steel research international最新文献

Herein, the 20Cr3MoWVA steel is subjected to carburizing and plasma nitriding composite heat treatment for strengthening. Ball-disk friction wear tests are conducted on three states (Untreated, C, C + PN) of the samples. The results show that after the composite heat treatment, a composite diffusion layer composed of γ′-Fe₄N phase and ε-Fe_2-3N phase is obtained. This diffusion layer has no compound layer and no vein-like grain boundaries, and its thickness is 150 micrometers. The surface hardness of the C + PN sample (1004 HV) is 4.2 times and 1.3 times that of the Untreated sample and the C sample, respectively, and its wear rate decreases by 97.34% and 74.38% compared to the untreated sample and the C sample, respectively. The C + PN sample has the lowest friction coefficient (0.5887), and the surface residual compressive stress reaches −883 MPa. During the plasma nitriding process, Cr-rich M₇C₃ carbides and V-rich MC carbides transform into M_2-3(C, N) and M(C, N) carbonitrides, respectively. The wear mechanisms of the three specimen states involve oxidative wear and adhesive wear, with abrasive wear also present in the untreated and C specimens. During the wear process of the C + PN samples, nanocomposite self-lubricating oxides with excellent wear resistance are formed.

Seshadri Seetharaman was born on December 5th, 1943, in Pudukottai, Tamil Nadu, India. He embarked on his scientific journey in 1966 at the Indian Institute of Science, where he earned a PhD in Metallurgical Engineering in 1971. Following his doctoral studies and post-doctoral research, he joined the Department of Metallurgy at the Royal Institute of Technology (KTH) in Stockholm, Sweden. At KTH, he initially served as an associate professor before being appointed as Professor of Theoretical Metallurgy in 1990. In 1996, he became Head of the Department of Metallurgy and subsequently Pro-Dean of the Faculty of Mechanical and Materials Engineering.

Professor Seshadri Seetharaman's research has significantly advanced the fields of thermochemistry and thermophysics of high-temperature metal and oxide systems. His work includes experimental measurements and modeling of properties such as viscosities, thermal diffusivities, and surface and interfacial tensions. His investigations into high-temperature reaction kinetics, including heat and mass transfer, property-structure relationships, and micro-phenomena, have provided profound insights into gas-solid reactions and slag-metal interactions. Notably, he proposed the concept of interfacial velocity in slag-metal reactions and published extensively on the valence changes of metallic components in slags.

With over 400 publications in peer-reviewed journals, 160 conference presentations, and 10 patents, Professor Seetharaman's contributions bridge the gap between fundamental research and practical applications. He has been a key reader and member of the editorial boards of esteemed journals such as Metallurgical and Materials Transactions and steel research international. Additionally, he has organized and chaired numerous international conferences, promoting collaboration and innovation in the scientific community. Renowned as a dedicated educator, he has been an inspiring teacher, a supportive PhD supervisor, and a respected colleague.

Professor Seetharaman's exceptional teaching abilities have been widely recognized. He was nominated eight times as the best teacher in the materials design program at KTH and received the President's Award for meritorious teaching in 1994. In 2004, he was named the best teacher at KTH. Among his many honors, he received the Brimacombe Prize in 2010 and has been recognized as an honorary member of the Iron and Steel Institute of Japan, an honorary doctor at Aalto University in Finland, and an honorary professor at the Metallurgical Academy of Ukraine and the University of Science and Technology Beijing. His renowed career also includes serving as a Mercator Professor at TU Bergakademie Freiberg, Germany (2011–2012), and a visiting professor at Kyoto University, Japan. In 2013, he was awarded the Distinguished Alumni Award by the Indian Institute of Science, Bangalore.

The scientific seminar marking Professor Seetharaman's retireme

The cover image is based on the article Extraction of Vanadium from CaO-SiO₂-MgO-Al2O₃ Slags Based on Vaporization of Vanadium Pentoxide by Lukas Neubert et al., https://doi.org/10.1002/srin.202300681.

Biomass and H₂ are characterized as environment-friendly, and can be used as reductant in the reduction process of iron oxides, therefore to achieve carbon neutrality of the shaft furnace direct reduction ironmaking process, and meanwhile produce carbon-containing direct reduced iron (DRI). For the synergistic utilization of biomass and H₂, this study used H₂ to reduce biomass embedded self-reducing pellets (SRP) to produce DRI. The relative mass loss ratio, reduction degree and metallization degree, and microstructure of pellets reduced under different conditions (750–950 °C, CO involved, H₂ involved and N₂ atmosphere) are analyzed to clarify the reduction behavior of torrefied biomass- and charcoal-embedded pellets. Results indicate that higher temperature, H₂ involved atmosphere, and higher embedded biomass content favors the hybrid reduction of iron oxides; addition of biomass affects the reduction efficiency of pellets from two aspects, porosity and solid carbon reduction. Under the optimal reducing condition (950 °C and 40% H₂%–60% N₂ atmosphere), reduction degree of 87% can be achieved by reducing torrefied biomass embedded SRP, and DRI with acceptable carbon content is expected be produced.

