In this study,the effect of decarburization annealing temperature and time on the carbon content,microstructure,and texture of grain-oriented pure iron was investigated by optical microscopy and scanning electron micr...In this study,the effect of decarburization annealing temperature and time on the carbon content,microstructure,and texture of grain-oriented pure iron was investigated by optical microscopy and scanning electron microscopy with electron-backscatter diffraction. The results showed that the efficiency of decarburization dramatically increased with increasing decarburization temperature. However,when the annealing temperature was increased to 825°C and 850°C,the steel's carbon content remained essentially unchanged at 0.002%. With increasing decarburization time,the steel's carbon content generally decreased. When both the decarburization temperature and time were increased further,the average grain size dramatically increased and the number of fine grains decreased; meanwhile,some relatively larger grains developed. The main texture types of the decarburized sheets were approximately the same: {001}<110> and {112~115}<110>,with a γ-fiber texture. Furthermore,little change was observed in the texture. Compared with the experimental sheets,the texture of the cold-rolled sheet was very scattered. The best average magnetic induction(B_(800)) among the final products was 1.946 T.展开更多
According to the balance of carbon and oxygen, a decarburization model for the RH treatment has been developed. in which the influence of the mass transfer of carbon and oxygen in the liquid steel and the stirring ene...According to the balance of carbon and oxygen, a decarburization model for the RH treatment has been developed. in which the influence of the mass transfer of carbon and oxygen in the liquid steel and the stirring energy (ε) in the vacuum vessel on decarburization rate has been considered. The conclusion that the volumetric coefficients of the mass transfer of carbon is proportional to ε(1.5) is drawn. Industrical experiment proves this model is reliable. The influence of some factors on decarburization rate has been obtained. which can provide directions for RH treatment The decarburization behavior of steel with RH-OB treatment is also studied. The OB-or-not curve, the optimized OB time and OB amount are discussed.展开更多
The electrochemical mechanism of the reaction between Fe-C melts and CaO-SiO2-Al2O3-FeOx slag systems has been carried out. The experimental results suggest that the final content of carbon in melt increases as the pa...The electrochemical mechanism of the reaction between Fe-C melts and CaO-SiO2-Al2O3-FeOx slag systems has been carried out. The experimental results suggest that the final content of carbon in melt increases as the partial oxygen pressure of gas decreases no matter whether there is electronic conductor or not. However, the final content of carbon in the system with electronic conductor is much lower than that without electronic conductor. It can be deduced that the transfer ability of oxygen in slag is dominated by electrons. When an electronic conductor exists, an easy pathway for the electrons is provided and the oxygen transfer rate is accelerated.展开更多
By altering the electrochemical properties of slag, the decarburization reaction of Fe3+-based slag withFe-C droplet was studied. The results showed that a lot of free electrons and holes exist in the slag containing ...By altering the electrochemical properties of slag, the decarburization reaction of Fe3+-based slag withFe-C droplet was studied. The results showed that a lot of free electrons and holes exist in the slag containing transition metal oxides (such as TiO2 and Fe2O3). So electronic conduction in the slag increases. Finally, it led to the increment of the decarburization reaction rate between slag and Fe-C droplet, and mass fraction of carbon remaining indroplet decreases to a lower level.展开更多
An improved mathematical model to describe the decarburization process in basic oxygen furnaces for steelmaking is presented in this work. This model takes into account those factors or parameters that determine the b...An improved mathematical model to describe the decarburization process in basic oxygen furnaces for steelmaking is presented in this work. This model takes into account those factors or parameters that determine the bath-oxygen impact area, such as the cavity depth, the lance height, the number of nozzles and the nozzles diameter. In the thermal issue, the model includes the targeted carbon content and temperature. The model is numerically solved, and is validated using reported data plant. The oxygen flow rate and the lance height are varied in the numerical simulations to study their effect on the carbon content and decarburization rate.展开更多
