Materials Processing Fundamentals 2024

The geometric model is set up for a 1:1 three-phase fluidized bed, simulated calculations in the base of the air–tailings–water hot gas–solid–liquid fluidized bed experimental device. The Computational Fluid Dynamics (CFD) model utilizes the Eulerian–Eulerian multiphase modeling method and incorporates the dense discrete-phase (DDPM) model to simulate the flow of water droplets, introduced heat transfer, turbulence, and evaporation models to achieve a coupled solution. The simulation focuses on analyzing the flow, heat transfer, and superheated evaporation of water droplets during the fluidized treatment of tailings. The feasibility of the numerical simulation is verified through visualization experiments. Furthermore, the CFD model is employed to investigate the flow, evaporation, and interaction behaviors of water droplets of different sizes sprayed into a hot gas–solid fluidized bed and their effects on the fluidization state.

Søderberg electrodes, used commonly in submerged arc furnaces for production of ferroalloys and non-ferrous metals, are used to supply AC current into the furnace. These electrodes consists of paste (a mixture of calcined anthracite/petroleum coke and coal tar pitch) that eventually gets baked—a temperature-driven process. With increase in the electrode size and current supplied, safe operation of the electrode requires models that can predict the conditions experienced during operation. In this work, a novel axisymmetric transient Søderberg electrode model is presented. The model is used to simulate an electrode undergoing various slipping sequences, variations in electrode current, casing/briquette addition, and other operational scenarios, such as shut down operation. The model is observed to run much faster than real time, thus enabling its potential use in hybrid digital twin type of applications in industries.

Nowadays, most steelmaking plants still rely on manual experience to perform Kambara Reactor (KR) desulfurization, which makes it difficult to accurately control the endpoint [S] content for different steel grades, and can easily cause the waste of resources. To achieve cost reduction and efficiency increase, a KR desulfurization process model with production rhythm as the core was developed. The model included three desulfurization modes based on different requirements, namely process priority, time priority, and desulfurizer priority. The self-learning function to regress historical data of past heats was used in the modes of time priority and desulfurizer priority to obtain process parameters, while the process priority mode calculated process parameters just in the dependence of working conditions of current heat. After applying the developed model in a steelmaking plant, the average consumption of desulfurizer decreases from 6.41 to 5.27 kg/t. The one-time hit ratio of desulfurization pretreatment increases from 96.47 to 98.63%.

Following the absorption of inclusions, alterations occur in the microstructure of the tundish flux, thereby affecting its performance and diminishing the quality of continuous casting blanks. In this study, molecular dynamics simulations were employed to analyze the influence of varying levels of absorbed inclusions on the flux microstructure. The results indicate that the flux continuously absorbs inclusions, such as Al₂O₃ and SiO₂, during the continuous casting process, leading to an increase in the degree of microstructural polymerization. In the later stages of continuous casting, the proportion of bridging oxygen and tricluster oxygen in the tundish flux increased by 3.7% and 5.1%, respectively, while the average bond length of Al-O increased by 0.033 Å. The complexity of the microstructure leads to the deterioration of the physical and chemical properties of the coating, such as melting point and viscosity, and further reduces its ability to absorb inclusions.

Fe–Mn–Al–C steel can form AlN particles because of its high [Al] content (w[Al] = 8–12 wt%), which can affect the properties of slag during continuous casting. In this study, the dissolution behavior of AlN in a new CaO–Al₂O₃-based slag without SiO₂ was investigated by a static experiment method. Results demonstrated AlN rod could be dissolved in the liquid slag and it only reacted with Li₂O, which caused the increase of Al₂O₃ and the decrease of Li₂O in the slag. The interface between slag and AlN was examined by scanning electron microscopy, and the products near the slag side were Al₂O₃–CaO–BaO–CaF₂ complexes, while individual Al₂O₃ and AlN–Al₂O₃ complexes were dispersed near AlN side. Additionally, the viscosity and break temperature of the slag increased greatly with the increase of AlN. XRD showed the primary crystalline phase in the slag was 11CaO·7Al₂O₃·CaF₂. This work provided theoretical guidance for future application of the slag for high-Al steel.

