查看更多>>摘要：Carbon dioxide(CO2)emissions have become an important factor limiting the high-quality development of the Chinese steel industry.To achieve the goal of carbon peak and carbon neutrality,the strategic planning and technological layout of low-carbon development have been carried out by the Chinese steel industry and enterprises.Based on the summary and analysis of the technology roadmap of low-carbon development in the steel industry and an evaluation of the current research progress of low-carbon technologies,the prospects for the low-carbon development of the steel industry in the future were provided.The results indicate that some steel enterprises in China have already released their low-carbon development roadmaps with a focus on achieving carbon neutrality,which will be realized through advancements in system energy efficiency improvement,resource recycling,process optimization and innovation,breakthrough in smelting technology,product iteration and upgrading,and carbon capture,utilization,and storage(CCUS).The technology development of hydrogen metallurgy and CCUS has shown rapid progress.In the future,the Chinese steel industry must continue to prioritize low-carbon technology and promote the utilization of clean energy.The ratio of electric arc furnace steel should be increased gradually,and the development and application of CCUS technology should be promoted,to ensure the achievement of the"carbon peak and carbon neutrality"goal.
查看更多>>摘要：SiO2 is the main component of gangue in sinters and a crucial constituent in the formation of the SiO2-Fe2O3-CaO(SFC)system.The non-isothermal crystallization kinetics of the SFC system were investigated using differential scanning calorimetry.The crystallization process of SFC was studied under different cooling rates(5,10,15,and 20 K/min),and the crystalline phases and microstructures of the SFC crystals were verified through X-ray diffraction and scanning electron microscopy.The results indicate that when the SiO2 content is 2 wt.％,increasing the cooling rate promotes the precip-itation of CaFe2O4(CF)in the SFC system,thereby inhibiting the precipitation of Ca2Fe2O5(C2F).In contrast to the CaO-Fe2O3(C-F)system,the addition of SiO2 does not alter the precipitation mechanisms of C2F and CF.By further adding SiO2,the precipitation of Ca2SiO4(C2S)significantly increases.Simultaneously,the CaO content in the liquid phase decreases.This leads to the crystallization process of the CF4S(4 wt.％SiO2)system bypassing the precipitation of C2F and directly forming CF and CaFe4O7(CF2).In the case of the CF8S(8 wt.％SiO2)system,the crystallization process skips the precipitation of C2F and CF,directly yielding CF2.The crystallization process of both CF2S(2 wt.％SiO2)and CF is similar,comprising two reaction stages.The Ozawa method was used to calculate the activation energy for the crystallization of C2F and CF as-329 and-419 kJ/mol,respectively.Analysis using the Malek method reveals model functions for both stages.
查看更多>>摘要：The steel belt roasting process has the advantages of low cost,small footprint,and high thermal efficiency,making it widely used in the smelting of ferroalloys such as ferrochrome,ferromanganese,and ferroniobium.However,its appli-cation in preparing iron ore oxidized pellets has not been sufficiently explored.The optimal thermal process conditions for magnesium-containing oxidized pellet preparation by steel belt roasting machine were investigated based on the roasting properties of high-magnesium iron concentrate and typical iron concentrate.The results indicate that,for the blending scheme of 70 wt.％high-magnesium iron concentrate and 30 wt.％typical iron concentrate,the appropriate preheating temperature for pellets is 950-975 ℃ and the suitable roasting temperature is 1250-1275 ℃,during which the com-pressive strength of pellets can exceed 2500 N pellet-1.During the steel belt roasting process,SO2 is primarily released in the preheating zone,and the maximum exhaust gas temperature in the roasting zone can reach 637 ℃.High-temperature sulfur-containing exhaust gas causes oxidation corrosion,sulfide corrosion,and deformation of the steel belt.To enhance the steel belt longevity,it is recommended to appropriately reduce the wind velocity in the preheating zone and roasting zone,while also decreasing the ratio of pellet bed height to hearth layer height.By adopting the system of"low wind velocity,thin pellet bed,fast steel belt speed,"the exhaust gas temperature can be reduced to 463 ℃.The prepared pellet maintains a compressive strength of 2607 N pellet-1 and exhibits excellent metallurgical properties.