To elucidate the diffusion behavior of carbon atoms within the austenite region,the decarbonization of 72LX steel bloom was investigated.Experimental studies were performed to obtain the depth profiles of the decarbur...To elucidate the diffusion behavior of carbon atoms within the austenite region,the decarbonization of 72LX steel bloom was investigated.Experimental studies were performed to obtain the depth profiles of the decarburized layers within the temperature range of 950-1250℃.The findings show that,within a temperature range of 950-1200℃,both the depth of the decarburization layer of the grain interior(h_(in))and the depth of the decarbonization effect zone of the grain boundary(h_(b))increase concurrently with increasing holding temperatures and times and an inflection point is observed at 1200℃.By measuring the change in the sample diameter before and after the experiment,the change in the radius reduction of h_(Fe) causes by oxidation is obtained.Minimal changes are observed in h_(Fe) when the temperature is below 1050℃.As the temperature increases to 1100℃,a sudden change in h_(Fe) is observed,which corresponds to a rapid increase in oxidation.At temperatures above 1100℃,a more gradual change is observed.From the experimental results,a two-dimensional decarburization mathematical model is established and the carbon diffusion coefficients at different temperatures are obtained by simulation and regression fitting.The simulation values obtain from the carbon diffusion model matched well with the experimental values,thereby confirming the accuracy of the simulation process.展开更多
The characteristics of argon oxygen decarburization slag(AODS)for smelting stainless steel that has been aged for 10 years were analyzed.Three types of AODSs distributed at three positions in a slag heap were sampled ...The characteristics of argon oxygen decarburization slag(AODS)for smelting stainless steel that has been aged for 10 years were analyzed.Three types of AODSs distributed at three positions in a slag heap were sampled for comparison experiments.Chemical analysis,mineral phase identification,thermogravimetric analysis,and micromorphology analysis were used to study the element migration trends and carbonation behavior of AODS after long-term aging.Sequential leaching tests were performed to study the chromium leachability of the aged AODS.The results show that during the long-term aging process,the AODS heap had undergone oxidation and carbonation,accompanied by element migration and mineralogical evolution.The surface slag had the highest degree of carbonation but the weakest chromium leachability.The chemical composition of the middle slag was the closest to that of the original slag.In the bottom steel slag,in addition to magnesium,certain depositions of other elements were present.The matrix phases in the aged slag were dicalcium silicate and merwinite,and the chromium was mainly wrapped in these matrix phases in the form of oxides,spinels,or alloys.Under the combined effects of carbonation and oxidation,the leaching characteristics of the chromium in the aged slag varied greatly depending on the location.The bottom slag had the strongest chromium leachability,and the hexavalent chromium had long-term continuous leachability.展开更多
The reactions between CO_(2) gas and liquid Fe-C alloy with different initial carbon concentrations at 1873 K were investigated using experimental results,thermodynamic equilibrium,and kinetic analysis.The average CO_...The reactions between CO_(2) gas and liquid Fe-C alloy with different initial carbon concentrations at 1873 K were investigated using experimental results,thermodynamic equilibrium,and kinetic analysis.The average CO_(2) conversion is greater than 80%when the carbon content ranges from 4.0 to 1.0 wt.%.When the carbon content decreases from 0.5 to 0.1 wt.%,the average CO_(2) conversion diminishes from 83.50%to 40.84%.This proves that CO_(2) gas and liquid Fe-C alloy reaction does not reach equilibrium under experimental conditions compared with the calculated thermodynamic data.Through the kinetic analysis,it is shown that in the medium-to high-carbon liquid Fe-C alloys,the rate-controlling step involves CO_(2) gas mass transfer or mixed rate-controlling of CO_(2) gas mass transfer with adsorption and dissociation of CO_(2) gas.In contrast,in the low-carbon liquid Fe-C alloy,carbon mass transfer occurs in the molten alloy.The critical carbon content of the rate-controlling step transformation is 0.7937 wt.%.展开更多
Corrosion test of a Ni–16Mo–7Cr alloy with a decarburized layer was conducted in FLiNaK salt at 700 °C. A detailed microstructure study was performed to investigate the corrosion behavior and mechanisms. The re...Corrosion test of a Ni–16Mo–7Cr alloy with a decarburized layer was conducted in FLiNaK salt at 700 °C. A detailed microstructure study was performed to investigate the corrosion behavior and mechanisms. The results show that the Ferich layers were formed on the corroded alloys with and without decarburization. The surface decarburization had little influence on the corrosion resistance of the alloy, whereas it caused more M_2C carbide formation beneath the corrosion layer. That is attributed to the higher concentration of C gradient near the alloy surface, which was resulted from the increase in C content liberated from graphite crucible wall during the corrosion process.展开更多
