increased by the techniques developed, with one technique meeting and exceeding the requirements to replace fluoride in terms of thermal resistance needs for peritectic steel grades.

Iron oxides in mould fluxes enhance heat extraction from the molten steel to the mould due to energy absorption by d-d transitions of Fe2+ and re-emission. Thus, the existence of iron oxides is against mild cooling of molten steel. In this study, mould flux powders containing ca 2 mass% Fe₂O₃ were mixed with sufficient amounts of CaSi₂. The mixtures were contained in alumina crucibles and melted at 1673 K in Ar-H₂ atmosphere. The melts were poured into brass moulds to obtain glassy samples 5 mm thick. The Fe₂O₃ concentration was analysed by a scanning electron microscope with an energy dispersive spectrometer. The concentration decreased from ca 1.71 mass% to 0.49 mass% within 5 min and then settled down. Mass transfer of Fe₂O₃ is supposed to be the rate-controlling step at high temperature. The mass transfer coefficient has been calculated to be 1.8×10-3cms-1, which seems reasonable. Since crystallisation of mould flux enhance heat reflection from the molten steel to reduce heat transfer, crystallisation kinetics of mould fluxes has been investigated using the Avrami equation, which suggests that additions of reducing agents such as CaSi₂ suppress the crystallisation process. In addition, CaSi₂ additions result in a dramatic decrease in the total radiative heat flux across mould fluxes in glassy state and would be effective for mild cooling of molten steel.

Many papers have been presented, and the sessions well attended, on the viscosity measurements of silicate and calcium ferrite based slag systems since this conference series inception in 1980 in Halifax. Over the years, the emphasis has been spent on developing reliable measurement techniques of pure liquids, trustworthy datasets, extending the slag systems and the number of components in the liquids, understanding the behaviour of amphoteric oxides, and extending measurements to two phase systems.This paper reviews the viscosity measurement papers presented at Halifax through to Beijing, with the view to showing how the understanding and practise of viscosity measurement has changed, along with our understanding of the nature of the liquids being measured and ultimately mathematically modelled. Much of the development can be attributed to Professor Ken Mills, and this review attempts to pay tribute to his outstanding contribution to the field.

Based on the thermodynamic associate species model, a new viscosity model and database are currently being developed for the fully liquid system SiO₂-Al₂O₃-CaO-MgO-Na₂O-K₂O-FeO-Fe₂O₃-P₂O₅and its subsystems in the Newtonian range. The modified Arrhenius model, employed in this database, is a structure-based viscosity model, in which the associate species link the viscosity to the internal structure of melts. Both the temperature- and composition-induced structural changes of melts are then described by a set of monomeric associate species in combination with the critical clusters induced by self- and inter-polymerization. The viscosity, therefore, is well described over the whole range of compositions and a broad range of temperatures by using only one set of model parameters, which have clear physico-chemical meaning. Moreover, the model is self-consistent, meaning the extension of viscosities from lower order systems to higher order systems is valid, and vice versa.

Cost issues and decrease of high grade raw materials has sparked interest in the use of other potential sources of iron bearing materials once regarded as uneconomical. China is rich in mineral resources of titanium, After decades of basic research and industrial production practice, a complete set of blast furnace-converter smelting process has been successful developed to produce steel and vanadium/titanium products. This paper begins with an introduction to the sever defects of blast furnace process and focuses on elucidating the effect of TiO₂ on the thermo-physical-chemical properties of blast furnace slag including viscosity, surface properties, foaming performance and formation and regulation mechanism of TiCN. Using molecular dynamics simulation and spectroscopy techniques, the viscous behavior and the structure of the slag system were correlated. Models were used and compared with experimental data.

TiO₂ has been approved as a viscosity-decreasing agent in blast furnace slag under inert atmosphere both by experimental and structure calculation. However, the validity of the above conclusion in a much bigger zone in CaO-SiO₂-Al₂O₃-MgO phase diagram has not approved. The viscosity of slag dependent on the TiO₂ content and basicity were measured in the present work. It was found that the viscosity and viscous activation energy decrease with increasing TiO₂ content and basicity at a reasonable range, indicating TiO₂ behaved as a viscosity-decreasing agent by depolymerizing the silicate network structure when its less than 50wt. %. The liquidity of the slag can be improved when TiO₂ content less than 50wt. % and basicity from 0.5 to 1.1. The free running temperature increase at TiO₂ content from 10wt.% to 30wt. %. The results of calculation does not agree well with the experimental values at a high basicity of 1.3 with TiO₂ content from 20wt.% to 30wt.% and the lower basicity of 0.5 with TiO₂ content more than 50wt.%.

Electrorheology of Ti-bearing slag was investigated by a reconstructive equipment at 1723K. The slag samples were based on slag of Panzhihua Steel and the viscosity was measured with different composition of TiC. The constitutive equations which simulated the Herschel-Bulkley model were established by the relationship between shear rate and shear stress of slag, thus the fluid type was confirmed under the condition of different electric field intensity. The result was that the slag sample containing TiC had an obvious phenomenon of electrorheology, the increase of electric field intensity gave rise to the increase of viscosity and shear stress. It can be extracted from the constitutive equations of 4% TiC slag that the fluid type converted into a Bingham fluid with application of the electric field.

The apparent viscosities of foaming silicon oil and foaming slag was measured. In both studies, the rotating cylinder method was used for the measurements. Additionally, the movement of particles in foaming silicon oil and the behavior of pig iron droplets in foaming slag was investigated. An increase of the apparent viscosity compared to the dynamic viscosity could be observed. The apparent viscosities decreased with increasing rotation speed of the spindle. The moving particles in the foaming silicon oil gave reasonable information regarding the behavior of particles and droplets in foam. This information are needed to get a better understanding of the behavior of iron droplets in foaming slag. After high temperature experiments, the pig iron droplets were collected and analyzed. Conclusions were made regarding mass transfer between foaming slag and iron droplets.

The effect of solid phases and SiO₂ and Al₂O₃ additions on the viscosity of BOF slag was measured with a rotational viscometer in the temperature range of 1500°C-1700°C. Various viscosity models for completely liquid slag were evaluated and parameters in the Einstein-Roscoe equation were optimized to estimate the influence of the solid phases on the BOF slag viscosity.

CaO-SiO₂-CaF2 based flux in a continuous steel caster has to show dual viscous functions to minimize slab defects - high viscosity enough to avoid flux entrainment at mold top surface and low viscosity enough to maximize lubrication capability at oscillated mold wall region. Liquid flux could show a shear thinning behavior when its viscosity decreases with increasing shear rates. Flux viscosity was measured by a rotational type viscometer as a function of shear rates. Raman and XPS analysis were employed to understand structural changes of flux for correlating with shear thinning behavior. The present work has focused on developing an optimum mold flux system with strong shear thinning behavior. The strong shear thinning behavior appropriate for dual viscous functions could be achieved by incorporating borate or silicon nitride into the flux. The flux compositions with a strong shear thinning behavior will be presented from the viewpoint of clean slab production.

The viscosity and structure characteristics of FeO-SiO₂-V₂O₃-TiO₂-Cr₂O₃ systems as the main composition of V-slag were investigated with different Cr₂O₃ and TiO₂ contents using the rotating cylinder method and Raman. The results showed that the viscosity was below 3.5 Pa sat 1540 K, and the polymerization degree of the silicate structure was lower than the main monomer structure (Q°) in FeO-SiO₂-V₂O₃ system. With the induction of Cr₂O₃ to FeO-SiO₂-V₂O₃ system, the viscosity obviously increased ( 3.5 Pa sat 1770 K), with the polymerization degree of molten structures enhanced drastically as formation of a chain structure (Q2 and the O-Cr-O band) and a sheet structure (Q3). With the further induction of TiO₂ to the FeO-SiO₂-V₂O₃-Cr₂O₃ system, the viscosity was 3.5 Pa sat 1630 K, and the polymerization degree became weaker as the forms of discrete Si-O-Ti and Ti-O-Ti decrease to Q3 in a sheet structure.

Eutectic MgF₂-CaF₂ based salt containing YF₃, CaO and Al₂O₃ additions were used in this study. The electrical conductivity was measured as a function of temperature by a calibration-free coaxial electrode setup. The materials selection and setup design were optimized to accurately measure the electrical conductivity of the highly conductive molten salts (>1 S/cm). The solubility and diffusion behavior of alumina and zirconia in the molten salts were investigated by drawing and holding the molten salt for different lengths of time within capillary tubes made of alumina and zirconia, respectively. After the time-dependent high temperature holds, the samples were cooled and the solubility of the solute within the molten salt was determined using scanning electron microscopy, energy-dispersive X-ray spectroscopy analysis and wavelength-dispersive X-ray spectroscopy analysis.

A new quasi-steady state hot plate method has been proposed to measure heat flux across a sheet sample such as mould flux film, finally to determine its apparent thermal conductivity via Fourier’s equation. The heat flux across the sheet sample is derived from the volume change caused by melting of ice utilizing a modified Bunsen Ice Calorimeter. This measurement method was applied to Ni-base super alloy (Inconel 600), alumina and PTFE (Teflon) with known thermal conductivity values to confirm the reliability of this new method. The experimental thermal conductivity values obtained were in good agreement with the respective reported values. Measurements were also conducted on sheet silica glasses which sized 20 × 20 × 0.5 mm3 and 20 × 20 × 1.0 mm3, and produced a value of 1.34 ± 0.03 Wm -1K-1 at 293 K − 303 K under a temperature gradient of 20 Kmm-1, which value is reasonable compared with the reported one. In addition, a process simulation has been applied to confirm the applicability of the present method to mould flux used in continuous casting under a steep temperature gradient at high temperature.

Regulating thermal behavior between the solidifying shell and a mold is one of primary roles of the mold flux film during continuous casting of steel. This is particularly important as excessive heat flux through slag film will induce surface defects on cast steel. This study focuses on controlling radiative heat transfer through liquid slag film by utilizing finely dispersed metallic particles in commercial CaO-SiO₂-CaF₂-Na₂O based mold flux system. In order to investigate the scattering effect on heat transfer during industrial casting processes, the extinction coefficient of various mold fluxes was measured using an FT-IR and a UV-visible spectrometer. Also, series of IET (Infrared Emitter Technique) tests were conducted in order to simulate mold heat transfer during commercial casting processes. Finally, it is found that the Mie scattering effect due to metallic particles will reduce the overall heat flux density through mold slag film by 10% or more.

This paper presents the results of two experimental studies on diffusion of SiO₂ in “silicomanganese” (SiO₂-MnO-CaO-Al₂O₃- MgO) slag and CaO in calcium aluminosilicate slag. The diffusivity of SiO₂ was measured in the temperature range of 1400–1550 °C; while the diffusivity of CaO was determined at 1430–1600°C. The effects of additives on the chemical diffusivities of SiO₂ and CaO were also examined. Addition of CaO and MnO to the silicomanganese slag increased silica diffusivity, while addition of SiO₂ and Al₂O₃ slowed it down. Addition of TiO₂ and MnO_x to the aluminosilicate slag increased the diffusivity of CaO, while the addition of SiO₂ had a negative effect on the diffusivity of CaO. Analysis of diffusivity in relation to the structure of silicate melts demonstrated a good correlation between diffusion coefficients of SiO₂ and CaO and NBO/T (non-bridging oxygen per tetrahedrally coordinated atom).

