Ironmaking at Baosteel has focused on blast furnaces over the last 30 years. After passing through the stages of ＂learning＂, ＂tracking＂, ＂usage＂, ＂experimentation＂, ＂innovation＂ and ＂development＂, Baosteel...Ironmaking at Baosteel has focused on blast furnaces over the last 30 years. After passing through the stages of ＂learning＂, ＂tracking＂, ＂usage＂, ＂experimentation＂, ＂innovation＂ and ＂development＂, Baosteel ＇ s production capacity has grown steadily and its standard of technology is increasing. Remarkable progress has been made in the technologies of blending stack, thick layer sintering, low silicon and high anhydroferrite sintering, coal blending, and the high productivity with high pulverized coal injection （PCI） rate and long campaign of the blast furnaces. The entire ironmaking process is developing in the direction of high efficiency, low energy consumption, clean production, and environmental protection because the zero discharge of solid waste and industrial sewage has been achieved. After 20 years of development, Baosteel has become a modernized iron producer with an annual capacity of 28.85 Mt of sinter,7.26 Mt of coke and 22.50 Mt of hot metal （Pugang Corex furnace output included）, and its main economic and technological indices have reached a world-class level.展开更多
The utilization of iron coke provides a green pathway for low-carbon ironmaking.To uncover the influence mechanism of iron ore on the behavior and kinetics of iron coke gasification,the effect of iron ore on the micro...The utilization of iron coke provides a green pathway for low-carbon ironmaking.To uncover the influence mechanism of iron ore on the behavior and kinetics of iron coke gasification,the effect of iron ore on the microstructure of iron coke was investigated.Furthermore,a comparative study of the gasification reactions between iron coke and coke was conducted through non-isothermal thermogravimetric method.The findings indicate that compared to coke,iron coke exhibits an augmentation in micropores and specific surface area,and the micropores further extend and interconnect.This provides more adsorption sites for CO_(2) molecules during the gasification process,resulting in a reduction in the initial gasification temperature of iron coke.Accelerating the heating rate in non-isothermal gasification can enhance the reactivity of iron coke.The metallic iron reduced from iron ore is embedded in the carbon matrix,reducing the orderliness of the carbon structure,which is primarily responsible for the heightened reactivity of the carbon atoms.The kinetic study indicates that the random pore model can effectively represent the gasification process of iron coke due to its rich pore structure.Moreover,as the proportion of iron ore increases,the activation energy for the carbon gasification gradually decreases,from 246.2 kJ/mol for coke to 192.5 kJ/mol for iron coke 15wt%.展开更多
The transformation mechanism of the inclusions and microstructure in 316L stainless steel after post-isothermal heat treatment(IHT)was revealed,along with the pitting behavior of the inclusions in a chloride environme...The transformation mechanism of the inclusions and microstructure in 316L stainless steel after post-isothermal heat treatment(IHT)was revealed,along with the pitting behavior of the inclusions in a chloride environment before and after the transformation.The effect of the inclusion transformation on the pitting corrosion behavior of 316L stainless steel and its intrinsic mechanism was also revealed.Results revealed a gradual transformation of MnO-SiO_(2)inclusions into MnO-Cr_(2)O_(3) within the temperature range of 1373 to 1573 K.MnO-Cr_(2)O_(3)inclusions exhibited minimal dissolution in chloride ion corrosion environments,while MnO-SiO_(2)oxides demonstrated higher electrochemical activity and were more prone to dissolve and form pits.Meanwhile,IHT significantly reduced the dislocation density of stainless steel,rendering it more stable in corrosive environments.X-ray photoelectron spectroscopy peak distributions of the passive films demonstrated that IHT increased the proportion of Cr and Fe oxides and hydroxides in the passive film which improved the stability and corrosion resistance of the steel.展开更多
In order to mitigate the harm of alumina,calcium aluminate,and magnesium aluminum spinel inclusions on the fatigue performance of bearing steel,the effect of Ce-Mg composite treatment on the cleanliness of silicon-kil...In order to mitigate the harm of alumina,calcium aluminate,and magnesium aluminum spinel inclusions on the fatigue performance of bearing steel,the effect of Ce-Mg composite treatment on the cleanliness of silicon-killed GCr15 bearing steel and the evolution of Ce-Mg-Mn-O-S composite inclusions during heat treatment of the steels at 1523 K were investigated in this present work.The results indicate that the cleanliness of S2 with 0.0045 wt%Ce and 0.0016 wt%Mg is better than that in S1 with0.0020 wt%Ce and 0.0011 wt%Mg,which is attributed to the more effective removal of Ce-Mg-Mn-O-S composite inclusions,with help of good aggregation capacity of Ce-containing inclusions and small volume density of Mg-containing inclusions,due to the increase of rare earth and magnesium content.The aspect ratio and area fraction of the Ce-Mg-Mn-O-S composite inclusions in as-cast steel decrease significantly with isothermal treatment at 1523 K for 150 min,due to the effect of(ⅰ)Ostwald aging mechanism of inclusions and(ⅱ)sulfide solid solution during isothermal treatment.With the increase of isothermal treatment time from 150 to 550 min,the aspect ratio and area fraction of the inclusions in SO(untreated steel)and S1 decrease slightly,because spheroidization and solid solution of inclusions reach their basic equilibrium at 1523 K.However,the aspect ratio and area fraction of the Ce-Mg-Mn-O-S composite inclusions in S2 actually increase,and the inclusions evolve into three-phase(two-phase)inclusions,which is attributed to(ⅲ)transformation of phase compositions in inclusions and interfacial reaction between inclusions and steel matrix during isothermal heating.Therefore,the control of inclusions in silicon-killed bearing steel with Ce and Mg composite treatment should be combined with specific heat treatment processes and appropriate rare earth and magnesium contents,to minimize the damage of inclusions on the fatigue performance of bearing steel products.展开更多
The Ni-ZnFe_(2)O_(4)(NixZn_(1-x)Fe_(2)O_(4),x=0.4-0.7)spinel was synthesized using Zn2+extracted from electric arc furnace dust(EAFD),nickel chloride hexahydrate,and Fe^(3+)extracted from iron scale as raw materials.T...The Ni-ZnFe_(2)O_(4)(NixZn_(1-x)Fe_(2)O_(4),x=0.4-0.7)spinel was synthesized using Zn2+extracted from electric arc furnace dust(EAFD),nickel chloride hexahydrate,and Fe^(3+)extracted from iron scale as raw materials.The zinc was selectively extracted from EAFD using CaO roasting followed by NH_(4)Cl solution leaching.The ferric ion was leached from iron scale using HCl solution as acid lixiviant.The experimental results demonstrate a high level of efficiency in the extraction of zinc,with a rate of 97.5%,and the leaching rate of ferric ion is 96.89%.The composition of the leaching solution is primary zinc and iron with low calcium,which is beneficial to the preparation of spinel ferrite.The influence of Ni content(x)and calcination temperature on the synthesis and magnetic properties of NixZn_(1-x)Fe_(2)O_(4)compounds was investigated by X-ray diffraction,scanning electron microscopy,and vibrating sample magnetometry.The results revealed that both Ni content and calcination temperature significantly affect the synthesis and magnetic properties of spinel NixZn_(1-x)Fe_(2)O_(4).Under the conditions of Ni content set at x=0.6,calcination temperature of 1100℃,and a duration of 2 h,a spinel NixZn_(1-x)Fe_(2)O_(4)with high saturation magnetization(Ms=65.7 A m2 kg-1)and low coercivity(Hc=0.056 A m^(-1))was obtained.展开更多
