steel research international最新文献

Ferritic/martensitic steels and austenitic stainless steels are high-strength steels, and highly recommended in high-temperature and high-pressure application. In general, multimetallics with different Inconel alloys are used for joining. This is quite a complex and time-consuming procedure. The current work demonstrates the efforts made to weld 8 mm-thick P91 steel and 316L SS plates in a single pass using activating flux tungsten inert gas (A-TIG) welding process without any interlayers. The main challenge is to get the symmetric weld bead profile. Flux coating is optimized in terms of flux composition, coating density, and coating pattern to get the full penetration with symmetric appearance. The current work discusses the possible cause and their solution of asymmetricity during dissimilar welding. Differential flux coating density is found to be very effective in controlling the arc column shape, fluid flow, and consequently the bead geometry. High coating density is used in the P91 side compared to 316L side. Symmetric weld profile with full penetration is achieved by applying multicomponent flux (33–38% TiO₂, 38–43% SiO₂, 13–17% NiO, and 8–10% CuO) during A-TIG welding.

The viscosity of CaO–SiO₂–FeO_t–Al₂O₃–BaO steel slag with the BaO substitution for CaO is measured. Calculation of the corrected optical basicity and the apparent activation energy of the steel slag are executed. The effect of substituting CaO with BaO on structure evolution is studied. The measured results show that the viscosity of molten slag increases with the BaO substitution. The values of corrected optical basicity decrease from 0.63441 to 0.62329 with the BaO substitution. The apparent activation energy shows an upward trend from 152.78 to 160.62 kJ mol⁻¹ with the BaO substitution. The Fourier transform infrared reflection analysis indicates that the structure complexity of the [SiO₄] and [AlO₄] tetrahedrons is increased with the BaO substitution. The Raman analysis indicates that the translation of Q⁰ and Q¹ to Q² and Q³ is advanced with the substitution of BaO for CaO in molten slag. The conversion of O²⁻ to O⁰ is promoted with the substitution of BaO for CaO using X-Ray photoelectron spectrometer analysis. The complexity of the molten slag network structure and the degree of polymerization are all increased by the substitution of BaO for CaO, which sits comfortably with measured viscosity results.

In this work, the influence of part dimensions on the microstructure of low-alloy steel during its austempering has been studied. 0.41C-0.24Si-0.63Mn-0.93Cr steel of different diameters ranging from 5 to 16 mm has been austempered at 350 °C for 10 min. Despite similar austempering conditions, an increase in the size and fraction of acicular/polygonal ferrite has been noted with an increase in the diameter of the samples. From the experimental observations and analytical calculations based on multi-dimensional transient heat transfer analysis, the cooling rate during austempering has been observed to increase with a decrease in the sample diameter. Variation in ferrite grain size and fraction is due to different cooling rates encountered by different sized specimens during austempering. Close agreement between the experimental and theoretically estimated ferrite grain size due to variation in cooling rate during austempering has been noted.

Currently, the typical charge structure for blast furnace smelting of vanadium–titanium magnetite (VTM) is the addition of acidic pellets, high-basicity sinters, and lumps. To increase the percentage of pellets entering the blast furnace, it is necessary to transfer the basicity burden to the pellets. In this study, the effect of basicity on the phase transition and oxidation hardening mechanism of VTM pellets is investigated. In the results, it is indicated that when the preheating temperature is 950 °C, the preheating time is 15 min, the roasting temperature is 1260 °C, and the roasting time is 15 min, with the basicity (CaO/SiO₂) increasing from 0.08 to 1.3, the compressive strength of pellets shows a trend of “increasing first and then decreasing,” with the highest value reaching 3159 N pellet⁻¹ at basicity of 0.5. As the basicity increases, calcium ferrate can be generated by CaO in the liquid phase with Fe₂O₃ in addition to silicate with SiO₂, which will increase the amount of the liquid phase. With the increase of basicity, the oxide-bonded induration is gradually weakened, and the slag-bonded induration is gradually enhanced. A moderate amount of liquid phase can play the role of bonding and filling, thereby improving compressive strength.

Digital image correlation (DIC) technology can capture strain anomalies and predict crack initiation providing early warning of material failure. Herein, DIC technique is used to calculate the full-field strain by analyzing the grayscale patterns of speckle images during the tensile process. This allowed for an analysis of the microstructure evolution of the 316LN austenitic stainless steel (SS) at cryogenic temperatures. Deformation behavior of the 316LN SS at cryogenic temperatures is further analyzed using electron backscatter diffraction technology and transmission electron microscopy. Based on the strain field obtained by the DIC technique, a comprehensive analysis of the martensite volume fraction at different strains can be conducted. The results show that the strain localization under cryogenic deformation is related to martensitic transformation, while the random distribution of slip bands aligns with local strain peak values. Notably, fracture under cryogenic deformation occurs in regions where the strain field reaches its peak, rather than at locations with the maximum strain value.

In the continuous casting process, the heat transfer effect of secondary cooling plays an important role in the quality of the slab. The cooling intensity and cooling uniformity of the secondary cooling nozzle need more efficient spray cooling to achieve. Herein, the cold characteristics of different types of nozzles were compared. It is found that the second type of air mist nozzles have more uniform water density and striking force. On this basis, high-temperature heat transfer experiments for casting billets were carried out to study the heat transfer coefficients of different air mist nozzles in the secondary cooling zone of continuous casting. It is found that the heat transfer coefficient increases as the distance of the temperature measurement point from the nozzle directly below increases. The heat transfer coefficients of the casting billet in both the jet and non-jet zones are decreasing to varying degrees. When the temperature drops to 600 °C, the second type of air mist nozzle shows a faster temperature drop at the point of measurement, a smaller difference in time taken for temperature drop between jet and non-jet zones, and faster and more uniform spraying, leading to a more significant trend of increasing heat transfer coefficient.

The formation of the solid phases CaS, 3CaO.SiO₂ and CaO.Al₂O₃ around the lime particle decreases the efficiency of desulfurization by the kanbara reactor (KR) process. The addition of fluxes reduces the formation of these phases. The addition of Al and Si can also have this effect, depending on the added levels. In this study, different mixtures based on CaO with different levels of fluorspar, sodalite (Nepheline Syenite), and SiO₂ and Al₂O₃ content were studied and used in the desulfurization process of hot metal. These mixtures were added to a bath of liquid hot metal at 1400 °C. All experiments were performed with mechanical agitation. Samples were taken at times of 5, 10, 15, and 20 min, and analyses were performed to evaluate the variation of sulfur over time. The Thermo-Calc software was used to determine the formed phases, solid fraction, and liquid fraction of the different mixtures. With this data, different values of the Global Desulfurization Factor (FG_DeS) were calculated, which was developed to evaluate and predict the efficiency of hot metal desulfurizing mixtures by the KR process. The results of showed that fluorspar was more efficient than sodalite. The FG_DeS had a correlation factor (R²) above 0.9 with the desulfurization efficiency.