A study on the effect of cation species on the viscosity and electrical conductivity of CaO-MgO-SiO₂ system is carried out. Rotating cylindrical and two-plate method is used for viscosity and electrical conductivity measurements, respectively. Raman spectroscopy is also carried out to understand the structure of the slags. Experimental results indicated that the cationic effect on viscosity and ionic conductivity is governed by classical Anderson-Stuart theory: The dominance of electrostatic interaction on steric hindrance is confirmed for depolymerized melts (NBO/T=2.0). For polymerized melts (NBO/T=0), however, the major cationic effect on transport properties are examined to be a strain field distortion energy. The viscosity and ionic electrical conductivity are in strong correlation and assumed as the structure-dependent property. The structure of polymerized melts is also affected by the transition in primary solidification phase: Abnormal changes in properties and structure are observed at diopside congruent composition. Such a change at the congruent composition is assured by the entropy calculation and the stability function, Ψ

Iron oxide slags play a critical role in both ferrous and non-ferrous metallurgical processes. The relative abundance of FeO and Fe₂O₃ will determine the slag oxidation potential and influence transport properties, which makes an accurate prediction of their proportions crucial to process operations. The nature of the iron oxide structures in the liquid slag has been a long standing issue, which is in part related to the variety of structural species that can be formulated to accommodate the observed property changes. In this study, spectroscopic data is used to clarify the dual structural behaviour of both ferric and ferrous iron oxide. The identified oxide structures are shown to have characteristic effects on the thermodynamic properties and viscosity of Na₂O-CaO-SiO₂-FeO-Fe₂O₃ melts. These insights into the structural behaviour of iron oxide and its composition dependence can also improve the mathematical modelling of these properties.

Borosilicate glass is used in mixture of high-level radioactive waste (HLW) generated by nuclear spent fuel. Thermophysical property data of borosilicate melts in molten state during processing of HLW were studied to investigate a possibility of a simpler and flexible process for immobilisation of high level wastes. Especially, these data are indispensable information to optimize the process of the temperature distribution in the glass melting furnace. In this study, the thermal effusivity of B₂O₃-CaO-SiO₂ melt was measured using a front heating-front detection laser flash method. The thermal conductivity was evaluated by combining the measured thermal effusivity data with specific heat capacity and density. In these results, the thermal conductivity of CaO-B₂O₃-SiO₂ melt was increased with temperature.

MgCl₂-containing salt is one of the candidates for the solar thermal energy storage applications. To protect the structural alloy from corrosion, the addition of Mg to salt as a corrosion inhibitor is considered. Melting point, heat capacity, enthalpy, entropy and Gibbs energy of MgCl₂ with different amount of Mg are studied in this paper. Depression of melting point is calculated using a derivation of Raoul-Van’t Hoff formula. The MgCl₂ rich phase diagram is constructed. The MgCl₂ with a small amount of Mg addition shows no significant effect on melting point of the salt mixture. Moreover, it can be a candidate as heat transferring fluid for MgCl₂ in solar thermal energy storage applications.

In view of the nature of heterogeneous reaction of many materials processes, great attention has been paid to the reaction interfaces. Very often, the interfacial tension is given the foremost importance in the study of interfaces in general and slag-metal reactions in particular. As an example, the dependence of entrainment of ladle slag into liquid steel on interfacial tension has been the topic of many researchers.In the present work, the interface between liquid silicon and CaO-SiO₂ slag and the interfacial reaction between silicon and graphite were studied experimentally to gain an insight into the impacts of chemical driving force and interfacial tension on the interfacial phenomena. The results strongly suggested that the chemical driving force could play dominating role in determining the interface, while the interfacial tension would only become important when the slag and metal were reaching equilibrium. Based on the experimental findings, the kinetics of the slag-metal reaction was discussed. Also, the possibility of the entrainment of ladle slag as a source of nonmetallic inclusions was evaluated. The present study would like to draw researchers’ attention regarding the important role of Gibbs energy of the reaction at the interface in the interfacial phenomena and therefore getting an improved understanding of the reaction process.

A unique cross tube furnace was designed to focus on the study, development and control of molten oxide jets. The cross alumina tube along with a high speed camera arrangement facilitated observations of jet formation and break up at temperatures 1550 – 1700°C. The slag flow rate was controlled with the help of a nozzle-plunger system along with suitable back pressure of argon. Various phenomena like drop formation and pinch off, drop oscillation and jet breakup was observed. Surface tension of calcia-alumina slags with composition close to its eutectic was studied using dynamic methods like oscillating jet as well as elliptical jet technique. The values were observed to be comparable with existing literature as well as independent sessile drop measurements. The current paper discusses the jet technique for surface tension measurements as well as other dynamic phenomena involved during jet formation. It also discusses the effect of phenomena like wetting on the jet method.

Physical properties of slag are critical in the design and operation of refining technologies and slagging energy systems. The surface tension of slag impacts phenomena such as granulation, foaming, removal of solid inclusions, erosion of refractory and fouling. In this study, slag sessile drops formed on graphite, alumina and molybdenum substrates were compared. Use of graphite resulted in the largest contact angles, a desirable trait for surface tension measurements, but also led to reactions with the slag. Alumina and molybdenum were less reactive, but resulted in contact angles too small for measurements. When sessile drops were constrained by small substrate diameters to increase the apparent contact angle, surface tension measurements could be achieved with alumina and molybdenum substrates. The surface tension of coal slag was measured at up to 1600 °C in oxidizing and reducing gas atmospheres.

In this study, the spreading and infiltration behavior of slag in contact with different grades of graphite was investigated. The wetting and infiltration of slag into graphite were found to be highly material dependent. Temperature and silica content of the slag also have a major influence on how slag spreads and infiltrates: The higher the temperature and silica content, the greater the slag infiltration, and the faster the rate of spreading. Reactions that generate gaseous products occurred during spreading of slag on graphite was evidenced by the observation of bubble formation. Silicon infiltrated into the graphite substrates much deeper than the slag phase, indicating gas-phase transport of silicon-bearing vapor species. Complete wetting of the interface and reduction of silica in the slag near the interface may lead to passivation by formation of a solid, CaO-rich layer.

Wetting angle and spreading rate between slags and refractory ceramics such as Al₂O₃, MgO, MgO-C or SiC have been recently determined by using dispensed drop technic with a high speed camera. Intrinsic value of wetting angle and the effect of reactions on wetting and spreading are reviewed and discussed. Role of carbide or graphite in refractories are also reviewed when these were in contact with reducible slags. Driving force for spreading and a spreading model (non-reactive viscous model) are discussed.

A generic model was conceived for predicting the diffusion coefficient of species in slag. The diffusion coefficient of sulfur in CaO-Al₂O₃-SiO₂ slag with low silica was measured using a combinational technique of the generic model and experiments. The uniqueness of the experiments was in the method of collecting samples. Another milestone was that the diffusion coefficient of sulfur in the slag was obtained through the sulfur levels in the metal (silver). Later the order of magnitude of the diffusion coefficient of sulfur in slag was used to estimate the time required for sulfur to reach the slag- metal interface of an iron drop immersed in CaO-Al₂O₃-FeO-SiO₂ slag. This estimated time for arrival of sulfur at the interface was comparable to the actual observation. The current paper describes the challenges in measuring the diffusion coefficient of sulfur. It also describes the time estimates calculated based on the X-ray image for sulfur to reach the slag-metal interface.

The transient behavior of the immiscible two liquids interface, which is initiated by the rising gas bubble was investigated using Smoothed Particle Hydrodynamics (SPH) model. This developed numerical method is using fully Lagrangian particle-based model, which can track the movement of both the gas and the liquid phase directly. Numerical simulations have been performed for different conditions corresponding to different values of Eö number, and the predicted topological changes as well as the theoretical pressure and interfacial shape of bubbles are validated. In the case of immiscible two liquids, the column of a lower liquid phase penetrating into the upper liquid phase influences interface area, whose shape strongly depends on the wake flow pattern of a bubble. Thus, the dynamic balance between the buoyancy and the liquid-liquid interfacial tension determines an interface area. Under higher surface tension condition, such as molten metal-slag system, the liquid-liquid interface shape is greatly influenced by the fluctuation of a bubble. Then, non-linearly changed interface shape can be observed, indicating that this shape becomes easily unstable by slight change of the curvature.

Two techniques were used to determine the surface characteristics of a molten fluoride-based salt. The maximum bubble pressure method was used to measure the surface tension of the molten salt. Regulated Ar-2%H₂(g) was passed through a steel tube into a molten salt at high temperature. The surface tension of the gas-liquid interface was calculated by measuring the maximum pressure within the tube using a pressure transducer. Contact angles between the flux and solid interfaces were measured by imaging droplets of the molten flux on various surfaces using a camera with a high shutter speed. The camera took images of the high temperature sessile droplet on a solid surface through an optically clear pane. This image was processed through multiple software packages to determine the contact angle and surface tension between the solid-liquid interfaces. The surface properties measured were used to optimize the salt for electrolytic metals production processes.

A study on the effect of FeO and MgO content on foaming index in EAF slag system was carried out. The height of the slag foam was measured by electric probe maintaining steady state in gas formation and escape. Foaming index, which is the measurement of gas capturing potential of the slag, is calculated from the foam height and gas flow rate. Viscosity and surface tension, which are the key properties for the foaming index, are calculated by Urbain’s model and additive method, respectively. Dimensional analysis also performed to determine the dominancy of properties and resulted that the important factor was a ratio between viscosity and surface tension. The effect of each component on the viscosity, surface tension and foaming index of the slag is evaluated to be in strong relationship.

Degradation of refractory liners is one of the key factors limiting the service life of entrained flow slagging gasifiers, which is caused primarily by refractory/slag interactions. Slag originates from impurities in the carbon feedstock, typically coal and/or petcoke, which melt and coalesce during gasification, flowing over the refractory liner in the gasifier and interacting with it. Slagging gasifier operators attempt to minimize refractory degradation by controlling slag viscosity (and interactions) through the gasification process temperature. A computer model utilizing empirical and neural network calculations was developed to predict T₁₀₀, T₂₅₀, fluid temperature, and liquidus temperature of slag compositions based on chemistry and a newly developed “similarity index”. Development of the model and its application in designing slags to minimize refractory degradation will be discussed.

Large quantities of carbon dioxide gas and slag are generated as waste byproducts through iron & steelmaking and slagging gasification processes, using carbon feedstock to produce metal, electric power, and/or chemicals. The increasing use of petroleum coke in the modern gasification industry has changed slag chemistry — causing it to become rich in vanadium (III) oxide. When the vanadium rich gasification slag is interacted with metallurgical slag targeting a specific slag chemistry and temperature; calcium orthovanadate forms, changing vanadium valence from 3+ to 5+. This valence change involves oxygen removal from the surrounding environment. The reaction is highly exothermic, which is more than enough to break bonding in carbon dioxide and water molecules and to still have excess thermal energy. In this work, generation of carbon monoxide from carbon dioxide was investigated using synthetic slag mixtures containing vanadium. Results indicated rapid CO₂→CO conversion occurred at temperatures below those at which metallurgical slag is typically tapped out of furnaces in industries.