The dissolution behaviors of lime,limestone,and core–shell structured lime,as well as their effects on dephosphorization behavior were studied.The results show that the slow dissolution of lime in converter slag is m...The dissolution behaviors of lime,limestone,and core–shell structured lime,as well as their effects on dephosphorization behavior were studied.The results show that the slow dissolution of lime in converter slag is mainly attributed to the calcium silicate layer at the lime/slag interface.CO_(2)generated by CaCO_(3)decomposition can destroy the calcium silicate layer,and thus accelerates the dissolution of limestone and core–shell structured lime.However,in the initial stage,a large amount of CO_(2)emission generated by limestone decomposition results in the poor contact between molten slag and limestone,and the dissolution rate is slower in the test of limestone than that of lime.For core–shell structured lime,the initial dissolution rate is not affected due to the lime surface,and is accelerated by the appropriate CO_(2)emission.Rapid CaO pickup in molten slag by fast dissolution of the lime sample can remarkably accelerate the dephosphorization reaction.Because of the fastest dissolution rate,the core–shell structured lime slagging mode shows the most promising prospects for the efficient dephosphorization.展开更多
During the sintering process of iron ore,a large amount of nitrogen oxides is generated,for which there is currently no efficient and economical treatment process.Therefore,it is necessary to implement process control...During the sintering process of iron ore,a large amount of nitrogen oxides is generated,for which there is currently no efficient and economical treatment process.Therefore,it is necessary to implement process control in sintering production to keep the mass concentration of NO_(x)in sintering flue gas at a low level.Through industrial trials at sintering sites,methods such as correlation analysis,path analysis,and multiple linear regression were applied to analyze the influence of various factors on NO emissions during the sintering process.The results indicate that negative correlations exist between nitrogen monoxide(NO)emissions and negative pressure,permeability index,O_(2) concentration,CO concentration,and flue gas temperature.Conversely,positive correlations exist between NO emissions and dust concentration,water vapor volume fraction,and sintering bed speed.Among these factors,O_(2) concentration and dust concentration are identified as the most significant influencing factors on NO emissions.By analyzing the masses and modes of influence of different factors,the mechanisms of action of each factor were obtained.Specifically,O_(2) concentration,dust concentration,permeability index,CO concentration,and flue gas temperature play a direct dominant role in NO emissions during the sintering process,while water vapor volume fraction,sintering trolley speed,and negative pressure have an indirect effect.A predictive model for NO mass concentration in flue gas was established with an accuracy rate of 91.6%,showing consistent overall trends with actual values.Finally,denitrification strategies for sintering industrial production were proposed,along with prospects for preliminary denitrification of sintering flue gas using fluidized bed conditions in the duct.展开更多
Coke is the only solid charge component in the lower part of the blast furnace,and its strength is crucial to its production.Si and Al are the two most abundant elements in coke ash.The influences of these oxides on t...Coke is the only solid charge component in the lower part of the blast furnace,and its strength is crucial to its production.Si and Al are the two most abundant elements in coke ash.The influences of these oxides on the tensile strength of the coke matrix were studied by splitting tests.According to the Weibull analysis,with increasing Si and Al oxide concentrations,the fracture stress range of the coke widened,the upper and lower limits decreased,the probability of fracture under the same stress conditions increased,and the randomness and dispersion of strength increased.These results can be attributed to the inhibitory effect of ash during coal pyrolysis.Ash impedes the growth and contact of mesophase,leading to a decrease in graphitic carbon structures and an increase in edge carbon and aliphatic carbon structures in the resulting coke.Consequently,the overall ordering of the carbon structure is reduced.Moreover,SiO_(2)and Al_(2)O_(3)promoted the development of coke pores,thinned the coke pore wall,and significantly increased the proportion of large pores(>500μm).Moreover,Al_(2)O_(3)had more significant influences on the coke strength,carbon structure and stomatal ratio than SiO_(2).In addition,the position where the ash particles bonded to the carbon matrix easily produced cracks and holes,and the sharp edge of the matrix was likely to produce stress concentration points when subjected to an external force,leading to structural damage.Therefore,controlling the concentration of ash could effectively reduce the number of structural defects inside coke,which is conducive to improving the strength.展开更多
The productivity of the chrome-containing semi-steel converter smelting process is directly affected by the slag-forming speed during the converter preliminary stage.The effects of Cr_(2)O_(3) content on the physicoch...The productivity of the chrome-containing semi-steel converter smelting process is directly affected by the slag-forming speed during the converter preliminary stage.The effects of Cr_(2)O_(3) content on the physicochemical properties of the CaO-SiO_(2)-Fe_(t)O-MgO system,such as melting temperature,solidification behavior,mineral composition,and lime dissolution rate,were studied.The results showed that the slag was an amorphous phase at 1500℃.When Cr_(2)O_(3) was added,Ca(Fe,Mg)Si_(2)O_(6) and spinel were formed in the slag.With the increase in Cr_(2)O_(3) content,the amount of spinel precipitation increased,and the dendritic FegO_(4) crystal gradually changed into the granular(Fe,Mg)(Fe,Cr)2O_(4) crystal.As the Cr_(2)O_(3) content increased from O to 2.91 wt.%,the melting temperature of the slag rose,and the melting range of the slag expanded slightly,but the lime dissolution rate did not change.When the Cr_(2)O_(3) content further increased to 9.09 wt.%,the melting temperature continued to rise,the melting range rapidly expanded,and the lime dissolution rate decreased.展开更多
In continuous casting production,droplet characteristics are important parameters for evaluating the nozzle atomization quality,and have a significant impact on the secondary cooling effect and the slab quality.In ord...In continuous casting production,droplet characteristics are important parameters for evaluating the nozzle atomization quality,and have a significant impact on the secondary cooling effect and the slab quality.In order to study the behavior of atomized droplets after reaching the slab surface and to optimize the spray cooling effect,the influence of droplet diameter and droplet velocity on the migration behavior of droplets in the secondary cooling zone was analyzed by FLUENT software.Results show that the droplets in the spray zone and on the slab surface are mainly concentrated in the center,thus,the liquid volume fraction in the center is higher than that of either side.As the droplet diameter increases,the region of high liquid volume fraction on the slab surface becomes wider,and the liquid phase distribution in the slab width direction becomes uneven.Although increasing the droplet velocity at the nozzle exit has little effect on droplet diffusion in the spray zone,the distribution becomes more uneven due to more liquid reaches the slab surface per unit time.A prediction formula of the maximum water flow rate on the slab surface for specific droplet characteristics was proposed based on dimensionless analysis and validated by simulated data.A nozzle spacing of 210 mm was recommended under the working conditions in this study,which ensures effective coverage of the spray water over the slab surface and enhances the distribution uniformity of water flow rate in the transverse direction.展开更多
