This study investigates the oxidation behavior of MgO–C refractories containing a combined antioxidant system of Al (2 wt%) and B₄C (0–4 wt%). Oxidation tests were conducted under air conditions at 1200°C, 1300°C, and 1400°C for 60 and 180 minutes. As the temperature was increased from 1200°C to 1400°C, the non-oxidized area increased by 1.4, 3.3, and 14.1 times, respectively. The weight loss ratio decreased with the B₄C content and the temperature. Above 3 wt% of added B₄C, the weight loss ratio remained the same. At 1200°C, the weight loss ratio decreased from 14.2% to 9.9% as the addition of B₄C was increased to 3 wt%. At 1300°C, the weight loss ratio decreased from 14.8% to 6.7%. At 1400°C, the weight loss ratio decreased from 16.0% to 1.88%. These findings demonstrate that the effect is significant as the temperature increases. After the experiments, an XRD analysis confirmed the formation of Al₂O₃, B₂O₃, Mg₂B₂O₅, Mg₃B₂O₆, and MgAl₂O₄. Thermodynamics analysis indicates that Mg₃B₂O₆ melts at 1400°C, enabling effective pore sealing. At 1300°C, however, the combined reaction between Al₂O₃ and magnesium borates generates low-melting phase that provides a remarkably strong antioxidation effect even at this lower temperature, making 1300°C the critical point where the Al–B₄C system becomes highly effective. However, at 1200°C, only B₂O₃ is present as a liquid and subsequently forms solid magnesium borates with MgO, offering only a limited improvement in oxidation resistance.

COREX shaft furnace adopts screws and corresponding guiding flow insert for burden discharge. To understand and then control burden flow in the furnace, it is essential to study the influence of discharge conditions and other factors on granular flow. Common CFD method cannot predict the orientation and size of stagnant zone formed by discharge in lower part of the furnace and thus is not easy to reasonably examine the effect of distribution of discharge conditions. Although the influence of discharge conditions could be studied by DEM, numerical studies of COREX shaft furnace by the method had obvious deviations in predicting descent velocity and resident time of burden in the furnace due to limitation of computational cost. In this paper, appropriate boundary conditions were used to describe lower screw discharger and guiding flow insert in moving bed, and a new CFD method based on novel potential flow model was used to numerically study 3D granular flow field including stagnant zone in a physical simulation bed of COREX shaft furnace. With the movement times of granular materials in bed reasonably predicted, the influences of not only screw discharger and guiding flow insert but also shaft angle of furnace on granular flow were investigated by the method in detail. Present work may provide a more reliable numerical basis for studying and then controlling burden flow in COREX shaft furnace.

The utilization of bauxite residue (BR) was experimentally studied through hydrogen reduction, focusing on iron oxide reduction and the formation of leachable alumina phases. Three different types of pellets were made: one from bauxite residue, and the other two via calcite addition with varying calcite amounts. All pellets were isothermally reduced by H₂ gas in a thermogravimetry furnace at constant temperature under fixed hydrogen flow rate and reduction times. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) coupled with Energy dispersive spectroscopy (EDS), were used for the phase and microstructural analysis. The hydrogen reduction rate is influenced by iron-bearing oxides formed during heating. Bauxite residue pellets exhibit a higher initial reduction rate than bauxite residue–calcite pellets as brownmillerite formation occurs in the latter one, which hinders iron oxide phase reducibility. The reduction kinetics are affected by the reduction temperature and calcite quantity added, while dominant phase formation during hydrogen reduction depends on their combined effect. There is no mayenite (Ca₁₂Al₁₄O₃₃) phase formation in reduced BR pellets, while with the addition of calcite, small amount of mayenite phase starts to appear during reduction, which increases with more calcite addition.