Rare earth is an important additive to improve the comprehensive properties of steel products. To precisely control the amount of rare earth in the molten steel and rare earth inclusions is a fundamental issue that has not been effectively solved due to the lack of accurate thermodynamic data. The equilibrium between yttrium and oxygen in the liquid iron was investigated using pure Y₂O₃ crucibles for smelting experiments, and accurate thermodynamic data were obtained in the range of 1600–1700 °C. The results show that the deoxygenation product of yttrium was Y₂O₃ and the equilibrium constant of the reaction Y₂O₃(s) = 2[Y] + 3[O] can be expressed as follows: While the deoxidation product, \(K^{\prime}_{{\text{Y}}} ( = [\% {\text{Y}}]^{2} [\% {\text{O}}]^{3} )\), was expressed as follows:By the use of the interaction parameter \(e_{{\text{O}}}^{{\text{Y}}} = - 19591/T + 1.72\).

The interfacial contact area between molten steel and slag is one of the key factors influencing the efficiency of chemical reactions. This study reconstructs the phenomenon of gas bubbles traversing the slag-steel interface by constructing a physical model of the water–oil system and employing image processing techniques. The study focuses on the effects of bubble size, slag density, viscosity, and interfacial tension on the entrainment volume of steel and the slag-steel interface area. The entrainment volume increases with the increase of bubble size or slag density, but decreases with the increase of slag viscosity. The interface area shows a trend of first increasing and then decreasing with the increase of bubble size, and increases with the increase of slag density or the decrease of slag viscosity. As the oil-air interfacial tension increases, the water–air interfacial tension decreases, or the water–oil interfacial tension decreases, the liquid–liquid interface area increases.

In the settlement zone of the copper smelting furnace, SO₂ bubbles will be generated due to the insufficient oxidization of copper matte concentrate by injected oxygen-rich air in the reaction zone, entailing mass transfer in the liquid–liquid system by a rising bubble penetrating through the liquid–liquid interface. Different operating conditions between the bottom blown furnace and side blown furnace lead to different slag and matte viscosity. To investigate the copper smelting slag viscosity effect on the matte entrainment volume, cold model experiments using high-speed imaging techniques and high-temperature experiments were carried out. Results show that the lower liquid entrainment volume increases with the decreasing upper liquid viscosity and increasing bubble size. Higher slag viscosity and more SO₂ bubbles generated in the side blown furnace probably deteriorate the matte entrainment in the slag phase, while matte viscosity exerts slight influences due to the stable viscosity variation.

Controlling the heat flux at meniscus is one of the key aspects to prevent the formation of cracks during the continuous casting of crack-sensitive steel. This study investigated the influence of MgO addition on the performance of mold slag in the production of ultra-wide strand with a cross-section of 3000 mm × 150 mm. The main results indicated that when MgO increased from 0 to 8 wt%, the crystallization of slag film gradually decreased to 0% and then gradually increased. The break temperature and melting point also have the same change rule. When MgO was below 6 wt%, the O²⁻ ionized from MgO destroyed the silicon-oxygen tetrahedron structure of the flux and inhibited crystallization. Conversely, magnesia alumina spinel would form in the flux. XRD results also confirmed these results. This study provided a new idea for the composition optimization of mold flux for continuous casting of large cross-section peritectic steel.

The solidification shrinkage behavior of beam blank is critical for the mold design. In this study, a three-dimensional high temperature strain model was developed, with which the deformation trends of the Q235 steel 435 mm × 320 mm × 90 mm section beam blank were obtained. The results showed that the complex geometry led to significant differences in shrinkage behaviors in various regions. The maximum deformation occurred at the outer corner of flange reaching 1.9 mm, while the minimum occurred at the web was merely 0.1 mm. Besides, the shrinkage of the narrow face would generate a disturbance on flange-tip causing it to bend outwards to the narrow face. The shrinkage rate at the narrow face and flange gradually increased in the range of 100 mm below meniscus and gradually decreased beyond 100 mm. Results provide fundamental data for the control and improvement of the surface quality of beam blanks.