To avoid coarse crystallization of glassy inclusions in Si–Mn deoxidized steel during hot rolling, the effect of MgO on the structure and crystallization behavior of CaO–SiO_(2)–Al_(2)O_(3) inclusions was investiga...To avoid coarse crystallization of glassy inclusions in Si–Mn deoxidized steel during hot rolling, the effect of MgO on the structure and crystallization behavior of CaO–SiO_(2)–Al_(2)O_(3) inclusions was investigated. The results showed that the crystallization temperature of the oxide melts decreased with increasing MgO content from 0 to 15.7 wt.%, which suggested that the addition of MgO would increase the temperature range of the crystalline transition. The increase in MgO content could decrease the crystallization activation energy of inclusions. With the increase in MgO content, the relative fractions of O_(Si)^(0) and O_(Si)^(1) structure units increased, and those of structure units O_(Si)^(2), O_(Si)^(3), and O_(Si)^(4) decreased, increasing the depolymerization degree of the silicate structure. The crystallization ratio of glassy inclusions in the steel crucible increased from 19.7% to 98.3% with increasing MgO content from 0 to 15.7 wt.%. The addition of MgO improved the crystallization ability of inclusions, because MgO provides free oxygen O_(2−) to destroy the bridging oxygens and form non-bridging oxygens O^(−), which depolymerizes silicate network structure and simplifies the [SiO_(4)]-tetrahedral structure. In addition, MgO would promote the precipitation of the Mg-containing phases with a high melting point. When the MgO content was increased above 12.1 wt.%, MgO·Al_(2)O_(3) and 2MgO·SiO_(2) crystalline phases would precipitate from the inclusions.展开更多
The service life of a blast furnace depends largely on the degree of damage to the carbon brick in the hearth.Carbon brick and ramming material in the hearth of a 1780 m3 blast furnace after shutdown were sampled and ...The service life of a blast furnace depends largely on the degree of damage to the carbon brick in the hearth.Carbon brick and ramming material in the hearth of a 1780 m3 blast furnace after shutdown were sampled and investigated.It was found that the substances in the cracks of the carbon brick near and above the taphole were ZnO and Zn_(2)SiO_(4),whereas the substances in the cracks of the carbon brick below the taphole were ZnS.The reaction of Zn with CO,SiO_(2),and Fes generates ZnO,Zn_(2)SiO_(4),and ZnS,resulting in volume expansion,which is an important reason for the cracking of carbon brick.Simultaneously,several obvious Zn vapor flow channels were found in the ramming material,through which Zn vapor could enter the carbon brick,causing damage to the carbon brick.Increasing the compactness of the ramming material is beneficial to preventing Zn vapor from entering the carbon brick through the voids in the ramming material,reducing the destructive effect of Zn on the carbon brick and further extending the service life of the blast furnace.展开更多
A three-dimensional mathematical model has been established for a novel metallurgy process coupling an annular gas curtain with swirling flow at tundish upper nozzle. The discrete phase model and volume of fluid model...A three-dimensional mathematical model has been established for a novel metallurgy process coupling an annular gas curtain with swirling flow at tundish upper nozzle. The discrete phase model and volume of fluid model were applied to simulate the gas–liquid multiphase flow behavior in tundish and nozzle. The effect of argon flow rate on the migration behavior of bubbles and interface behavior between steel and slag was also investigated. The presented results indicate that the novel coupling process can significantly change the flow pattern in the stream zone of a tundish, prolong the average residence time of liquid steel, and reduce the dead fraction. A complete annular gas curtain is formed around the stopper rod of tundish. Under the action of drag force of liquid steel, a part of small bubbles enter the nozzle through the swirling grooves and gather toward the center of the nozzle by centripetal force. As the argon flow rate increases, the volume fraction of argon gas entering the nozzle increases, which enhances the swirl intensity and increases the concentration of bubbles in the nozzle. To avoid the formation of slag open eye in tundish, the argon flow rate should not exceed 8 L min−1.展开更多
A rotating stopper-rod technique was proposed to suppress the formation of free-surface vortex in the tundish.The large eddy simulation model coupled with volume of fluid model was developed to study the steel–slag–...A rotating stopper-rod technique was proposed to suppress the formation of free-surface vortex in the tundish.The large eddy simulation model coupled with volume of fluid model was developed to study the steel–slag–gas three-phase flow behavior.The critical slag entrapment height of the free-surface vortex and mass of residual steel were predicted at different rotating speeds(30,60,90 and 120 r/min)of the rotating stopper-rod.The numerical model was verified by water model experiment.The results showed that by rotating the stopper-rod in the opposite direction of the vortex above the submerged entry nozzle,the formation of vortex can be effectively disturbed and the critical height of the free-surface vortex can be reduced.Particularly for the 2nd strand,when the rotating speeds are 30,60,90 and 120 r/min,the critical height of the free-surface vortex above the 2nd strand is 7.3,4.7,6.3 and 7.4 cm,respectively.A reasonable rotating speed should be 60 r/min,which can reduce about 2 tons of residual steel.Other rotating speeds just can reduce about 1.6 tons of residual steel.展开更多
To investigate the evolutionary behavior of the MnO–SiO_(2)–Al_(2)O_(3)–MgO inclusions during heat treatment,water quenched samples were isothermally held at 1100°C for 120 min in Ar and air atmosphere,and the...To investigate the evolutionary behavior of the MnO–SiO_(2)–Al_(2)O_(3)–MgO inclusions during heat treatment,water quenched samples were isothermally held at 1100°C for 120 min in Ar and air atmosphere,and the obtaining samples were analyzed by X-ray diffraction,scanning electron microscopy and energy dispersive spectrometer.It showed that 3MnO·Al_(2)O_(3)·3SiO_(2)and MnO·SiO_(2)were detected in the 5 wt.%MgO system after isothermal holding in Ar atmosphere,while MgO·Al_(2)O_(3),MnO·SiO_(2)and Mn7O8·SiO4 were detected in air atmosphere.The evolutionary behavior of the 10,15 and 20 wt.%MgO systems after isothermal holding in different atmosphere were consistent.Oxygen affected the solid phase transformation of the low MgO content systems.The calculation results of FactSage 8.1 showed that MgO·Al_(2)O_(3)was formed in the 5 wt.%MgO system with air atmosphere.The solid phase transformation was accompanied by grain coarsening during the isothermal holding process.The differences in the solid phase transformation in different atmosphere of the 5 wt.%MgO system indicated that it was a gas-phase transport grain coarsening mechanism.The enrichment of Al element in the liquid phase region at the grain edges,the homogeneous distribution of Mg element and the disappearance of the liquid phase within the crystal revealed that other MgO content systems were liquid–solid transport grain coarsening mechanism.展开更多