查看更多>>摘要：Metallurgical dust(MD)was used as raw material to prepare rare earth Ce-doped Fe-based catalysts.The results show that the Ce0.1/AMD-300 ℃ catalyst prepared from acid-modified diatomite(AMD)with mCe/mMD=0.1(mCe and mMD are the mass of Ce and MD,respectively)after being roasted at 300 ℃ can reach 99％NOx removal rate in the wide temperature range of 230-430 ℃ and exhibits excellent SO2 and H2O resistance.The MD effectively removes alkali metal elements by the modification process,increases the specific surface area and optimizes the pore structure of MD.The doping of Ce element makes Fe-based catalysts have more surface adsorbed oxygen Oα and a higher Ce3+/Ce4+ratio.Through ammonia temperature-programmed desorption and hydrogen temperature-programmed reduction,it was found that the strong interaction between cerium and iron promotes the formation of more oxygen cavities in the catalyst,thereby generating more active and easily reducible oxygen species and promoting the transformation of Brønsted acid site to Lewis acid site.The research results provide a theoretical basis for the preparation of efficient and inexpensive Fe-based catalysts from MD.
查看更多>>摘要：To reveal the intricate mechanisms underlying the melting and dissolution processes of scraps in the iron ladle,the melting characteristics of three carbon steels with different C concentrations at the bath temperatures of 1623 and 1723 K were studied.Upon immersing scraps into the molten metal,the liquid metal immediately froze around the submerged parts of scrap cylinders.Whereafter,the solid shell completely melted at both bath temperatures after the immersion time of 5 s.The maximum thickness of solidified steel shells significantly decreased with increasing the bath temperature.The findings also suggested that the melting rate of scrap cylinder exhibited a positive correlation with the C concentration in the scrap and the bath temperature.Quantitatively,the mass transfer coefficients of C for the low carbon(0.18 wt.％),medium carbon(0.32 wt.％),and high carbon(0.61 wt.％)concentrations in the scrap cylinders at 1723 K were determined by a kinetic model,which were 8.78 × 10-5,9.57 × 10-5 and 10.00 × 10-5 m s-1,respectively,and those corresponding values decreased to 3.87 × 10-5,4.49 × 10-5 and 3.54 × 10-5 m s-1 at 1623 K.However,there was little difference observed among the heat transfer coefficients of hot metal for the three carbon steels,which were estimated to have an average value of 16.36 and 18.82 kW m-2 K-1 at the experimental temperatures of 1623 and 1723 K,respectively.The results from the experiments and mathematical models showed good consistency at both bath temperatures,providing feasible guidance for efficient melting of steel scraps in the iron ladle.
查看更多>>摘要：A model combining kernel principal component analysis(KPCA)and Xtreme Gradient Boosting(XGBoost)was intro-duced for forecasting the final oxygen content of electroslag remelting.KPCA was employed to reduce the dimensionality of the factors influencing the endpoint oxygen content and to eliminate any existing correlations among these factors.The resulting principal components were then utilized as input variables for the XGBoost prediction model.The KPCA-XGBoost model was trained and proven using data obtained from companies.The model structure was adapted,and hyperparameters were optimized using grid search cross-validation.The model performance of the KPCA-XGBoost model is compared with five machine learning models,including the support vector regression model.The findings demonstrated that the KPCA-XGBoost model exhibited the highest level of prediction accuracy,indicating that the incorporation of KPCA significantly enhanced the regression prediction performance of the model.The accuracy of the KPCA-XGBoost model was 82.4％,97.1％,and 100％at errors of±1.5 × 10-6,±2.0×10-6,and±3 × 10-6 for oxygen content,respectively.
查看更多>>摘要：Drying shrinkage is an important factor affecting the durability of alkali-activated materials.The drying shrinkage of alkali-activated carbon steel slag and the effect of silica fume substitution were studied.The drying shrinkage test lasted for 300 d.The compressive strength,flexural strength,Vickers hardness,mass recovery and drying shrinkage recovery of the samples after drying shrinkage were tested.The hydration products and microstructure were characterized by X-ray diffraction,mercury intrusion porosimetry,thermogravimetry-differential thermogravimetry,and scanning electron microscopy-energy dispersive spectroscopy.The results show that although the chemical expansion compensates for the drying shrinkage in 42 d,the drying shrinkage increases continuously within 300 d.Silica fume affects drying shrinkage by refining pore size and increasing matrix microhardness.Solid surface tension and capillary pressure are the driving forces for drying shrinkage in the early and middle to late stages,respectively.The evolution of drying shrinkage is also influenced by chemical expansion,matrix microhardness and macropore collapse.
