steel research international最新文献

Herein, the effects of peak temperature on the microstructure and low-temperature impact toughness of coarse grain heat-affected zone (CGHAZ) of EH460 steel are investigated by Gleeble simulation welding. The low-temperature impact toughness of CGHAZ decreases with the increase of peak temperature. With the increase of peak temperature, the microstructure of CGHAZ gradually changes from bainite to a mixed structure composed of bainite, intragranular ferrite, side lath ferrite, and a small amount of grain boundary ferrite. The inclusions size decreases as the peak temperature increases. The existence of large-sized inclusions is conducive to the initiation and propagation of cracks, reducing the low-temperature impact toughness of the material.

The clogging of the submerged entry nozzle (SEN), as an important device to connect the tundish and the mold, has been widely concerned. However, until now, the clogging of the SEN cannot be eliminated during the casting. Herein, the clogging behavior of the SEN during the casting of ultralow-carbon steel is studied using an external DC electric field. The findings demonstrate that the DC electric field inhibits the growth of the clogging on the outlet and the thickness of the clogging layer is small, which ensures the integrity of the profile of the outlet. After DC treatment, the interface of the clogging is clear and the density is increased, which reduces the pollution to molten steel. At the same time, the fluctuation of the mold level is significantly improved, and the defect rate of cold rolling is effectively reduced to 30% of the original level, which is beneficial to the overall performance of the slab.

The carbide precipitation of H13 steel and its effect on hardness and friction and wear resistance are investigated by microstructure observation, phase analysis, and mechanical property test. Results show that the tempering hardness is mainly related to the content of secondary carbides. After solution treatment in the temperature range of 1040–1070 °C, quenching and tempering, with the increase of the solution temperature, the content of secondary carbides and hardness of H13 steel in the tempering microstructure increase first and then decrease, and both reach the maximum value when the solution temperature is 1060 °C. The change of hardness is consistent with that of the content of secondary carbides. When the solution temperature is 1040 °C, the wear mass loss of the tempered H13 steel is the least, which is 4.63 mg, indicating that its wear resistance is the best, and this is caused by the presence of more undissolved carbides in the tempering microstructure. With the increase of the solution temperature, the wear mass loss increases gradually, and the wear resistance decreases, which is mainly related to the content decrease of undissolved and secondary carbides and the content increase of residual austenite.

Herein, the optimized process parameters for the preparation of vanadium-titanium magnetite (VTM) pellets are determined, and an efficient and green utilization technology for VTM based on the integration of oxidation roasting-hydrogen-based shaft furnace direct reduction is established. The results indicate that the preferable VTM oxidized and pre-reduced pellets can be prepared by preheating at 925 °C for 18 min and roasting at 1200 °C for 25 min, followed by the reduction temperature of 1050 °C at the reduction atmosphere of 4% CO₂ and H₂/CO = 8. The corresponding compressive strength of the preheated and roasted pellets is 516 N per pellet and 2028 N per pellet, respectively. In addition, the LTD_+6.3 and LTD_UP of roasted pellets are 80.86% and 93.90%, and the corresponding reducibility index, reduction swelling index, and the reduction sticking index are 0.0428, 2.32%, and 2.50%, respectively. All of which meet the production requirements of hydrogen-based shaft furnace.

Herein, to improve the microstructure homogeneity of 12Cr10Co3MoWVNbNB steel for turbine blades after forging, the hot deformation behavior and microstructure evolution of the steel are systematically investigated using a hot-compression experimental setup under the conditions of 950–1150 °C and strain rate of 0.001–10 s⁻¹. A strain-compensated constitutive equation is established based on the flow curves and the accuracy of its prediction is verified. By combining hot processing map with microstructure observation, the optimal hot processing window is determined to be 1075–1150 °C and 1–10 s⁻¹, within which the grain size can be refined to 14.24 μm. Electron backscatter diffraction is employed to investigate the microstructural evolution and dynamic recrystallization (DRX) nucleation mechanism of the deformed samples, revealing that discontinuous DRX characterized by strain-induced grain-boundary migration is the dominant nucleation mechanism. Additionally, the deformation conditions significantly affect the distribution of dislocation density and local misorientation, as well as the transition from low-angle grain boundaries to high-angle grain boundaries, which ultimately lead to the differences in DRX fraction and microstructure.