How to manufacture the high magnetic induction grain-oriented silicon steel(Hi-B steel)by the process featured with the primary recrystallization annealing was demonstrated,during which nitriding and decarburizing wer...How to manufacture the high magnetic induction grain-oriented silicon steel(Hi-B steel)by the process featured with the primary recrystallization annealing was demonstrated,during which nitriding and decarburizing were simultaneously realized in laboratory.By the techniques of optical microscope,scanning electronic microscope and electron backscattered diffraction,both the microstructure and the texture in the samples were characterized.The samples had been subjected to nitriding to different nitrogen contents at two specified temperatures using the two defined microstructural parameters:the grain size inhomogeneity factorσ*and the texture factor AR.The former is the ratio of the mean value to standard deviation of grain sizes;the latter is the ratio of the total volume fraction of the harmful textures to that of beneficial textures including {110}<001>.When the N content increased from 0.0055%to 0.0330%after the annealing at both 835 and 875°C,the resultant recrystallized grain size decreased butσ*changed little;whilst the rise of annealing temperature from 835 to 875°C resulted in the increase in both grain size andσ*.Moreover,either the injected N content or temperature had insignificant influence on the components of primary recrystallization texture developed during annealing.However,the increase of temperature led to the decreases in both intensity and volume fraction of{001}<120>and{110}<001>textures but increases in the{114}<481>andγfiber textures and the resultant decrease of AR.展开更多
The production of low-temperature reheated grain-oriented silicon steel is mainly based on the acquired inhibitor method.Due to the additional nitriding process,a high nitrogen content exists in the oxide layer,which ...The production of low-temperature reheated grain-oriented silicon steel is mainly based on the acquired inhibitor method.Due to the additional nitriding process,a high nitrogen content exists in the oxide layer,which changes the structure of the oxide layer.In this study,the structure of the surface oxide layer after nitriding was analyzed by scanning electron microscopy(SEM),electron back-scattered diffraction(EBSD),glow discharge spectrometry(GDS),and X-ray diffraction(XRD).The size and orientation of ferritic grains in the oxide layer were characterized,and the distribution characteristics of the key elements along the thickness direction were determined.The results show that the oxide layer of the steel sample mainly comprised particles of Fe2SiO4 and spherical and lamellar SiO2,and Fe4N and fcc-Fe phases were also detected.Moreover,the size and orientation of ferritic grains in the oxide layer were different from those of coarse matrix ferritic grains beneath the oxide layer;however,some ferritic grains exhibited same orientations as those in the neighboring matrix.Higher nitrogen content was detected in the oxide layer than that in the matrix beneath the oxide layer.The form of nitrogen enrichment in the oxide layer was analyzed,and the growth mechanism of ferritic grains during the oxide layer formation is proposed.展开更多
Steel T8 treated by plasma surface decarburizing was alloyed by the Xu Tec process with Co,W and Mo. An alloyed layer of Fe Co W Mo with low carbon content was formed on the surface of the high carbon steel, thus an a...Steel T8 treated by plasma surface decarburizing was alloyed by the Xu Tec process with Co,W and Mo. An alloyed layer of Fe Co W Mo with low carbon content was formed on the surface of the high carbon steel, thus an advanced gradient composite was produced. The specimens then were treated by the solution and aging treatments. The characteristics of age hardening of the alloying layer were studied. The hardness of the surface layer increases from HV200 to HV1 200 after the solution treatment at 1 190 ℃ and aging at 400 ℃ for 30 min. The results show that the surface aged high speed steel possesses not only high surface hardness, but also enough bulk strength. [展开更多
Nowadays, the worsening environmental issue caused by CO2 emission is greatly aggravated by human activity. Many CO2 reduction technologies are under fast development. Among these, monoethanolamine (MEA) based CO2 cap...Nowadays, the worsening environmental issue caused by CO2 emission is greatly aggravated by human activity. Many CO2 reduction technologies are under fast development. Among these, monoethanolamine (MEA) based CO2 capture technology has been paid great attention. However, when connecting the CO2 capture process with a coal-fired power plant, the huge energy and efficiency penalty caused by CO2 capture has become a serious problem for its application. Thus, it is of great significance to reduce the related energy consumption. Based on an existing coal-fired power plant, this paper proposes a new way for the decarburized retrofitting of the coal-fired power plant, which helps to improve the overall efficiency of the power plant with less energy and efficiency penalty. The decarburized retrofitting scheme proposed will provide a new route for the CO2 capture process in China.展开更多
