steel research international最新文献

As a byproduct of the steelmaking process, ladle slag has the potential to be used as an auxiliary cement material in the construction field. However, ladle slag generated after secondary refining is typically handled by air cooling and stacking, leading to the presence of the typical mineral phase mayenite (Ca₁₂Al₁₄O₃₃, abbreviated as C₁₂A₇) in a crystalline form within the slag. This reduces its early hydration activity, which adversely affects the compressive strength of concrete and consequently lowers the resource utilization rate of ladle slag. Based on this, this article provides a comprehensive review of the generation process and composition of ladle slag. By discussing the hydration process and hydration products of the typical mineral phase C₁₂A₇ in ladle slag, as well as the mutual transformation of hydration products, it is shown that hydration products undergo transformation with increasing temperature. Compared to crystalline C₁₂A₇, amorphous, C₁₂A₇ exhibits excellent hydration activity. Building upon this, methods for amorphizing C₁₂A₇ are elucidated, wherein thermal activation or chemical activation is employed to alter the ordered arrangement of atoms within the crystal structure, thereby reducing the stability of the crystal structure to achieve amorphization of C₁₂A₇.

The liner is affixed to the inner side of the ball mill cylinder to protect the cylinder. Through isothermal compression experiments, Arrhenius constitutive models, peak strain models, critical strain models, dynamic recrystallization dynamic models, and grain size models suitable for the forging process of Mn–Cr–Ni–Mo steel used in ball mill liners were established. By utilizing Deform software, a 3D thermo-force-structure coupling model for the hot forging process of ball mill liners was constructed, and the volume fraction of dynamic recrystallization and average grain size during forging was predicted. The response surface model was employed to investigate how process parameters interacted with each other and affected microstructure uniformity in ball mill liners. After optimization, the optimal parameters were determined: initial forging temperature at 1200 °C, forging speed at 30 mm s⁻¹, and friction coefficient at 0.3. Subsequently, a hot forging experiment on ball mill liners was conducted using these optimized parameters; samples were analyzed through backscattered electron diffraction device experiments and microscopic tissue observations. Results demonstrated that microstructural changes observed during actual forging processes aligned with numerical simulation results—thus verifying both the accuracy of the Mn–Cr–Ni–Mo steel material model and numerical simulation method.

In practical applications, intermetallic compounds like Laves phase and metal carbides adversely affect the performance of nickel-based superalloys. Using a high-temperature confocal laser scanning microscope, the solidification process of as-cast GH3625 alloy containing Mg at different cooling rates (−20, −35, and −50 °C min⁻¹) is studied. Fitting curves of the volume fraction of the solid phase with solidification temperature before and after Mg treatment are obtained. Trends of solid phase transformation rates with solidification temperature are determined. Differential scanning calorimetry is employed to analyze and statistically evaluate the melting temperature range and enthalpy of each phase during the melting process. Experimental results demonstrate that Mg treatment significantly accelerates the alloy solidification at the cooling rates of −20 and −35 °C min⁻¹, while reducing the area of residual liquid phase at the same solidification temperature, disrupting the Laves/NbC eutectic relationship, and regularizing NbC morphology, transitioning its distribution from aggregation to dispersion. After Mg treatment, the precipitation of the Laves phase is significantly reduced. As a result, the influence mechanism of Mg treatment on the phase transformation and microstructure of GH3625 is clarified based on homogeneous nucleation theory.

In order to optimize the heating schedule before forging and improve the breaking and deformation effects of carbides in high-speed steel, it is of great significance to study the transformation of M₂C carbides at high temperatures. The evolution of carbides in the industrial-grade American Iron and Steel Institute M35 steel produced by electroslag remelting (ESR) is analyzed and observed using thermodynamic calculations and experimental methods. The results indicate that the carbides in the ESR ingot are mainly MC and M₂C, and the microstructures of M₂C carbides with the highest volume fraction are lamellar and brain like. As the heating temperature increases and holding time prolongs, the lamellar M₂C carbides gradually transform into MC and M₆C carbides, accompanied by protrusion, dissolution, separation, and spheroidization of the microstructure, until significant coarsening occurs at 1180 °C for 90 min. The newly transformed carbides are embedded and stacked with each other, occupying the original position of M₂C carbides. Based on the theories of Gibbs free energy and atomic diffusion, the evolution mechanism of M₂C carbides is discussed. Ultimately, the appropriate heating schedule is proposed, and it is validated by combining the characteristics of carbides after forging.

The microstructure characteristics and the properties of rolled steels are significantly affected by the heat transfer and boiling phenomena occurring during the jet impingement cooling on run-out tables (ROT). In this study, experiments are conducted using a full industrial-scale ROT facility with rectangular plates made of low-carbon stainless steel (type 316L). The plate is heated up to a temperature ranging from $��500�$ to $��900�\hspace{0.17em}�°�C�$, then rapidly impinged using a single circular water jet, and the temperature drop is captured using an infrared thermal camera (FLIR A615 25°–50 Hz type). The dissipated heat flux, estimated experimentally using a 2D inverse heat conduction analysis, ranges from 6.1 to 3.4 MW m⁻² across different zones along the plate surface. The impact of different initial plate temperature on the boiling behavior is studied by developing a 2D-computational fluid dynamics (CFD) model, and the results are closely aligned with the experimental findings. The results reveal that when estimating the heat flux from CFD simulations, the best accuracy is obtained when considering fluid temperature at a point close to the plate surface (about 1 μm above the surface). Furthermore, the maximum extracted heat flux (MHF) is significantly influenced by the initial temperature of the plate. Increasing the initial plate temperature from 500 to 900 °C led to an increase of 82% in the MHF in stagnation zone, and 137% increase in the parallel-flow region. The CFD model presented in this study and the full calculation of the boiling curves numerically will pave the road for investigating various practical parameters in jet impingement cooling.

The effect of the cerium addition on the microstructure and properties of the ductile iron is investigated. The ferrocerium is added to obtain ductile iron samples with cerium contents of 10–750 ppm. In the ductile iron with a cerium content of 60 ppm, the amount and the spheroidization rate of graphites are the highest. The tensile strength of the ductile iron is 488 MPa and the elongation rate reaches 20.17%. For the ductile iron with a high toughness demand, it is necessary to add 60 ppm Ce in the ductile iron to increase the number density and spheroidization rate of graphites. The formation of CeS inclusions effectively promotes the heterogeneous nucleation of graphites, increasing the amount of graphites. The stronger carbon diffusion during the eutectic process increases the ferrite formation in the ductile iron, leading to a lower tensile strength and a higher elongation rate. When the cerium content exceeds 460 ppm, the precipitated Ce₂C₃ significantly reduces the performance of the ductile iron.