The nitrogen content and solidification structure of the 1Mn18Cr18N ingots produced by the customized laboratory-scale vacuum induction melting furnace and the pressure electroslag remelting furnace (PESR) with novel composite electrode under different pressure and the same power consumption are compared and studied. The results show that there are perfectly uniform radial chromium and nitrogen profiles during the PESR process. The nitrogen uptake reaction in the PESR process with composite electrode takes place on the liquid metal film on the electrode. Nitrogen uptake could be improved by increasing the nitrogen partial pressure. In addition, the basin depth at a pressure of 0.1 and 1.22 MPa is about 41 and 38 mm, the angle of the grains with respect to the vertical axis is 35° and 31°, respectively. The flat metal basin profile resulted from the thermal resistance at the slag–mold interface decreasing with increasing pressure. Primary and secondary dendritic arm spacing (PDAS and SDAS) variations exhibit an increasing and subsequently decreasing the trend as they move further away from the center in a horizontal direction. Both PDAS and SDAS decrease with increasing pressure from 0.1 to 1.22 MPa.

The primary objective of this study is to investigate the corrosion resistance of Fe-36Ni Invar alloys with varying Mg contents in a 3.5 wt% sodium chloride solution. The electrochemical results reveal that the incorporation of Mg amplified the corrosion behavior of Fe-36Ni Invar alloy. The inclusion compositions undergo a transformation with the increase of Mg content, evolving from MnO–MnS in 0 Mg alloy to MnO–MnS–MgO in 0.0015 Mg alloy, and ultimately to MnS–MgO–MgS in 0.0030 Mg alloy. During the corrosion process, the small-sized MnS–MgO–MgS inclusions exhibit greater stability compared to the MnO–MnS inclusions, rendering them less susceptible to attack and dissolution. Adding Mg diminishes the size and number density of inclusions, which effectively decreases the susceptibility to pitting initiation. The introduction of Mg refines the microstructure and elevates the fraction of twin boundaries, which also is responsible for the enhancement of corrosion resistance.

This study investigates the effect of pressure (burn-off and forging) on the mechanical properties of the joint between a wear-resistant tool steel and a low-alloy steel using linear friction welding. The authors have previously demonstrated the feasibility of joining these dissimilar materials, but the impact of pressure on the mechanical properties of the bimaterial joint remains unclear. To address this, weld samples are prepared using different pressures and are characterized through microstructural analysis, microhardness, tensile testing, and fractography. The results show that the strength of the joint between the wear-resistant tool steel and the low-alloy carbon steel increases as the pressure increases up to a certain point, after which a decrease is observed. The highest joint strength is achieved at a pressure of 360 MPa. The microhardness profile measurement reveals a distinct transition zone at the interface between the two materials, with varying hardness values. The hardness of the low-alloy carbon steel increases near the interface, while that of the wear-resistant tool steel decreases. This transition zone is found to be narrower at higher pressures. Microstructural characterization shows that the grain structure near the interface differs from that of the starting base materials.

Recycled MgO–C lining bricks and 316L stainless steel are used to manufacture composite material for inert anode samples for aluminum electrolysis cell. The microstructure of the composite material is characterized after preoxidation thermal treatments at 800, 900, and 1000 °C as well as in its sintered state. Preoxidation (PO) process is designed to enhance the material's corrosion resistance in molten cryolite environments by developing robust Fe–Mg–O, Fe–Cr–O- containing phases. Analytical techniques including scanning electron microscopy, electron backscatter diffraction, and energy dispersive X-ray spectrometry are applied to characterize the phase formation, revealing the potential of these composites for use as inert anodes in aluminum electrolysis cells. PO at 800 °C is not sufficient to form adequate protective oxide layers. Whereas, PO at 900 and 1000 °C leads to the formation of protective oxide layers containing Mg–O Fe–O halite-like solid solutions and (Cr,Fe)₃O₄ spinel phase. Sample, preoxidized at 1000 °C is sealed in Mg–Fe–O spinel phase.

The effect of strand (S-) and final (F-) electromagnetic stirring (EMS) on solidification structure characteristic of a φ690 mm continuously cast round bloom has been investigated industrially and theoretically. The newly designed S1-EMS equipped just below the foot zone takes great effect on both equiaxed ratio and distribution alignment, as well as central porosity. Larger current S1-EMS leads to higher equiaxed ratio, more symmetrical equiaxed zone, and smaller diameter of central porosity, and the effect is much more obvious than conventional S2-EMS and F-EMS. It is also noticed that there should be a saturation effect of S1-EMS on the promotion of equiaxed dendrite nucleation. The S2-EMS is beneficial for the expanding of equiaxed zone and improving of central porosity. When S1-EMS is weak, strong S2-EMS results in more asymmetrical equiaxed zone. However, when S-EMS is strong, strong S2-EMS results in more symmetrical distribution of equiaxed zone. The F-EMS takes a little impact on the expanding of equiaxed zone in the large-sized round bloom, and almost no effect on the alignment. The central porosity, however, is improved by F-EMS with the help of decrease in temperature gradient and compensation of solidification contraction.