In this paper, the melting process of CuCr alloy is observed in-situ by high temperature confocal microscope, followed by process solidification at a solidification rate of 1 °C/s. It is found that the melting process of CuCr alloy is mainly divided into two steps: the first step is the complete melting of Cu-rich phase matrix, and the second step is that Cr phase is gradually dissolved in molten Cu matrix. The solidification process of CuCr alloy can be divided into three stages: initial solidification stage, stable solidification stage, and final solidification stage. The temperature range of stable solidification stage is 1400 ℃–1250 ℃, at which time the solidification rate of the alloy is the fastest, and the solidification structure with uniform distribution of Cr-rich phase is obtained. Finally, the model of CuCr alloy is firstly established by Materials studio based on heterostructure theory.

In the process of converter tapping, the process parameters of the tapping hole are essential for the flow characteristics of molten steel and the tapping time. ANSYS FLUENT19.3 software is used to establish a three-dimensional model of a 200t converter and ladle and investigate the distribution law of molten steel flow field during the tapping process of the converter under different tapping parameters by volume of fluid model. The molten steel flow rate is more uniform and stable, and the turbulence is significantly reduced when the shape of the tapping hole is a segmented variable diameter type, the diameter is 180–160 mm, and the angle to the horizontal direction is 10°, thereby reducing the degree of erosion at the tapping hole. The error between the simulation and the actual tapping time is within 5%, which verifies the accuracy of the model. It provides theoretical support for optimizing the process parameters of the converter tapping hole and studying the temperature drop law of the tapping process.

In the current study, the interaction between refractory rods and a high-carbon SiMn-killed steel was investigated via laboratory experiments and thermodynamic calculations. The carbon-bonded magnesia (MgO-C) refractory and the magnesite (MgO) refractory were compared. After 90 min of contact, the penetration of the molten steel into the MgO refractory was little and the interfacial reaction layer was little observed so the inclusions in the steel varied little. After 90 min of contact, the molten steel penetrated the MgO-C refractory for 1 mm through grain boundaries and C-phase channels in the lining refractory. A 80 μm thick CaO-CaS-MgO-MgS layer between the steel and the MgO-C refractory formed and inclusions in the steel were transformed from original SiO₂-MnO-Al₂O₃ ones with a spherical morphology to MgO and MgO-Al₂O₃ ones with an irregular shape, indicating the occurrence of the desulfurization of the steel by the CaO-phase in the grain boundary of the lining refractory.

In the current study, laboratory experiments were performed to investigate the interfacial reaction between the molten steel and the MgO-C refractory, and the effect of lanthanum in the steel was studied. A dense MgO reaction layer with a 50 μm thickness at the interface between the quiescent steel without lanthanum and the refractory was observed. Under stirring condition, the thickness of the MgO reaction layer was only 25 μm and the layer was non-continuous and broken at some places. For the interfacial interaction between the lanthanum-bearing steel and the MgO-C refractory, under quiescent condition, a double-layer structure was generated, with a MgO layer close to the refractory side and a La₂O₃ layer close to the steel side. Under stirring condition, a La₂O₃-La₂O₂S layer was generated and a few LaAlO₃ particles were embedded inside the MgO reaction layer. The stirring induced the dislodgement of MgO particles from the lining refractory into the molten steel.