A coupled volume of fluid–discrete phase model (DPM) model is used to simulate the single-flow postcombustion oxygen lance gas–metal interaction behavior and dephosphorization behavior in a 250 t converter. The effects of different lance heights and operating pressures on the molten pool flow rate, phosphorus content, and endpoint phosphorus content are investigated, while the influence of phosphorus distribution ratios on the dephosphorization rate is also analyzed. The results show that as the lance height increases, the droplet fraction (percentage of droplets relative to the liquid steel mass) decreases, the average velocity of the steel surface increases, the dead zone area first increases and then decreases, and the dephosphorization rate gradually declines. When the operating pressure increases from 0.8 to 1.1 MPa, surface fluctuations intensify, more droplets are splashed, and the dephosphorization rate increases from 61.9% to 81.0%. For phosphorus distribution ratios of 40, 80, 120, and 160, the dephosphorization rates are 48.5%, 60.7%, 69.2%, and 75.1%, respectively. Industrial tests on a 250 t converter using a single-flow postcombustion oxygen lance show that the higher the total iron and CaO content in the slag, the higher the phosphorus distribution ratio; the dephosphorization rate gradually increases with the gradual increase of the phosphorus distribution ratio.

The present investigation employs conventional hot-stamping methodology incorporating die quenching followed by 170 °C tempering to fabricate ultrahigh strength 40Mn2CrNbV hot-stamped steel. The alloy demonstrates exceptional mechanical characteristics, achieving an ultimate tensile strength of 2311 MPa while maintaining satisfactory ductility (total elongation of 9.8%). Quantitative evaluation of strengthening mechanisms reveals the dislocation strengthening as the predominant contributor (accounts for about 55.9% of yield strength), followed by precipitation strengthening. Compared with 30MnB5 steel and existing literature-reported systems, the 40Mn2CrNbV steel has excellent mechanical properties, mainly due to the synergistic interaction of Cr, Nb, and V microalloying elements. Specifically, the simultaneous incorporation of Nb and V facilitates the precipitation of nanoscale (Nb, V)C, induces grain refinement, and impedes dislocation motion through pinning effects. The average size of martensite block widths is 0.8 μm and the dislocation densities of 3.1 ± 0.4 × 10¹⁵ m⁻² for 40Mn2CrNbV hot-stamped steel.

Traditional spheroidization annealing of 100Cr6 bearing steel is time-consuming and energy-intensive. To address this, warm rolling is proposed as an efficient alternative for microstructure refinement and toughness enhancement. The influence of warm rolling at critical dual-phase (760 °C) and ferrite (700 °C, 650 °C) temperatures is investigated. At 760°C, dynamic recrystallization dominated with 90% recrystallized area, yielding equiaxed ferrite grains of 4–6 μm and normally distributed carbides averaging 0.37 μm in size with 32 vol%. Lower-temperature rolling at 650 °C intensified deformation bands to 3 μm spacing, promoting carbide precipitation to 47 vol% density at 15.7 particles μm⁻² while suppressing recrystallization (90% area with GOS >2). Nanoscale carbides of 0.094 μm pinned grain boundaries, transitioning deformation mechanisms from grain-boundary sliding to intragranular slip. Impact toughness increased by 30%–40% in ferrite-zone rolled specimens due to crack deflection by laminated fibrous grains and fine carbides. This work clarifies how distortion energy storage drives deformation-induced carbide precipitation, providing a pathway to achieve high toughness through tailored warm-rolling processes.

The present investigation employs conventional hot-stamping methodology incorporating die quenching followed by 170 °C tempering to fabricate ultrahigh strength 40Mn2CrNbV hot-stamped steel. The alloy demonstrates exceptional mechanical characteristics, achieving an ultimate tensile strength of 2311 MPa while maintaining satisfactory ductility (total elongation of 9.8%). Quantitative evaluation of strengthening mechanisms reveals the dislocation strengthening as the predominant contributor (accounts for about 55.9% of yield strength), followed by precipitation strengthening. Compared with 30MnB5 steel and existing literature-reported systems, the 40Mn2CrNbV steel has excellent mechanical properties, mainly due to the synergistic interaction of Cr, Nb, and V microalloying elements. Specifically, the simultaneous incorporation of Nb and V facilitates the precipitation of nanoscale (Nb, V)C, induces grain refinement, and impedes dislocation motion through pinning effects. The average size of martensite block widths is 0.8 μm and the dislocation densities of 3.1 ± 0.4 × 10¹⁵ m⁻² for 40Mn2CrNbV hot-stamped steel.

To test the ability of predicting earing height in finite element simulations with nonassociated flow rule for complex die configurations such as “varying-shoulder-radius die,” a 3D simulation of deep drawing of a commercially pure titanium sheet is conducted. Cup deep drawing experiments with single-radius die are first conducted to verify the accuracy of the simulation results, and the results are compared with the experimental measurements. Two types of nonassociated flow rules are applied: the Hill-Hill combination using Hill48 for both the yield function and plastic potential, and the Hill-Yld combination using Hill48 for the yield function and Yld2004-18p for the plastic potential. The results show that the Hill-Yld model reproduces the experimental results well in the range of 45°–90°. Subsequently, deep drawing using varying-shoulder-radius dies is simulated, and the results are compared with the experimental measurements. The results of the comparison show that the Hill-Yld model is able to qualitatively reproduce the experimental trend of the earing height. The results suggest that the Hill-Yld model with Yld2004-18p as the plastic potential can qualitatively reproduce the results of deep drawing experiments using varying-shoulder-radius dies.