A new Ruhrstahl-Heraeus(RH)equipment with a weir added to the vacuum chamber was designed to help improve refining efficiency of low-carbon steel production.The flow characteristics of the new RH equipment and a tradi...A new Ruhrstahl-Heraeus(RH)equipment with a weir added to the vacuum chamber was designed to help improve refining efficiency of low-carbon steel production.The flow characteristics of the new RH equipment and a traditional RH equipment were evaluated and compared through water modeling experiments and an optimized calculation model.In the water experiments,the mixing time,the residence time and the circulation flow rates were measured,and the flow simulating molten steel in the vacuum was photographed.The results show that the decarburization efficiency in the new RH equipment is much improved.The mixing time is equal to or less than that of the latter when the gas flow rate is higher than 2.33 m^(3)/h.The proportion of the piston flow increases by at least 40%,and the proportion of the well-mixed flow decreases from greater than 40%to less than 20%.The effective flow rate of the new RH equipment increases greatly in the piston flow zone and the total lag flow zone based on the residence time distribution experiment.In conclusion,when a weir is added to a RH vacuum chamber,the effective circulation flow increases significantly,and the decarburization rate KC of molten steel at low-carbon stage is improved.展开更多
The effect of nitrogen content on primary recrystallization microstructure,texture and magnetic property of Hi-B steel was studied by means of optical microscopy(OM),scanning electron microscopy(SEM),and electron back...The effect of nitrogen content on primary recrystallization microstructure,texture and magnetic property of Hi-B steel was studied by means of optical microscopy(OM),scanning electron microscopy(SEM),and electron backscatter diffraction(EBSD).When nitrogen content increased gradually from 0.005 5% to 0.031 0%,the primary grain size and variation coefficient of nitrided sheet reduced from 26.85μm,0.590 to 18.87μm,0.525-0.565,respectively.Meanwhile,the primary recrystallization texture style of nitrided sheet was nearly identical to the texture style of decarburized sheet before nitriding treatment,but exhibiting a certain change on texture intensity.The variation of average magnetic induction value(B_8)and core loss value(P_(17/50))were manifested to be Mshaped and W-shaped curves,respectively.When nitrogen content reached 0.016 0%,the best value of the average magnetic property of the final product was obtained as follows:the B_8 and P_(17/50) were 1.921 Tand 0.968W/kg,respectively.Meanwhile,the best performance,B_8 and P_(17/50),of single sheet was 1.964 Tand 0.854 W/kg.展开更多
The reaction of CO_2 gas with hot metal was investigated based on the thermodynamic analysis and experimental results.It shows that both silicon and carbon in hot metal can be oxidized by CO_2 gas in the temperature r...The reaction of CO_2 gas with hot metal was investigated based on the thermodynamic analysis and experimental results.It shows that both silicon and carbon in hot metal can be oxidized by CO_2 gas in the temperature range of 1 300-1 500 ℃.When using graphite crucible,temperature has little influence on final mass percent of carbon w[C]because of the carburization effect.Decarburization degree rises significantly with increasing gas injection rate and w[C]can be reduced to 3.2% at most when using MgO crucible.Lower temperature or higher gas injection rate is propitious to promote desilication reaction,but only 5%-10% of desilication ratio could be obtained in 20 min.The final mass percent of silicon w[Si]when using MgO crucible is lower than that when using graphite crucible.Experimental results also demonstrate that CO_2 injection has no effect on the concentration of manganese,sulfur and phosphorus in hot metal.In view of the weak oxidation ability and temperature drop of hot metal,CO_2 gas is suggested to be used as carrier gas in desilication process rather than oxidizing agent.展开更多
In this research,2205/Q235 B clad plates were prepared by a vacuum hot rolling composite process.The effects of adding Fe,Ni,and Nb interlayers on the bonding interface structures and the shear strengths of the clad s...In this research,2205/Q235 B clad plates were prepared by a vacuum hot rolling composite process.The effects of adding Fe,Ni,and Nb interlayers on the bonding interface structures and the shear strengths of the clad steel plates were studied.The results showed that 2205 duplex stainless steel and the three interlayers produced a large amount of plastic deformation and low-angle boundaries,and the main structures were the recrystallized and deformed grains.There were many recrystallized grains in the microstructure of the Q235 B low-carbon steel due to the low