Non-metallic inclusions in steel are a significant challenge, affecting material properties and leading to issues such as stress concentration, cracking, and accelerated corrosion. Current methods for removing inclusions, including bubble, electromagnetic stirring, filtration separation, fluid flow, and sedimentation, often struggle with the removal of fine inclusions. Apart from these known methods, pulsed electric current (PEC), as an emerging technology, has demonstrated immense potential and environmental advantages. PEC offers adjustable current parameters and simple equipment, making it an attractive alternative to traditional methods. Its green energy-saving features and excellent results in regulating inclusion morphology and migration, as well as inhibiting submerged entry nozzle (SEN) clogging, make it a promising technology. In comparison to continuous current technology, PEC has shown significant advantages in regulating inclusions, not only improving purification efficiency but also demonstrating outstanding performance in flow stability and energy consumption. The ability of PEC to efficiently reduce inclusion numbers enhances the purity and quality of molten steel, improving its mechanical properties. Currently, the theoretical basis for controlling the movement of inclusions by current is mainly composed of three major theories: the double electric layer theory, electromagnetic force reverse separation theory, and electric free energy drive theory. These theories together form an important framework for researchers to understand and optimize the behavior of impurity movement controlled by electric current. Looking ahead, PEC is expected to pave the way for new solutions in directional regulation of inclusion migration, efficient inclusion removal, SEN clogging prevention, and the purification of molten steel.

The iron and steel industry, standing as a quintessential manufacture example with high consumption, pollution and emissions, faces significant environmental and sustainable development challenges. Electric arc furnace (EAF) steelmaking process mainly uses scrap as raw material and is characterized by environmentally friendly and recyclable process. However, the further development of EAF route in China is limited by the reserve, supply, availability and quality of scrap resource. Direct reduced iron (DRI) is one of typical low-carbon and clean charges, which can effectively make up for the adverse effects caused by the lack of scrap. The physical and chemical properties, classifications, and production technologies of DRI are firstly reviewed. In particular, the reducing gas types, reduction temperature, and reduction mechanism of the DRI production with gas-based shaft furnace (SF) technology are detailed. Considering the crucial role played by DRI application in EAF, the influences of DRI addition on EAF smelting rules and operations including the blending and charging process, heat transfer and melting in molten bath, slag formation operation, refractory corrosion, and slag system evolution are then further discussed. Finally, the comparative analysis and assessment of the consumption level of material and energy as well as the cleaner production both covering the clean chemical composition of molten steel and the clean environment impact in EAF steelmaking with DRI charged are conducted. From perspectives of metallurgical process engineering, a suitable route of hydrogen generation and application (from coke oven gas, methanol, and clean energy power), CO₂ capture and utilization integrated with SF-EAF process is proposed. In view of the difficulties in large-scale DRI application in EAF, the follow-up work should focus on the investigation of DRI charging and melting, slag system evolution and molten pool reaction rules, as well as the developments of the DRI standardized use technology and intelligent batching and control models.

Erosion-corrosion (EC)-induced damage is a primary contributor to premature failures in hydraulic transport structures involving sudden changes in flow patterns, especially the hydraulic pipeline (tee, reducer, pipe bend, etc.), pumps, and valves. A comprehensive exploration of EC behavior of steels subjected to high tensile stress was provided, as most engineering structures are operated under high stress. The stress-accelerated erosion (SAE) and stress-accelerated corrosion (SAC) behaviors of highly stressed steel and their synergistic effect were mainly focused. SAE, SAC, and their synergistic mechanisms, existing debate, and possible reasons, as well as available analytic models with their advantages and limitations, are thoroughly discussed. The multiphysics simulation methods for modeling EC interactions with both static and cyclic stresses are also summarized, and EC mitigation strategies, especially the bionics-based strategies, were also summarized in detail.

High-temperature confocal laser scanning microscopy (HT-CLSM) is considered as a powerful tool for in situ observation of the phase transformation of steels at elevated temperatures. It breaks the limitation that conventional approaches on this aspect can only post-mortem the microstructure at room temperature. The working principle and major functions of HTCLSM in initial are introduced and the utilization in details with HT-CLSM is summarized, including the behaviors of melting-solidifying, austenite reversion, as well as the austenite decomposition (formation of Widmanstätten, pearlite, acicular ferrite, bainite and martensite) in steels. Moreover, a serie of HT-CLSM images are used to explore the growth kinetic of phase at elevated temperatures with additional theoretical calculation models. Finally, the in situ HT-CLSM observations of phase transformation, combined with post-mortem electron backscatter diffraction analysis, is also summarized to elucidate the crystallographic evolution.

Precipitation of carbides, nitrides, and carbonitrides is an important factor influencing the formation of surface transverse cracks in the continuous casting of microalloyed steel, affecting the quality and yield of the final product. Based on previous investigation, the precipitation sequence and temperature, position and mode, as well as the size, morphology, and number of different types of precipitates were reviewed. The effects of C, N, Nb, Ti, and V on the precipitation behavior and surface transverse cracks in continuous casting slabs were summarized, with a particular emphasis on the new achievements concerning Ti addition. The critical amounts of different elements to avoid serious surface cracks during continuous casting were proposed. The control mechanisms and industrial effects of composition optimization, cooling design, and chamfered mold configuration to improve surface transverse cracks in continuous casting slabs were also illustrated, and the recent application of surface microstructure control technology was emphasized. The characteristics, advantages, and shortcomings of existing theoretical and experimental methods in investigating continuous casting surface cracks regarding precipitation are finally discussed, and a new setup with advanced functions is introduced.