The value-added utilization of converter steel slag is crucial, with China’s annual production having reached 100 million tons. The utilization of converter slag in the construction materials sector is limited as it ...The value-added utilization of converter steel slag is crucial, with China’s annual production having reached 100 million tons. The utilization of converter slag in the construction materials sector is limited as it undergoes volume expansion during the aging process, mainly caused by the hydration reaction of free calcium oxide present in the slag. The influence of alumina addition on the mineral transformation of typical industrial converter slag was investigated. Different quantities of alumina were introduced into the slag, and the original and modified slags were remelted under argon atmosphere, followed by quenching. The experimental results were compared with thermodynamic simulation calculations for further analysis. As the alumina content increases, it reacts with the free calcium oxide in slag, leading to the formation of low-melting-point calcium aluminoferrite. Additionally, alumina addition effectively reduces slag viscosity. Finally, an assessment of the energy consumption for alumina-modified and silica-modified converter slags was presented.展开更多
In order to explore the corrosion mechanism of Al_(2)O_(3)-C refractories in the mold flux bearing MnO,the immersion test of Al_(2)O_(3)-C refractories in CaO-SiO2-CaF2-MnO slag with different MnO contents was carried...In order to explore the corrosion mechanism of Al_(2)O_(3)-C refractories in the mold flux bearing MnO,the immersion test of Al_(2)O_(3)-C refractories in CaO-SiO2-CaF2-MnO slag with different MnO contents was carried out at 1550℃.The results show that Mn particles were observed in the slag after experiment,due to the reduction of MnO by graphite in refractories.Large amounts of graphite were observed at the interface between refractories and slag,indicating that the oxidation of graphite is limited by the poor contact between graphite and molten slag.Therefore,the oxidation of graphite is not the main cause of damage to refractories.A small quantity of CaO·2Al_(2)O_(3)(CA_(2))and CaO·6Al_(2)O_(3)(CA_(6))adjacent to Al_(2)O_(3) grain was detected at the slag/reaction layer interface.CA_(2) and CA_(6) possess relatively high melting points,which is beneficial to hindering the further penetration of slag.However,the dissolution of Al_(2)O_(3) into slag is still the main cause for refractories damage.The increase in the MnO content of mold slag decreases the viscosity and then results in the severe corrosion of Al_(2)O_(3)-C bricks.展开更多
To clarify the deformation behavior of MnS inclusions in a non-quenched and tempered steel at three different positions (edge, 1/2 radius and center) in the cross-section of the billet in the course of hot rolling, is...To clarify the deformation behavior of MnS inclusions in a non-quenched and tempered steel at three different positions (edge, 1/2 radius and center) in the cross-section of the billet in the course of hot rolling, isothermal compression experiments were performed under the deformation temperature range from 1073 to 1473 K, the reduction rates from 25% to 75% and the strain rates from 0.01 to 10 s^(−1). The variations of deformability features (i.e., aspect ratios, size distributions, and morphologies) of MnS inclusions with those isothermal compression parameters were revealed. The evaluation of the probable maximum aspect ratio of MnS inclusions at the three different positions in the cross-section of the billet after hot rolling was examined using the statistical analysis of extreme values. Results showed that the number densities of MnS inclusions at three different positions (edge, 1/2 radius and center) in the cross-section of the steel billet only fluctuated slightly when the deformation parameters varied in the isothermal compression, while the average inclusion aspect ratios in all cases generally have a negative correlation with the deformation temperature and positive correlations with the reduction ratio and the strain rate. Statistical analysis reveals that larger inclusions deform more easily during hot rolling. The effect of rolling temperature on the extreme value of the aspect ratio of inclusions is the smallest, while the effects of initial size, reduction ratio and strain rate are more significant.展开更多
Refractories have an important effect on the cleanliness of molten steel.The interaction between CeAlO_(3) refractories and Ce treated steel was explored and compared with that between Al_(2)O_(3) refractories and Ce ...Refractories have an important effect on the cleanliness of molten steel.The interaction between CeAlO_(3) refractories and Ce treated steel was explored and compared with that between Al_(2)O_(3) refractories and Ce treated steel.The results show that the Ce content in steel decreases sharply after contact with Al_(2)O_(3) refractories and the pick-up of dissolved Al occurs.Compared with the test of Al_(2)O_(3) refractories,the loss of Ce content is less in the test of CeAlO_(3) refractory,and the total oxygen content and dissolved Al content in steel increase less.The dense and continuous Ce_(2)O_(2)S interface layer is observed at the CeAlO_(3) refractories/steel interface,which can serve as the metallurgical isolation layer and hinder the further interaction between refractories and steel.Therefore,the higher steel cleanliness and less penetration of refractories by molten steel are obtained in the test of CeAlO_(3) refractories.The CeAlO_(3) refractories show a promising prospect in the production of clean Ce treated steel.展开更多
Specific grades of high-entropy alloys(HEAs)can provide opportunities for optimizing properties toward high-temperature applications.In this work,the Co-based HEA with a chemical composition of Co_(47.5)Cr_(30)Fe_(7.5...Specific grades of high-entropy alloys(HEAs)can provide opportunities for optimizing properties toward high-temperature applications.In this work,the Co-based HEA with a chemical composition of Co_(47.5)Cr_(30)Fe_(7.5)Mn_(7.5)Ni_(7.5)(at%)was chosen.The refractory metallic elements hafnium(Hf)and molybdenum(Mo)were added in small amounts(1.5at%)because of their well-known positive effects on high-temperature properties.Inclusion characteristics were comprehensively explored by using a two-dimensional cross-sectional method and extracted by using a three-dimensional electrolytic extraction method.The results revealed that the addition of Hf can reduce Al_(2)O_(3)inclusions and lead to the formation of more stable Hf-rich inclusions as the main phase.Mo addition cannot influence the inclusion type but could influence the inclusion characteristics by affecting the physical parameters of the HEA melt.The calculated coagulation coefficient and collision rate of Al_(2)O_(3)inclusions were higher than those of HfO_(2)inclusions,but the inclusion amount played a larger role in the agglomeration behavior of HfO_(2)and Al_(2)O_(3)inclusions.The impurity level and active elements in HEAs were the crucial factors affecting inclusion formation.展开更多
文摘Ironmaking at Baosteel has focused on blast furnaces over the last 30 years. After passing through the stages of ＂learning＂, ＂tracking＂, ＂usage＂, ＂experimentation＂, ＂innovation＂ and ＂development＂, Baosteel ＇ s production capacity has grown steadily and its standard of technology is increasing. Remarkable progress has been made in the technologies of blending stack, thick layer sintering, low silicon and high anhydroferrite sintering, coal blending, and the high productivity with high pulverized coal injection （PCI） rate and long campaign of the blast furnaces. The entire ironmaking process is developing in the direction of high efficiency, low energy consumption, clean production, and environmental protection because the zero discharge of solid waste and industrial sewage has been achieved. After 20 years of development, Baosteel has become a modernized iron producer with an annual capacity of 28.85 Mt of sinter,7.26 Mt of coke and 22.50 Mt of hot metal （Pugang Corex furnace output included）, and its main economic and technological indices have reached a world-class level.