High temperature thermochemical equilibrium calculations are computationally expensive, taking several milliseconds to complete for simple systems on existing computer hardware. Integrating such calculations into a multiphysics model to describe thermochemical behavior in addition to fluid flow and heat transfer, may result in a model that cannot be solved with the available computing resources.This problem can be solved by pre-calculating, storing, recalling and interpolating the required thermochemical data. If recall and interpolation can be done quickly, the time required to obtain results can potentially be reduced by several orders of magnitude. Some researchers have implemented this approach on systems with small numbers of components. Pyrometallurgical processes, however, involve many system components, including, for example, Al-C-Ca-Cr-Fe-Mg-Mn-N-O-Si-Ti in significant amounts.An approach is demonstrated for binary and ternary slag systems using the Al₂O₃-CaO-SiO₂ system as example. The results are compared with ChemApp calculations.

In the present work, the effects of amount of coke, reduction temperature and furnace types on copper slag smelting in a dc arc furnace were studied. Optimum coke amount was found to be 10% of the slag weight in an open-top furnace for a 1 hour reduction time in the temperature between 1703 K and 1753 K. Similar conditions in a closed-top furnace resulted in higher cobalt and copper contents of the metallic matte, recoveries and reduction rates, as compared with the open-top furnace. In the covered system, for cobalt and copper, recoveries reach 95.7% and 90%, concentrations were 2.38% and 3.51% respectively, and reduction rate constants were found to be 1.7x10-3.s-1. For both furnaces, higher reduction temperatures yielded higher reduction rates but lower cobalt, copper and sulfur content in the metallic matte. The specific conductivity of the slag was also estimated by using furnace geometric factor given in the literature as an empirical formula and by using furnace resistance measured during smelting of the copper slag with or without different additives.

In the classical pyrometallurgical route for copper production from sulphide concentrates, the treatment of slags aims to recover copper through the coalescence of copper metal and copper sulphide particles. To assist with this settling process, a reductant is added to the slag to reduce the spinel precipitated phases (magnetite) in order to diminish the viscosity of the slag. While the impact on viscosity is typically the majority of reports in the literature, there is also the potential to reduce Cu₂O and Cu₂S dissolved in the slag. This can result in improved settling and increased recovery of copper.An experimental study on the reduction kinetic of industrial slags was done to evaluate the intrinsic rate of reduction of those types of copper slags by methane. The results are compared with the available literature on the rate of reduction for these types of reactions, showing that copper reduction is one the order of magnitude higher than the reduction of FeO, which is the key step of the smelting reduction processes developed in the ’80s.

Copper concentrates which have high silica but low iron contents are difficult to smelt using conventional two stage smelting processes. Direct to blister smelting is possible using either iron oxide fluxes to produce a fayalite type slag or silica and lime fluxes to produce a lime-silica-iron oxide slag. The benefits of lime and silica fluxing option, have been quantified using both thermodynamic modelling and a campaign of pilot scale TSL (Sirosmelt) direct to blister smelting.Direct to blister smelting simulations were made with the MPE thermodynamic package. The simulation results predicted that the copper losses to slag would be 7.9, 20.4 and 7.0% of input copper for the un-fluxed, iron oxide flux and the lime and silica fluxing scenario respectively. The slag make per unit of copper was 1.4 for the un-fluxed system, 2.4 for the iron oxide flux and 1.9 for the lime and silica fluxed systems.A series of pilot scale direct to blister smelting tests were conducted on the lime and silica fluxing system. The copper content of slag varied between 7 and 10% and increased slightly with excess oxygen in the system (smelting ratio). The slag make per unit of input copper varied between 1.5 and 2.4 which was in reasonable agreement with the calculated predictions. Copper losses to slag were mostly between 22 and 26% which is higher than predicted, due to the presence of entrained copper prills in the slag

Selenium is a value added by-product of copper process. The lower recovery of selenium from the copper process is attributed to the high loss of selenium in the discarded slag. Knowledge of selenium behavior in slag is very important in the control of the selenium loss. The samples of slag and matte were collected from the smelter exit before their separation. The experiments involving slag-matte separation were performed at 1250° C for 4 hours of soaking time under inert atmosphere in a vertical tubular furnace with the addition of selenium dioxide in different proportions. The association of selenium in various phases of the slag was determined using electron microscopic analysis. The selenium was found to be replacing the sulfur of the entrapped matte phase in slag. With an increase in selenium content, the size of entrapped matte phase decreased, thus causing high loss of copper in slag.

Molten oxidation is a sustainable process for direct precipitation of magnetite from melt copper smelter slag because it involves zero or less energy input due to the exothermic reaction and free reducing carbon addition. During molten oxidation, magnetite precipitation occurred preferentially because of its intensive ferromagnetism and large crystal size, which enables downstream magnetic separation. Previous milligram-scale experiments conducted using an infrared furnace show that magnetite could be precipitated, while precipitation of hematite was limited under an atmosphere of 1 vol% oxygen. In this study, gram-scale experiments were conducted using an electric furnace to verify larger-scale molten oxidation at 1 vol% oxygen.

CEQCSI is an ArcelorMittal in-house built thermodynamic equilibrium calculation software which is used both at high temperatures typically for slag-metal reactions but also at “low” temperatures to study solid phase transformations and precipitation in solid steel. It has been built to accommodate different thermodynamic models for slag (the Cell model, the Generalized Central Atom model - product of a collaboration between ArcelorMittal Global R&D Maizieres and CSIRO Melbourne), for steel (sublattice model, Wagner Interaction Parameter Formalism) as well as for oxide, sulfide, carbide… solid solutions. Examples of application concern Si, Mn, S slag-metal equilibrium in Blast-Furnace, P partition in BOF slags, slag-metal equilibrium for flat and long products in ladle… Apart from data relating to mass transfer between different phases at equilibrium, CEQCSI proposes several estimates for slag viscosities with among them one delivered by a new model based on the Generalized Central Atom thermodynamic model for slags. CEQCSI conception allows also handling some kinetic problems such as desulfurization in ladle or slag/metal reaction in mold.

Phase equilibria studies of the CaO-Fe₂O₃-SiO₂ system in air from 1200°C to 1260°C have been carried out at Fe-rich region with particular focus on the phase chemistry of Silico-Ferrite of Calcium (SFC) phase and associated equilibria. The measurements have been made possible through the use of a modified experimental technique involving high temperature equilibration, rapid quenching followed by electron probe X-ray micro analysis (EPMA). The compositions and temperatures determining the limits of the primary phase field of the SFC phase have been determined for the first time. Isothermal sections for 1220°C, 1240°C, 1255°C and 1260°C have been measured and the liquidus in the SFC primary phase field has also been determined.

The effect of Ca-Mn substitution on the sulfide capacity of the MnO-CaO-SiO₂ (-Al₂O₃-MgO) melts were explained from the Raman scattering data, from which the structure information for the network modifying role and sulfur stabilizing role of Ca2+ and Mn2+ ions were obtained. The effect of Ce₂O₃ on the sulfide capacity of the MnO-SiO₂-Al₂O₃-Ce₂O₃ melts were understood based on the structure data, from which the charge compensating role of Ce3+ and the amphoteric behavior of alumina were obtained. Employing the structure analysis, the thermochemical properties such as capacity of the oxide melts with no thermodynamic data can be understood in terms of ‘composition-structure-property’ relationship.

Rare earth (RE) elements are expected to be effective deoxidizing agents in steelmaking because of their strong affinity for oxygen. Deoxidation products would be composed of the CaO-AlO_1.5-REOx system with the existence of secondary refining fluxes and/or in case of complex deoxidation with Ca and Al. This study focuses on Cerium (Ce), which is one of the main components in the misch metal alloys. The phase relations for the CaO-AlO_1.5-CeO_1.5 system have been investigated at 1823 K and 1873 K by chemical equilibration technique also by clarifying the existence of ternary intermediate compounds, CaO·AlO_1.5·CeO_1.5 and CaO·3AlO_1.5·CeO_1.5. Also, by clarifying the activity of AlO_1.5 of the present system, Al-Ce complex deoxidation behavior is discussed.

Cr is an important alloying element for metal materials. Thermodynamic behaviors of Cr in metal and slag phase are basic knowledge for enhancing its yield ratio in pyrometallurgy process. In this research, laboratory experiments on distribution ratios of Cr between slag (CaO-SiO₂-Al₂O₃sat-CrOx, CaO-SiO₂-MgOsat-CrOx, and CaO-SiO₂-Al₂O₃-MgOsat-CrOx) and Fe-C(-Si/Al)-Cr metal phase were carried out under 1500°C–1600°C by using gas-slag-metal equilibrium method. The effects of influencing factors such as slag compositions, temperature, and metal melt compositions were examined. The results suggested that the distribution ratio of chromium between slag and metal phase increased with increasing the carbon and silicon contents in metal phase; Aluminum can reduce some silicon oxides into silicon in metal melt, which further promote the reduction of chromium oxides into metal phase. And the basicity, along with Al₂O₃ content in slag also gave important influence on L_Cr.

Ni-base alloys have been used for steam turbine in power plant that operates at temperatures higher than 873 K due to their high strength and superior heat resistance. Commercially, nickel alloys are generally produced by ESR (Electro-Slag Remelting) process with high cleanliness. During the ESR process, however, several alloying elements such as Ti and Al react with molten slag (2Ti+Al₂O₃=2Al+Ti₂O₃), resulting in a different composition between electrode and solidified ingot. Therefore, in the present study, we investigated the equilibrium between CaO-Al₂O₃-CaF₂-TiO_x type ESR slag and Ni-Ti-Al(-C) alloys at 1773 K to minimize the change in the alloy composition during ESR process.

It is commonly believed that the deoxidation of titanium (Ti), or the direct removal of oxygen (O) dissolved in metallic Ti, is practically impossible when magnesium (Mg) is used as the deoxidizing agent. In recent years, it has been experimentally demonstrated that O dissolved in Ti can be directly removed using MgCl₂ molten salt electrolysis. By the electrochemical deoxidation technique, Ti wires containing 0.12 mass% O were deoxidized to less than 0.02 mass% O. In some cases, the concentration of O in the Ti wires was reduced to the level of 0.01 mass% O, which cannot be attained using the current Kroll process. The possible application of this deoxidation technique to practical industrial recycling processes is also discussed.

The production of synthetic rutile using a novel electrochemical process using a molten salt electrolyte is described. The product produced by this process is of similar quality and composition to existing synthetic rutile materials, which are used as a feedstock to many titanium and pigment production processes. The mechanism that underlies this process is the solubility of iron(III) oxide in chloride salts, which can then be reduced electrochemically, producing metallic iron, and leaving behind synthetic rutile. The effect of electrolyte composition is also investigated.

Given the renewed interest in uranium from the pyroprocessing of used nuclear fuel in a molten salt system, the two biggest hurdles for marketing the uranium are radiation levels and transuranic content. A radiation level as low as possible is desired so that handling operations can be performed directly with the uranium. The transuranic content of the uranium will affect the subsequent waste streams generated and, thus also should be minimized. Although the pyroprocessing technology was originally developed without regard to radiation and transuranic levels, adaptations to the process have been considered. Process conditions have been varied during the distillation and casting cycles of the process with increasing temperature showing the largest effect on the reduction of radiation levels. Transuranic levels can be reduced significantly by incorporating a pre-step in the salt distillation operation to remove a majority of the salt prior to distillation.