Accumulative roll bonding (ARB) is a severe plastic deformation method to prepare the metallic composite material by physical method at room to elevate temperature, without the generation of additional waste solid or gas. With the physical characteristicsmulti-material and hybrid structure, the mechanical and function properties of the ARB composite material, like Al/steel, Al/Mg, Al/Cu, etc., shall have the “1+1>2” effect on the mechanical and functional properties, including the remarkable properties that include lightweight, high strength, thermal/electrical conductivity, electromagnetic shielding, and other functions. To deeply investigate the preparation method and microstructural evolution of various metal laminates by ARB, as well as the mechanical and functional properties of the laminate, an overview of the history of ARB technique, the breakthrough of ARB sheet properties, as well as the relative products in industries is provided. Additionally, the future development of ARB technology and the utilization of composite materials in different areas will be discussed.

The effect of (CaO+SiO₂) mass ratio on high-Ti vanadium titanomagnetite sintering was systematically studied at the fixed basicity (CaO/SiO₂) of 2.0. The results show that sinter matrix strength is improved with (CaO + SiO₂) mass ratio while the total iron content is reduced. Thermodynamic analysis indicates that the increase in (CaO + SiO₂) mass ratio from 15.0 to 22.5 wt.% contributes to the formation of liquid phase, especially silico-ferrite of calcium and aluminum (SFCA). In addition, the formation of perovskite is inhibited and liquid phase fluidity is improved. The porosity of sinter matrix is reduced by 34.5% and SFCA amount is increased by 47.2% when (CaO + SiO₂) mass ratio is increased from 15.0 to 18.0 wt.%. With the further increase in (CaO + SiO₂) mass ratio, the structure of sinter matrix is too dense and the improved extent of SFCA amount is increasingly low. The appropriate (CaO + SiO₂) mass ratio should be 18.0 wt.% overall. Under this condition, sinter matrix strength is greatly improved by over 13.5% compared with the base case and the total iron content can be maintained at about 49 wt.%.

Pursuing green, low-carbon ironmaking technology primarily aims to reduce fuel ratios, especially coke ratios. Simultaneously, the reduction in coke ratios causes the coke layer in the blast furnace (BF) to become thinner, deteriorating the gas and liquid permeability of the burden column. This exacerbates coke degradation, significantly impacting the smelting process and increasing the demand for high-quality coke. To investigate the existence state of coke in the hearth, a 2500 m³ BF in China was taken as the research object, and three sets of samples at different heights of the hearth were obtained during planned outage. The results indicate that coke undergoes a significant degradation upon reaching the hearth. The proportion of coke particles smaller than 50 mm ranges from 81.22% to 89.50%. The proportion of coke particles larger than 20 mm decreases as the distance from the centerline of the tuyere increases, while the proportion of particles smaller than 10 mm increases with this distance. Additionally, the closer the bottom of the furnace is, the smaller the coke particle size becomes. The composition of slag filling the coke pores is similar to that of the final slag in the blast furnace, and the graphitization of coke is comparable to that of the final slag. The graphitization of coke starts from the surface of coke and leads to the formation of coke fines, and the graphitization degree of - 74 lm coke fines is the highest. The temperature has an effect on the reaction rate of coke solution loss, and the higher the temperature is, the faster the reaction rate is. Keywords: Blast furnace; Hearth; Coke; Graphitization; Dissolution reaction

The thick layer and graded feeding technology of a belt roasting machine is an effective method for improving the production efficiency and quality index of pellet production, and a reasonable design of the mechanical structure of the layer is the basis for optimizing the heat andmass transfer performance of the layer. Janssen effect and von Mises yield criterion were used to establish a simplified mathematical model describing the elastic and plastic deformation of the green pellet under the action of an external force. The mechanical characteristics of extrusion, contact, and elastic-plastic deformation between green pellet particles in the material layer of the belt roastingmachine weremodeled usingEDEMsoftware.For a green pellet size of 12mm,as the layer height increases from 300 to 1000 mm, the maximum vertical pressure on the pellets increases from 11.64 to 24.01 N, and the porosity decreases from 27.04% to 22.01%. As the layer height increases, the contact between the green pellets becomes more intense, and the force chain structure of the layer becomes more stable; the Janssen effect is observed when the layer reaches 700 mm. The compressive strength of the green pellets is linearly related to the particle size, and the compressive strength increases with an increase in particle size.At a layer height of 600 mm, as the particle size of the green pellets increases from 8 to 20 mm, themaximum vertical pressure increases from 7.54 to 44.16 N, and the porosity increases from23.20% to 31.47%,while the yield per unit of the layer decreased by 12.1%. Small particles have a more stable force chain structure, larger comparative area, and higher production efficiency; however, their compressive strength is lower. Large particles have higher compressive strength and good permeability in the layer, but the production efficiency is relatively low. In actual production, a variety of factors should be integrated to optimize the feeding, and a multi-granularity graded feeding is the most ideal feeding.

