steel research international最新文献

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.

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.

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.

The 0.5C–1Cr–0.2Mo–0.1V spring steel without and with 0.0061 wt% rare earth (RE)-yttrium (Y) addition is prepared via vacuum induction melting, hot rolling, quenching and tempering, and the effects of Y addition on the microstructure evolution and mechanical properties of spring steel are investigated. The results show that Y addition can reduce the degree of microsegregation, refine the size of prior-austenite grains during the austenitization process after hot rolling, and effectively remove and modify oxide inclusions during the solidification process. The martensite block tends to be equiaxed and refined, and the size of the martensite lath within the block also decreases with Y addition after quenching. The lamellar M₃C carbide precipitates along the prior martensite lath boundary during tempering. Y addition can refine the lamellar M₃C carbides and promote the formation of spherical M₇C₃ carbides that are evenly distributed in laths. On the basis of the microstructure analysis mentioned above, the microstructure of 0.5C–1Cr–0.2Mo–0.1V spring steel can be improved by the addition of Y, resulting in a significant increase in the strength, yield ratio and ductility of the steel.

This study investigates the microstructural evolution and mechanical properties of steel subjected to high-temperature heat treatment, with a focus on the formation and effects of second-phase precipitates. High temperature confocal laser scanning microscopy is employed to observe the in situ changes in microstructure as the steel is heated from room temperature to 900 °C. During continuous heating, precipitates are first observed in situ at ≈820 °C. Both the size and number of precipitates reach their maximum at 900 °C. Compositional analysis identifies these precipitates as chromium carbides (Cr₇C₃). Scanning electron microscopy and energy-dispersive X-ray spectroscopy confirm that these precipitates significantly enhance the material's hardness, with microhardness values of 330 HV for the precipitates compared to 240 HV for the matrix. Tensile tests show that the tensile strength of the steel increases with soaking time at 900 °C, reaching a maximum after 3 min due to the strengthening effect of the precipitates. Beyond this point, strength decreases due to grain coarsening.

The effects of Al and Mn on the microstructure and mechanical properties of Fe–12Cr–5Ni–0.4C–(6,10)Mn–(0,2,4)Al (wt%) lightweight stainless steels are investigated. The results indicate that the as-referred 6Mn0Al and 6Mn2Al steels exhibit a fully austenitic microstructure. An increase in Al content results in ≈6% and 2% ferrite in the 6Mn4Al and 10Mn4Al steels, respectively, accompanied by refined austenite grains and an increase in yield strength. Deformation-induced α′-martensitic transformation (DIMT) and mechanical twinning are the dominant deformation mechanisms in 6Mn0Al steel, leading to a high work-hardening rate and a tensile strength of 863 MPa. The increased stacking fault energy due to higher Al content in 6Mn2Al steel suppresses DIMT, making mechanical twinning the primary deformation mechanism. The total elongation of 6Mn2Al steel reaches 77%, significantly higher than the 61% measured in 6Mn0Al steel. Additionally, the deformation mechanisms of 6Mn4Al and 10Mn4Al steels are dominated by mechanical twinning. The pre-existing ferrite leads to an increased work-hardening rate but reduced ductility, with total elongation decreasing to 56% and 50% for 6Mn4Al and 10Mn4Al steels, respectively. The lower elongation of 10Mn4Al steel compared to 6Mn4Al steel corresponds to a decreased work-hardening rate, as mechanical twinning is suppressed by the higher Mn content.

The formation and transformation of oxide inclusions in S32750 stainless steel with different Al contents during argon-oxygen decarburization-ladle furnace (AOD-LF) refining are studied based on industrial trials, inclusion characterization, and thermodynamic analysis. The inclusions at LF arrival stage are CaO–SiO₂–MgO–Al₂O₃–CaF₂ inclusions originated from slag entrainment and the newly formed CaO–SiO₂–MgO–Al₂O₃ inclusions which are the products of the chemical reactions caused by the increased Al content and reoxidation of liquid steel during AOD tapping. The types of inclusion at LF end stage are the same as that at LF arrival stage. The compositions of the newly formed inclusions which are originated from reoxidation of liquid steel during LF refining are consistent with the compositions of the newly formed inclusions at LF arrival stage. The mass fractions of SiO₂ in the CaO–SiO₂–MgO–Al₂O₃–CaF₂ inclusions in liquid steel with 0.0100 and 0.0320 mass% Al decrease from 27.7 and 13.1 mass% before AOD tapping to 14.1 and 5.4 mass% at LF arrival stage, respectively. The inclusions in the forged bar are MgO·Al₂O₃ spinel precipitated from liquid steel during its cooling and dual-phased spinel + CaOSiO₂ with minor amount of MgO and Al₂O₃ inclusions formed through the crystallization of CaO–SiO₂–MgO–Al₂O₃ inclusions during liquid steel cooling.

Super duplex stainless steel has excellent mechanical properties and corrosion resistance, but wire arc additive manufacturing super duplex stainless steel generally suffers from a two-phase ratio imbalance, which limits its application. This study implemented three distinct cooling strategies during the manufacturing process: natural cooling, common interlayer forced cooling with compressed air (AC) and a novel vortex tube cooling of compressed air (VC). Through systematic comparison, investigation is done on how these thermal management approaches influence the microstructure and mechanical properties of wire arc additive manufactured duplex stainless steel, with particular focus on phase ratio optimization. The findings demonstrate that the interlayer forced cooling process effectively enhances ferrite content, achieving phase ratio optimization. Furthermore, it is revealed that over 80% of ferrite/austenite phase boundaries conform to the Kurdjumov–Sachs orientation relationship. This characteristic induces plastic coordinated deformation behavior, thereby enabling the material to exhibit concurrent excellent strength (UTS ≈ 850 MPa and YS ≈ 600 MPa) and elongation (EL ≈ 40%).

Relatively high-efficiency and low-cost steel slag adsorbents are prepared for desulfurization and denitrification in simulated sintering flue gas through high-temperature mineral reconstruction technology. Steel slag adsorbents are successfully prepared at a holding temperature of 1300 °C with a picking concentration of 1% and an adsorption temperature of 200 °C, in which the T_90% value of the denitrification efficiency reaches 107.58 min, and the T_50% value of the desulfurization efficiency reaches 72.31 min. The results indicate that competition and synergistic adsorption between SO₂ and NO_x can occur in the desulfurization and denitrification process of steel slag adsorbents. In the competition process, since the adsorption capacity for NO_x is greater than that for SO₂, the adsorption sites are preferentially occupied by NO_x. Consequently, the desulfurization effect is inhibited in the adsorption process. The activation sites of free CaO in the steel slag adsorbents react with SO₂ and NO_x to form a stable calcium nitrate or sulfate phase that blocks the adsorption sites, which in turn result in adsorbent poisoning. Moreover, unstable sulfur–nitrogen complexes can be captured by NO_x and SO_x in the synergistic adsorption process. This study provides a feasible strategy to address steel slag disposal and flue gas emission synergistically.