This research aimed to investigate the influence of Fe-based addition on the solution-loss kinetics of coke in hydrogen-enriched blast furnace. The solution-loss reactions of base coke (BC) and Fe-based coke (BC+Fe) in the CO₂ + 20%H₂O atmosphere across the temperature 1000–1200°C were carried out by a homemade coke reactivity measurement device with continuous water inflow. The kinetics of the Boudouard reaction (C + CO₂ = 2CO) and the water-gas reaction (C + H₂O = CO + H₂) were assessed by monitoring the outlet gas composition (CO and H₂) to quantitatively evaluate the catalytic influence of Fe₂O₃ on the solution-loss reaction. The results indicate that the solution-loss rates of BC+Fe coke are more those of BC coke, and the solution-loss ratios of BC+Fe coke are 10.5–26.8% for the Boudouard reaction and 12.1–42.2% for the water-gas reaction higher than those of BC coke. Furthermore, Fe₂O₃ lowers the apparent activation energy (E_a) of the Boudouard reaction by 4.2% and that of the water-gas reaction by 7.8%, which shows that the catalytic effect of Fe₂O₃ is stronger for the water-gas reaction than for the Boudouard reaction. SEM analysis shows that the BC+Fe coke has a more varied pore structure and wider range of pore sizes on the surface. XRD analysis indicates that Fe₂O₃ reacts with Si and Al species in the minerals to form Fe-based silicates and aluminosilicates, which could contribute to the catalytic effect of the coke solution-loss reaction.

To clarify the sticking mechanism and discuss its suppression during hydrogen reduction in the fluidized bed, in-situ observation of the reduction behavior of wüstite using high-temperature microscope and the reduction experiment were carried out under various conditions such as gas composition, temperature, and total pressure.

First, hydrogen reduction leads to the formation of porous structure of wüstite phase. Then, reduction to metallic iron proceeds concentrically, and porous iron forms. A part of metallic iron nuclei grows vertically to the wüstite surface, and iron whisker forms under specific conditions. Under atmospheric pressure conditions, higher temperature and higher hydrogen partial pressure make the surface porous, and iron whisker forms through 100%H₂ reduction at 900°C and 950°C. Increasing total pressure enlarges the formation area of iron whiskers to lower temperature. Furthermore, three-step fluidized bed reduction process was suggested to control the sticking phenomenon of raw materials.

This study has analyzed the growth and removal mechanisms of Al₂O₃, MgO, MgAl₂O₄, ZrO₂, SiO₂, and Ti₃O₅ inclusions in molten steel formed through the addition of various deoxidizing elements by dividing them into single inclusions and cluster inclusions resulting from the agglomeration of these inclusions with a focus on kinetics. Additionally, we have evaluated the maximum particle diameter of cluster inclusions from both thermodynamic and agglomeration force perspectives to examine the agglomeration properties and mechanisms of various inclusions. The growth mechanism of various single inclusions, measuring several micrometers in diameter and suspended in molten steel, is governed by Ostwald ripening with collision agglomeration due to Brownian motion and turbulent stirring. Contrarily, cluster inclusions with diameters of 10 µm or more float in molten steel agglomerate with suspended single inclusions. Depending on the inclusion type, they also agglomerate with other clusters along their floating paths, growing larger and undergoing floating separation. Furthermore, the agglomeration strengths of various inclusions in molten steel follows the order MgO < Ti₃O₅, SiO₂ < MgAl₂O₄ < ZrO₂ < Al₂O₃. The kinetic mechanism of agglomeration growth is explained in a unified manner by the interparticle interactions of agglomeration force driven by cavity bridge forces.

A non-oriented Fe-0.7% Si steel as-cast strip was produced by an industrial twin-roll strip casting production line. The evolution of the microstructure, texture, and properties was characterized along the entire processing route. The microstructure of each cross-section of the industrial cast strip was found to be uniform, with low texture strength and random orientation distribution. After cold rolling, a mixed microstructure formed, consisting of deformation structures and shear bands alternating in the thickness direction. The texture exhibited a mixed texture combining α-fiber texture (<110>//RD) and γ-fiber texture (<111>//ND). During the 850°C annealing process, recrystallized grains nucleated preferentially in shear bands, and α texture and Goss texture began to form. The final annealed sheet texture was composed of Goss texture and γ-fiber texture, with favorable textures constituting the major part. The final sheets exhibited excellent magnetic properties: P_1.5/50 = 4.915 W/kg, B₅₀ = 1.856 T in RD direction, and P_1.5/50 = 5.347 W/kg, B₅₀ = 1.765 T in TD direction. Its average yield strength was approximately 278.77 MPa, and the average tensile strength was approximately 505.47 MPa. After aging at 300°C for 10 hours, only a few precipitates formed in the final sheets, and their magnetic properties remained highly stable with little to no change.