Dissolution kinetics of CaO·2Al₂O₃ (CA₂) particles in a synthetic CaO-Al₂O₃-SiO₂ steelmaking slag system have been investigated using the high-temperature confocal laser scanning microscope. Effects of temperature (i.e., 1500, 1550, and 1600 °C) and slag composition on the dissolution time of CA₂ particles are investigated, along with the time dependency of the projection area of the particle during the dissolution process. It is found that the dissolution rate was enhanced by either an increase in temperature or a decrease in slag viscosity. Moreover, a higher ratio of CaO/Al₂O₃ (C/A) leads to an increased dissolution rate of CA₂ particle at 1600 °C. Thermodynamic calculations suggested the dissolution product, i.e., melilite, formed on the surface of the CA₂ particle during dissolution in slag with a C/A ratio of 3.8 at 1550 °C. Scanning electron microscopy equipped with energy dispersive X-ray spectrometry analysis of as-quenched samples confirmed the dissolution path of CA₂ particles in slags with C/A ratios of 1.8 and 3.8 as well as the melilite formed on the surface of CA₂ particle. The formation of this layer during the dissolution process was identified as a hindrance, impeding the dissolution of CA₂ particle. A valuable reference for designing or/and choosing the composition of top slag for clean steel production is provided, especially using calcium treatment during the secondary refining process.

The continuous growth behavior of austenite grain in 20Cr peritectic steel was analyzed by experiment and theoretical modeling. The peculiar casting experiment with different cooling rates was achieved by multigradient operation scheme, and different morphologies in austenite grain were observed at the target location. The increase in austenite grain size with increasing cooling rate was firstly revealed in steels. The anomalous grain growth theoretically results from the mechanism of peritectic transformation transiting from the diffusional to massive type, and the additional energy storage stimulates the grain boundary migration. A new kinetic model to predict the growth behavior of austenite grain during continuous cooling process was developed, and the energy storage induced by massive type peritectic transformation was novelly taken into account. The parameters in the model were fitted by multiphase field modeling and experimental results. The kinetic model was finally verified by austenite grain size in laboratory test as well as the trial data at different locations in continuously cast bloom. The coarsening behavior of austenite grain during continuous casting was predicted based on the simulated temperature history. It is found that the grain coarsening occurs generally in the mold zone at high temperature for 20Cr steel and then almost levels off in the following process. The austenite finish transformation temperature T_γ and primary cooling intensity show great influence on the grain coarsening. As T_γ decreases by 1 ℃, the austenite grain size decreases by 4 μm linearly. However, the variation of T_γ against heat flux is in a nonlinear relationship, suggesting that low cooling rate is much more harmful for austenite grain coarsening in continuous casting.

Accurate prediction of strip width is a key factor related to the quality of hot rolling manufacture. Firstly, based on strip width formation mechanism model within strip rolling process, an improved width mechanism calculation model is delineated for the optimization of process parameters via the particle swarm optimization algorithm. Subsequently, a hybrid strip width prediction model is proposed by effectively combining the respective advantages of the improved mechanism model and the data-driven model. In acknowledgment of prerequisite for positive error in strip width prediction, an adaptive width error compensation algorithm is proposed. Finally, comparative simulation experiments are designed on the actual rolling dataset after completing data cleaning and feature engineering. The experimental results show that the hybrid prediction model proposed has superior precision and robustness compared with the improved mechanism model and the other eight common data-driven models and satisfies the needs of practical applications. Moreover, the hybrid model can realize the comple-mentary advantages of the mechanism model and the data-driven model, effectively alleviating the problems of difficult to improve the accuracy of the mechanism model and poor interpretability of the data-driven model, which bears significant practical implications for the research of strip width control.

Against the background of ‘‘carbon peak and carbon neutrality,’’ it is of great practical significance to develop non-blast furnace ironmaking technology for the sustainable development of steel industry. Carbon-bearing iron ore pellet is an innovative burden of direct reduction ironmaking due to its excellent self-reducing property, and the thermal strength of pellet is a crucial metallurgical property that affects its wide application. The carbon-bearing iron ore pellet without binders (CIPWB) was prepared using iron concentrate and anthracite, and the effects of reducing agent addition amount, size of pellet, reduction temperature and time on the thermal compressive strength of CIPWB during the reduction process were studied. Simultaneously, the mechanism of the thermal strength evolution of CIPWB was revealed. The results showed that during the

A novel Al-alloyed press-hardening steel (PHS) was developed, which exhibits excellent tensile, bending and antioxidation properties. Al is a ferrite-forming element that can hinder the formation of cementite and enhance the stability of austenite. The incorporation of Al not only induces the formation of ferrite within martensitic matrix but also enhances the stability of retained austenite (RA). The microstructure of novel steel consists of martensite, ferrite, and RA after press hardening. Investigations into the role of Al in RA development were supported by thermo-kinetic calculations. The simultaneous introduction of ferrite and RA into the martensitic matrix via tailored chemical compositions significantly enhances the elongation and bending toughness of the novel PHS. Additionally, Al can form a dense Al oxide at the bottom of oxide layer, resulting in the improved antioxidant properties. Compared to 22MnB5 steel, it is an exciting discovery as there is a significant improvement in total elongation and bending toughness of novel PHS without compromising strength. The novel PHS, with its exceptional balance of strength and ductility, will play a crucial role in reducing weight when it replaces the existing class 22MnB5 PHS in different structural components of vehicle bodies.

