Journal of Iron and Steel Research International最新文献

The production of ferroalloys is a resource-intensive and energy-consuming process. To mitigate its adverse environmental effects, steel companies should implement a range of measures aiming at enhancing the utilization rate of ferroalloys. Therefore, a comprehensive ferroalloy model was proposed, incorporating a prediction model for alloying element yield based on case-based reasoning and support vector machine (CBR–SVM), along with a ferroalloy batching model employing an integral linear programming algorithm. In simulation calculations, the prediction model exhibited exceptional predictive performance, with a hit rate of 96.05% within 5%. The linear programming ingredient model proved effective in reducing costs by 20.7%, which was achieved through accurate adjustments to the types and quantities of ferroalloys. The proposed method and system were successfully implemented in the actual production environment of a specific steel plant, operating seamlessly for six months. This implementation has notably increased the product quality of the enterprise, with the control rate of high-quality products increasing from 46% to 79%, effectively diminishing the consumption and expenses associated with ferroalloys. The reduced usage of ferroalloys simultaneously reduces energy consumption and mitigates the adverse environmental impact of the steel industry.

The effect of Zr on the microstructure and mechanical properties of 304 stainless steel joints brazed with Ag–Cu fillers was studied. The incorporation of Zr had little effect on the solid–liquid phase line of the fillers, and the melting temperature range of the fillers was narrowed, which enhanced their fluidity and wettability. The presence of Zr in the form of heterogeneous particles augmented the nucleation rate during solidification, transforming the intermittently distributed gray-black coarse dendrites into cellular crystals. This structural transformation led to fragmentation and refinement of the microstructure. The dissolution of Zr into Ag and Cu promoted the transformation of low-angle grain boundaries to high-angle grain boundaries (HAGBs), hindering crack propagation. Zr element in the brazing seam led to grain refinement and increased density of grain boundaries. The grain refinement could disperse the stress, and HAGBs could resist the dislocation movement, improving the joint strength. The results display that when Zr content was 0.75 wt.%, the maximum strength was 221.1 MPa. The fracture occurred primarily at the brazing seam, exhibiting a ductile fracture.

The GH4720Li alloy is one of the most widely used precipitation-strengthened nickel-based superalloy. However, systematic study about effect of strain rate on the plastic deformation behavior of GH4720Li alloy at intermediate temperature is lacking. The evolution of the tensile properties and plastic deformation mechanism of GH4720Li alloy with the strain rate at 650 °C were systematically studied with the help of transmission electron microscopy analysis. The results show that the tensile strength of the alloy increases and the plasticity decreases with the increase in strain rate. When the strain rate is 5 min⁻¹, the tensile strength of the alloy is 1448 MPa and the tensile plasticity is 18%. As the strain rate increases from 0.05 to 0.5 min⁻¹, the size and morphology of the primary γ′ phase of the alloy remain unchanged, with an average size of about 1.8 μm. However, when the strain rate further increases to 5 min⁻¹, the average size of the primary γ′ phase increases to 2.5 μm. In addition, the increase of strain rate has no significant effect on the size and distribution of secondary and tertiary γ′ phases. As the strain rate increases from 0.05 to 5 min⁻¹, the deformation mechanism of alloy gradually evolved from dislocation slip and twin to dislocation slip, indicating that the plastic deformation mechanism of the alloy presents a high strain rate sensitivity at 650 °C.

Laboratory experiments and thermodynamic calculations were performed to investigate the interfacial reactions between the MgO–C refractory and the steel with and without the lanthanum (La) addition. Following a reaction time of 50 min, a reaction layer comprised MgO and CaS with a thickness of 30 μm was observed at the interface between the La-free steel and refractory. The MgO layer was observed in La-bearing steel after just 10 min of reaction. The addition of La to the steel accelerated the formation of the MgO layer. As the reaction time increased, a La-containing layer was formed at the La-bearing steel/refractory interface. This La-containing layer progressed through stages from La₂O₂S + La₂O₃ → La–Ca–O–S → La–Ca–O → La–Ca–Al–O. Furthermore, the evolution of oxide inclusions in the La-free steel followed the sequence of MgO⋅Al₂O₃, Ti–Ca–Al–O and Ti–Mg–Al–O → MgO·Al₂O₃ and MgO with increasing the reaction time. In contrast, the sequence for the La-bearing steel was: La₂O₂S and La₂O₃ → La₂O₂S and La–Ti–Al–Mg–O → La–Ti–Al–Mg–O, MgO and MgO·Al₂O₃. The average penetration depth of the La-bearing steel into the refractory was notably lower than that of the La-free steel, revealing that the incorporation of rare earth element La in steel exhibits a significant inhibitory effect on the penetration of molten steel into the MgO–C refractory.

Based on the two-pass differential temperature rolling bonding method, the effects of prefabricated steel/aluminum composite panel temperature on interface characteristics and microstructure properties were investigated through experimental analysis and finite element simulations. When the temperature exceeds 400 °C, the effective preparation of the steel–aluminum transition joint can be achieved, and with the increase in temperature, the interface shear and pull-off strength of the steel–aluminum transition joint exhibits an initial decrease followed by an increase. Both the interface shear and pull-off fractures are in 1060 aluminum matrix. As the temperature increases, the size of the average grain in 1060 aluminum matrix increases and then decreases. When the temperature reaches 550 °C, the comprehensive performance of the prepared steel–aluminum transition joint is the best, with the interface shear strength of 77 MPa and the interface pull-off strength of 153 MPa, exceeding the bonding strength of the explosive compounding method. There are no pinholes, wrinkles, or cracks in the lateral bending matrix and the interface.