This work deals with the development of new Compacted Graphite Cast Iron Composite Castings as an alternative to Si–Mo ductile iron. The new material is a silicon-molybdenum cast iron (Si–Mo), transformed into a cast composite using the Self-propagating High-temperature Synthesis in Bath (SHSB) method, which synthesizes ceramic carbide particles of metals such as Ti, W, Nb, Mo, Zr. SHSB is used to ensure the formation of thermodynamically stable ceramic phases, in this case, carbide phases. Among the listed metals, titanium was selected for the SHSB synthesis process due to the exceptionally favorable physicochemical properties of titanium carbide and its highly exothermic enthalpy of formation. The described process strengthens the matrix of the material, changing its characteristic operational properties. The resulting composite is designated as Si–Mo TiC. Conventional Si–Mo cast iron is widely applied in the automotive industry, where it is used, for instance, in the production of exhaust manifolds and turbocharger components, where high resistance to thermal shock and excellent heat resistance are required. Transforming this material into a composite material improves many physicochemical parameters. Additionally, titanium desferoidizing effect helps stabilize graphite in the compacted (vermicular) form. Castings of both conventional Si–Mo iron and the TiC-reinforced Si–Mo composite with compacted graphite were produced with varying wall thicknesses. The microstructural characteristics and thermophysical properties, such as thermal conductivity and thermal stability, of the classical and composite materials were compared. The new Si–Mo cast iron reinforced with thermally stable TiC particles has been demonstrated to exhibit excellent structural integrity and thermal stability.

Low ductility is the intrinsic cause of cracking in slab, and cooling rate is a key factor affecting the hot ductility of steel. This article focuses on low carbon V–N steel, and explores the growth characteristics of carbonitride precipitation and microstructure at different cooling rates through thermal simulation tensile experiments. The results show that increasing the cooling rate can improve the ductility in the third brittle zone. The cooling rate increases from 0.5°C/s to 7°C/s, the minimum of the reduction of area increases from 38.1% to 38.9%, 39.8%, 44.9%, and 48.4%, and the third brittle temperature zone shrinks from 725–860°C to 725–820°C. Increasing the cooling rate has little effect on austenite grain size, but it will significantly reduce the proeutectoid ferrite formed at austenite grain boundary. With the cooling rate increasing, due to the accelerated transition from austenite to ferrite, the average thickness of the proeutectoid ferrite film decreases from 38 µm to 4 µm, and no proeutectoid ferrite is formed at some grain boundaries. The cooling rate ≤ 5°C/s, the carbonitrides are distributed in a chain like manner at austenite grain boundary, and the size is large. However, when the cooling rate is ≥5°C/s, the time for the microstructure to remain in the austenite temperature zone and the high fluidity of the γ/α interface cause some carbonitrides to precipitate in the ferrite matrix, with small and uniform distributions in the original austenite grains.

In this research, to clarify the void closure behavior of large-scale voids elongated in the normal direction, artificial void was introduced to steel plate and hot rolling experiments were conducted at 1000°C. The void height was systematically changed to investigate the influence on the closure behavior. The closure process was compared with a predicting criterion called Q value. The results show that the closure behavior varies significantly with the increasing of height, the dominant closing direction shifts from the normal direction to the transverse direction, and the critical Q value criterion was not applicable for all cases. To discuss the applicability of the Q value, a representative volume element was built, and finite element analysis under systematically controlled stress state was conducted. The Q value criterion under different stress states has been established.

