steel research international最新文献

The influence of different microstructures on the plastic stability of an air-hardened industrially produced medium-manganese steel is presented. For this matter, heat treatment parameters before and during intercritical annealing (IA) are varied, to achieve different microstructures. The resulting duplex microstructure is consecutively tested by tensile tests, which are monitored by digital image correlation (DIC) to obtain information on the local plastic deformation. The tests are accompanied by microstructure investigations using optical, scanning electron, and transmission electron microscopy. Finally, X-ray and electron backscatter diffraction experiments are performed before and after deformation, to describe the altering phase fractions. It is demonstrated that the effect of the deformation temperature prior to IA treatment has a significant influence on the duplex microstructure, as it changes the austenite morphology from lamellar to globular and increases the phase fraction. The change in austenite phase fraction and morphology results in a higher yield strength (≈100 MPa), as well as higher uniform and total elongations (+2% and +5%, respectively). The DIC and tensile tests reveal that these differences in the austenite phase lead to a complete change in the strain hardening behavior, from continuous flow to discontinuous serrated flow, with clearly visible deformation bands during plastic deformation.

A physically based mean field model developed to predict the microstructural evolution during the thermomechanical control process of X70 high-strength low-alloy (HSLA) steels is presented. The physically based mean field model incorporates a new integrated precipitation and recrystallization model developed to describe the interaction between strain-induced precipitation of niobium and titanium carbonitrides and static recrystallization of austenite. The integrated model considers an effective Zener pinning force for the multimodal particle size distribution (PSD) of precipitates, an effective grain-boundary mobility for the solute drag effect of niobium, and an inhomogeneous stored energy for austenite recrystallization. Given a processing route, the model predicts the variation of austenite grain size, recrystallized and precipitated fractions, and evolution of PSDs of precipitates. Model predictions reveal an excellent agreement with experimental grain size measurements and a final average ferrite grain size of 3.81 μm is achieved. The proposed model considers the heterogeneous nature of recrystallization and precipitation and can contribute to the process design of the HSLA and microalloyed steels.

Microalloying of Nb has been commonly utilized to enhance the structure and mechanical properties of advanced high-strength steel (AHSS), but its application in medium-Mn low-density steel has been relatively understudied. This study aims to investigate the evolution of nano-scale precipitates and mechanical properties of Fe-12Mn-9Al-3Cr-1.4C-0.02/0.04Nb low-density steels. The findings reveal that the austenite grain size of 0.04Nb steels is approximately half that of 0.02Nb steels due to the precipitation of NbC particles. Moreover, the addition of Nb is found to elevate the formation energy of κ-carbide, thereby impeding its growth and coarsening. Consequently, the intragranular κ-carbides in 0.04Nb steels are consistently smaller than those in 0.02Nb steels, with no coarsened intergranular κ-carbides detected in either steel variant after aging treatment at 723–823 K. Despite a slight reduction on precipitation strengthening of κ-carbides with higher Nb content, the yield strength of 0.04Nb steels exceeds that of 0.02Nb steels by ≈71 MPa, mainly due to additional fine grain strengthening and dislocation strengthening. The strengthening mechanisms in the Nb-containing low-density steels are analyzed quantitatively. The role of Nb in regulating the microstructure and mechanical properties of medium-Mn low-density steels is comprehensively discussed, offering valuable insights for the alloy design of low-density steel.

The microstructural and textural evolution, as well as the recrystallization kinetics under different cold-rolling methods and their influencing mechanism on the properties of the thin-gauge 3.5%Si nonoriented silicon steel, are investigated by electron backscattering diffraction, X-ray diffractometer, tensile, and magnetic properties test. The results indicate that compared with the primary cold-rolling process, the reduction rate of secondary cold-rolling process is lower (58.3%), and many shear bands are formed in the coarse cold-rolled sheet, which leads to the formation of strong Goss and cube texture after recrystallization annealing. Owing to the high annealing temperature, the average grain size of finished annealed sheet is little different under different cold-rolling processes, so the mechanical properties and high-frequency iron loss are basically the same. The iron loss of the secondary cold-rolled products decreases with an increase in frequency, and the improvement in the iron loss of the high field (1.5 T) becomes larger than that of the low field (1.0 T). Given the high anisotropy index of the Goss texture, the iron loss anisotropy of the secondary cold-rolled sheet is higher. Considering the magnetic and mechanical properties, the optimum process is the secondary cold rolling with the intermediate annealing temperature of 900 °C.

To realize the overall optimization of electric arc furnace (EAF) steelmaking system, a multi-objective optimization model including smelting cost, energy consumption per ton of steel, and carbon emission per ton of steel is established. The model is optimized by multi-objective genetic algorithm to improve the charging structure. At the same time, the data in the optimal solution set are used to analyze the influence of the change of scrap ratio on smelting cost, carbon emission per ton of steel, and smelting cycle. According to the actual working conditions and the demand of steel plant, the optimized results are selected. Compared with the actual production data, the proportion of scrap steel increases to 50.9%, the ratio of molten iron decreases to 38.8%, the smelting cost per ton of steel decreases by 12 Yuan, the energy consumption per ton of steel decreases by 4%, the carbon emission per ton of steel significantly decreases by 13%, and the smelting cycle is shortened by 2 min, but at the cost of increasing the power consumption per ton of steel. The optimized results and the analysis of the change of scrap ratio provide reference for the optimization of EAF steelmaking system.

Additive manufacturing (AM) is a cutting-edge technique for constructing intricate components with unique microstructural features and strength comparable to wrought alloys. Due to their exceptional corrosion resistance and mechanical properties, duplex stainless steels (DSS) are used in a wide range of critical applications. Over the past several years, a substantial body of research has been conducted on the AM of DSS. In-depth knowledge is required to understand the complete benefits of the AM process. This review overviews the AM-processed DSS parts based on process-specific microstructural changes, mechanical behavior, electrochemical performance, and postheat treatment processes based on the classifications of directed energy deposition and powder bed fusion AM techniques along with future perspectives. Major challenges in AM of DSS are optimizing the austenite–ferrite fractions and controlling the formations of deleterious phases. This review will be extensively useful to researchers and industries working in the AM of DSS.

Herein, the influence of P₂O₅ on the break temperature and phase composition of slag from the double slag converter steelmaking process is investigated comprehensively. The composition and micromorphology of crystallized phase are analyzed by X-Ray diffractometer and scanning electron microscope equipped with energy dispersive spectrometer. The results reveal that the break temperature of slag increases owing to an increase of P₂O₅ content. When the P₂O₅ content is 2%, the break temperature is 1198 °C, and it increases to 1209 °C for the slag with 4% P₂O₅. With the increase of P₂O₅ content from 2% to 8%, the activation energy for viscous flow shows an upward trend. The crystallized phase at the same temperature with different P₂O₅ contents remains nearly unchanged, but the diffraction peak intensity is different. When the P₂O₅ content remains constant, a decrease in temperature results in significant changes in the micromorphology of crystallized phases. The present results improve the knowledge about the P-rich slag, and are also significant in optimizing the double slag converter steelmaking process.