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The fluid flow and slag entrainment in a slab continuous casting mold were investigated by establishing a full-scale water model. Meanwhile, the heat transfer and solidification process of liquid steel in the mold were studied through numerical simulation. The effect of two different submerged entry nozzles (SENs) was compared and analyzed, named as original SEN and L1 SEN, respectively. The results indicate that the structure of the SEN has a significant influence on the fluid flow pattern and solidification process in the slab mold. For the original SEN, the liquid level in the mold fluctuated obviously and the slag phase was easily entrained into the mold. The percentage of ±3mm level fluctuation was 57.2-74.3%. By enlarging the exit size, the L1 SEN considerably reduced the jet velocity at the nozzle exit and subsequently decreased the surface velocity at the top surface. The level fluctuation and slag entrainment in the mold have been effectively controlled. The percentage of ±3mm level fluctuation was increased to 91.7-98.6%. Furthermore, under the condition of L1 SEN, the thickness of the solidifying shell at the mold outlet was increased from 13.5 mm to 16.4 mm, which was beneficial to decrease the risk of breakouts and quality problems.

When analyzing the strip coiling process, the finite element (FE) method is closer to the actual working conditions compared to the analytical method. However, due to the large number of strip elements and contact elements, it often leads to problems such as long-time consumption and non-convergence. Meanwhile, traditional FE methods are still unable to solve the problem of additional contact deformation between layers. Therefore, in order to overcome the shortcomings of the above methods, the FE software MSC Marc is used to establish a strip coiling model. The distribution pattern of interlayer friction and contact stress are analyzed to propose a new step-by-step bonding FE model, which greatly reduces the computing time. Through laminated compression experiments, the variation curve between additional contact deformation and pressure is obtained. The curve is introduced into the gasket elements to consider the additional contact deformation between the layers, and the effect of additional contact deformation between the layers on the stress of the coil and the pressure on the mandrel is studied. Finally, the analytical solution is compared with the FE solution proposed in this paper, and the errors generated by the analytical method are analyzed.

The effect of rare earth on the solidification structure of 3.2%Si-0.9%Al non-oriented silicon steel was investigated using industrial trials. The outputs demonstrated that increasing rare earth content leads to a decrease in the average size of equiaxed crystals in the casting billets. In order to further understand the rare earth on the grain refinement of δ-ferrite, the conventional inclusion detection technology, was used to investigate the distribution characteristics of inclusions, together with theoretical calculation of the equilibrium partition coefficients, pinning forces and mismatch degrees. The detection results of inclusions and the calculation results of pinning force showed that the effect of rare earth on the pinning force of inclusions was marginal. Thermodynamic calculation indicated that Ce addition had negligible effect on the equilibrium partition coefficient of Si, Al and Mn. Combined with the calculation results of GRF model, it is reasonable to consider that the contribution of rare earth element to the refinement of equiaxed crystals can be ignored. Further, the outcomes obtained from the E2EM model calculations revealed that the principal mechanism responsible for the refinement of equiaxed crystals through rare earth treatment can be attributed to the heterogeneous nucleation effect of (La, Ce)₂O₂S.

The low-cost production of high-purity metallic iron is of great practical importance. Herein, we report the direct production of high-purity metallic iron (99.92 %) via a one-step electrochemical strategy in molten CaCl₂-CaO-Fe₂O₃ system at 850 ^oC. The involved CaO-assisted dissolution of Fe₂O₃ and electrodeposition mechanism were systematically studied, and the obtained iron products were characterized using scanning electron microscopy, inductively-coupled high-frequency plasma emission spectrometry, and glow discharge mass spectrometry. The results show that the crystalline iron products with tunable morphologies can be obtained in a controlled manner. The electrolysis parameters (voltage, current density, electrodeposition time and substrate material) have significant effects on the electrodeposition process and the characteristics of iron products. In particular, high-purity dense iron film can be directly electrodeposited at 15 mA∙cm^-2, and its thickness increases considerably with increasing electrodeposition time. Furthermore, the as-deposited iron product can also be processed into bulk iron materials with high-purity of 99.995 wt.% by plasma melting for the potential applications. In general, this one-step electrodeposition process provides an acid-/alkaline-free strategy for the facile production of high-purity iron materials direct from Fe₂O₃.

The effect of iron carbon agglomerates (ICA) on the reduction of sinter is very important to blast furnace (BF) ironmaking. In this paper, the isothermal reduction kinetics of ICA-sinters mixture and the coupling synergistic mechanism between ICA and sinter are comprehensively studied. The results show that the early stage of isothermal reduction of ICA-sinters mixture is jointly controlled by the interfacial chemical reactions of FeO being reduced to Fe in sinter and gasification reaction in ICA, and the later stage is controlled by the internal diffusion. As the reactivity of ICA improves from 52.81% to 69.71%, the isothermal reduction reaction activation energy of ICA-sinters mixture decreases from 84.22 to 72.58 kJ/mol in early stage and decreases from 110.78 to 97.41 kJ/mol in late stage. Meanwhile, the activation energy of isothermal reduction reaction for the mixture of ICA and sinter with a higher reducibility is lower. There is a coupling synergistic effect between ICA and sinters, and ICA plays a continuous role in circulating CO and transferring oxygen during the reduction of sinter, which can significantly promote the reduction of iron oxides in sinter. The synergistic effect gradually increases with the improvement of the reactivity of ICA and the reducibility of sinter.