A zero-direct-carbon-emission solid oxide membrane (SOM) electrolysis process was designed and developed to produce high purity aluminum metal. An inert anode assembly containing liquid silver in a one-end-closed YSZ (yttria-stabilized zirconia) membrane tube and LSM (La_0.8Sr_0.2MnO₃-δ)-Inconel inert anode current collector was immersed in an alumina containing molten fluoride flux. A proof-of-concept electrolysis experiment was performed to confirm the aluminum production by depositing liquid aluminum directly on a TiB₂ cathode. An improved setup employing liquid aluminum cathode was subsequently used to produce high purity aluminum using the SOM electrolysis process. The membrane stability was confirmed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. High purity aluminum (>99wt%) was produced and collected after the electrolysis.

The length of aluminium electrolysis cells have constantly increased over the last decades. The drive to increase productivity resulted in the need to feed and dissolve more alumina in less electrolyte. There is mounting evidence that these two trends are pushing the electrolysis cells above their capability to maintain alumina concentration, through time and space, at levels preventing both conventional and non-propagating anode effects. Alumina concentration gradient measurements were performed within large industrial cells and showed that large gradients occurred between locations in cells.

In aluminum production, the electrolyte is a molten fluorides mixture typically around 1000°C. In order to have a better understanding of the industrial process, it is necessary to have a model which will describe the molten salts on a wide range of compositions and temperatures, to accurately cover all the combinations that may be encountered in an operating electrolysis vessel. The aim of this study is to describe the speciation in the electrolyte in terms of anionic species in the bulk materials far from electrodes. To determine the speciation in situ at high temperature in the absence of an electrical field, we develop an original approach combining experimental methods such as Nuclear Magnetic Resonance spectroscopy (NMR) at high temperature with Molecular Dynamics (MD) simulation coupled with first principle calculations based on Density Functional Theory (DFT). This approach allows the calculation of NMR parameters and the comparison with the experimental ones. It will be provide an additional validation and constraint of the model used for MD. We test this approach on the model NaF-AlF₃ system.

The nucleation mechanism of Co(II) in urea-choline chloride-CoCl₂ melt at 373 K was studied using chronoamperometry. Chronoamperometry experiments confirm that the electrodeposition of cobalt on tungsten electrode is governed by three-dimensional (3D) progressive nucleation and diffusion-controlled growth mechanisms. The average diffusion coefficient of Co(II) in the melt at 373 K is 1.1 × 10-6 cm2 s-1, which is in good agreement with the estimated value obtained from cyclic voltammetry data. Characterization of the Co electrodeposit using scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) techniques indicate that the electrodeposit obtained at -0.75 V and 373 K contain dense and compact surface formed from pure cobalt metal.

Controlled laboratory experiments were carried out to determine the current efficiency for aluminium deposition from fluoride electrolytes containing dissolved alumina. Electrolysis was performed at constant current density, and the amount of deposited aluminium was determined. Effects of temperature, cathodic current density, electrolyte composition and the presence of dissolved impurities were studied. The loss in current efficiency is strongly linked to the solubility of dissolved aluminium. The rate of the so called back reaction between dissolved aluminium and CO₂ depends on the diffusion of dissolved aluminium near the cathode. Both dissolved aluminium and dissolved alkali metals must be considered. Impurities with several oxidation states, such as phosphorus, cause a loss in current efficiency by undergoing cyclic red/ox reactions at the electrodes. The results are of interest for the industrial process of producing aluminium.

Steelmaking slag is one of major by-products from steelmaking process and its efficient recycling is essential to establish the environmentally-friendly steelmaking industry. Recently steelmaking slag has been recognized as an effective supplier of nutrient elements to recover the ocean environment from sea desertification. It is believed that the efficient dissolution of iron ion is critical to rehabilitate the damaged sea coast, while the solubility of iron ion in seawater is much below the required concentration. Therefore, the simultaneous addition of humic acids to steelmaking slag is necessary to produce the stable chelated iron ion in seawater. In the present paper, the effect of natural substances containing humic acids or a chemical organic acid on the dissolution behavior of nutrient elements from steelmaking slag was studied and the dissolution mechanisms of steelmaking slag into seawater were discussed.

Slag is a by-product of different metal extraction and refining processes. This paper reports the results of an experimental study on replacing part of ordinary Portland cement (OPC) with iron and steel slags. In Iranian iron and steel plants, slags are generated at three different stages of processing; Basic Oxygen Furnace (BOF), Electrical Arc Furnace (EAF) and Granulated Blast Furnace (GBF) are the slags used in this study. In this respect, some mixtures were made with 10%, 20% and 30 wt% of each slag replaced in ordinary Portland cement. For this study, the effects of slag additions in cement was determined by measuring of electrical conductivity and pH of slurry, setting time of paste and mechanical strength of mortar at various ages. According to the results, 10% EAF or BOF slag can safely replace part of OPC in mortars.

The use of metallurgical slags in cement manufacturing depends on the phases that compose such slags, which are affected by changes in slag chemical composition as well as by cooling rates adopted during solidification. Two different slags were produced in a pilot scale metallurgical reactor by mixing additives into 300 kg of re-melted BOF slag followed by natural cooling or by adding of steel balls to it. Quantitative XRD, SEM and Raman analysis of slag samples revealed the relationship among cooling conditions and crystalline phases.The modified slags had CaO/SiO₂ between 1.8 and 2.0 which is lower than the 3.8 for Steelmaking slag. This reduced basicity resulted in the presence of di-calcium silicates (C₂S) in higher amounts than in the Steelmaking slag. These di-calcium silicates were part composed of β-C₂S and part of Bridigite when slag solidified slowly or α’-C₂S when slag was cooled faster by the addition of steel balls.Cement samples were produced by mixing 25% of treated steelmaking slag with 75% of Portland cement, resulting in expansion lower than 0,1% in the autoclave tests and compressive strength higher than 42 MPa after 28 days. The process indicates potential to be applied as a steelmaking slag treatment.

Cr(VI) formation in low cement Cr₂O₃-containing refractory castables was examined by reacting pre-synthesized calcium aluminate phases (C₃A, C₁₂A₇, CA and CA₂) with Cr₂O₃ at 1300°C. In order to investigate the effect of oxygen partial pressure on Cr(VI) formation, experiments were conducted in both air and in a CO₂ atmosphere. XRD results indicated that the Cr(VI)-containing phase Ca₄Al₆CrO₁₆ formed in all the examined samples in air, while a Cr(III)-containing phase Ca₆Al₄Cr₂O₁₅ formed in samples (C₃A+Cr₂O₃) and (C₁₂A₇+Cr₂O₃) in CO₂. Cr(VI) in the samples was extracted according to the TRGS 613 standard method, and then quantified using the diphenylcarbazide spectrophotometric method. The amount of water soluble Cr(VI) exceeded the allowable EPA U.S. limit of 5 mg/l only in samples (CA+Cr₂O₃) and (CA₂+Cr₂O₃) in air.

Chromium is an essential element which contributes to our life activity. However, since the hexavalent chromium causes health damage, its content in water is strictly limited below 0.05 mg/L as the aqueous and soil environment standard values in Japan. The development of high-efficient stabilization method of the steelmaking slags containing chromium is urgent in order to utilize the slags to civil engineering works. In present work, the elution behavior of chromium from stainless steelmaking slags was clarified. Then, a principle of prevention of hexavalent chromium formation and chromium immobilization by the hydrate formation was discussed.

For the recovery of aluminium from industrial waste bottom ash, a new concept was developed for smelting reduction in presence of metal solvent bath. Nitrogen plasma arc was generated by passing current and nitrogen gas through a hollow graphite electrode. Nitrogen plasma generated heat for reduction as well as melting under inert atmosphere inside the furnace. Pellets containing 50%bottom ash, 50% iron slime and charcoal were fed in the plasma zone above the liquid steel bath which was acted as for the absorption of reduced metals after reduction of oxides present in the wastes. Due to the immediate absorption of aluminium in the liquid steel bath after subsequent reduction from waste, vaporization loss of aluminium metal got minimized. The percent recovery of aluminium were determined in case of different exposure time, types of arcing and plasma gas etc. Maximum recovery of aluminium was recovered upto 21% with 30 minute exposure of pellets containing 50% bottom ash and 50% iron slime. It was observed that aluminum, could be recovered effectively from the wastes.

A critical review of the technical literature on slag chemistry in lead recycling is presented. Laboratory methods used to improve our understanding of these systems is described. Ongoing investigations in the Kroll Institute for Extractive Metallurgy are presented.

Silicate slags produced from smelting copper concentrates contains valuables such as Cu and Fe as well as heavy metals such as Pb and As which are considered hazardous. In this paper, various slags were characterized with several techniques: SEM-MLA, XRD, TG-DTA and ICP-MS. A recovery process was developed to separate the valuables from the silicates thereby producing value-added products and simultaneously reducing environmental concerns. Results show that the major phases in air-cooled slag are fayalite and magnetite whereas the water-cooled slag is amorphous. Thermodynamic calculations and carbothermal reduction experiments indicate that most of Cu and Fe can be recovered from both types using minor amounts of lime and alumina and treating at 1350°C (1623K) or higher for 30 min. The secondary slag can be recycled to the glass and/or ceramic industries.

Bottom-up process design is performed for an antimony white fuming approach from antimonyrich lead refining residues. Thermochemical modelling is used to evaluate process boundaries regarding temperature and slag composition allowing the fuming of qualified antimony white from mentioned residues. Fuming boundaries indicate that state of the art drosses are not suitable for fuming qualified antimony white. Slag conditioning by antimony enrichment of the slag has to be carried out in advance. Carbothermic reduction of lead oxide from named oxides is simulated and evaluated in lab scale to achieve optimal slag enrichment while avoiding antimony losses to the metal phase.

Steelmaking slag is a potential P resource in Japan, because the P quantity in it is almost equal to that in imported phosphate ores. P₂O₅ is mainly concentrated in the 2CaO·SiO₂-3CaO·P₂O₅ solid solution in slag. It has been clarified that P can be selectively leached out from C₂S-C₃P rather than the matrix phase of slag. To recover P from slag, its dissolution ratio from C₂S-C₃P should be increased. In this study, the effects of leaching agent and Na₂SiO₃ modification on the dissolution of the C₂S-C₃P solid solution and slag in aqueous solutions have been investigated. H₃C₆H₅O₇ is beneficial for P dissolution from C₂S-C₃P in aqueous solutions because of the formation of the CaC₆H₅O₇- complex, which can suppress phosphate precipitation. The P-rich phase is changed from the original C₂S-C₃P to C₂S-C₂NP with higher water solubility by Na₂SiO₃ modification, which facilitates P dissolution. At pH=5, 85.7% of P from the modified C₂S-C₃P can be dissolved in the H₃C₆H₅O₇ solution. The selective leaching of P from the CaO-SiO_2- Fe₂O₃ system slag can be achieved by Na₂SiO₃ modification and leaching in the H₃C₆H₅O₇ solution at pH=5. The P dissolution ratio reaches 78.4%, and only 19.7% of Fe is dissolved.

The distribution of chromium between liquid silicate slags and copper-iron-nickel matte phases encountered in electric smelting of PGM containing South African sulphide concentrates were experimentally studied under controlled partial pressures of oxygen and sulphur. The reported experiments were conducted under silica saturation through the use of silica crucibles. Seven representative slag compositions were equilibrated with a typical sulphur deficient matte containing 18% Ni, 11% Cu, 42% Fe and 29% S. The slag constituents varied in the following ranges: SiO₂: 42–58%, Al₂O₃: 3.5–9.0%, Fe₂O₃: 13–21%, MgO: 15.6–25%, CaO: 2–15%, Cr₂O₃: 0.2–3.5%. The slag and matte samples were synthetically prepared from pure components. The chromium content of the two phases was analysed chemically. According to the present available results of this ongoing research it was found that the partition of chromium to the matte phase decreased with an increase in the partial pressures of both oxygen and sulphur where the value of the distribution coefficient of chromium between the matte and the slag phase varied from as low as 0.07 to as high as 5.5.