This paper reports about the key technology of preparing vanadium base alloy (vanadium nitrogen alloy) for nuclear power. The large particle ammonium metavanadate and the control of low-temperature carbonization and high-temperature nitriding reaction process were studied; ultimately, the high nitrogen type vanad-based alloy was obtained. The results show that ammonium metavanadate particles with an average particle size of more than 100 μm can be obtained by metastable control. After physical densification, the maximum compressive strength of the material particles is 120 N/cm², and high-density V₂O₃ raw materials are obtained. When the double nitriding method was used in bidirectional nitriding reaction, the nitrogen content in the product was significantly increased, N/V reached 0.22, and the nitriding rate was increased by more than 4.5%. This method breaks through the technical bottleneck of low N/V in traditional vanadium alloys and has a good industrial application prospect.

In the process of silicon steel sheet production, the hydrochloric acid pickling process was employed to remove the oxides on the surface of the silicon steel sheet. In this process, a lot of pickling sludge was generated and suspended in the acid, which could seriously block the effect of the pickling process, so it must be removed from the acid. However, silicon is not used effectively, which results in a waste of resources. In this study, a new utilization method, synthesis of ferrosilicon alloy from pickling sludge by vacuum carbothermal reduction, has been proposed. The Gibbs free energies of reductions and the reduction sequence had been calculated. The results showed that it obeyed the step-by-step reduction process, and the formation temperature of ferrosilicon alloy decreased with the gas pressure drop. The appropriate reaction conditions were ascertained, which can be employed in the experiments.

Soft magnetic composites are a necessary component to produce efficient electric vehicles. However, the relationship between structure and material properties results in a nearly inevitable trade-off between efficiency and strength. The work presented here investigates a means of directly addressing improvement in both strength and magnetic properties by use of cold sintering technique. The technique utilizes surface modification of individual particles which are warm compacted to improve strength and provide the necessary insulating properties to attain the characteristic soft magnetic properties required for use in electric motors. Materials are investigated using scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, electron energy loss spectroscopy, 3-point bending tests, 4-point probe tests, permeability measurement, and AC and DC magnetic testing. These characterization methods are used to qualitatively and quantitatively inspect the applicability of the material as a soft magnetic composite. Finally, this study contributes to understanding how to improve strength at relatively low temperature via cold sintering method.

The tundish structure is a very important factor to remove the inclusions and unify the molten steel. In the condition of four-strand asymmetrical tundish form, there are many problems in Al-deoxidized steel, such as a large number of inclusions and excessive inclusion size. In order to remove the inclusions and increase the cleanliness of molten steel, the crutch-shaped baffle was designed for the four-strand asymmetrical tundish. The numerical simulation results showed that by applying the proposed baffle, the average residence time of the molten steel in the tundish is increased by 43.1 s, the dead zone ratio is decreased by 3.4%, and the flow consistency among strands is apparently increased. Industrial experiments showed that the excessive-sized inclusions are eliminated and the inclusion number is decreased by 46.23% when adding the crutch-shaped baffle in four-strand asymmetrical tundish. Therefore, the inclusion removal rate and the cleanliness of molten steel are greatly improved.

Extracted titanium tailings are produced by high-titanium blast furnace slag using “high-temperature carbonization–low-temperature chlorination” technology. In this paper, the flow characteristic of extracted titanium tailings is experimentally investigated on the base of the fluidized furnace over a range of superficial gas velocity and bed temperatures. The evaporation rate of liquid addition was studied at different temperatures. The influence of superficial gas velocity, temperatures, and height-to-diameter ratio on flow characteristics was analyzed. The particle microstructures of the tailings were characterized by scanning electron microscopy and energy dispersive spectroscopy (SEM–EDS). The results show that there exists a linear correlation between the actual amount of liquid before and after entering into the bed at different temperatures. The mean pressure drop and standard deviation show an overall enhancing trend with the increasing gas velocity and height-to-diameter ratio of bed. However, the bed temperature poses a significant effect on the bed pressure after liquid addition.