Cleanliness control of advanced steels is of vital importance for quality control of the products. In order to understand and control the inclusion removal during refining process in molten steel, its motion behaviors at the multiple steel/gas/slag interfaces have attracted the attention much of metallurgical community. The recent development of the agglomeration of non-metallic inclusions at the steel/Ar and steel/slag interfaces has been summarized, and both the experimental as well as theoretical works have been surveyed. In terms of in situ observation of high-temperature interfacial phenomena in the molten steel, researchers utilized high-temperature confocal laser scanning microscopy to observe the movement of more types of inclusions at the interface, i.e., the investigated inclusion is no longer limited to Al₂O₃-based inclusions but moves forward to rare earth oxides, MgO-based oxides, etc. In terms of theoretical models, especially the model of inclusions at the steel/slag interface, the recent development has overcome the limitations of the assumptions of Kralchevsky-Paunov model and verified the possible errors caused by the model assumptions by combining the water model and the physical model. Last but not least, the future work in this topic has been suggested, which could be in combination of thermal physical properties of steels and slag, as well as utilize the artificial intelligence-based methodology to implement a comprehensive inclusion motion behaviors during a comprehensive metallurgical process.

An industrial experiment was conducted at a certain steel plant in China to compare and analyze the effects of Ca treatment and Mg-Ca treatment on inclusions in 45MnVS non-quenched and tempered steel. Through scanning electron microscopyenergy dispersive scanning analysis of the morphology and composition of inclusions, as well as Aspex quantitative analysis of their quantity, type and size, the formation mechanism of MnS-oxide (MnS inclusions with oxide cores) was intensively studied. The influence of sulfide morphology on the impact properties of steel was also analyzed. The results show that the quantity percentage of spindle-shaped sulfides in Ca-treated steel is 19.99%, and that in Mg-Ca-treated steel is 35.38%. Compared with Ca-treated steel, there are more MnS-oxide inclusions in Mg-Ca-treated steel. Controlling the content of Ca and Mg in the oxide core of MnS-oxide inclusion above 10 wt.% and the area ratio below 5 would contribute to the formation of spindle-shaped inclusions after rolling. The mismatch between MnS and oxides decreases with the increase in MgO content in the oxides, which is beneficial to nucleation and precipitation of MnS with this type of oxides as the core. Under the same deformation conditions, the size of sulfide does not affect its aspect ratio. Under the experimental conditions, the inclusion containing a certain amount of MgO can enhance its sulfur capacity, facilitating the formation of composite sulfides. The transverse impact energy of Ca-treated steel is 25.785 J, and that of Mg-Ca-treated steel is 32.119 J. Compared with the traditional Ca-treatment, Mg-Ca treatment can increase the number of spindle-shaped sulfides in the steel, thereby improving the transverse impact toughness of the steel and reducing the anisotropy of the mechanical properties of the material.

Ultrafine iron powder is widely used due to its excellent performance. Hydrogen reduction of fine-grained high-purity iron concentrate to prepare ultrafine iron powder has the advantages of low energy consumption, pollution-free, and low cost. The hydrogen reduction of high-purity iron concentrates, characterized by the maximum particle size of 6.43 lm when the cumulative distribution is 50% and the maximum particle size of 11.85 lm when the cumulative distribution is 90% while the total iron content of 72.10%, was performed. The hydrogen reduction could be completed at 425 °C, and the purity of ultrafine iron powders was more than 99 wt.% in the range of 425-650 °C. Subsequently, the effect of reduction temperature on various properties of ultrafine iron powder was investigated, including particle morphology, particle size, specific surface area, lattice parameters, bulk density, and reaction activity. It was found that the reaction activity of the iron powders prepared by hydrogen reduction was much higher than that of the products of carbonyl and liquid phase synthesis. Below 500 °C, the reduced iron powders were nearly unbound, with a small particle size and a low bulk density. The particles had a porous surface, with a specific surface area as high as 11.31 m² g^-1. The crystallization of reduced iron powders was imperfect at this time, the amorphization degree was prominent, and the interior contained a high mechanical storage energy, which had shown high reaction reactivity. It was suitable for catalysts, metal fuels, and other functionalized applications.

Understanding the solidification characteristics and microsegregation under varying cooling rates is essential to comprehend the formation of center cracks in large section round billets. P91 high-alloy steel was taken as the research object. The peritectic solidification process, steel solidification shrinkage and microsegregation of solute elements at different cooling rates were studied and revealed by high-temperature confocal scanning laser microscopy, Thermo-Calc thermodynamic software, hybrid laser microscopy and electron probe microanalysis. The results showed that as the cooling rate increased from 10 to 100 °C/min, the percentage of δ-Fe involved in peritectic reaction decreased from 98.6% to 36.4%, the surface roughness of the sample decreased from 8.59 to 5.14 lm, and the volume shrinkage decreased from 5.92% to 2.18%. Moreover, the solidification path enters the crack sensitivity area at lower cooling rates (10 and 50 °C/min), while the solidification path is far from the crack susceptibility area at higher cooling rate (100 °C/min). With the increase in cooling rate, the segregation deviation parameters of the elements V, C, Mo and Cr were decreased by 9.52%, 22.2%, 29.4% and 70.5%, respectively. Solidification path changed and microsegregation weakened by adjusting cooling mode might be a way to improve central crack.

