steel research international最新文献

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.

The impact toughness, microstructure, and carbide precipitation behavior of austenitic hot-forging die steel after holding at different temperatures (740–780 °C) for various times (0–48 h) are investigated. The results showed that the hardness of SDHA steel decreases with increasing holding time due to the precipitation and coarsening of M₂₃C₆ and M₂C carbides. During the holding process, M₂₃C₆ carbides precipitate on the grain boundaries and inside the grains (near grain boundaries), and M₂₃C₆ carbides precipitate on the grain boundaries are interconnected to form a chain-shaped distribution. The impact toughness of materials severely deteriorates due to this distribution of carbides, and the fracture morphology is characterized by intergranular fracture and secondary cracks. The maturation equations of M₂₃C₆ carbides at the grain boundaries at 740, 760, and 780 °C are obtained. Besides, the nanoscale MC carbides maintain a coherent relationship with the matrix after a long holding time at high temperatures, so it is an important secondary precipitation for maintaining the thermal stability of materials.

The cooperative growth of eutectoid structures represents a fundamental phase transformation phenomenon in carbon steels. However, current research predominantly focuses on eutectoid growth within single grains, neglecting the influence of interactions among lamellae with diverse orientations. The present study employs a simulation-based approach to address this gap, utilizing the widely studied Fe–C binary alloy as the model system. Building upon an improved pearlite nucleation and growth model for Fe–C alloys, a multiisland pearlite cooperative nucleation and growth model is established. This framework enables a systematic investigation of the evolutionary behavior of multiisland lamellar growth in Fe–C alloys, with experimental validation confirming the model's reliability. Furthermore, the study examines the influence of varying isothermal temperatures and nucleation orientations on the cooperative growth of multiisland lamellae in Fe–C alloys. The results demonstrate that when two islands with distinct orientations interact, the growth direction is predominantly governed by the island exhibiting the larger misorientation. Conversely, when the misorientation between two islands is minimal, the growth direction tends to align with the angular bisector of their boundary.

The cooperative growth of eutectoid structures represents a fundamental phase transformation phenomenon in carbon steels. However, current research predominantly focuses on eutectoid growth within single grains, neglecting the influence of interactions among lamellae with diverse orientations. The present study employs a simulation-based approach to address this gap, utilizing the widely studied Fe–C binary alloy as the model system. Building upon an improved pearlite nucleation and growth model for Fe–C alloys, a multiisland pearlite cooperative nucleation and growth model is established. This framework enables a systematic investigation of the evolutionary behavior of multiisland lamellar growth in Fe–C alloys, with experimental validation confirming the model's reliability. Furthermore, the study examines the influence of varying isothermal temperatures and nucleation orientations on the cooperative growth of multiisland lamellae in Fe–C alloys. The results demonstrate that when two islands with distinct orientations interact, the growth direction is predominantly governed by the island exhibiting the larger misorientation. Conversely, when the misorientation between two islands is minimal, the growth direction tends to align with the angular bisector of their boundary.

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.

This study systematically investigates and optimizes refining process parameters to enhance molten steel cleanliness for automotive hollow stabilizer bars. Through thermodynamic calculations and industrial trials on a 110 ton converter–Ladle furnace(LF)–Ruhrstahl Heraeus (RH)–continuous casting production line, key process improvements are identified. Thermodynamic analysis reveals that increasing the CaO/Al₂O₃ ratio from 1.03 to 1.39 enhances slag inclusion absorption capacity (K⁰) from 12.9 to 30.25. Industrial trials demonstrate that an 8 min RH circulation reduces total oxygen content to 11 ppm, while 7 min of static blowing at 5 Nm³ h⁻¹ minimizes inclusion size and density. Microstructural characterization indicates that the steel primarily contains finely dispersed Al₂O₃ inclusions , with trace sulfides and TiN. Optimization of the secondary cooling system reduces TiN inclusion density from 53 to 36 mm⁻², area fraction from 123.64 to 98.77 ppm, and average diameter from 3.52 to 3.29 μm, confirming effective refinement. Furthermore, this study elucidates TiN formation mechanisms during secondary cooling. Process optimization reduces banded structures to grade 2.0–2.5 and limits decarburization depth to ≤0.03 mm, increasing the product qualification rate from 75.6% to over 92.5%. These findings provide a systematic framework for clean steel production, yielding significant industrial and economic benefits.