Molten slag and welding flux are important materials for steel processing. Due to lack of durable refractory materials, there is limited publication data on the thermophysical properties of these slags. Therefore, in this study, we measured density and viscosity of CaO-Al₂O₃-SiO₂ slag and welding flux using Aerodynamic Levitation (ADL) with CO₂-laser heating in which can be achieve containerless and non-contacting conditions for measurements. For density measurements, in order to obtain correct shape of the droplet we used high-speed camera with the extended He-Ne laser to project the shadow image without the influence of the selfluminescence at the high temperature. For viscosity measurement, we also have a unique vibration method; it caused oscillation in a sample by letting gas for levitation vibrate by an acoustic speaker. Using these techniques, we succeeded to measure systematically density and viscosity of molten oxides system.

Solubilities of CaO and Al₂O₃ in copper rich molten oxide phases have wide industrial applications in various copper smelting and refining operations producing copper matte or blister copper. However, experimentally determined solubility data on these simple systems are still scarce even after a long spell of industrial copper making. In this experimental study, these solubilities have been quantified by a static equilibration technique at 1250 °C in an inert atmosphere of purified argon gas. The compositions of condensed molten phases and all solids in equilibrium have been analyzed and quantified using Electron Probe Micro-Analyzer (EPMA).

The chemistries of industrial pyrometallurgical non-ferrous smelting and recycling processes are becoming increasingly complex. Optimisation of process conditions, charge composition, temperature, oxygen partial pressure, and partitioning of minor elements between phases and different process streams require accurate description of phase equilibria and thermodynamics which are the focus of the present research. The experiments involve high temperature equilibration in controlled gas atmospheres, rapid quenching and direct measurement of equilibrium phase compositions with quantitative microanalytical techniques including electron probe X-ray microanalysis and Laser Ablation ICP-MS. The thermodynamic modelling is undertaken using computer package FactSage with the quasi-chemical model for the liquid slag phase and other advanced models. Experimental and modelling studies are combined into an integrated research program focused on the major elements Cu-Pb-Fe-O-Si-S system, slagging Al, Ca, Mg and other minor elements. The ongoing development of the research methodologies has resulted in significant advances in research capabilities. Examples of applications are given.

Laboratory studies have been carried out to determine the slag/matte/metal/tridymite four condensed-phase equilibria in the “Cu-Fe-Si-S-O” system and the minor element distributions between the equilibrated phases at 1200°C. A combined quantitative microanalysis technique including electron probe X-ray microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been developed to accurately characterize the equilibrated system for both major and minor elements. Analysis precision, estimated accuracy and current limitations are discussed. The resulting elemental distributions are plotted against matte grade and compared to FactSage predictions. It was found that the experimental results for major elements are in good agreement with FactSage predictions. The simultaneous distributions of Ag and Au between slag, matte and metal phases are reported for the first time.

Thermodynamic information of the Cu-ZnO-SiO₂-O system has significant importance for high temperature industries. By employing the equilibration/quenching/EPMA technique, phase relation and liquidus surface of the Cu-ZnO-SiO₂-O system at 1473 K has been systematically studied at various oxygen partial pressures (pure argon and 0.21 atm). No ternary compound was found. A pseudo-ternary phase diagram (Cu₂O-ZnO-SiO₂) was used to represent the liquidus of Cu-ZnO-SiO₂-O system in equilibrium with air (P_O2 = 0.21 atm). Two univariant equilibria (SiO₂ + Zn₂SiO₄ + Oxide liquid, and Zn₂SiO₄ + ZnO + Oxide liquid) were found in the experiments. The phase equilibria of the Cu-ZnO-SiO₂-O system in equilibrium with copper has also been studied at a fixed mole ration between SiO₂ and SiO₂ + ZnO. With increasing SiO₂ content in initial pellets, the concentration of Cu in liquid oxide phase decreases rapidly. Solubility data of Cu in solid phases of Zn₂SiO₄, ZnO and SiO₂ is also reported.

Thermodynamic properties of Te-O-Na₂O-SiO₂ system at high temperatures are essential for improving the metallurgical processes especially for smelting the anode slime which contains tellurium compounds. However, the literatures review of previous investigation, showed that there are no liquidus data reported for this system. In the present study the experimental data were obtained by equilibrating the high purity of oxide mixtures at selected temperature, followed by rapid quenching of the equilibrated samples in cold water and compositional analysis using electron probe X-ray microanalyzer. Phase characteristic and the liquidus in the Te-O-Na₂O-SiO₂ system have been investigated at silica saturation between 1000 and 1200 °C in equilibrium with air. New data sets of the liquidus in the Te-O-Na₂O-SiO₂ system have been generated and evaluated.

Knowledge of oxygen potential is crucial for better understanding of fundamentals of refining reactions kinetics within droplets during oxygen steelmaking. In this study, the changes in the phosphorus content of droplets were measured with time using X-ray fluoroscopy technique at 1853K. Specifically, the effects of sulfur content on dephosphorization kinetics of droplets were investigated during periods of intense decarburization. The experimental results showed that the droplets with low sulfur contents (0.007wt%, 0.011wt%) exhibit a lower minimum phosphorous level and an earlier and more significant reversion compared to those with high sulfur contents. The authors suggest that dephosphorisation rate and maximum partition are favored at lower CO evolution rates as well as lower amount of CO gas generation which result in a higher interfacial oxygen potential between slag and bloated droplets. Equating the rate of CO evolution with that of FeO mass transport allowed mass transfer coefficient of FeO to be calculated, which show that FeO mass transport in dense slag is faster than it is in foaming slag.

The argon-oxygen decarburization (AOD) process is the most common process for refining stainless steel. High blowing rates and the resulting efficient mixing of the steel bath are characteristic of the AOD process. In this work, a 1:9-scale physical model was used to study mixing in a 150 t AOD vessel. Water, air and rapeseed oil were used to represent steel, argon and slag, respectively, while the dynamic similarity with the actual converter was maintained using the modified Froude number and the momentum number. Employing sulfuric acid as a tracer, the mixing times were determined on the basis of pH measurements according to the 97.5% criterion. The gas blowing rate and slag-steel volume ratio were varied in order to study their effect on the mixing time. The effect of top-blowing was also investigated. The results suggest that mixing time decreases as the modified Froude number of the tuyères increases and that the presence of a slag layer increases the mixing time. Furthermore, top-blowing was found to increase the mixing time both with and without the slag layer.

A fully transient 3D CFD modeling approach capable of predicting the three phase (gas, slag and steel) fluid flow characteristics and behavior of the slag/steel interface in the argon gas bottom stirred ladle with two off-centered porous plugs (Ladle Metallurgical Furnace or LMF) has been recently developed. The model predicts reasonably well the fluid flow characteristics in the LMF system and the observed size of the slag eyes for both the high-stirring and low-stirring conditions. A desulfurization reaction kinetics model considering metal/slag interface characteristics is developed in conjunction with the CFD modeling approach. The model is applied in this study to determine the effects of processing time, and gas flow rate on the efficiency of desulfurization in the studied LMF system.

Slags have a central role in pyro-metallurgical processes. They bind impurity compounds and absorb reaction products like oxides and sulfides. Functional slags are made by adding lime, magnesia, fluorspar, bauxite, calcium aluminate or other compounds into the reactor vessel where they form the slag together with the targeted reaction products. Additionally, refractory materials of the vessel tend to dissolve into the slag and thus influence its properties.Slag formation is extremely essential in rapid processes, to ensure sufficient time for desired purifying reactions and to avoid harmful reactions with the refractory materials. Slag formation is a complex series of numerous phenomena. In this contribution, thermodynamic constraints, kinetic aspects and mechanisms in slag formation and in adjustment of properties were reviewed. Slag formation and conditioning in steel converter process and in secondary metallurgy aiming for improved desulfurization and steel cleanliness, were examined and discussed as examples.

The reduction experiment of iron ore containing high Alumina content with petroleum coke was carried out in the temperature range of 1673 to 1773K by changing the slag composition. The sulfur and phosphorous content in the reduced iron nugget were measured to investigate the desulfurization and dephosphorization behavior during the reduction. The mineralogy of iron ore and additives to the carbon composite agglomerate (CCA) highly influenced on not only the reduction itself but also the melting, carburization, metal-slag separation, desulfurization and dephosphorization. High basicity of slag retarded the melting of CCA and the metal-slag separation, but enhanced sulfur and phosphorous removal degrees in the separated metal.

Slag is a by-product formed in most metallurgical process. During the steelmaking process a large amount of slag is produced, which becomes a source of waste, which in many instances is land filled. Such areas filled with waste materials have become a significant source of pollution. Slag recycling is then becoming important in recent years. Recycling can be an efficient option to reduce such waste. Fluorspar (Calcium Fluoride) is generally used to help fluidize the slag; however, Fluorspar has a corrosive effect on the ladle refractory and is environmentally harmful. Alternatively, Calcium Aluminate synthetic slag is very effective in making the slag more fluid, but it is costly. The slag generated in Al-killed treatment at ladle can provide a material with advantages over Calcium aluminate synthetic slags and Fluorspar, by being low-cost, noncorrosive, and less environmentally harmful. Plant trials conducted at Hadeed indicate that Al-killed ladle slags coming from its Flat Product Ladle Furnace process could be used in place of Calcium Fluoride/ Bauxite/Calcium Aluminate fluxes for the production of Si- killed steel grades, thus reducing Lime consumption, reducing waste and improving desulphurization levels.

A mathematical model using Fluent 14.0 was implemented in order to describe the flow of Nitrogen and slag under transient and isothermal conditions in the slag splashing process for the improvement of refractory life. The influence of parameters affecting this process and the consequent effects on refractory linings has been investigated applying the model. For a given blow pattern, the influence of parameters such as temperature, density, viscosity and interfacial tension of the fluids involved have been discussed. The results are compared with projection data available in the literature.

Corrosion in refractories in a commercial furnace is a very complex phenomenon which involves chemical and physical wear. In this work three refractory castables (A, B and C) are being characterized and studied to compare their properties and determine their corrosion mechanisms in the presence of slag obtained from a steel furnace. The chemical composition of the slag consists mainly of CaO, SiO2, alumina and Fe2O3. Using a heating microscope, it was determined that the slag starts to melt around 1350 ºC. The chemical composition of the castables consist mainly of alumina (86%, 90% and 92% respectively) with a variation in material A which contains 5.8% MgO. Prismatic bars were made and sintered at 1400 C to run the hot modulus of rupture at 1000 C. A non-destructive technique was used to investigate the Young’s modulus of the specimens before and after sintering.The corrosion tests were performed at 1400 C in cubic crucibles (8x8 cm) with 50 g of slag.The investigated castable samples exhibited low values of Young’s Modulus and HMOR. The corrosion tests showed a high impact on the castables integrity, which can be seen in the multiple cracks and spalling formed after the test.