基金financially supported by the National Science Foundation of China(Nos.51974212 and 52274316)the China Baowu Low Carbon Metallurgy Innovation Foundation(No.BWLCF202116)+1 种基金the Science and Technology Major Project of Wuhan(No.2023020302020572)the Foundation of Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education(No.FMRUlab23-04)。
文摘The utilization of iron coke provides a green pathway for low-carbon ironmaking.To uncover the influence mechanism of iron ore on the behavior and kinetics of iron coke gasification,the effect of iron ore on the microstructure of iron coke was investigated.Furthermore,a comparative study of the gasification reactions between iron coke and coke was conducted through non-isothermal thermogravimetric method.The findings indicate that compared to coke,iron coke exhibits an augmentation in micropores and specific surface area,and the micropores further extend and interconnect.This provides more adsorption sites for CO_(2) molecules during the gasification process,resulting in a reduction in the initial gasification temperature of iron coke.Accelerating the heating rate in non-isothermal gasification can enhance the reactivity of iron coke.The metallic iron reduced from iron ore is embedded in the carbon matrix,reducing the orderliness of the carbon structure,which is primarily responsible for the heightened reactivity of the carbon atoms.The kinetic study indicates that the random pore model can effectively represent the gasification process of iron coke due to its rich pore structure.Moreover,as the proportion of iron ore increases,the activation energy for the carbon gasification gradually decreases,from 246.2 kJ/mol for coke to 192.5 kJ/mol for iron coke 15wt%.
基金the support from the National Natural Science Foundation of China(Grant Nos.52074198,52374342,and U21A20113)the Department of Science and Technology of Hubei Province(Grant Nos.2023AFB603 and 2023DJC140).
文摘The transformation mechanism of the inclusions and microstructure in 316L stainless steel after post-isothermal heat treatment(IHT)was revealed,along with the pitting behavior of the inclusions in a chloride environment before and after the transformation.The effect of the inclusion transformation on the pitting corrosion behavior of 316L stainless steel and its intrinsic mechanism was also revealed.Results revealed a gradual transformation of MnO-SiO_(2)inclusions into MnO-Cr_(2)O_(3) within the temperature range of 1373 to 1573 K.MnO-Cr_(2)O_(3)inclusions exhibited minimal dissolution in chloride ion corrosion environments,while MnO-SiO_(2)oxides demonstrated higher electrochemical activity and were more prone to dissolve and form pits.Meanwhile,IHT significantly reduced the dislocation density of stainless steel,rendering it more stable in corrosive environments.X-ray photoelectron spectroscopy peak distributions of the passive films demonstrated that IHT increased the proportion of Cr and Fe oxides and hydroxides in the passive film which improved the stability and corrosion resistance of the steel.
基金Project supported by the National Natural Science Foundation of China(52174323,52231003)。
文摘In order to mitigate the harm of alumina,calcium aluminate,and magnesium aluminum spinel inclusions on the fatigue performance of bearing steel,the effect of Ce-Mg composite treatment on the cleanliness of silicon-killed GCr15 bearing steel and the evolution of Ce-Mg-Mn-O-S composite inclusions during heat treatment of the steels at 1523 K were investigated in this present work.The results indicate that the cleanliness of S2 with 0.0045 wt%Ce and 0.0016 wt%Mg is better than that in S1 with0.0020 wt%Ce and 0.0011 wt%Mg,which is attributed to the more effective removal of Ce-Mg-Mn-O-S composite inclusions,with help of good aggregation capacity of Ce-containing inclusions and small volume density of Mg-containing inclusions,due to the increase of rare earth and magnesium content.The aspect ratio and area fraction of the Ce-Mg-Mn-O-S composite inclusions in as-cast steel decrease significantly with isothermal treatment at 1523 K for 150 min,due to the effect of(ⅰ)Ostwald aging mechanism of inclusions and(ⅱ)sulfide solid solution during isothermal treatment.With the increase of isothermal treatment time from 150 to 550 min,the aspect ratio and area fraction of the inclusions in SO(untreated steel)and S1 decrease slightly,because spheroidization and solid solution of inclusions reach their basic equilibrium at 1523 K.However,the aspect ratio and area fraction of the Ce-Mg-Mn-O-S composite inclusions in S2 actually increase,and the inclusions evolve into three-phase(two-phase)inclusions,which is attributed to(ⅲ)transformation of phase compositions in inclusions and interfacial reaction between inclusions and steel matrix during isothermal heating.Therefore,the control of inclusions in silicon-killed bearing steel with Ce and Mg composite treatment should be combined with specific heat treatment processes and appropriate rare earth and magnesium contents,to minimize the damage of inclusions on the fatigue performance of bearing steel products.
基金supported by the National Natural Science Foundation of China(No.52374344).
文摘The Ni-ZnFe_(2)O_(4)(NixZn_(1-x)Fe_(2)O_(4),x=0.4-0.7)spinel was synthesized using Zn2+extracted from electric arc furnace dust(EAFD),nickel chloride hexahydrate,and Fe^(3+)extracted from iron scale as raw materials.The zinc was selectively extracted from EAFD using CaO roasting followed by NH_(4)Cl solution leaching.The ferric ion was leached from iron scale using HCl solution as acid lixiviant.The experimental results demonstrate a high level of efficiency in the extraction of zinc,with a rate of 97.5%,and the leaching rate of ferric ion is 96.89%.The composition of the leaching solution is primary zinc and iron with low calcium,which is beneficial to the preparation of spinel ferrite.The influence of Ni content(x)and calcination temperature on the synthesis and magnetic properties of NixZn_(1-x)Fe_(2)O_(4)compounds was investigated by X-ray diffraction,scanning electron microscopy,and vibrating sample magnetometry.The results revealed that both Ni content and calcination temperature significantly affect the synthesis and magnetic properties of spinel NixZn_(1-x)Fe_(2)O_(4).Under the conditions of Ni content set at x=0.6,calcination temperature of 1100℃,and a duration of 2 h,a spinel NixZn_(1-x)Fe_(2)O_(4)with high saturation magnetization(Ms=65.7 A m2 kg-1)and low coercivity(Hc=0.056 A m^(-1))was obtained.
基金gratefully acknowledge the support from National Natural Science Foundation of China(Nos.52274305,52374309 and 52004189)Project of Hubei Provincial Department of Science and Technology(No.2022BAA021)+2 种基金China Postdoctoral Science Foundation(Nos.2023T160210 and 2022M721109)Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC001)Open Foundation of Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education(FMRUlab-25-05).