A novel integrated constitutive equation of the flow curve for Ti–6Al–4V alloys is proposed by incorporating the effects of phase fraction in the hot-forging temperature range. The flow curve was obtained using hot-compression tests in the temperature range of 750–1050 °C and strain rate range of 1–25 s^-1. The effects of friction and deformation heat generated during compression were corrected using the inverse analysis method to identify the ideal uniaxial flow curve. The obtained stress parameters were satisfactorily regressed using the rule of mixtures on the α and β phases considering changes in the phase fraction. The integrated flow curve equation incorporating the rule of mixtures of the two phases effectively expressed the flow curve throughout the investigated temperature range. The internal microstructural observation showed that the continuous dynamic recrystallization of the α phase is dominant in the α+β two-phase region, while the deformation of the β phase becomes dominant just below the β transus. The constitutive equation presented here is in good agreement with the temperature dependence of the microstructure.

The key to a better understanding of phosphorus removal from hot metal is to know the thermochemical properties of solid solution between Ca₂SiO₄ and Ca₃P₂O₈. Although the solid solutions would inevitably incorporate iron oxide in steelmaking slags, there is a still lack of knowledge about the solid solutions containing iron oxide. The present study focused on the effect of FeO dissolution on the activities of components in the Ca₂SiO₄-Ca₃P₂O₈ solid solution. The P₂O₅ activities were measured in the solid solution containing FeO at 1573 K. Subsequently, the activities of Ca₂SiO₄, Ca₃P₂O₈, and Fe₂SiO₄ were derived from the Gibbs-Duhem equation with the measured P₂O₅ activities and reported FeO activities. When iron oxide dissolved into the Ca₂SiO₄-Ca₃P₂O₈ solid solution, the Ca₃P₂O₈ activity decreased, while the Ca₂SiO₄ activity was insensitive. As a result, the dissolution of iron oxide into the solid solution caused a drastic decrease in the P₂O₅ activity.

Martensitic steels of Fe-0.1%C-2%Mn-1.6%Mo and Fe-0.1%C-2%Mn-0.2%V alloys were subjected to tempering at 873 K to investigate the hydrogen trapping of Mo and V carbides. We analyzed the alloy carbides in detail via atomic-resolution scanning transmission electron microscopy and atom probe tomography, and evaluated hydrogen trapping energy via ab initio calculations. The hydrogen content of the Mo-added steel tempered for 1.8 ks increased from that of the quenched Mo-added steel, and the hydrogen content monotonically decreased as the tempering time increased. The hydrogen content of the V-added steels increased during tempering up to 7.2 ks and then remained almost constant. A plate-shaped B1-type Mo carbide with a chemical composition of MoC_0.50 precipitated in the Mo-added steel tempered for 3.6 ks. Needle-shaped HCP Mo₂C precipitated and the B1-type Mo carbide decreased in the Mo-added steel tempered for 14.4 ks. A plate-shaped B1-type V carbide with a chemical composition of VC_0.75 precipitated in the V-added steel tempered for 14.4 ks. We found a positive correlation between the hydrogen content and the product of the interface area and the carbon vacancy fraction of the B1-type alloy carbide. The hydrogen trapping energy of the carbon vacancy at the interface between BCC-Fe and the B1-type Mo carbide was higher than that of the interstitial sites in BCC-Fe. These results suggest that the main trapping site in the tempered Mo-added steel was the carbon vacancy at the interface of B1-type MoC_0.50, not HCP Mo₂C.

The residual stresses at a circular punched end face in tempered martensitic high-strength steel sheets were investigated using triaxial stress analysis via X-ray diffraction. The maximum principal stress and its direction were calculated from the measured nine stress components. The relationship between the directions of the maximum principal stress and hydrogen cracks was verified by generating hydrogen cracks on the punched end face in the same specimen using cathodic hydrogen charging. The direction of the cracks was perpendicular to that of the maximum principal stress. This result indicates that hydrogen embrittlement at the sheared end face is caused by the maximum principal stress. Moreover, the distribution of the residual stresses toward the thickness direction and the relationship between residual stresses and tensile strength of the specimens were investigated. The maximum principal stress on the punch side was lower than that on the dice side. Unlike the maximum principal stresses, the normal stresses did not increase monotonically with the tensile strength of the specimens. Therefore, it was concluded that investigating the maximum principal stress at any area between the dice side and a line located midway from the end face and dice side is crucial for considering the hydrogen embrittlement criteria.

The hydrogen diffusion behavior in a tempered martensitic steel sheet with 1-GPa grade tensile strength was investigated using a newly developed hydrogen visualization technique with an Ir complex, whose color changes from yellow to orange due to its reaction with hydrogen. Hydrogen permeation through the steel sheet could be monitored via the color change of the Ir complex. Furthermore, the breakthrough time of hydrogen through the specimen could be qualitatively evaluated based on changes in the brightness of the Ir complex. Additionally, this hydrogen visualization technique was applied to a stretch-formed steel sheet using a hemispherical punch to simulate the press-forming of automotive structural components. The hydrogen breakthrough time around the top of the specimen increased and then decreased as the distance from the top increased. Based on the plastic strain distribution of the specimen calculated using the finite element method, the hydrogen breakthrough time increased with the plastic strain. The introduction of plastic strain decreased the hydrogen diffusion coefficient due to the introduction of dislocations acting as hydrogen trap sites, thus increasing the hydrogen breakthrough time.