Recovering iron from bauxite residue (red mud) by carbothermic reduction creates, depending on the composition of bauxite, slag phases with high amounts of alumina and titania which are commonly known as amphoteric slag components. In this case the prediction of slag properties and even the calculation of basicity are very difficult since the slag consists of about 50 wt.-% amphoteric components. As a consequence the correct choice of refractory materials has to be taken into consideration as well. In this study synthetic slags similar to the compositions which occur during the reductive smelting of bauxite residue are mixed and melted. By the addition of CaO and Na2O and SiO2 the basicity is constantly adjusted to 1 [(CaO+Na2O)/SiO2] to monitor the influence of the addition of amphoteric compounds regarding the viscosity and refractory corrosion. In advance thermodynamic calculations concerning the liquidus temperature and viscosity of the examined slag are done by the software FactSage (vers. 6.4). The molten slags are qualitatively examined regarding the viscosity and later on exposed to three different types of refractory materials (MgO, Al2O3, mullite) in order to observe the refractory corrosion and infiltration behavior.

The molten oxides (slag), matte and metal charges during smelting, converting and refining stages of the pyrometallurgical coppermaking processes are contained in refractory-lined vessels. The refractory materials are selected so as to provide resistance to corrosion by molten phases and thermal insulation to minimize heat losses while maintaining the charge in a molten state. However, high process temperature, highly agitated and chemically aggressive melts in furnaces can result in rapid degradation of the refractory and premature shutdown of the reactor for relining; imposing additional costs on processes in the form of planned and unplanned maintenance.The focus of the present study is on detailed characterization of the phase chemistry and slag interactions with refractories. The rate of reactions between refractories and liquids depends on the phase equilibria. Post-mortem analysis of the spent brick from Isa smelter was followed by isothermal finger laboratory test under controlled conditions. Electron probe X-ray microanalysis (EPMA) is used to measure the compositions of the phases across the samples. This information is linked to the phase equilibria. Thermodynamic modelling is carried out by FactSage to assist in interpretation of the results.Phase analysis of used refractory and laboratory tests for Isa smelter indicate formation of a protective spinel layer on the hot face slowing refractory dissolution.

The study of chemical interactions between slag / metal / matte and refractory materials has been an ongoing theme from the time when the first metals and alloys were produced. Over the years the refractory industry has seen extraordinary technological progress such as the development of the magnesia-carbon bricks and self-flowing castables. The advances that take place in high temperature processes, specifically the iron and steel industry, drive innovations in the refractories industry. Since these pyrometallurgical processes are dynamic, continuously improving and changing to process inter alia lower grade ores in energy more efficient and environmentally more friendly ways, the refractories industry has to keep current. This paper discusses the important role that the study of molten liquid — refractory interactions plays in understanding wear mechanisms and directing the development of refractory materials. It also gives relevant examples from refractories used in the production of different commodities.

This work aims at studying the volume change of bauxite corroded by a molten slag. Cylindrical samples were prepared by mixing ground bauxite with slag. Optical measurement at high temperature (1450 °C) of deformation with a high-resolution camera has been developed. Image processing allowed for determining the change in diameter of the sample. We showed that the deformation was induced by the precipitation of new expansive crystallised phases observed by SEM-EDS analyses. Adding pellets of the same slag upon the samples allowed to emphasize the effect of the slag amount on the size change. The change in diameter significantly increased in the impregnated area.

Appropriate selection of refractories for high temperature processes is vital to the production. Magnesia-chromite refractory has been widely used in copper making industry. However, the risk of generating high poisonous Cr6+ drives the researchers to find Cr-free refractories for copper industry.Different materials were synthesized as raw materials of refractory in Cr-free chemical systems that are based on the MgO-Al₂O₃ system with additions of other SiO₂, TiO₂ and CaO. SEM and EPMA analyses were performed to investigate their morphologies and the homogeneities after sintering process. These refractory materials were also tested by reactions with industrial copper smelting slag under the same conditions. The corrosion resistances of different refractory materials to the slag and changes of the morphologies after the high temperature experiments were analysed and compared. The present studies will lead to the development and applications of Cr-free refractories in copper industry and reduce the potential hazards to the environment and cost of the copper production.

Gasification is a high-temperature/high-pressure process that converts carbonaceous materials such as coal and/or petcoke into CO and H₂, feedstock materials used in power generation and chemical production. Gasification is considered an important technology because of its high process efficiency and the ability to capture environmental pollutants such as CO₂, SO₃ and Hg. Ash impurities in the carbon feedstock materials melt and coalesce during gasification (1325-1575 °C), becoming slag that attaches to and flows down the gasifier sidewall, corroding and eroding the high Cr₂O₃ refractory liner used to protect the gasification chamber. Phosphate additions to high Cr₂O₃ refractory have been found to alter slag/refractory interactions and dramatically reduce refractory wear by the following mechanisms: a) spinel formation, b) slag chemistry changes, c) two phase liquid formation, and d) oxidation state changes. The mechanisms and how they work together to impact material wear/corrosion will be discussed.

In this work, ion currents of gaseous species from synthetic slag mixtures mimicking those from coal-petcoke feedstock were measured by double Knudsen cell mass spectrometry at a temperature range of 1000 °C to 1300 °C and an oxygen partial pressure of approximately 10-10 atm. The majority of gaseous vanadium was found to be present in the form of V₂O₃, whose vapor pressure rapidly increased with increasing petcoke slag addition to coal slag. Effects of temperature, vanadium content in slags, and coal/petcoke ratios, with an emphasis on vanadium and alkali vapor species, are discussed.

Results from experiments in a physical model of a steel ladle in respect of slag eye formation during inert gas bubbling have been compared with those obtained by simulation with mathematical model , solved with Ansys Fluent software. The influence of gas flow rate, liquid metal level, thickness of slag layer, gas distribution between plugs and density difference between the two liquids on plume eye area have been studied. On the basis of experimental results regression equations for evaluating slag eye area have been developed.

Entrained flow slagging gasifiers are used to covert coal, petcoke and other carbon feedstock to syngas (CO and H₂), which is used as a fuel in power generation or is converted into chemical products. During the gasification process, gasifier components such as refractory liners, syngas coolers, and thermocouples are aggressively attacked by corrosive slags and gases originating from the carbon feedstock, materials that contain arsenic, sulfur, phosphorous and other impurities; –all of which are in a mixed equilibrium condition during gasification. This research evaluated the effect of phosphorous gas generated during gasification on the corrosion degradation of Pt-Rh thermocouple sensor materials. Phosphorous interactions with Pt-Rhx (x = 0 – 30 wt.%) alloys have been analyzed isothermally at 1012 °C. Phosphorous diffusion into the alloy is discussed.

The viscosity was the main reason that converter smelting process of slag containing vanadium caused bonding converter mouth. The study on viscosity of FeO-SiO₂-V₂O₃-TiO₂ quaternay slag system with V₂O₃ level varied from 5 to 15 mass %, TiO₂ contents in the range from 5 to 15 mass % and three different FeO/SiO₂ mass ratio in the range from 1.4 to 2.2 is important for steelmaking. The rotation cylinder method was used the determinations of the viscosity. The influence of V₂O₃, TiO₂, FeO/SiO₂ ratio and temperature on viscosity were investigated. It was found that the viscosity of compositions with temperature shift from Newtonian fluid to non-Newtonian fluid and obey the Arrhenius law. the slag viscosity increased with increasing V₂O₃ level, and decreased with increasing temperature and FeO/SiO₂ ratio. In the Newtonian fluid , the viscosity of slag decreased with increasing TiO₂ content. In the Non-Newtonian, viscosity of slag increased remarkably with increasing TiO₂ from 5 to 10 mass % and decreased with increasing TiO₂ from 10 to 15 mass%. viscosity ηo in the Non-Newtonian fluid could obtain by extrapolating viscosity of Newtonian fluid, viscosity η for Non-Newtonian fluid could be measured by the Einstein-Roscoe type equations. The measured viscosity fit with the experimental data in the Non-Newtonian fluid.

In industrial submerged arc furnaces, SiO in the off-gas from the furnace leads to Si losses that reduces Si yield and thereby increases specific energy consumption. An understanding of formation of SiO gas and condensation of this gas to form solid / liquid SiO₂ in industrial furnace is important for improving Si yield and reduce formation of dense layers in a charge that generate operational challenges. Understanding of these mechanisms is also vital for an enhanced energy recovery from smelters. Two main goals of this research was to:a) verify a system designed to extract gaseous samples from the charge of a SFA,b) capture and analyze industrial SiO gas condensates.This paper presents the industrial trial on capturing SiO gas and initial analysis of the samples taken from a 33 MW Si furnace.

An electrochemical cell containing molten Li₂CO₃-Li₂O has been proposed for the conversion of the greenhouse gas CO₂ to CO, which can then either be used to power gas turbines or converted to methanol. Since efficient electrolysis takes place at 900°C, the materials which can be used in such a cell must satisfy stringent requirements. In the current work, we have examined the static corrosion resistance of zirconia, beryllia and magnesia ceramics at 900°C in the Li₂CO₃-Li₂O mixture and in a Li-Na-K carbonate eutectic mixture with the ultimate objective of identifying suitable electrically insulating materials. Conclusions regarding material stability were based on elemental analysis of the melt, primarily via X-ray photoelectron spectroscopy, a particularly sensitive technique. It was found that magnesia is completely stable for at least 33 hrs in a Li₂CO₃-Li₂O melt, while a combined lithium titanate/lithium zirconate layer forms on the zirconia ceramic as detected by XRD. Under the same melt conditions, beryllia shows considerable leaching into solution. In a Li-Na-K carbonate eutectic mixture containing 10.2 mol% oxide at 900°C under standard atmospheric conditions, magnesia showed no signs of degradation. Stabilization of the zirconia content of the eutectic mixture at 0.01-0.02 at% after 2 hrs is again explained by the formation of a lithium titanate/ lithium zirconate coating. On the basis of these results, we conclude that only magnesia can be satisfactorily used as an insulating material in electrolysis cells containing Li₂CO₃-Li₂O melts.

The MgCl₂-contained salt is considered as one of the candidates for the solar thermal energy storage applications. To protect the structural alloy from corrosion, the addition of Mg as corrosion inhibitor was investigated. Several physical properties such as density, viscosity, vapor pressure and thermal conductivity of MgCl₂ with different amount of Mg additions are studied in this paper. A slight variation of density and viscosity while the increase in vapor pressure and large increase of thermal conductivity were observed with the addition of Mg to MgCl₂ salt mixtures.

The “Slag-Remaining+Double-Slag” BOF steelmaking process has been developed and applied in Shougang Corporation, Ltd., by which consumption of lime and volume of slag in BOF steelmaking are remarkably decreased. In this paper, three important technologies taken in application of the new steelmaking process are introduced: 1. To solve the two most serious problems, i.e. difficult to make fast and enough amount of deslagging and decrease the metallic Fe droplets in the slag, low basicity slag is used in the dephosphorization stage. 2. Hard blow pattern is adopted to utilize the top blown O₂ jet to strengthen agitation of the bath in the dephosphorization stage, through which good dephosphorization has been obtained. (3) By speeding up the steelmaking operations and particularly better matching the BOF, secondary refining and continuous casting productions, productivity has not been reduced though the BOF tap to tap time has been increased by about 4min after using the new process.