deformation in the rolling process.The Fe interlayer had better wettability with the two kinds of steel,but the lower strength led to the reduction of shear strength by about14 MPa compared with the original clad steel plate.The C element in the Q235 B low-carbon steel easily diffused into the Fe interlayer,and the clad steel plate attained a poor corrosion resistance because a large decarburization area was formed.The Nb interlayer reacted with the Mo element in the 2205 duplex stainless steel to form an Nb-Mo binary alloy,which generated long-banded ferrite.The decarburization area was also produced because the Nb reacted with the C element in the Q235 B to form hard and brittle NbCx.As a result,the shear strength was significantly reduced by about 282 MPa,and the corrosion resistance of the bonding surface was deteriorated.The Ni interlayer did not react with the alloy elements in both sides,and therefore effectively prevented element diffusion and improved the corrosion resistance of the bonding surface.Due to the low strength of the Ni interlayer and the increased number of bonding surfaces of the clad steel plates,the shear strength was reduced to some extent(about 40 MPa),but it still met the engineering application standards.展开更多
The clean steel refining tests carried out in a 100 kg plasma ladle furnace(PLF)were to show the metallurgical effects of the different plasma gases such as Ar-H_2 and Ar-CO_2.The variations of carbon,nitrogen content...The clean steel refining tests carried out in a 100 kg plasma ladle furnace(PLF)were to show the metallurgical effects of the different plasma gases such as Ar-H_2 and Ar-CO_2.The variations of carbon,nitrogen contents in steels and the mechanism of denitrogenation were studied.Compared with the conventional ladle furnace,when the plasma gases were injected into the ladle furnace,there was a decarburization process,the carburetion rates were reduced obviously.The carburetion rate is 3.6×10^(-6)per minute for the steel heated by conventional LF,and is 2.20 and 1.35 times of the heats blown 85%Ar-15%H_2 and 85%Ar-15%CO_2,respectively.When the plasma ladle furnace operated with Ar-H_2 plasma gas,the denitrogenation of the molten steel occurs.The lowest denitrogenation rate is 0.30×10^(-6)per minute when Ar-H_2 gas mixtures were used.The main reactant gas is monatomic hydrogen and the main product of denitrogenation is NH_3 for Ar-H_2 injection.展开更多
2205/Q235B clad steel plates were fabricated using a thermal simulator.The metallographic microscope,scanning electron microscope,energy-dispersive spectrometer,shear test,electrochemical corrosion test and acid immer...2205/Q235B clad steel plates were fabricated using a thermal simulator.The metallographic microscope,scanning electron microscope,energy-dispersive spectrometer,shear test,electrochemical corrosion test and acid immersion test were used to study the influence of the pass reduction ratio on the microstructure and properties of 2205/Q235B clad steel plate.The results show that the clad steel plates had a good bonding surface when the pass reduction ratios were between 16.3%and 36.0%.There existed the mutual diffusion effect of elements near the bonding surface,which caused the long austenite strip on the side of 2205 stainless steel and the decarburization layer on the side of Q235B low-carbon steel.The transformation ofδferrite toγaustenite and the generation of the decarburization layer were promoted because of the lower pass reduction ratio.The corrosio n resista nee of 2205 duplex-phases stainless steel worse ned by the decrease in 8 ferrite con tent.The increase in the decarburization layer thickness made the shear strength of the clad steel plates reduce from 453 to 390 MPa.The potential of the decarburization layer was lower than that of 2205 stainless steel and Q235B low-carb on steel,which was easily corroded in the corrosive medium.展开更多
文摘In this study,the effect of decarburization annealing temperature and time on the carbon content,microstructure,and texture of grain-oriented pure iron was investigated by optical microscopy and scanning electron microscopy with electron-backscatter diffraction. The results showed that the efficiency of decarburization dramatically increased with increasing decarburization temperature. However,when the annealing temperature was increased to 825°C and 850°C,the steel's carbon content remained essentially unchanged at 0.002%. With increasing decarburization time,the steel's carbon content generally decreased. When both the decarburization temperature and time were increased further,the average grain size dramatically increased and the number of fine grains decreased; meanwhile,some relatively larger grains developed. The main texture types of the decarburized sheets were approximately the same: {001}<110> and {112~115}<110>,with a γ-fiber texture. Furthermore,little change was observed in the texture. Compared with the experimental sheets,the texture of the cold-rolled sheet was very scattered. The best average magnetic induction(B_(800)) among the final products was 1.946 T.
