steel research international最新文献

Based on the 3D heat transfer numerical simulation model, the evolution mechanism of blast furnace cooling plate slag-hanging behavior with different cooling system structures is analyzed. Cooling plate reduced by 20 mm will not affect its slag-hanging behavior. Copper cooling plate is best suited for high heat load areas. The vertical spacing of cooling plate is extended by 200 mm, the uniformity of the slag layer decreases by 5%, and the temperature of cooling plate and refractory material increases by 11 and 50 °C. Cooling plate vertical spacing of 510 mm or less can ensure stable slag hanging in the blast furnace. When using a single refractory material, the average uniformity of the slag layer is 95%, 86%, and 79% for graphite brick, semigraphite brick, and sialon-SiC brick, respectively. Si₃N₄-SiC brick cannot operate properly in high heat load areas. The factory can consider setting 125 mm sialon-SiC brick in the furnace; graphite brick is used outside the furnace lining. The slag layer is well distributed, and the average value of uniformity is about 90%. Even if the slag layer is fully dislodged, the hot surface temperature of the furnace lining is 785 °C, and it can be quickly reslag hanging.

A robust static model, which incorporates emerging steelmaking scenarios in terms of solid charge mix with the given hot metal in basic oxygen furnace process, is developed. It employs mass and enthalpy balances to comprehend nonequilibrium conditions, considering four key empirical parameters: iron loss, post-combustion ratio, heat loss, and undissolved lime content in slag, which are fine-tuned using plant data through a multivariate approach, ensuring the reliability. The model is validated in a basic oxygen furnace (BOF) shop using data from over 4000 heats, achieving a strike rate of ≈77% for input lime prediction within ±1 ton and ≈80% for input oxygen prediction within ±600 Nm3. Model implementation in BOF shop provides valuable guidance to the operators, resulting in the reduction of average oxygen and lime consumption by 139 Nm³ and 652 kg heat⁻¹, respectively. The model also enables the determination of the maximum scrap utilization of ≈16% for 0.8% silicon and ≈14% for 0.6% silicon in hot metal, respectively. The model aids in calculating the maximum tap temperature for varying hot metal silicon and iron ore addition. Overall, the model optimizes primary steelmaking, enhancing efficiency, reducing resource consumption, and offering insights into alternative iron sources like direct reduced iron.

The residual stress in low-carbon high-strength steel is not effectively relaxed during alloy carbide precipitation but is fully relaxed during manganese partitioning. The specific microscopic mechanisms responsible for this observed phenomenon have yet to be fully elucidated. This study employs first-principles calculations in conjunction with experiments to demonstrate that alloy carbide precipitation leads to the formation of dense dislocation tangles that hinder carbon diffusion and carbide precipitation. Conversely, manganese partitioning aids carbon diffusion by altering dislocation morphology while also causing plastic deformation. The simultaneous occurrence of partitioning plasticity and precipitation plasticity during manganese partitioning results in a more significant relaxation of residual stress compared to alloy carbides precipitation: The plasticity coefficient for alloy carbide precipitation is 1.303 × 10⁻⁵, while the plasticity coefficient for manganese partition is 2.691 × 10⁻⁵. During alloy carbide precipitation, the elastic strain energy decreases to 43.48% of its initial value, whereas it can be further reduced to 25.29% after manganese partitioning.

By adjusting the parameters in the additive manufacturing process, the optimization of the microstructure and mechanical properties of 2205 duplex stainless steel (DSS) is of great significance to ensure the reliability of the material in harsh environments. The 2205 DSS samples are prepared by cold metal transfer conditions of interlayer cooling time of 0, 30, 60, and 120 s, respectively, and the microstructure and properties of the samples are characterized in detail. With the increase of cooling time, the height of the samples increases, and the width decreases, and no defects are found in all the samples. It also reduces the grain size and contributes to the uniform distribution of grains. With the extension of cooling time, the proportion of austenitic phase gradually increases from 41.60% to 47.36%, while the proportion of ferrite decreases correspondingly. The mechanical properties of the samples are tested. With the increase of cooling time, the hardness of the samples increases from 646.32(±1.46) to 679.36(±7.27) MPa, and the ductility decreases from 60.10(±0.50)% to 43.67(±2.10)%. The results show that the interlayer cooling time can be used to regulate the formation, microstructure, and properties of DSS.