文摘The dissolution behaviors of lime,limestone,and core–shell structured lime,as well as their effects on dephosphorization behavior were studied.The results show that the slow dissolution of lime in converter slag is mainly attributed to the calcium silicate layer at the lime/slag interface.CO_(2)generated by CaCO_(3)decomposition can destroy the calcium silicate layer,and thus accelerates the dissolution of limestone and core–shell structured lime.However,in the initial stage,a large amount of CO_(2)emission generated by limestone decomposition results in the poor contact between molten slag and limestone,and the dissolution rate is slower in the test of limestone than that of lime.For core–shell structured lime,the initial dissolution rate is not affected due to the lime surface,and is accelerated by the appropriate CO_(2)emission.Rapid CaO pickup in molten slag by fast dissolution of the lime sample can remarkably accelerate the dephosphorization reaction.Because of the fastest dissolution rate,the core–shell structured lime slagging mode shows the most promising prospects for the efficient dephosphorization.
基金supported by the National Natural Science Foundation of China(No.51974131)Hebei Outstanding Youth Fund Project(No.E2020209082),Tangshan Key R&D Program project(No.22150232J)Sixth Division Wujiaqu City Science and Technology Plan Project(2410).
文摘During the sintering process of iron ore,a large amount of nitrogen oxides is generated,for which there is currently no efficient and economical treatment process.Therefore,it is necessary to implement process control in sintering production to keep the mass concentration of NO_(x)in sintering flue gas at a low level.Through industrial trials at sintering sites,methods such as correlation analysis,path analysis,and multiple linear regression were applied to analyze the influence of various factors on NO emissions during the sintering process.The results indicate that negative correlations exist between nitrogen monoxide(NO)emissions and negative pressure,permeability index,O_(2) concentration,CO concentration,and flue gas temperature.Conversely,positive correlations exist between NO emissions and dust concentration,water vapor volume fraction,and sintering bed speed.Among these factors,O_(2) concentration and dust concentration are identified as the most significant influencing factors on NO emissions.By analyzing the masses and modes of influence of different factors,the mechanisms of action of each factor were obtained.Specifically,O_(2) concentration,dust concentration,permeability index,CO concentration,and flue gas temperature play a direct dominant role in NO emissions during the sintering process,while water vapor volume fraction,sintering trolley speed,and negative pressure have an indirect effect.A predictive model for NO mass concentration in flue gas was established with an accuracy rate of 91.6%,showing consistent overall trends with actual values.Finally,denitrification strategies for sintering industrial production were proposed,along with prospects for preliminary denitrification of sintering flue gas using fluidized bed conditions in the duct.
基金supported by the National Natural Science Foundation of China(No.51974212)the China Baowu Low Carbon Metallurgy Innovation Foundation(No.BWLCF202116)+2 种基金the Science and Technology Major Project of Wuhan(No.2023020302020572)the Postdoctor Project of Hubei Province(No.2024HBBHCXA074)the Foundation of Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education(No.FMRUlab23-04).
文摘Coke is the only solid charge component in the lower part of the blast furnace,and its strength is crucial to its production.Si and Al are the two most abundant elements in coke ash.The influences of these oxides on the tensile strength of the coke matrix were studied by splitting tests.According to the Weibull analysis,with increasing Si and Al oxide concentrations,the fracture stress range of the coke widened,the upper and lower limits decreased,the probability of fracture under the same stress conditions increased,and the randomness and dispersion of strength increased.These results can be attributed to the inhibitory effect of ash during coal pyrolysis.Ash impedes the growth and contact of mesophase,leading to a decrease in graphitic carbon structures and an increase in edge carbon and aliphatic carbon structures in the resulting coke.Consequently,the overall ordering of the carbon structure is reduced.Moreover,SiO_(2)and Al_(2)O_(3)promoted the development of coke pores,thinned the coke pore wall,and significantly increased the proportion of large pores(>500μm).Moreover,Al_(2)O_(3)had more significant influences on the coke strength,carbon structure and stomatal ratio than SiO_(2).In addition,the position where the ash particles bonded to the carbon matrix easily produced cracks and holes,and the sharp edge of the matrix was likely to produce stress concentration points when subjected to an external force,leading to structural damage.Therefore,controlling the concentration of ash could effectively reduce the number of structural defects inside coke,which is conducive to improving the strength.
基金supported by the National Natural Science Foundation of China(Nos.52074197 and 51974210)Hubei Provincial Natural Science Foundation(No.2019CFB697)State Key Laboratory of Refractories and Metallurgy,Wuhan University of Science and Technology.
文摘The productivity of the chrome-containing semi-steel converter smelting process is directly affected by the slag-forming speed during the converter preliminary stage.The effects of Cr_(2)O_(3) content on the physicochemical properties of the CaO-SiO_(2)-Fe_(t)O-MgO system,such as melting temperature,solidification behavior,mineral composition,and lime dissolution rate,were studied.The results showed that the slag was an amorphous phase at 1500℃.When Cr_(2)O_(3) was added,Ca(Fe,Mg)Si_(2)O_(6) and spinel were formed in the slag.With the increase in Cr_(2)O_(3) content,the amount of spinel precipitation increased,and the dendritic FegO_(4) crystal gradually changed into the granular(Fe,Mg)(Fe,Cr)2O_(4) crystal.As the Cr_(2)O_(3) content increased from O to 2.91 wt.%,the melting temperature of the slag rose,and the melting range of the slag expanded slightly,but the lime dissolution rate did not change.When the Cr_(2)O_(3) content further increased to 9.09 wt.%,the melting temperature continued to rise,the melting range rapidly expanded,and the lime dissolution rate decreased.
基金funded by the National Natural Science Foundation of China(Nos.51974213 and 52174324)。
文摘In continuous casting production,droplet characteristics are important parameters for evaluating the nozzle atomization quality,and have a significant impact on the secondary cooling effect and the slab quality.In order to study the behavior of atomized droplets after reaching the slab surface and to optimize the spray cooling effect,the influence of droplet diameter and droplet velocity on the migration behavior of droplets in the secondary cooling zone was analyzed by FLUENT software.Results show that the droplets in the spray zone and on the slab surface are mainly concentrated in the center,thus,the liquid volume fraction in the center is higher than that of either side.As the droplet diameter increases,the region of high liquid volume fraction on the slab surface becomes wider,and the liquid phase distribution in the slab width direction becomes uneven.Although increasing the droplet velocity at the nozzle exit has little effect on droplet diffusion in the spray zone,the distribution becomes more uneven due to more liquid reaches the slab surface per unit time.A prediction formula of the maximum water flow rate on the slab surface for specific droplet characteristics was proposed based on dimensionless analysis and validated by simulated data.A nozzle spacing of 210 mm was recommended under the working conditions in this study,which ensures effective coverage of the spray water over the slab surface and enhances the distribution uniformity of water flow rate in the transverse direction.
