steel research international最新文献

In this work, a low-carbon Nb + V microalloyed steel has been thermo-mechanically processed at 1100 °C, followed by water-quenching. The sample processing results in dynamically recrystallized (DRX) austenite along with coarse deformed pancake grains at a high strain rate deformation. The primary objective brings into inspection the effects of austenite processing and parent austenite grain sizes on lath martensite nucleation and growth. A high surface/volume ratio of DRX grains enhances the nucleation rate; however, the observed grain size of ≈2–3 μm interrupts the growth to a premature halt. The unannihilated crystal defects and dynamically recovered sub-boundaries inside pancake-shaped grains also constrain martensitic reaction with a selective variant growth by maintaining Kurdjumov–Sachs orientation relationships. The orientation mismatch between the variants leads to delving deep into the hierarchical structure of martensite such as packets, blocks, sub-blocks, and laths, forming differentially in DRX versus pancake grains. Fundamentally, the austenite to martensite lattice change incorporates dilatation (≈0.03) and shear (≈0.22) strain. The demonstration of variant pairing helps to conceptualize the large shear strain component minimization. The stress concentration at the hierarchical structure has been analyzed. A comprehensive nature of this work also enlightens the effect of crystallographic texture on slip, retarding lath-formation from deformed austenite.

In this study, the effect of the slab continuous casting mold thickness on the mold flow field, the fluctuation of the mold flux and molten steel interface (MF-MSI), the solidification of molten steel, and the removal and capture of bubbles and inclusions is investigated by numerical simulation and high-temperature quantitative measurement of the mold surface flow velocity (MSFV). With an increase in the thickness from 180 to 250 mm and 320 mm, the measurement results decrease from 0.2148 m s⁻¹ to 0.2074 m s⁻¹ and 0.1875 m s⁻¹, respectively. The numerical simulation results present excellent alignment with high-temperature measurement results of MSFV. The occurrence ratios of the mold flux, bubble, and inclusion defects are all reduced. The values of ΔH decrease from 12.91 mm to 11.79 mm and 9.43 mm. The ratios of the bubbles captured by the solidified shell decrease from 1.25% to 0.86% and 0.58%, the ratios of inclusions removed by the mold flux layer increase from 29.01% to 29.80% and 33.90%, and the ratios of inclusions captured by the solidified shell decrease from 33.69% to 28.76% and 23.54%, respectively.

Herein, five refractory materials—MgO, MgO–CaO, MgO–Al₂O₃, MgO–C, and ZrO₂—are selected to smelt 65Si2CrV valve spring steel. The influence of refractory materials on molten steel cleanliness is systematically studied. The lowest N, O, P, and S contents are observed in the steel smelted with MgO–CaO refractory materials, with uniformly distributed inclusions. Most of the inclusions are located in the low-melting-point region, with both the number of inclusions per unit area and average inclusion diameter maintained at low levels. The inclusions in the experimental steel are primarily Ca–Mg–Al–Si–O composite inclusions, partially encapsulated by CaS and MnS. When molten steel and refractory materials interact, a distinct reaction layer forms on the inner walls of the MgO and MgO–CaO crucibles. In contrast, no significant reaction layer is observed in the MgO–C, MgO–Al₂O₃, and ZrO₂ crucibles, with the MgO–C crucible exhibiting pronounced erosion. During the slag–refractory interaction, although Ca, Si, and Al penetrate the inner walls of the MgO, MgO–Al₂O₃, and ZrO₂ crucibles, the erosion of the MgO–CaO and MgO–C crucibles is more severe.

A mathematical model is adopted to explore the initial solidification and slag consumption behavior within the mold under both nonsinusoidal and sinusoidal oscillation modes. Differences in liquid slag infiltration, pressure distribution, heat transfer, transient slag consumption, and oscillation mark profiles are also revealed. The results show that during the positive strip time, the mold, carrying the slag rim, moves upward relative to the shell, and the widening of the channel facilitates the infiltration of liquid slag. Although the velocity profile during the negative strip time is steeper under the nonsinusoidal oscillation, the shorter duration of this phase leads to weaker pressure fluctuations and a reduced impact on the meniscus profile compared to the sinusoidal oscillation mode. Owing to the weaker influence of the nonsinusoidal oscillation on the meniscus profile, the average depth of oscillation marks decreases from 0.30 mm under the sinusoidal mode to 0.26 mm under the nonsinusoidal mode. Meanwhile, compared to the sinusoidal oscillation mode, although the oscillation mark slag consumption decreases under the nonsinusoidal oscillation mode, the lubrication slag consumption increases. As a result, the total slag consumption under the nonsinusoidal oscillation mode increased from 5.24 g (m s)⁻¹ under the sinusoidal oscillation mode to 6.43 g (m s)⁻¹.

The study employs thermal desorption spectrum analysis, hydrogen microprinting technology, internal friction test, and slow strain rate tensile test, alongside microstructural characterization to examine the hydrogen embrittlement failure behavior in the coarse-grained heat-affected zone in welded AH36 steel. The results demonstrate that the hydrogen atoms primarily accumulated at the phase and grain boundaries and a small amount existed within the grains, leading to higher dislocation density. The internal friction spectrum of hydrogen-charged experimental steel exhibits an H-Snoek peak between −35 and 25 °C caused by hydrogen atom diffusion. As the hydrogen charging current density increases, the activation energies of all internal friction peaks decrease, indicating that the hydrogen atom content affects its interaction with the microstructure. As the hydrogen content in the steel increases, the crack sensitivity rate rises, and both tensile strength and elongation at break decrease significantly, indicating heightened sensitivity to hydrogen embrittlement. In addition, the fracture surface becomes flatter, and the fracture morphology shifts from ductile dimples to river patterns, signifying the transition from ductile to brittle fracture.