In response to the new mechanism of direct vortex melting reduction of vanadium-titanium magnetite, the reaction control mechanism and the migration regularity of valuable components in the process of direct melting reduction were inves-tigated using kinetic empirical equation by fitting and combining with X-ray diffraction, X-ray fluorescence, scanning electron microscopy, energy-dispersive spectrometry, and optical microscopy. The results show that iron reduction is controlled by the mass transfer process of (FeO_x) in the slag, while vanadium reduction is controlled by both the mass transfer of (VO_x) in the slag and the mass transfer of [V] in the molten iron, and the slag-metal interfacial reaction is the only pathway for vanadium reduction. The reduction of iron and vanadium is an obvious first-order reaction, with activation energy of 101.6051 and 197.416 kJ mol^-1, respectively. Increasing the vortex rate and reaction temperature is beneficial to improving the reaction rate and reduction efficiency. The mineral phase variation of iron and vanadium in the slag during the reduction process is Fe₂O₃→Fe₃O₄/FeV₂O₄→FeTiO₃ and FeV₂O₄→MgV₂O₅; titanium in slag is mainly in the form of Mg_xTi_3-xO₅ (0≤x≤1) and CaTiO₃. As the reaction time went on, the molar ratio (n_Ti/n_Mg)in MgxTi₃-xO₅ (0≤x≤1) and the Ti₂O₃ content in the slag gradually went up, while the area proportion of MgxTi₃-xO₅ (0≤x≤1) went up and then down, and the porosity of the slag and the grain size of MgxTi₃-xO₅ (0≤x≤1) got smaller.

The phase volume fraction has an important role in the match of the strength and plasticity of dual phase steel. The different bainite contents (18-53 vol.%) in polygonal ferrite and bainite (PF + B) dual phase steel were obtained by controlling the relaxation finish temperature during the rolling process. The effect of bainite volume fraction on the tensile deformability was systematically investigated via experiments and crystal plasticity finite element model (CPFEM) sim-ulation. The experimental results showed that the steel showed optimal strain hardenability and strength-plasticity matching when the bainite reached 35%. The 3D-CPFEM models with the same grain size and texture characters were established to clarify the influence of stress/strain distribution on PF + B dual phase steel with different bainite contents. The simulation results indicated that an appropriate increase in the bainite content (18%-35%) did not affect the interphase strain difference, but increased the stress distribution in both phases, as a result of enhancing the coordinated deformability of two phases and improving the strength-plasticity matching. When the bainite content increased to 53%, the stress/strain difference between the two phases was greatly increased, and plastic damage between the two phases was caused by the reduction of the coordinated deformability.

The permeability of the sintering process can be significantly improved by the pellet sintering, but the excessive permeability will impact the heat accumulation of the sinter bed. Thus, it is very essential to clarify the influence of the pellet particle size on the heat transfer process of sintering. Therefore, pilot-scale sinter pot tests of pellet sintering with manganese ore fines of different particle sizes were conducted, and traditional sintering was compared to reveal the heat transfer process of sintering and its impact on the microstructure of sintered ore. The results indicate that under suitable pellet sizes (8-12 mm), the heat transfer efficiency and the heat accumulation effect between the layers of sinter bed are strengthened by the pellet sintering, as well as the highest temperature in the combustion zone and the duration of hightemperature zone. This also leads to the further growth of ferrotephroite or hausmannite in liquid phase and its more reasonable crystal distribution. Ultimately, compared with the traditional sintering process, the total solid fuel consumption can be reduced by 20%-30%, and the productivity can be increased by 11.71%-16.21%.

The mechanism of strength and toughness variation in Ti microalloyed steel within the range of 0.04-0.157 wt.% was investigated. By adding 0.13 wt.% Ti, the steel achieves higher strength while maintaining a certain level of elongation and low-temperature impact toughness. With increasing Ti content, the grain size in the steel decreased from 17.7 to 8.9 lm. This decrease in grain size is accompanied by an increase in the percentage of low-angle grain boundaries and dislocations, which act as barriers to hinder crack propagation. The Ti microalloyed steel exhibits a 20% increase in yield strength and a 14% increase in tensile strength. The transformation of steel plasticity occurs when the Ti content exceeds 0.102 wt.%. The low-temperature impact toughness of the steel gradually decreases with increasing Ti content. At low Ti content, the low-temperature impact toughness is reduced due to crack initiation by large-size inclusions. At high Ti content, the low-temperature impact toughness of the steel deteriorates due to several factors. These include the narrower tough-brittle transition zone, grain boundary embrittlement caused by small-sized grains, and the decrease in the solid solution strengthening effect.

Microwave pre-oxidation and biomass reduction were adopted to enhance the separation of titanium and iron in vanadium-titanium magnetite. The effects of microwave pre-oxidation temperature and time, as well as biomass reduction temperature and time, were investigated. The results showed that the average particle size of vanadium-titanium magnetite decreased, and the specific surface area increased with the increase in pre-oxidation temperature and time. The reaction pathway (Fe_3-xTi_xO₄ → Fe_2-xTi_xO₃ → Fe₂TiO₅) was proved in microwave pre-oxidation process. The results of biomass reduction roasting showed that biomass reduction could effectively reduce ferric oxide to metallic iron while Ti was enriched in a solid solution of magnesium anosovite, which was beneficial to the subsequent grinding and acid leaching separation. The combined process of microwave pre-oxidation and biomass reduction achieved a high separation efficiency of titanium and iron in vanadium-titanium magnetite without forming complex titanium minerals. The titanium grade in the vanadium-titanium-rich material was 32.10%, and the recovery rate was 91.51%. The iron grade in the iron concentrate (metallic iron) was 90.90%, the recovery rate was 93.47%, and metallization rate was 93.87%.