Importance of DFT simulation of microsurface properties of FeO in ironmaking research is emphasized, as FeO serves as a limiting factor in the iron reduction process. The interface reaction mechanisms involved in CO reduction of FeO are revealed, adsorption properties are predicted, and crucial parameters such as surface energy and electronic structure are provided. Additionally, the formation modes of defects for various types of atoms are anticipated. These results offer powerful tools and a theoretical foundation for understanding and optimizing the ironmaking process, thereby contributing to increased production efficiency, reduced energy consumption, and the promotion of sustainable development within the iron and steel industry.

With the rapid development of the electrical and electronic industries, the quality requirements for oxygen-free copper (OFC) materials have become increasingly stringent, and the difficulty of oxygen removal content in OFC has increased accordingly. In this paper, the effect of super-gravity field on the purification of high-purity metals was investigated using oxygen-free copper. Microanalysis revealed that the oxygen elements in the samples primarily existed in the form of cuprous oxide. The effects of different gravity coefficients (G) and centrifugal time (t) on the distribution of oxygen in samples at 1200 ℃ were studied. The results showed that oxygen elements move in the opposite direction of the super-gravity. Moreover, the oxygen content in the sample could be significantly reduced from 31.37 ppm to 2.47 ppm at G = 1000 and t = 60 s, while the electrical conductivity improved from 103.23% IACS to 105.95% IACS. It is concluded that solidification under super-gravity conditions promotes grain refinement in the sample, with an increase in the gravity coefficient being advantageous.

Predicting the temperature drop of hot metal is greatly significant for the decision-making of scrap steel amount in basic oxygen furnace (BOF). In addition, accurate prediction of temperature drop can guide the scheduling of hot metal, keeping the steelmaking process stable. In this paper, a prediction model of temperature drop was developed by integrating heat-transfer mechanisms and machine learning models. Extreme learning machine (ELM) was applied to establish the machine learning model (MLM). Further, the performance of MLM was optimized by introducing regularization and particle swarm optimization (PSO). Based on actual data from a steelmaking plant in China, the above models were trained and verified. The results show that the hit ratio of the integration model is 88.53% when the prediction error is within 10 ℃, which is higher than those of the heat-transfer mechanism and the optimized machine learning models. Meanwhile, the robustness of the integration model is also optimal.

Technical transformation and modification have been carried out on the dense flow absorber for desulfurization of 360 m² sintering machine in Shougang Qian’an Iron and Steel Company. Also, selective catalytic reduction (SCR) denitrification system was added at the same time. Desulfurization efficiency of sintering flue gas was improved by changing the desulfurization agent and expanding the capacity of desulfurization system. The desulfurization efficiency increased to over 95%. By applying selective catalytic reduction (SCR) denitrification technology, the nitrogen oxide emission at the outlet is reduced to about 30 mg/m³. Through the above technical transformation measures, the sintering process has achieved ultra-low emissions of pollutants. The outlet dust is lower than 10 mg/m³, the outlet concentration of SO₂ is lower than 35 mg/m³, and NOx is lower than 50 mg/m³.

Severe reactions occur at the steel-slag interface during continuous casting of high-Ti steel, leading to the interruption of smooth operation and strand defects. To settle the issue, this study proposed a new slag system with high basicity (the ratio of CaO/SiO₂: 1.5–1.9), aiming to maintain the stability of slag properties by providing sufficient O²⁻ ions from CaO. The main results indicate that as the basicity ranged from 0.8 to 1.5, the viscosity and melting temperature decreased first and then increased with the increase of TiO₂/SiO₂ ratio, and the precipitation transformed from glassy to high-melting temperature perovskite. In the range of 1.5 to 1.9, the melting and flow also deteriorated as the rise of TiO₂/SiO₂, but the extent of deterioration was greatly suppressed compared with that with low basicity, and no perovskite precipitated. This study could provide a new strategy to optimize the mold slag for high-Ti steel continuous casting.