基金supported by the National Natural Science Foundation of China(Nos.52274341 and 51974210).
文摘To avoid coarse crystallization of glassy inclusions in Si–Mn deoxidized steel during hot rolling, the effect of MgO on the structure and crystallization behavior of CaO–SiO_(2)–Al_(2)O_(3) inclusions was investigated. The results showed that the crystallization temperature of the oxide melts decreased with increasing MgO content from 0 to 15.7 wt.%, which suggested that the addition of MgO would increase the temperature range of the crystalline transition. The increase in MgO content could decrease the crystallization activation energy of inclusions. With the increase in MgO content, the relative fractions of O_(Si)^(0) and O_(Si)^(1) structure units increased, and those of structure units O_(Si)^(2), O_(Si)^(3), and O_(Si)^(4) decreased, increasing the depolymerization degree of the silicate structure. The crystallization ratio of glassy inclusions in the steel crucible increased from 19.7% to 98.3% with increasing MgO content from 0 to 15.7 wt.%. The addition of MgO improved the crystallization ability of inclusions, because MgO provides free oxygen O_(2−) to destroy the bridging oxygens and form non-bridging oxygens O^(−), which depolymerizes silicate network structure and simplifies the [SiO_(4)]-tetrahedral structure. In addition, MgO would promote the precipitation of the Mg-containing phases with a high melting point. When the MgO content was increased above 12.1 wt.%, MgO·Al_(2)O_(3) and 2MgO·SiO_(2) crystalline phases would precipitate from the inclusions.
基金financially supported by the National Natural Science Foundation of China(62071034).
文摘The service life of a blast furnace depends largely on the degree of damage to the carbon brick in the hearth.Carbon brick and ramming material in the hearth of a 1780 m3 blast furnace after shutdown were sampled and investigated.It was found that the substances in the cracks of the carbon brick near and above the taphole were ZnO and Zn_(2)SiO_(4),whereas the substances in the cracks of the carbon brick below the taphole were ZnS.The reaction of Zn with CO,SiO_(2),and Fes generates ZnO,Zn_(2)SiO_(4),and ZnS,resulting in volume expansion,which is an important reason for the cracking of carbon brick.Simultaneously,several obvious Zn vapor flow channels were found in the ramming material,through which Zn vapor could enter the carbon brick,causing damage to the carbon brick.Increasing the compactness of the ramming material is beneficial to preventing Zn vapor from entering the carbon brick through the voids in the ramming material,reducing the destructive effect of Zn on the carbon brick and further extending the service life of the blast furnace.
基金funded by the National Natural Science Foundation of China(Nos.51874215 and 52204351)the China Postdoctoral Science Foundation(2022M722487).
文摘A three-dimensional mathematical model has been established for a novel metallurgy process coupling an annular gas curtain with swirling flow at tundish upper nozzle. The discrete phase model and volume of fluid model were applied to simulate the gas–liquid multiphase flow behavior in tundish and nozzle. The effect of argon flow rate on the migration behavior of bubbles and interface behavior between steel and slag was also investigated. The presented results indicate that the novel coupling process can significantly change the flow pattern in the stream zone of a tundish, prolong the average residence time of liquid steel, and reduce the dead fraction. A complete annular gas curtain is formed around the stopper rod of tundish. Under the action of drag force of liquid steel, a part of small bubbles enter the nozzle through the swirling grooves and gather toward the center of the nozzle by centripetal force. As the argon flow rate increases, the volume fraction of argon gas entering the nozzle increases, which enhances the swirl intensity and increases the concentration of bubbles in the nozzle. To avoid the formation of slag open eye in tundish, the argon flow rate should not exceed 8 L min−1.
基金the National Natural Science Foundation of China(52004191)the China Postdoctoral Science Foundation(2022M711120)+1 种基金the Science and Technology Research Project of Education Department of Hubei Province(B2022020)Besides,the numerical calculation is supported by High-Performance Computing Center of Wuhan University of Science and Technology.
文摘A rotating stopper-rod technique was proposed to suppress the formation of free-surface vortex in the tundish.The large eddy simulation model coupled with volume of fluid model was developed to study the steel–slag–gas three-phase flow behavior.The critical slag entrapment height of the free-surface vortex and mass of residual steel were predicted at different rotating speeds(30,60,90 and 120 r/min)of the rotating stopper-rod.The numerical model was verified by water model experiment.The results showed that by rotating the stopper-rod in the opposite direction of the vortex above the submerged entry nozzle,the formation of vortex can be effectively disturbed and the critical height of the free-surface vortex can be reduced.Particularly for the 2nd strand,when the rotating speeds are 30,60,90 and 120 r/min,the critical height of the free-surface vortex above the 2nd strand is 7.3,4.7,6.3 and 7.4 cm,respectively.A reasonable rotating speed should be 60 r/min,which can reduce about 2 tons of residual steel.Other rotating speeds just can reduce about 1.6 tons of residual steel.
基金supported by the National Natural Science Foundation of China(Nos.52274341 and 51974210).
文摘To investigate the evolutionary behavior of the MnO–SiO_(2)–Al_(2)O_(3)–MgO inclusions during heat treatment,water quenched samples were isothermally held at 1100°C for 120 min in Ar and air atmosphere,and the obtaining samples were analyzed by X-ray diffraction,scanning electron microscopy and energy dispersive spectrometer.It showed that 3MnO·Al_(2)O_(3)·3SiO_(2)and MnO·SiO_(2)were detected in the 5 wt.%MgO system after isothermal holding in Ar atmosphere,while MgO·Al_(2)O_(3),MnO·SiO_(2)and Mn7O8·SiO4 were detected in air atmosphere.The evolutionary behavior of the 10,15 and 20 wt.%MgO systems after isothermal holding in different atmosphere were consistent.Oxygen affected the solid phase transformation of the low MgO content systems.The calculation results of FactSage 8.1 showed that MgO·Al_(2)O_(3)was formed in the 5 wt.%MgO system with air atmosphere.The solid phase transformation was accompanied by grain coarsening during the isothermal holding process.The differences in the solid phase transformation in different atmosphere of the 5 wt.%MgO system indicated that it was a gas-phase transport grain coarsening mechanism.The enrichment of Al element in the liquid phase region at the grain edges,the homogeneous distribution of Mg element and the disappearance of the liquid phase within the crystal revealed that other MgO content systems were liquid–solid transport grain coarsening mechanism.
基金support from National Natural Science Foundation of China (No. 52004189)Project of Hubei Provincial Department of Science and Technology (Nos. 2022BAA021 and 2022CFB051)+2 种基金China Postdoctoral Science Foundation (Nos. 2023T160210 and 2022M721109)Young Elite Scientists Sponsorship Program by CAST (No. 2022QNRC001)Wuhan University of Science and Technology Graduate Innovation and Entrepreneurship Fund (No. JCX2022009).