The variations in the mechanical and magnetic properties of cold-rolled 20Mn23AlV non-magnetic structural steel after annealing at different temperatures were investigated. The microstructure and precipitation changes during annealing were studied by optical microscopy, scanning electron microscopy, and transmission electron microscopy. The results show that recrystallization completed after annealing at 620 ℃, resulting in grain sizes of approximately 800 nm and the best combination of strength and plasticity. The yield-to-tensile ratio of the non-magnetic structural steel after cold rolling continuously decreases from low to high temperatures after annealing, with the highest value being 0.89 and the lowest value being 0.43, indicating a wide range of yield-to-tensile ratio adjustment. The introduction of numerous dislocations during cold rolling provided favorable nucleation sites for precipitation, leading to abundant precipitation of the fine second-phase V(C, N). The phase composition of the samples remained unchanged as single-phase austenite after annealing, and the relative permeability values were calculated to be less than 1.002, meeting the requirements for nonmagnetic steel in terms of magnetic properties.

The effect of rare-earth cerium on impurity P-induced embrittlement for an advanced SA508Gr.4N reactor pressure vessels steel is investigated by virtue of microstructural characterization, Auger electron spectroscopy (AES), and spin-polarized density functional theory (DFT) calculations. The ductile-to-brittle transition temperatures (DBTTs) are evaluated by Charpy impact testing, and grain boundary segregation (GBS) of P is quantified by AES. Trace addition of Ce can effectively reduce GBS level of P, thereby substantially decreasing the embrittlement induced by P. A linear correlation between DBTT (℃) and GBS level of P (C_p, at.%) is observed for both undoped and Ce-doped samples, being expressed as DBTT=13.13C_p-335.70 (undoped) and DBTT=12.67C_p-350.78 (Ce-doped). In the absence of GBS of P, the incorporation of Ce appears to play a pivotal role in augmenting the intrinsic toughness. These results imply that the impact of Ce on impurity P-induced embrittlement may be attributed to a combination of increasing the intrinsic toughness and lowering GBS of P. DFT calculations indicate that there is a negligible interaction between Ce and P in the ternary alloy, and thus GBS of P and Ce is mainly site-competitive.

The mathematical model between laser cladding parameters and coating properties was established by the response surface method (RSM). Ni-WC-reinforced CoCrNiFeAl high-entropy alloy (HEA) composite coatings were prepared on the surface of 0Cr13Ni5Mo steel by laser cladding to study the addition of Ni-WC on slurry erosion resistance of coatings. The optimal parameters obtained by RSM are laser power of 1450 W, scanning speed of 4.3 mm/s, powder feeding speed of 1.3 r/min and overlap rate of 60%, respectively. The grains of CoCrNiFeAl composite coatings are refined by adding Ni-WC-reinforced powder. 15 wt.% Ni-WC composite coating presents the maximum microhardness with the value of 655 HV_0.3. The cumulative mass loss of the composite coatings at different erosion angles is lower than that of the pure CoCrNiFeAl coating. In addition, at low erosion angles, the cumulative mass loss of the composite coatings gradually decreases with the increase in the mass fraction of Ni-WC. Ploughing and microcutting are the primary erosion mechanisms of CoCrNiFeAl composite coatings at low erosion angles. When erosion damage occurs at high erosion angle, the erosion mechanisms of composite coating material loss are dominated by lip formation and craters. The proposed high-entropy alloy composite coatings can be applied to improve the erosion resistance of components in contact with high-speed fluids, such as ship propellers and centrifugal pump blades.

High-temperature confocal scanning laser microscopy (HT-CSLM) is a potent methodology for investigating various phenomena in the field of metallurgy. Initially applied to the observation of solid phase transformations and solidification, this method has gained traction in the field of non-metallic inclusion in steels in recent years. An overview of the experimental capabilities of HT-CSLM and the most important results of recent investigations regarding the topics of clean steel production are provided. It includes the formation of intragranular acicular ferrite (IAF) from the surface of nonmetallic inclusions during the continuous cooling and heat treatment, which can be especially beneficial in the toughness of heat-affected zones of welded pieces. Furthermore, the investigation of agglomeration mechanisms of non-metallic inclusions (NMIs) in liquid steel is discussed to improve the insight into attraction forces between particles and clogging phenomena during continuous casting. Also, the dissolution of NMIs in various steelmaking slags can be observed by HTCSLM to compare dissolution rates and mechanisms of NMI, where significant influences of temperature and chemical composition of the slag were shown. Last but not least, the experimental work regarding the interface between steel and slag is discussed, where novel techniques are currently being developed. A comprehensive summary of experimental techniques using HT-CSLM equipment to investigate different interactions of NMIs with steel and slag phases is compiled.

The failure analysis was conducted on unqualified torsion bar spring in automobile suspension system used for light vehicles during engine test. The effects of through hardening, surface induction hardening, quenching and tempering, and tempering temperature on the microstructure and fatigue life of 45CrNiMoVA steel torsion bars were also investigated. Results showed that only the torsion bar spring after through quenching and tempering is subjected to surface induction quenching and tempering to achieve the fatigue life of the qualified torsion bar. The fatigue life of torsion bar spring reaches 3×10⁵ cycles more than the required 2×10⁵ cycles. This is because the distribution of gradient microstructure was helpful to relieve the applied stress during the fatigue process. The microstructure of the non-hardened region, which consists of tempered sorbite regardless of whether it is tempered at 330 or 430 °C, contributes to minimizing the impact of temper brittleness on the fatigue life of the torsion bar. Consequently, the fatigue life of the torsion bar is relatively unaffected by temper brittleness due to the presence of tempered sorbite in its non-hardened regions. And the reason for the unqualified fatigue life was that the depth and hardness of the hardened region did not meet the standard requirements of 5-7 mm and 47-52 HRC, respectively.