2205 duplex stainless steel samples underwent high-temperature prolonged solution treatment, cold rolling (10%–80% deformation), and low-temperature short-time solution treatment to obtain microstructures with similar ferrite (α) + austenite (γ) phase ratios but distinct grain/phase boundary distributions. Characterization via scanning electron microscopy-electron backscatter diffraction (SEM-EBSD), X-ray diffraction (XRD), and transmission electron microscopy (TEM) revealed deformation's impact on boundary characteristics. Tensile tests and double loop electrochemical potentiodynamic reactivation (DL-EPR) assessed mechanical/corrosion properties. The results show that, after sensitization, chromium carbides (Cr₂₃C₆) preferentially precipitated at α–γ phase boundaries. Increased deformation elevated twin boundary (TB) density while reducing α–γ phase boundaries; concurrently, Cr₂₃C₆ distribution homogenized, shortening elemental diffusion distances and enhancing intergranular corrosion resistance. Phase boundaries hosted denser dislocation sources with carbon segregation, but reduced α–γ boundaries diminished segregation-induced obstruction to ductile deformation, thereby improving plasticity. Therefore, employing appropriate processes to manipulate the internal interface characteristic distributions can achieve simultaneous enhancement of mechanical properties and intergranular corrosion resistance.

This study investigates the development of an AlCrCoFeNi high-entropy alloy (HEA) coating on an AISI 304L stainless steel substrate using the most economical process tungsten inert gas (TIG) arcing. X-ray diffraction analysis reveals the formation of single-phase solid solutions with both face-centered-cubic and body-centered-cubic structures in the HEA coating. Scanning electron microscopy with energy-dispersive spectroscopy confirms uniform elemental distribution throughout the coating. MATLAB coding and finite element analysis are also done to validate the experimental data. The HEA-coated samples exhibit a hardness of 750 HV_0.2 and a reduced coefficient of friction ranging from 0.6 to 0.8 indicating superior tribological performance. In comparison with uncoated and TIG-treated samples without AlCrCoFeNi HEA layer, the coated specimen demonstrates significantly enhanced hardness and improved wear resistance with refined microstructure. These results highlight the potential of HEA coatings for industrial applications demanding high wear resistance and long-term durability.

Nonmetallic inclusions in steel directly affect the cleanliness of molten steel. The separation of inclusions at the steel–slag interface, as the final step of inclusion removal, plays a critical role in determining overall removal efficiency. Therefore, it is essential to investigate the separation behavior of inclusions at the steel–slag interface and the factors influencing their removal for producing high–quality steel. In this article, numerical simulations of the separation process of the inclusion cluster at the steel–slag interface are conducted by using the volume of fluid (VOF), six degrees of freedom (6-DOF) model, dynamic mesh, and overset mesh. The effects of various physical parameters on the separation behavior of the inclusion cluster in the molten steel–inclusion cluster–slag system are systematically studied. The results show that the inclusion cluster exhibits three distinct motion behaviors at the interface: complete transfer to the slag phase, oscillation between molten steel and slag, and stable retention at the interface. By comparing the displacement and velocity of the inclusion cluster under different parameter conditions during the separation process, the sensitivity of these parameters on inclusion cluster removal is ranked as follows: contact angle > interfacial tension > slag viscosity > inclusion cluster density.

Wheels, as the core load-carrying parts of electric multiple unit (EMU) trains, are prone to wear and tear during long-term use. In this work, Fe/tungsten carbide (WC) composite coatings with varying WC contents are prepared on ER8 carbon steel for EMU train wheels using laser cladding with a semiconductor laser. WC content is taken as the key variable in the experiment. The microstructure, hardness, and wear performance of the coatings are primarily analyzed. These results indicate that the coating without WC particles outperforms the substrate. The addition of WC particles leads to grain refinement and the formation of M₂₃C₆, M₇C₃ (M=Fe, Cr), and Fe₃W₃C carbides from WC decomposition, which contribute to solid solution strengthening and second-phase strengthening, thus increasing the hardness and wear resistance of the coatings. The wear mechanisms are mainly abrasive and oxidative wear, and fatigue rupture of the WC particles is also observed. During the wear process, the hard phase WC serves as a structural backbone, reducing cutting actions, interrupting scratches, and retaining fragmented wear debris.

This study systematically investigates the effects of heat treatment processes on the microstructure and mechanical properties of 2Cr13MoV martensitic stainless steel. By analyzing the influence of heat treatment temperature on the kinetics of martensitic phase transformation, the synergistic effect of multiscale strengthening–toughening mechanisms are revealed, providing a theoretical foundation and technical pathway for the development of high-performance martensitic stainless steel. Experimental results show that a short-time heat treatment process of 990 °C quenching and 250 °C tempering successfully achieves the formation of fine lath martensite (LM) and optimized carbide precipitation. Among them, the coprecipitation strengthening effect of spherical M₂₃C₆ and plate-like M₃C carbides significantly enhances the yield strength of the material; at the same time, the autocatalytic effect at the carbide/matrix interface promotes the formation of fine LM. The specimens treated by this process exhibit excellent comprehensive mechanical properties, with an ultimate tensile strength of 1601 MPa and an impact toughness of 64.2 J cm⁻², achieving a good balance between high strength and good toughness.