Slag valorization in added value construction applications can contribute substantially to the sustainability of steel industry. The present work aims to investigate the crystallization behavior of a typical industrial Basic Oxygen Furnace (BOF) slag (CaO-FeO_x-SiO₂-based slag) by varying the basicity through hot stage engineering. A sample of industry Basic Oxygen Slag (BOF) was mixed with different quantities of silica (SiO₂) to modify basicity. The effect of basicity on solidification microstructure and mineralogy was studied. The results suggest that the mineralogy of the solidified slag can be manipulated to enhance its suitability as raw material for construction applications.

Bearing steel required high cleanliness. During LF refining, the type of slag has obvious effect on its cleanliness. Two kinds of refining slags have been prepared with different cooling methods after pre-melting. Another slag was used by only mixing the raw materials .Then six heats steelmaking experiments were carried out in the MoSi₂ electric resistance furnace to study their effect on the cleanliness of bearing steel GCr15. The results show that: The water-cooled slag is full of glass phase or microcrystal phase inside, and it has the lowest melting point, the shortest melting time, the fastest desulfurization velocity and the smallest average size of inclusions. Those effects of the air-cooled slag are better than the mixed-slag’s. Under the same process, the inclusion numbers and area in the steel refined by the slag with CaO/Al₂O₃=1.65 are smaller than those of the slag with CaO/Al₂O₃=0.94.

The intrinsic corrosion behavior of Haynes 230 and NS-163 alloys after adding corrosion inhibitor Zr to LiF-NaF-KF (FLiNaK) salts was evaluated. Thermodynamic modeling studies were performed to investigate the compatibility of Haynes alloys for solar thermal energy storage applications in the molten salts. Equilibrium conditions were considered for predicting the corrosion products and weight loss of salts at higher temperatures (700 – 1000°C). Weight loss of FLiNaK salt after corrosion with or without inhibitor is less than 5%, indicating no significant change in compositions of FLiNaK even with Zr inhibitor. Furthermore, to compare with experimental data, modeling calculation with known amount of trace impurities (Ni2+, Fe3+ and so on) added to the molten salts, shows similar trend and corrosion product with and without Zr inhibitor.

New data on gas/slag/matte/spinel equilibrium in the Cu-Fe-O-S-Si system at T=1200 °C and P(SO₂)=0.25 atm covering a wide range of matte grades for copper smelting and converting are presented. High temperature equilibration and rapid quenching technique, followed by Electron Probe X-ray Microanalysis are used. The use of substrate made of solid spinel ensures equilibration strictly within the Cu-Fe-O-S-Si system and avoiding contaminants from crucible. The research is extended to measure partitioning of minor elements between slag and matte phases using this technique based on microanalysis. The system selected closely resembles the equilibrium condition of the actual copper smelting process. The information provided is essential for the evaluation of effect of fluxing towards the amount of chemically dissolved copper and quantity of solid in the slag. Present study is part of a larger integrated experimental and thermodynamic modelling research program on copper-making high-temperature systems.

Limited data are available on phase equilibria of the “FeO”-SiO₂-PbO slag system at conditions used in the lead smelting due to difficulties from lead vaporization and interactions with metal and ceramic crucibles. Recently experimental procedures have been developed and successfully applied to complex industrial slag-metal-matte systems involving high temperature equilibration on a primary phase substrate and rapid quenching followed by the electron probe X-ray microanalysis. The liquidus isotherms and invariant lines in the “FeO”-SiO₂-PbO slag system in equilibrium with air and with metallic lead have been constructed. Preliminary data compared to the FactSage package predictions demonstrate differences in some aspects, indicating the possibility for further improvement of the thermodynamic database. The present work is a part of the integrated experimental and thermodynamic modelling research program on multi-phase lead systems in support of the optimization and development of complex lead smelting, refining and recycling technologies.

The growth rate of copper sulfide precipitates has been measured in low carbon steel samples such as Fe-0.3mass%Cu-0.03mass%S-0.1mass%C and Fe-0.1mass%Cu-0.01mass%S- 0.1mass%C. Heat-treatment of the samples was conducted at 1273, 1423 and 1573 K for 100 s – 14.4 ks for precipitation of copper sulfides and then the samples were observed by a scanning electron microscope and a transmission electron microscope to measure the diameter of copper sulfides precipitated in the samples. The growth rate of copper sulfide has been found to be well described by the Ostwald growth model, as follows: <msubsup> <mrow> <mi>R</mi> </mrow> <mi>t</mi> <mn>3</mn> </msubsup> <mo>&#x2212;</mo> <msubsup> <mrow> <mi>R</mi> </mrow> <mi>t</mi> <mn>3</mn> </msubsup> <mo>=</mo> <mo stretchy="false">(</mo> <mrow class="MJX-TeXAtom-ORD"> <msub> <mi>k</mi> <mi>o</mi> </msub> </mrow> <mrow> <mo>/</mo> </mrow> <mi>T</mi> <mo stretchy="false">)</mo> <mi>t</mi> </math>$$\mathop R\nolimits_t^3 - \mathop R\nolimits_t^3 = ({k_o}/T)t$$ where R _t and R₀ are the radii of copper sulfide precipitates, respectively, at t = t and t = 0 where t is time, k_O is the rate constant in this model and T is thermodynamic temperature. The values of k_O produced diffusion coefficient and activation energy, which values are close to those of copper in austenite iron. In addition, the existence of copper sulfide has been confirmed in samples of Fe-0.1mass%Cu-0.01mass%S-0.1mass%C, without and with annealing for the homogenization after melting and solidification process. The annealed sample did not show any copper sulfide precipitates in SEM images. The long homogenization treatment confirms that copper sulfide precipitation is meta stable phase caused micro-segregation by rapid solidification.

Steel slags, untapped at 1450–1650 °C, represent a large potential of energy saving and material recycling in metallurgical industry. Conventionally, the methods used for the heat recovery could be categorized into two types and the chemical methods offered the advantage of combination of multiple industrial sectors and production of the high value syngas. Herein, a novel chemical method was investigated, i.e., gasification reaction in the atmosphere of CO₂ where both raw coal and raw char from coal pyrolysis were employed. Not only the thermodynamics of the gasification process in terms of syngas yields but also the kinetic mechanisms of the char gasification process were analyzed. It was clarified that the slag additions showed a great catalytic effect of the char gasification. Furthermore, the transformation of the iron valence state during the gasification was clarified and the potential of energy saving and emission reduction were estimated.

At present, interfacial phenomena between molten steel and oxides, usually called slag or mold flux, play an important role in steel processing for material design. Therefore, understanding interfacial tension is important for process control. From this, we propose an interfacial tension measurement technique between molten steel and oxides using a modified oscillating drop method with levitation techniques. The interfacial tension data using traditional techniques based on the sessile drop method have been obtained only at temperatures around the melting point of iron due to dissolution of containers and the substrate into molten steel and oxides in higher temperature regions. Our proposed technique to obtain the temperature dependence of interfacial tension between molten iron and oxides is to use a core-shell form droplet including an interface between two liquids using electrostatic levitation, which negates the use for containers. The experiment was performed on the International Space Station using the electrostatic levitation furnace (ELF) in the KIBO module.

Current processes for beneficiation of titaniferous minerals are energy-intensive and produce significant waste. The benefit of alkali roasting over existing process is that it minimises waste. Previous studies on liquid phase formation during alkali roasting of titaniferous minerals were based on the use of Na₂CO₃, whereas this study focuses on oxidative roasting of titaniferous minerals with either NaOH or KOH, using different alkali to mineral ratios. Phase equilibria of the Na/K-Fe-Ti-O system are calculated the results compared to observed results. This work attempts to characterise the alkali-rich liquid phase formed during roasting and determine its impact on alkali titanate and alkali ferrite separation, as it has been found that Ti-K-Fe-O and Ti -Na-Fe-O ternary phases can be present. The presence of the liquid phase at the reaction interface adversely affects the oxygen diffusion during roasting, which has consequences on the products formed.

Effect of titania content and the basicity on precipitation behavior of bearing titanium blast furnace slag have been investigated with confocal scanning laser microscope. The results show that Ca₂MgSi₂O₇ and Ca₂Al₂SiO₇ are the main phases CaTiO3crystallized from the molten slag with 10 mass percent TiO₂ . While there is only one phase crystalized when the mass percent of TiO₂ reaches 30%. On the other hand, CaMg_0.39Al_0.87Ti_0.48Si_1.26O₆, CaTiSiO₅, CaMgSi₂O₆ are the main crystallization phases when the basicity is 0.8, which differs from the thermaldynamics calculation. It is suggested that such a difference is due to the complicated crystallization of the multiple slag under large cooling rate. When the slag basicity is 1.1, which equals to industry basicity, the crystallization phase is CaTiO₃ due to the crystallization temperature of CaTiO₃ is higher than other phases.

Gold tailing, red mud and waste limestones are industrial wastes that are mostly landfilled near the process plants. These increase the environmental risks as well as the necessity of waste management. Recycling of materials has been limited due to the fine particle sizes, heavy metals and unique oxide compositions. The authors investigated the potential utilization of these industrial wastes by melting and granulation technique. As quartz, hematite, alumina and lime consist more than 90wt% of mine wastes, CaO-Fe_tO-Al₂O₃-SiO₂ quaternary oxide system was applied to the thermodynamic calculations. Compositions of molten oxides were designed considering the lowest melting temperature and the adequate viscosity for atomization. Samples were melted by high frequency induction furnace then the atomization was carried out by air blowing technique. Viscosities of the melts were measured to quantify the optimum melting and atomization condition. Size distribution of the produced ceramic balls was investigated to estimate potential of the product to be used as abrasive materials.

Bayer red mud is characterized as highly oxidizing (high Fe₂O₃ content) and highly alkaline (high Na₂O content), which tends to act as a flux and strong dephosphorizer in the steelmaking process. In this study, firstly, the thermodynamical properties of Bayer red mud based flux were predicted including the melting temperature and phosphorus capacity. Further, laboratory experiments on application of Bayer red mud-based flux in hot metal dephosphorization. The effects of influencing factors such as flux composition and basicity were discussed. The results gave necessary basic knowledge for promoting the application of Bayer red mud in the steelmaking process.

The reduction behavior of raw materials from Assmang and Comilog based charges were experimentally investigated with CO gas up to 1600 °C. Quartz, HC FeMn slag or limestone were added to Assmang or Comilog according to the SiMn production charge, and mass loss results were obtained by using a TGA furnace. The results showed that particle size, type of manganese ore and mixture have close relationship to the reduction behavior of raw materials during MnO and SiO₂ reduction. The influence of particle size to mass loss was apparent when Assmang or Comilog was mixed with only coke (FeMn) while it became insignificant when quartz and HC FeMn slag (SiMn) were added. This implied that quartz and HC FeMn slag had favored the incipient slag formation regardless of particle size. This explained the similar mass loss tendencies of SiMn charge samples between 1200–1500 °C, contrary to FeMn charge samples where different particle sizes showed significant difference in mass loss. Also, while FeMn charge samples showed progressive mass loss, SiMn charge samples showed diminutive mass loss until 1500 °C. However, rapid mass losses were observed with SiMn charge samples in this study above 1500 °C, and they have occurred at different temperatures. This implied rapid reduction of MnO and SiO₂ and the type of ore and addition of HC FeMn slag have significant influence determining these temperatures. The temperatures observed for the rapid mass loss were approximately 1503 °C (Quartz and HC FeMn slag addition in Assmang), 1543 °C (Quartz addition in Assmang) and 1580–1587 °C (Quartz and limestone addition in Comilog), respectively. These temperatures also showed indications of possible SiMn production at process temperatures lower than 1550 °C.