The microstructure–texture–tensile property relationships in a Ni-containing medium-Mn steel (Ni-MMS), subjected to limited thermomechanical processing steps (i.e., hot forging and hot rolling), have been established in this study. The microstructure of the specimens hot rolled (HR) at 1173 (HR-1173K) and 1373 K (HR-1373K) exhibits ferrite and austenite phases. The austenite phase fraction in the HR-1173K specimen is found to be higher than the HR-1373K condition. The volume fraction of austenite to martensite transformation during tensile testing is also observed to be higher in the HR-1173K specimen (≈13%) than the HR-1373K condition (≈2%). This suggests the occurrence of more efficient transformation-induced plasticity effect in the HR-1173K specimen in comparison to the HR-1373K condition, resulting in improved strength–ductility synergy in the former specimen. The smaller grain size of both the phases and higher fraction of twin boundaries as well the evolution of higher intensity γ-fiber <111>//ND in the HR-1173K specimen leads to better tensile properties. In addition, the overall activation of the primary slip systems (combination of face-centered cubic and body-centered cubic phases slip system), estimated through visco-plastic self-consistent simulation, is higher in HR-1173K specimens, resulting in improved strain hardening response as compared to HR-1373K one.

Bainitic microstructures in high-strength steels are obtained either by continuous cooling or isothermal holding. Both scenarios necessitate faster cooling to keep the parent austenite phase untransformed till the bainite-start temperature. The present study reports the development of bainitic microstructure in a low-carbon steel with minimal alloying additions, under continuous cooling at very slow rates, similar to furnace cooling. For understanding the related transformation pathways, samples from the forged-steel ingot are austenitized and cooled at different rates, viz. water quenching, air cooling, and furnace cooling. Microstructural characterization reveals development of acicular microstructures in all samples including the forged one, with gross absence of carbides. X-ray diffraction confirms the ferritic nature of acicular plates and also indicated retained austenite present in some samples, the content of which could be correlated to the extent of bainitic transformation. Thermodynamic calculations together with microstructural observations (e.g., ferrite plate size) and hardness data established the development of fully martensitic microstructure on water quenching, while that of a mixed microstructure comprising predominantly of bainite in the forged, air cooled, and furnace-cooled condition. The aforementioned findings could have wider implications in developing fully bainitic microstructures in large components, where uniform rapid cooling is not practically feasible.

In this study, how crystallographic texture and changes in microstructure affect the magnetic properties of a semi-processed non-oriented (NO) electrical steel, which is investigated in its as-received state and after heat treatment, is evaluated. Electron backscattered diffraction analysis shows the variation in texture with a crystallographic orientation changing from a predominance of γ and α fibers to a random one after heat treatment, with a significant increase in components with <100> directions in the sheet plane, which are desired for NO steels because they are parallel to the direction of easy magnetization. Heat treatment has also increased the average grain size of the samples from 18 to 128 μm. Magnetic properties are analyzed over a wide frequency range and induction, presenting different behaviors in permeability and magnetic loss for the samples before and after heat treatment. The components of total magnetic loss are also evaluated, and the hysteresis loss of heat-treated sample decreases significantly. This demonstrates that heat treatment reduces microstructural imperfections, causing a decrease in hysteresis losses. Therefore, it is concluded that the improvement in magnetic performance observed with heat treatment has its origin in the increase in fiber components related to the <100> directions and a decrease in microstructural imperfections.

Sintering dust is a typical refractory secondary iron resource. A technology-based utilization of sintering dust as iron carbide by applying chlorination, carburization, and magnetic separation is proposed. Under optimized conditions, an electric furnace burden comprised of 83.51% Fe and 6.52% C and with a corresponding iron recovery rate of 81.21% is prepared. Meanwhile, 96.97% Pb can be removed by chlorination and magnetic separation. Furthermore, the separation mechanism is revealed using scanning electron microscopy, X-ray powder diffraction, and optical microscopy. The results show that sodium sulfate can promote the carburizing efficiency of sintering dust, strengthen the growth of iron carbide particles, and improve the embedding relationship between iron carbide and gangue minerals, which significantly promotes the separation efficiency. The study demonstrates that the preparation of iron carbide from sintering dust using the proposed technology is a feasible method.

To enhance the quality of the microtitanium alloy steel, this study is the first to utilize the addition of trace amounts of magnesium in 20CrMnTi gear steel to improve the TiN inclusions and microstructure within this type of steel. Herein, the effect of different magnesium contents (0–50 ppm) on nonmetallic inclusions in steel is taken as a starting point. Simultaneously, the pinning effect of the modified inclusions on the microstructure is also explored. The results indicate that after adding magnesium, the average size of the inclusions decreases from 2.8 to 2.3 μm, and the grain boundary mobility M decreases from 16 to 1.27 × 10⁻¹¹ m⁴ kJ⁻¹ s⁻¹. Mg can reduce Ca and Ti in oxide inclusions, forming finer MgAl₂O₄ particles, thereby refining their size. The formed MgO and MgAl₂O₄ act as inhomogeneous nucleation sites for nitrides, resulting in smaller size, more uniform distribution, and less harmful TiN. Notably, TiN can provide nucleation sites for MnS. The size and distribution of sulfides are also improved during the modulation of TiN. It is found that the modulated TiN–MgO–MnS microinclusions can be used as austenitic pinning particles. These particles increase the pinning resistance and improve the grain boundary mobility, thus contributing to grain refinement.