The top-bottom combined blowing converter mainly adopts the blowing method of top-blowing oxygen and bottomblowing nitrogen. In the production process, there are some disadvantages, such as a significant temperature difference between the top and bottom of the molten pool, inadequate gas permeability of bottom blowing, and low decarburization efficiency. Therefore, we propose a novel bottom-blowing gas doped oxygen process to enhance the smelting conditions in the converter. The 500 kg medium frequency induction furnace with top and bottom-blowing function was used to explore the influence of the proportion of bottom-blowing gas doped oxygen on the smelting effect in different smelting cycles. Subsequently, industrial experimental verification was carried out on a 60 t converter. The results of intermediate frequency furnace experiments demonstrate that the bottom-blowing gas doped oxygen process exhibits a superior heating rate and decarburization efficiency during the initial and final stages of blowing compared to pure N₂ used for bottomblowing. Simultaneously, the dephosphorization efficiency exhibited an initial increase followed by a subsequent decrease as the bottom-blowing oxygen content increased. The industrial test of 60 t converter validates the findings above. Moreover, when the oxygen content in bottom-blowing gas is 5%, the average blowing time reduces by 54 s, and the minimum endpoint carbon-oxygen equilibrium reaches 0.00219 under this condition. The results demonstrate that the appropriate amount of oxygen doped in bottom-blowing gas can effectively enhance the metallurgical conditions of the converter and improve production efficiency.

An opposite combined vertical linear electromagnetic stirring (CV-LEMS) was proposed, which is applied in the final solidification zone of bloom continuous casting. The melt flow, heat transfer, and solidification under CV-LEMS were investigated by establishing a three-dimensional numerical simulation model and a pilot continuous casting simulation experiment and compared with the conventional rotary electromagnetic stirring (REMS). The results show that a longitudinally symmetric linear magnetic field is formed in the liquid core of the bloom by applying CV-LEMS, which induces a strong longitudinal circulation flow both on the inner arc side and the outer arc side in the liquid core of the bloom. The height of the melt longitudinal effective mixing range under CV-LEMS reaches 0.9 m, which is greater than that of the REMS and makes up for the deficiency of REMS sensitivity to the position of the final solidification zone. CV-LEMS strongly promotes the mixing of upper melt with high temperature and the lower part melt with low temperature in the liquid core, improves the uniformity of melt temperature distribution and significantly increases the melt temperature near the solidification front, and the width of the liquid core increases by 4.2 mm at maximum. This shows that the appliction of CV-LEMS is more helpful to strengthen the feeding effect of the upper melt to the solidification shrinkage of the lower melt than the conventional REMS and inhibits the formation of porosity, shrinkage cavity and crack defects in the center of the bloom.

The free-surface vortex is a rotational flow phenomenon characterized by two-phase coupling, formed by the rupture of surface fluid in the final stage of discharge. It is a significant concept with broad applications in engineering fields like metallurgy and hydraulics. The basic concepts and characteristics of free-surface vortices were introduced, and their hazards in various fields were discussed. The development of theoretical and numerical models over recent decades was reviewed, and the factors affecting vortex formation and existing suppression methods were outlined. Finally, the key challenges and focus areas on the study of free-surface vortex were summarized. With the ongoing advancements in computational fluid dynamics and experimental technology, research on free-surface vortices will become more in depth and precise. Additionally, interdisciplinary cooperation and technological innovation are expected to achieve precise control and optimal design of free-surface vortices, offering more efficient and sustainable solutions for metallurgy and related engineering fields.

The use of an alternative magnetic field during vacuum arc remelting (VAR) can have significant effects on the primary carbide and mechanical properties of M50-bearing steel. The solidification structure and the primary carbide morphology of the VAR ingot were analyzed by optical microscopy and scanning electron microscopy. Characterization and analysis of the growth direction of primary carbides were conducted using high-resolution rapid electron backscatter diffraction. Solute elements segregation was analyzed using an electron probe microanalyzer. FLUENT was utilized to conduct numerical simulations to validate the experimental findings and elucidate the underlying mechanism. Compared to tra-ditional VAR, magnetic-controlled VAR generates a horizontal circulation, which makes a shallower and flatter molten pool and a more even temperature distribution. In the time dimension, the local solidification time is shortened, and the concentration of solute elements will be alleviated. In the spatial dimension, the secondary dendrite arm spacing decreases, alleviating the degree of inter-dendritic segregation. Consequently, the possibility of forming a segregation diminishes. Both aspects promote the even distribution of solute atoms, resulting in less segregation and hindering the development of primary carbide. This leads to the refinement of primary carbide size and its uniform distribution. The magnetic-controlled vacuum arc melting not only refines the dendritic structure in the M50 ingot, causing it to expand more axially along the ingot, but also refines primary carbides and improves tensile and wear-resistant mechanical properties.