文摘The value-added utilization of converter steel slag is crucial, with China’s annual production having reached 100 million tons. The utilization of converter slag in the construction materials sector is limited as it undergoes volume expansion during the aging process, mainly caused by the hydration reaction of free calcium oxide present in the slag. The influence of alumina addition on the mineral transformation of typical industrial converter slag was investigated. Different quantities of alumina were introduced into the slag, and the original and modified slags were remelted under argon atmosphere, followed by quenching. The experimental results were compared with thermodynamic simulation calculations for further analysis. As the alumina content increases, it reacts with the free calcium oxide in slag, leading to the formation of low-melting-point calcium aluminoferrite. Additionally, alumina addition effectively reduces slag viscosity. Finally, an assessment of the energy consumption for alumina-modified and silica-modified converter slags was presented.
基金the National Natural Science Foundation of China(52274305 and U1860205)Young Elite Scientists Sponsorship Program by CAST(2022QNRC001).
文摘In order to explore the corrosion mechanism of Al_(2)O_(3)-C refractories in the mold flux bearing MnO,the immersion test of Al_(2)O_(3)-C refractories in CaO-SiO2-CaF2-MnO slag with different MnO contents was carried out at 1550℃.The results show that Mn particles were observed in the slag after experiment,due to the reduction of MnO by graphite in refractories.Large amounts of graphite were observed at the interface between refractories and slag,indicating that the oxidation of graphite is limited by the poor contact between graphite and molten slag.Therefore,the oxidation of graphite is not the main cause of damage to refractories.A small quantity of CaO·2Al_(2)O_(3)(CA_(2))and CaO·6Al_(2)O_(3)(CA_(6))adjacent to Al_(2)O_(3) grain was detected at the slag/reaction layer interface.CA_(2) and CA_(6) possess relatively high melting points,which is beneficial to hindering the further penetration of slag.However,the dissolution of Al_(2)O_(3) into slag is still the main cause for refractories damage.The increase in the MnO content of mold slag decreases the viscosity and then results in the severe corrosion of Al_(2)O_(3)-C bricks.
基金supported by the National Natural Science Foundation of China(Grant Nos.52074198,52374342 and U21A20113)also supported by the Department of Science and Technology of Hubei Province(Grant No.2023AFB603 and No.2023DJC140).
文摘To clarify the deformation behavior of MnS inclusions in a non-quenched and tempered steel at three different positions (edge, 1/2 radius and center) in the cross-section of the billet in the course of hot rolling, isothermal compression experiments were performed under the deformation temperature range from 1073 to 1473 K, the reduction rates from 25% to 75% and the strain rates from 0.01 to 10 s^(−1). The variations of deformability features (i.e., aspect ratios, size distributions, and morphologies) of MnS inclusions with those isothermal compression parameters were revealed. The evaluation of the probable maximum aspect ratio of MnS inclusions at the three different positions in the cross-section of the billet after hot rolling was examined using the statistical analysis of extreme values. Results showed that the number densities of MnS inclusions at three different positions (edge, 1/2 radius and center) in the cross-section of the steel billet only fluctuated slightly when the deformation parameters varied in the isothermal compression, while the average inclusion aspect ratios in all cases generally have a negative correlation with the deformation temperature and positive correlations with the reduction ratio and the strain rate. Statistical analysis reveals that larger inclusions deform more easily during hot rolling. The effect of rolling temperature on the extreme value of the aspect ratio of inclusions is the smallest, while the effects of initial size, reduction ratio and strain rate are more significant.
基金the National Natural Science Foundation of China(Nos.U1860205 and 52004189)Project of Hubei Provincial Department of Science and Technology(Nos.2022BAA021 and 2022CFB051)+1 种基金China Postdoctoral Science Foundation(Nos.2022M721109 and 2023T160210)Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC001).
文摘Refractories have an important effect on the cleanliness of molten steel.The interaction between CeAlO_(3) refractories and Ce treated steel was explored and compared with that between Al_(2)O_(3) refractories and Ce treated steel.The results show that the Ce content in steel decreases sharply after contact with Al_(2)O_(3) refractories and the pick-up of dissolved Al occurs.Compared with the test of Al_(2)O_(3) refractories,the loss of Ce content is less in the test of CeAlO_(3) refractory,and the total oxygen content and dissolved Al content in steel increase less.The dense and continuous Ce_(2)O_(2)S interface layer is observed at the CeAlO_(3) refractories/steel interface,which can serve as the metallurgical isolation layer and hinder the further interaction between refractories and steel.Therefore,the higher steel cleanliness and less penetration of refractories by molten steel are obtained in the test of CeAlO_(3) refractories.The CeAlO_(3) refractories show a promising prospect in the production of clean Ce treated steel.
基金the Swedish Foundation for International Cooperation in Research and Higher Education(STINT,Nos.IB2020-8781 and IB20229228)for the collaboration between KTH<U(Sweden),HYU(Korea),and NEU(China)VINNOVA(No.2022-01216),the SSF Strategic Mobility Grant(No.SM22-0039),the?Forsk(No.23-540),and the Swedish Steel Producers’Association(Jernkontoret),in particular,Axel Ax:-son Johnsons forskningsfond,Prytziska fondennr 2,Gerhard von Hofstens Stiftelse f?r Metallurgisk forskning,and Stiftelsen?veringenj?ren Gustaf Janssons Jernkontorsfond for the financial support.Key Lab of EPM(NEU)is acknowledged for supporting the partial FactSage calculation+2 种基金the Key Laboratory for Ferrous Metallurgy and Resources Utilization of the Min-istry of Education and Hubei Provincial Key Laboratory for New Processes of Ironmaking and Steelmaking(No.FMRUlab-22-1)for supporting this researchThe Natural Science Foundation of Liaoning Province,China(No.2023MSBA-135)the Fundamental Research Funds for the Central Universities(No.N2409006)are also acknowledged。
文摘Specific grades of high-entropy alloys(HEAs)can provide opportunities for optimizing properties toward high-temperature applications.In this work,the Co-based HEA with a chemical composition of Co_(47.5)Cr_(30)Fe_(7.5)Mn_(7.5)Ni_(7.5)(at%)was chosen.The refractory metallic elements hafnium(Hf)and molybdenum(Mo)were added in small amounts(1.5at%)because of their well-known positive effects on high-temperature properties.Inclusion characteristics were comprehensively explored by using a two-dimensional cross-sectional method and extracted by using a three-dimensional electrolytic extraction method.The results revealed that the addition of Hf can reduce Al_(2)O_(3)inclusions and lead to the formation of more stable Hf-rich inclusions as the main phase.Mo addition cannot influence the inclusion type but could influence the inclusion characteristics by affecting the physical parameters of the HEA melt.The calculated coagulation coefficient and collision rate of Al_(2)O_(3)inclusions were higher than those of HfO_(2)inclusions,but the inclusion amount played a larger role in the agglomeration behavior of HfO_(2)and Al_(2)O_(3)inclusions.The impurity level and active elements in HEAs were the crucial factors affecting inclusion formation.