Porous baffle wall is a common flow control device in tundish. The flow field in the tundish can be improved by adjusting the elevation angle and position of the deflector hole on porous baffle wall, so the residence time of liquid steel is prolonged, inclusions easily to be removed. In this paper, the method of orthogonal experimental design is used to simulate and optimize the deflector hole on the porous baffle wall. The results showed that the flow field of the casting region in tundish can be improved significantly with proper elevation angle and location of the deflector hole. The volume of dead zone decreased from 23.1% to 18.4%, the average residence time of each outlet changed from 572.6 s, 594.6 s, and 794.4 s to 663.5 s, 633.6 s, and 663.2, the standard deviation decreased from 99.8 to 14.0, and consistency of outlet was greatly improved.

Bloom continuous casting is widely used in steel production. The flow state and liquid level fluctuation of molten steel inside the bloom continuous casting mold directly affect the quality of the bloom. In this study, numerical simulations are conducted with different immersion depths and side hole inclination angles of the submerged nozzle during the bloom continuous casting process, and the F index is used to judge the liquid level fluctuation during the casting process. The results show that the optimal nozzle combinations are 100 mm submerged depth with 15° port angle and 110 mm submerged depth with 15° port angle, when the continuous casting speed is 0.55 m/min. The flow field of the molten steel in the mold is appropriate, and the narrow surfaces are less impacted. Also, the fluctuation of the liquid level is appropriate. This method can be emulated to optimize the mold parameters in most steel production processes. In addition, as the chamfer decreases, the heat flux density at the corners continues to increase.

This paper analyzes the formation law of liquid phase in the process of ultra-thick bed sintering and emphatically expounds the key technology and production practice effect of two 500 m² sintering machines of Shougang Jingtang. Through the implementation of ultra-thick bed sintering, Jingtang sintering machine has achieved good results in terms of sintered ore quality, process energy consumption and pollutant discharge. The comprehensive solid fuel consumption of sintering has dropped from 53.95 kg/t in the base period to 48.86 kg/t, ignition gas consumption decreased from 2.391 m³/t to 1.553 m³/t; sintering utilization coefficient increased from 1.27 t/(m² h) to a relatively high level of 1.40 t/(m² h), sintering return fines rate decreased, quality indicators such as drum strength and screening index of sinter remained stable; flue gas volume decreased from 2280 Nm³/t to 1779 Nm³/t, a decrease of 21.0%; and NOx emission decreased from 0.58 kg/t to 0.46 kg/t, 20.3% reduction.

The desulfurization ash contains high content of CaSO₃, which makes it difficult for its resource utilization. In the present study, the physical–chemical performance of the sintering flue gas desulfurization ash from a typical steel corporation was analyzed. On this basis, the H₂O₂ oxidation modification, MnSO₄ catalytic modification and air oxidation test with different process conditions of it were studied, and the best process conditions of desulfurization ash modification were analyzed. Considering the test results and the industrial practice, the optimal process conditions were thought as: hydrogen peroxide was oxidant, pH value was 5.5, the molar ratio of H₂O₂ and CaSO₃ was 1:1, the slurry solid content was 10%, and the reaction time was 1.5 h, and under these conditions, the CaSO₃ conversion rate reached 98%. However, MnSO₄ was not suggested to be added for oxidation of sintering semi-dry desulphurization ash.

With the wide application of electromagnetic stirring in continuous casting and the rapid development of low reactive mold flux, the effect of low-frequency electromagnetic field on the assimilation and absorption rate of Al₂O₃ inclusion in the low reactive mold flux was studied by using the rotating cylinder method, and the relationship between electromagnetic field parameters and the dissolution rate of Al₂O₃ inclusion was also studied. The results show that the low-frequency electromagnetic field can obviously promote the assimilation and absorption of Al₂O₃ inclusion in low reactivity mold flux. When the magnetic field intensity (MFI) is 30 mT and the magnetic field frequency (MFF) is 12 Hz, the maximum dissolution rate of Al₂O₃ inclusion is 2.66 × 10^–4 g mm⁻²min⁻¹, which is 10.64 times higher than in the absence of magnetic field. Furthermore, the higher the MFI and MFF, the faster the dissolution rate of Al₂O₃ inclusion.