查看更多>>摘要：Ordinary refractory ceramics are multi-phase materials,and their inhomogeneous microstructures induce the scatter of properties.The definition of a reasonable number of samples is important to obtain representative results from experiments and simulations,and this reasonable number might be property or microstructure relevant.Stochastic discrete element(DE)simulations of cold crushing tests with homogeneous interface properties were performed.Three minimum DE size ranges were used to represent matrix variation at different levels.Statistical methods,i.e.,Kolmogorov-Smirnov(K-S)test,t-test,and correlation analysis,were utilized to study the influences of minimal number of samples on mechanical properties and crack density.It revealed that a relatively small number of samples are sufficient to obtain representative cold crushing strength(CCS)and Young's modulus,whilst a large number of samples are favourable when the fracture energy and crack density under cold crushing conditions are of interest.The analysis also showed that the fracture energy under cold crushing condition generally correlates positively with CCS,and the static Young's moduli determined from the stress-piston displacement curves with different definitions are divergent,caused by contact compliance and premature cracking.The data from the stress-strain curves recorded directly on the sample are required for the accurate static Young's modulus calculation.
查看更多>>摘要：A three-dimensional finite element model coupled with heat transfer,shrinkage accumulation and high temperature deformation was established for φ690 mm round bloom in continuous casting,and it was verified by surface temperature,shell thickness,contour shape and porosity size by measurement.The compensation area of the shrinkage zone increases as the reduction amount increases.The compensation effect by the reduction of the unit with liquid core is about two times higher than others with fully solid matrix at a given reduction amount.A mathematical method to determine the reduction parameters for large-sized round bloom during continuous casting was proposed by the multi-rollers strategy.For theφ690 mm round bloom,the suitable reduction parameters for Nos.2-6 units are suggested as 15,15,10,10,10 mm with a casting speed of 0.26 m min-1 to close the shrinkage with a diameter of about 17.5 mm in average.The industrial test on the reduction of large-sized round bloom for LZ50 steel was carried out.A total amount of 65-70 mm reduction was realized in the bloom for different casting speeds.The maximum diameter of the central porosity is about 16.3 mm in the longitudinal section at the casting speed of 0.24 m min-1,and it decreases to 7.3 mm after 65 mm reduction.Meanwhile,the maximum diameter of the central porosity is about 18.7 mm at 0.26 m min-1,while it decreases to 4.1 mm by a reduction of 70 mm.Finally,the difference of the solidification end reduction on round bloom and rectangular or square bloom is theoretically compared.Low deformation resistance and high bulge effect were found in round bloom compared to rectangular bloom.According to the results about solidification contraction accumulation and reduction efficiency in round bloom,the suitable reduction zone to control the central porosity during continuous casting is suggested to be 0.5-1.0.
查看更多>>摘要：To solve the problems of severe interface oxidation at high temperature,low interface bonding strength at low temperature,and severe plate shape warping in the traditional flat rolling process for preparing Ti/steel clad plates,a new corrugated-flat rolling(CFR)process is adopted to prepare Ti/steel clad plates with corrugated interface.The study investiagtes the effects of different heating temperatures on the interface morphology,mechanical properties and corrosion resistance.Ti/steel clad plates prepared by CFR process have a distinct corrugated three-dimensional interface.The diffusion range of interface elements and the thickness of solid solution diffusion layer change with different heating temperatures.The tensile-shear strength of the clad plate increases first and then decreases with the increase in heating temperature,peaking at 327 MPa at 900 ℃.The tensile strength is less affected by heating temperature,and the maximum tensile strength is achieved at a heating temperature of 800 ℃,with a value of 766 MPa.During the fracture process of the clad plates,the steel exhibits plastic fracture characteristics,while Ti exhibits a mixture of plastic and brittle fracture characteristics.The overall corrosion resistance of Ti surface in the clad plate is good.As the heating temperature increases,the polarization resistance of Ti surface decreases,the current density in the passivation zone increases,and the active sites and energy required for the formation of the passivation film decrease.
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