文摘According to the balance of carbon and oxygen, a decarburization model for the RH treatment has been developed. in which the influence of the mass transfer of carbon and oxygen in the liquid steel and the stirring energy (ε) in the vacuum vessel on decarburization rate has been considered. The conclusion that the volumetric coefficients of the mass transfer of carbon is proportional to ε(1.5) is drawn. Industrical experiment proves this model is reliable. The influence of some factors on decarburization rate has been obtained. which can provide directions for RH treatment The decarburization behavior of steel with RH-OB treatment is also studied. The OB-or-not curve, the optimized OB time and OB amount are discussed.
文摘The electrochemical mechanism of the reaction between Fe-C melts and CaO-SiO2-Al2O3-FeOx slag systems has been carried out. The experimental results suggest that the final content of carbon in melt increases as the partial oxygen pressure of gas decreases no matter whether there is electronic conductor or not. However, the final content of carbon in the system with electronic conductor is much lower than that without electronic conductor. It can be deduced that the transfer ability of oxygen in slag is dominated by electrons. When an electronic conductor exists, an easy pathway for the electrons is provided and the oxygen transfer rate is accelerated.
文摘By altering the electrochemical properties of slag, the decarburization reaction of Fe3+-based slag withFe-C droplet was studied. The results showed that a lot of free electrons and holes exist in the slag containing transition metal oxides (such as TiO2 and Fe2O3). So electronic conduction in the slag increases. Finally, it led to the increment of the decarburization reaction rate between slag and Fe-C droplet, and mass fraction of carbon remaining indroplet decreases to a lower level.
文摘An improved mathematical model to describe the decarburization process in basic oxygen furnaces for steelmaking is presented in this work. This model takes into account those factors or parameters that determine the bath-oxygen impact area, such as the cavity depth, the lance height, the number of nozzles and the nozzles diameter. In the thermal issue, the model includes the targeted carbon content and temperature. The model is numerically solved, and is validated using reported data plant. The oxygen flow rate and the lance height are varied in the numerical simulations to study their effect on the carbon content and decarburization rate.
基金Funded by the National Natural Science Foundation of China(U20A20272)the Special Projects for Military-Civilian Collaborative Innovation in Science and Technology of Hebei Province(202231401010003)the Open Topic of Key Laboratory of Material Forming and Structure Property Control from University of Science and Technology Liaoning(USTLKFSY201708)。
文摘To elucidate the diffusion behavior of carbon atoms within the austenite region,the decarbonization of 72LX steel bloom was investigated.Experimental studies were performed to obtain the depth profiles of the decarburized layers within the temperature range of 950-1250℃.The findings show that,within a temperature range of 950-1200℃,both the depth of the decarburization layer of the grain interior(h_(in))and the depth of the decarbonization effect zone of the grain boundary(h_(b))increase concurrently with increasing holding temperatures and times and an inflection point is observed at 1200℃.By measuring the change in the sample diameter before and after the experiment,the change in the radius reduction of h_(Fe) causes by oxidation is obtained.Minimal changes are observed in h_(Fe) when the temperature is below 1050℃.As the temperature increases to 1100℃,a sudden change in h_(Fe) is observed,which corresponds to a rapid increase in oxidation.At temperatures above 1100℃,a more gradual change is observed.From the experimental results,a two-dimensional decarburization mathematical model is established and the carbon diffusion coefficients at different temperatures are obtained by simulation and regression fitting.The simulation values obtain from the carbon diffusion model matched well with the experimental values,thereby confirming the accuracy of the simulation process.