WC-Co nanoparticles were directly recycled via sodiothermic reduction in NaCl-52mol%CaCl₂ molten salts using oxidized hard metal scrap as the raw materials. The as-prepared samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that a series of cemented carbide, such as W, W-Co, WC and WC-Co nanoparticles, were successfully recycled using the molten salt systems. The results show that WC/WC-Co nanoparticles can be recycled form oxidized hard metal scrap via sodiothermic reduction in the NaCl-52mol%CaCl₂ molten salts.

A fayalite based slag is formed during the smelting process of secondary copper containing resources. Of particular importance is the slag viscosity which quantifies the flow properties of the slag and affects the reaction kinetics, the refractory corrosion in the smelter and operational practice. In the present work, a high temperature rheometer system has been employed to study the rheological behavior of the industrial slag system FeO-ZnO-SiO₂-Al₂O₃-CaO (FeO/SiO₂ = 1–1.5, ZnO = 6–8 wt %, CaO = 1.5 wt % and Al₂O₃= 4.5 wt %) at 1150 °C with iron saturation. The slag behaves as a shear thinning fluid. The degree of shear thinning was quantified by fitting the flow curve with the Oswald-De Waele power law model. The relation between the slag composition and the flow behavior index has been discussed.

Equilibrium between MnO-CaO-MgO-SiO2-Al2O3 slags and carbon saturated Mn-Si-Fe-C alloys was investigated under CO at 1500oC. Manganese and silicon activities were obtained by using the present data and the previously determined MnO and SiO₂ activities of the slag. Quadratic multi-coefficient regression equations were developed for activity coefficients of manganese and silicon. The conclusions of this work are:(i)increase in the basicity and the CaO/Al2O3 ratios decreases the Mn distribution ratio,(ii)increase in the silica concentration and the MgO/CaO ratio increases the Mn distribution ratio, iii)carbon and manganese as well as carbon and silicon of the metal phase are inversely proportional,(iv)as Mn/Fe and Mn/Si ratio increases in the metal the carbon solubility increases,(v)decrease in the basicity increases the silicon content of the metal and (vi)increase in the silica content of the slag increases the silicon content of the metal and this effect is more pronounced at the higher Mn/Fe and Mn/Si ratios.

B₂O₃ and Na₂O are key components of fluorine-free mould fluxes for continuous casting, but both are highly volatile which affects the flux stability. This paper investigates evaporation of the SiO₂-CaO-Al₂O₃-B₂O₃-Na₂O fluxes (Na₂O: 6–10 wt%, CaO/SiO₂ ratio: 0.8–1.5) in the temperature range 1573 to 1673K using a thermogravimetric analysis method. The weight loss as a result of the flux evaporation increased with increasing temperature. The rate of evaporation increased significantly with the increase in the Na₂O content. The effect of the CaO/SiO₂ ratio in the range 0.8–1.3 on the evaporation rate was marginal. However, the increase of this ratio to 1.5 slowed down evaporation after approximately 1000 s. When 6.2 wt% Na₂O was added to the SiO₂-CaO-Al₂O₃-B₂O₃ flux, the apparent activation energy E _a for the evaporation reaction decreased from 365 to 193 kJ/mol, while a further increase in the Na₂O content to 9.1 wt% had a minor effect on E _a . The high evaporation rate of boracic fluxes in the presence of B₂O₃ and Na₂O was attributed to the formation of highly volatile NaBO₂.

Liquid copper was used as reference metal phase to equilibrate with CaO-SiO₂-MgO and CaO-SiO₂-MnO-Al₂O₃-MgO slags under a controlled oxygen partial pressure (p_O2 =1.76x10_-6 Pa) at 1873K. Based on the activity of Mn in Cu-Mn melts, the activities of MnO in slags were determined. The activities of MnO in the two kinds of slags increase gradually with the increasing of MnO content. For the slags with the same MnO content, the activity of MnO in the ternary slags is smaller than that in the five components slags. Furthermore, according to the measured activities of MnO in slags, the conversion factor in the quadratic formalism based on regular solution model was corrected. And an expression was obtained; it can estimate the activities of MnO in the both slags satisfactorily.

As a fundamental study on properties of the Fe_xO-bearing slags, the total electrical conductivity and electronic/ionic properties of Fe_xO-SiO₂-CaO-Al₂O₃ slags were measured at different oxygen potentials (controlled by CO-CO₂ mixture gas) and temperatures by using four-electrode method. From experiments results, it can be seen that the total conductivity changes little as increasing the ratio of CO to CO₂ (decreasing the oxygen potential), while the electronic and ionic conductivities of all slags decreases and increases monotonously, respectively. The temperature dependences of the total electrical conductivity, electronic, and ionic conductivities follow the Arrhenius law. It was also found that with increasing CaO/Al₂O₃ ratio, the total electrical conductivity and ionic conductivity firstly decrease and then increase, while electronic conductivity firstly almost keeps constant but then increases from CaO/Al₂O₃=1. The minimum values of the total electrical conductivity and ionic conductivity occurs near the ratio of CaO/Al₂O₃ = 1, which is mainly resulted from the charge compensation effect of Al3+ ions.

In ISA copper smelting process, recovery Co from the converter slag usually through reduction and vulcanization method. While Co usually exists in fayalite and iron oxide, in the form of isomorphism-phase by replace of Fe. By analyses different micro areas of the converter slag using SEM and EDS, the distribution trends of Fe and Co, Cu and Co were acquired. The results indicate that the percentage of compositions of Fe and Co present positive correlation, while those of Cu and Co present negative correlation. According to the distribution trends, the distribution curves of Fe ∼ Co and Cu ∼ Co are fitted, and the mechanism has been studied based on the oxidation order of the three metal sulfide as FeS > CoS > Cu2S, and the similarity of the element property of Cu and Co such as atom outer shell electron distribution and ionic radius, which will provide necessary theoretical reference for effective recovery of cobalt by reduction smelting process.

Based on the placement of lead and its consumption in industry branches, the paper deals with the composition of lead in the ores of Kopaonik, grinding and flotation recovery of galena. In the flotation process, the flotation machine, the flotation reagents, chemical composition of the flotation concentrates and tailings were discussed in this paper. Verification of the chemical composition of Pb concentrates with Pb, Zn, and Ag, etc. was conducted in this study. It is special that the ratio of Pb to Zn in Kopaonik massive composition is 1.4:1.0. During the flotation, lead tends to float with concentrate more than allowed. In this investigation, effects have been made to minimize the loss of Pb to concentrates. This paper as such gave the first effects in optimizing of these parameters with positive effects in the flotation process in Trepca.

The lead smelting dusts contain complex composition such as Pb, Zn, Cd, S and As, which pose serious environment problem. This research used several physical and chemical methods to study the basic properties of different lead smelting dusts including blast furnace dust, reduction furnace dust, reverberatory furnace dust and bottom blowing furnace dust. The results of characterization showed that these dusts have different phases, element composition and surface morphology. In addition, the distribution of elements and compounds presented a certain trend, which will impact the leachability of their major elements. At the same time, leaching experiments were carried out on thefour types lead smelting dusts to provide leachability information for metal recovery.

The effect of temperature and elemental concentrations of phosphorous, sulphur and titanium in high alloyed Cr-Mn-Ni TRIP/TWIP steels (16 %Cr, 7 %Mn, 6 % Ni) on the wettability of MgO partially stabilized zirconia (Mg-PSZ) substrates was studied. The investigation of the wetting behavior is of a major importance of the infiltration of steel into open foam ceramics and in interfacial contact of steel & ceramic powder in the spark plasma sintering. The interfacial reaction was characterized using X-ray and secondary neutral mass spectrometry analysis. The contact angle was investigated between 1500 ℃ and 1600 ℃ in argon (99.999 vol% Ar) atmosphere and was found to decrease with increasing temperature. At 1600 ℃ sulphur decreased the contact angle from 103 ° (100 ppm S) to 92 ° (1000 ppm S) in Fe-Cr-Mn-Ni. Increasing phosphorous content was found to increase the interfacial oxygen content in samples and the contact angle decreased to ca. 97 °. For titanium alloyed Cr-Mn-Ni sample, a TixOy interfacial layer was found after experiments and the contact angle was ca. 87 ° at maximum Ti content of 0.232 %.

Computer simulation plays an increasingly important role in improving the environmental and economic performance of pyrometallurgical extraction processes. The thermodynamic description of the chemical systems involved is at the core of such advanced simulation software. A thermodynamic database has been developed to describe the phase relations and chemical reactions in the Al—Ca—Cu—Fe—Mg—O—S—Si chemical system with support from the leading copper producers. The database contains model parameters for gas, liquid slag, liquid matte and metal, spinel and numerous solid phases. Models based on the Modified Quasichemical Formalism were used for the slag, matte and liquid metal. The internal consistency of the database provides accurate and reliable predictions outside of the usual operating conditions. The development of the database was closely integrated with the experimental studies of this chemical system. The database works in the environment of FactSage software. The application of thermodynamic modelling is illustrated by the example of the Peirce-Smith converter.

Recently the application of CaO-based multi-phase flux has received much attention and thus various physicochemical properties of the CaO-FeO-SiO₂ slags have been investigated. In the present paper, the thermodynamic properties of the 2CaO·SiO₂-3CaO·P₂O₅ solid solution which is the main solid phase constituting the multi-phase flux were studied. The activity of P₂O₅ was measured by the chemical equilibration method between molten iron and the solid solution, the solid solution and CaO mixture, or the solid solution and MgO mixture at 1823 and 1873 K with low oxygen partial pressure. The activities of P₂O₅, 3CaO·P₂O₅ and 3MgO·P₂O₅ were calculated by analyzed compositions and reported thermodynamic data. The activity of P₂O₅, 3CaO·P₂O₅ or 3MgO·P₂O₅ increased with the increase of 3CaO·P₂O₅ content in the solid solution.

In modern high temperature entrained flow gasifiers, the extensive use of petroleum coke (petcoke) as a replacement for or an addition to coal as a carbon feedstock introduces an appreciable amount of vanadium in the molten slag, resulting in unknown chemical and physical slag properties. A long-term research effort to understand phase equilibria of Al₂O₃-CaO-FeO-SiO₂-V₂O₃ slag system representative of that commonly found in coal/petcoke carbon feedstock mixtures was initiated by the U.S.-DOE NETL. In collaboration with CanmetENERGY and McGill University, synthetic vanadium bearing slag was investigated for phases formed under controlled temperature, partial pressure of oxygen, and composition. The slag compositions representing U.S. and Canadian coal and petcoke ashes are considered in this work. Equilibrium phase diagrams of the vanadium slag systems are reported.

Vanadium is found in slags produced during metal refinement and fossil fuel combustion/gasification. The oxidation state of vanadium in slag has technological and environmental implications. For example, it may affect slag flow and refractory wear inside reactors, as well as leachability and toxicity of industrial by-products. Determination of vanadium’s oxidation state in crystalline phases can be achieved via the widely adopted X-ray diffraction (XRD) technique. However, this technique does not provide information on vanadium in amorphous phases. The objective of this research is to determine the oxidation state of vanadium in petroleum coke gasification samples and laboratory samples using X-ray absorption spectroscopy (XAS) with Canadian Light Source’s soft X-ray micro-characterization beamline (SXRMB). Linear combination fitting of XAS spectra with reference samples allowed quantitative determination of vanadium speciation.