This study investigates the enhancement of surface properties of OPTI N+ high-nitrogen stainless steel through a duplex treatment combining ion nitriding and CrSiN coating deposition via DC magnetron sputtering. Ion nitriding produced a hardened layer approximately 50 µm thick with a surface hardness of 1037.1 HV_0.05, primarily composed of Fe₂N, Fe₃N and Fe₄N phases. CrSiN coatings deposited at various temperatures showed that the sample coated at 300°C exhibited the highest hardness (13.07 GPa), optimal H/E ratio (0.055), and superior tribological performance, including the lowest friction coefficient (0.5773), wear loss volume (7.67×10⁻⁴ mm³), and specific wear rate (3.23×10⁻⁷ mm³·m⁻¹·N⁻¹) under a 5N load. Electrochemical tests confirmed enhanced corrosion resistance, with the lowest corrosion current density (1.38 × 10⁻⁶ A·cm⁻²) and highest polarization resistance (339.98 Ω·cm²). HRTEM analysis revealed a nanocomposite microstructure consisting of crystalline CrN and amorphous SiN. These results demonstrate that the CrSiN/ion nitriding duplex treatment significantly improves the mechanical, tribological, and corrosion resistance of high-nitrogen stainless steel.

Material applied in low-temperature liquefied gas storage tanks is required to have sufficient toughness. In recent years, high Mn austenitic steel has attracted attention for use in this application. In this study, the basic deformation characteristics and toughness of high Mn steel containing about 25% Mn were compared with those of 9% Ni steel in order to investigate the applicability of high Mn steel to LNG tanks. The high Mn steel showed larger uniform elongation than the 9% Ni steel due to higher strain-hardening, but elongation after the maximum load was significantly smaller. The plastic flow stress of the high Mn steel increased with decreasing temperature and showed temperature dependence similar to that of 0.2% proof stress in the 9% Ni steel. The Charpy absorbed energy of the high Mn steel was about half that of the 9% Ni steel, with an average value of 86 J at 77 K. Cleavage fracture surfaces were not observed in the fracture surfaces obtained at any temperature, indicating the micro-void coalescence type of fracture. The characteristics of ductile damage in the high Mn steel were discussed based on observation of micro-voids.

Planar slips have been frequently recognized in nitrogen-added austenitic stainless steels, and often discussed in terms of stacking-fault energy (SFE). On the other hand, nitrogen addition promotes the formation of N–Cr short-range order (SRO), which has been proposed to cause the planar slips. In this study, a chromium-free Fe–N binary austenite with 2.4 mass% of fully solid-solutioned N was fabricated to simplify the relationship among deformation structures, SFE and N–Cr SRO. The Fe–N alloy was found to exhibit wavy slips and possess almost the same SFE as a nitrogen-added austenitic stainless steel with planar slips. TEM results indicate the formation of modulated structures along <001> in the nitrogen-added austenitic stainless steels, which should be attributed to the presence of N–Cr SRO, as reported previously in the literature. These results indicate that the planar slips are primarily caused by N–Cr SRO rather than by SFE.

Steelmaking slag contains valuable components. Its high phosphorus content hinders its reutilization in the steelmaking process. This study proposes an efficient phosphate removal process using molten CaCl₂ as the reaction medium, aiming to enable slag recycling and P recovery. Experimental results show that nearly all P-bearing phases in steelmaking slag are leached into molten CaCl₂ under the tested conditions (850 to 1000°C, slag/CaCl₂ mass ratios 1:10 to 1:2.5). The leaching mechanism involves the reaction of slag’s P-bearing phases with CaCl₂ to form intermediates (Ca₂PO₄Cl and Ca₃SiO₄Cl₂), which dissociate into PO₄^3– and other ions in the melt. For other elements: Si(IV) leaches continuously but incompletely; Fe(II) and Mn(II) concentrations in the melt first increase then decrease, attributed to the evaporation of volatile FeCl₂ and MnCl₂; Mg and Al remain nearly unleachable. After leaching, adding carbon to the P-enriched melt achieves complete P(V) removal via carbothermal reduction. This molten CaCl₂-based approach provides a sustainable alternative to conventional technologies, offering valuable insights for the comprehensive utilization of P-bearing solid wastes.