基金All the authors acknowledge the support of this study by the National Natural Science Foundation of China(Nos.51704119 and 51574108)the Key Research and Development Project of Tangshan(No.19140205F).
文摘The characteristics of argon oxygen decarburization slag(AODS)for smelting stainless steel that has been aged for 10 years were analyzed.Three types of AODSs distributed at three positions in a slag heap were sampled for comparison experiments.Chemical analysis,mineral phase identification,thermogravimetric analysis,and micromorphology analysis were used to study the element migration trends and carbonation behavior of AODS after long-term aging.Sequential leaching tests were performed to study the chromium leachability of the aged AODS.The results show that during the long-term aging process,the AODS heap had undergone oxidation and carbonation,accompanied by element migration and mineralogical evolution.The surface slag had the highest degree of carbonation but the weakest chromium leachability.The chemical composition of the middle slag was the closest to that of the original slag.In the bottom steel slag,in addition to magnesium,certain depositions of other elements were present.The matrix phases in the aged slag were dicalcium silicate and merwinite,and the chromium was mainly wrapped in these matrix phases in the form of oxides,spinels,or alloys.Under the combined effects of carbonation and oxidation,the leaching characteristics of the chromium in the aged slag varied greatly depending on the location.The bottom slag had the strongest chromium leachability,and the hexavalent chromium had long-term continuous leachability.
基金support of the National Natural Science Foundation of China(Nos.51674021,52004023)Major Science and Technology Innovation Project of Shandong Province of China(No.2019JZZY010358).
文摘The reactions between CO_(2) gas and liquid Fe-C alloy with different initial carbon concentrations at 1873 K were investigated using experimental results,thermodynamic equilibrium,and kinetic analysis.The average CO_(2) conversion is greater than 80%when the carbon content ranges from 4.0 to 1.0 wt.%.When the carbon content decreases from 0.5 to 0.1 wt.%,the average CO_(2) conversion diminishes from 83.50%to 40.84%.This proves that CO_(2) gas and liquid Fe-C alloy reaction does not reach equilibrium under experimental conditions compared with the calculated thermodynamic data.Through the kinetic analysis,it is shown that in the medium-to high-carbon liquid Fe-C alloys,the rate-controlling step involves CO_(2) gas mass transfer or mixed rate-controlling of CO_(2) gas mass transfer with adsorption and dissociation of CO_(2) gas.In contrast,in the low-carbon liquid Fe-C alloy,carbon mass transfer occurs in the molten alloy.The critical carbon content of the rate-controlling step transformation is 0.7937 wt.%.
基金supported financially by the National Natural Science Foundation of China (Nos. 51601214, 51674237 and 11705264)the National Key Research and Development Program (No. 2017YFA0402803)
文摘Corrosion test of a Ni–16Mo–7Cr alloy with a decarburized layer was conducted in FLiNaK salt at 700 °C. A detailed microstructure study was performed to investigate the corrosion behavior and mechanisms. The results show that the Ferich layers were formed on the corroded alloys with and without decarburization. The surface decarburization had little influence on the corrosion resistance of the alloy, whereas it caused more M_2C carbide formation beneath the corrosion layer. That is attributed to the higher concentration of C gradient near the alloy surface, which was resulted from the increase in C content liberated from graphite crucible wall during the corrosion process.
基金financially sponsored by the State Key Special Project of Key Basic Material Technical Promotion and Industrialization(2016YFB0300305)
文摘How to manufacture the high magnetic induction grain-oriented silicon steel(Hi-B steel)by the process featured with the primary recrystallization annealing was demonstrated,during which nitriding and decarburizing were simultaneously realized in laboratory.By the techniques of optical microscope,scanning electronic microscope and electron backscattered diffraction,both the microstructure and the texture in the samples were characterized.The samples had been subjected to nitriding to different nitrogen contents at two specified temperatures using the two defined microstructural parameters:the grain size inhomogeneity factorσ*and the texture factor AR.The former is the ratio of the mean value to standard deviation of grain sizes;the latter is the ratio of the total volume fraction of the harmful textures to that of beneficial textures including {110}<001>.When the N content increased from 0.0055%to 0.0330%after the annealing at both 835 and 875°C,the resultant recrystallized grain size decreased butσ*changed little;whilst the rise of annealing temperature from 835 to 875°C resulted in the increase in both grain size andσ*.Moreover,either the injected N content or temperature had insignificant influence on the components of primary recrystallization texture developed during annealing.However,the increase of temperature led to the decreases in both intensity and volume fraction of{001}<120>and{110}<001>textures but increases in the{114}<481>andγfiber textures and the resultant decrease of AR.