Utilizing ultrafine iron ore concentrate for pellet production can expand domestic iron ore resources in China and promote the utilization of low-grade ores. However, a challenge arises with the low decrepitation temperature and reducibility in the preparation process of ultrafine iron ore concentrate pellets. To address the challenge, a novel approach was proposed, which incorporated straw powder as an additive to enhance pellet porosity, thereby improving the decrepitation temperature and reducibility of ultrafine iron ore concentrate pellets. The effect of varying proportions of straw powder (0.0-2.0%) on the characteristics of ultrafine iron ore concentrate pellets was examined. Results indicate that at a 2.0% straw powder ratio, pellet decrepitation temperature notably rises from 380 to 540 °C, while the reducibility index escalates from 25.7% to 48.1%. Nevertheless, the addition of straw powder results in diminished drop strength, compressive strength of green pellets, and cold crushing strength of fired pellets. In addition, enhanced pellet reducibility leads to exacerbated reduction swelling index and reduction degradation index. Despite these effects, all parameters remain within an acceptable range.

The high-temperature dissolution behavior of primary carbides in samples taken from GCr15 continuous-casting bloom was observed in-situ by confocal laser scanning microscopy. Equations were fitted to the dissolution kinetics of primary carbides during either heating or soaking. Dissolution of carbides proceeded in three stages (fast → slow → faster) as either temperature or holding time was increased. During the heating process and during the first and third stages of the soaking process, the original size of the carbides determined the steepness of the slope, but during the middle (“slow”) stage of the soaking process, the slope remained zero. The initial size of the carbides varied greatly, but their final dissolution temperature fell within the narrow range of 1210-1235 °C, and the holding time remained within 50 min. Fractal analysis was used to study the morphological characteristics of small and medium-sized carbides during the dissolution process. According to changes in the fractal dimension before and after soaking, the carbides tended to evolve towards a more regular morphology.

The hardenability of steel is crucial for its durability and performance in engineering applications, significantly infiuencing mechanical properties such as hardness, strength, and wear resistance. As the engineering field continuously demands higher-performance steel materials, a deep understanding of the key infiuencing factors on hardenability is crucial for developing quality steel that meets stringent application requirements. The effects of some specific elements, including carbon (C), vanadium (V), molybdenum (Mo), and boron (B), as well as heat treatment process parameters such as austenitizing temperature, austenitizing holding time, and cooling rate, were examined. It aims to elucidate the interactions among these factors and their infiuence on steel hardenability. For each infiuencing factor, the heat treatment procedure, characteristic microstructure resulting from it, and corresponding Jominy end quench curves were discussed. Furthermore, based on the continuous development of big data technology in the field of materials, the use of machine learning to predict the hardenability of steel and guide the design of steel material was also introduced.

Herein, the effect of direct current (DC) attached the mold on refining the microstructure and alleviating the central segregation of a tin-bismuth (Sn-10 wt.% Bi) alloy ingot during the solidification process has been investigated. The experiment used a self-made device, which can achieve the effect of refining the solidified structure and alleviate the segregation of the metal casting. Numerical simulations were performed to calculate the Lorentz force, Joule heating and induced melt vortex flow for the magneto-hydrodynamic case. Our results show that the maximum velocity of the global electro-vortex reached 0.017 m s^-1. The DC-induced electro-vortex was found to be the primary reason of refining the equiaxed grain and alleviating the segregation of the b-Sn crystal boundary. The grain refining effect observed in these experiments can be solely attributed to the forced melt flow driven by the Lorentz force. DC field attached the mold can lead to grain refinement and alleviate the segregation of the ingot via a global vortex. The technology can be applied not only to opened molds, but also toward improving the quality in closed molds.

A low-carbon, low-cost, and high-efficient method was reported for remarkably improving corrosion resistance of C-Mn structural steel by weak deoxidation. The results showed that, with the total oxygen content (w_OT) increasing in the tested steel from 41 9 10^-6 to 195 9 10^-6, both the degree of element segregation and the level of banded microstructure weakened, presenting the lower potential difference between pearlite (P) and ferrite (F), and then smaller galvanic corrosion driving force, and thus effectively improving general corrosion properties. In addition, with w_OT growing up, the number and size of inclusions increased, and the shape also changed from long chain or small particle to large particle ball with typical mosaic structure, which could effectively inhibit the preferential dissolution of local component due to multiple complex interfaces, and correspondingly suppress the pitting susceptibility. However, the impact toughness at low temperature of the tested steel reduced with w_OT increasing, and then, taking the mechanical properties and corrosion resistance all into account, 160 9 10^-6 was the optimal oxygen content within the present scope.

Understanding the motion behaviors of non-metallic inclusions in the liquid metal is important for clean steel production. High-temperature confocal laser scanning microscopy is applied to investigate the effect of different Ti and Al contents on the agglomeration behavior of non-metallic inclusions in low carbon steels. Furthermore, the agglomeration mechanism of inclusions was investigated through quantitative analysis of in-situ observation experiments and a modified Kralchevsky- Paunov model. The obtained results indicate that Al₂O₃ is the main type inclusion in the low-alloys steels with both Al and Ti addition. This type of inclusion is more likely to absorb surrounding small-size inclusion particles, leading to a further growth for the cluster formation and contributing to a serious engineering problem, nozzle clogging. Besides, TiO_x is the main type inclusion in the molten steel with only Ti addition, and this type of inclusion is less likely to agglomerate and the individual inclusion particles show a ‘free’ motion with the fluid of molten steel. The difference between these two types of inclusions is due to the difference in attractive force and action distance at the meniscus created by the inclusion/steel/Ar multiple interfaces and influenced by the physical parameters, e.g., contact angle and interface energy between inclusion and steel, and surface tension of the melt.