基金financially supported by the Fundamental Research Funds for the Central Universities (No. FRF-IC-18-006)
文摘The production of low-temperature reheated grain-oriented silicon steel is mainly based on the acquired inhibitor method.Due to the additional nitriding process,a high nitrogen content exists in the oxide layer,which changes the structure of the oxide layer.In this study,the structure of the surface oxide layer after nitriding was analyzed by scanning electron microscopy(SEM),electron back-scattered diffraction(EBSD),glow discharge spectrometry(GDS),and X-ray diffraction(XRD).The size and orientation of ferritic grains in the oxide layer were characterized,and the distribution characteristics of the key elements along the thickness direction were determined.The results show that the oxide layer of the steel sample mainly comprised particles of Fe2SiO4 and spherical and lamellar SiO2,and Fe4N and fcc-Fe phases were also detected.Moreover,the size and orientation of ferritic grains in the oxide layer were different from those of coarse matrix ferritic grains beneath the oxide layer;however,some ferritic grains exhibited same orientations as those in the neighboring matrix.Higher nitrogen content was detected in the oxide layer than that in the matrix beneath the oxide layer.The form of nitrogen enrichment in the oxide layer was analyzed,and the growth mechanism of ferritic grains during the oxide layer formation is proposed.
文摘Steel T8 treated by plasma surface decarburizing was alloyed by the Xu Tec process with Co,W and Mo. An alloyed layer of Fe Co W Mo with low carbon content was formed on the surface of the high carbon steel, thus an advanced gradient composite was produced. The specimens then were treated by the solution and aging treatments. The characteristics of age hardening of the alloying layer were studied. The hardness of the surface layer increases from HV200 to HV1 200 after the solution treatment at 1 190 ℃ and aging at 400 ℃ for 30 min. The results show that the surface aged high speed steel possesses not only high surface hardness, but also enough bulk strength. [
文摘Nowadays, the worsening environmental issue caused by CO2 emission is greatly aggravated by human activity. Many CO2 reduction technologies are under fast development. Among these, monoethanolamine (MEA) based CO2 capture technology has been paid great attention. However, when connecting the CO2 capture process with a coal-fired power plant, the huge energy and efficiency penalty caused by CO2 capture has become a serious problem for its application. Thus, it is of great significance to reduce the related energy consumption. Based on an existing coal-fired power plant, this paper proposes a new way for the decarburized retrofitting of the coal-fired power plant, which helps to improve the overall efficiency of the power plant with less energy and efficiency penalty. The decarburized retrofitting scheme proposed will provide a new route for the CO2 capture process in China.
文摘A new Ruhrstahl-Heraeus(RH)equipment with a weir added to the vacuum chamber was designed to help improve refining efficiency of low-carbon steel production.The flow characteristics of the new RH equipment and a traditional RH equipment were evaluated and compared through water modeling experiments and an optimized calculation model.In the water experiments,the mixing time,the residence time and the circulation flow rates were measured,and the flow simulating molten steel in the vacuum was photographed.The results show that the decarburization efficiency in the new RH equipment is much improved.The mixing time is equal to or less than that of the latter when the gas flow rate is higher than 2.33 m^(3)/h.The proportion of the piston flow increases by at least 40%,and the proportion of the well-mixed flow decreases from greater than 40%to less than 20%.The effective flow rate of the new RH equipment increases greatly in the piston flow zone and the total lag flow zone based on the residence time distribution experiment.In conclusion,when a weir is added to a RH vacuum chamber,the effective circulation flow increases significantly,and the decarburization rate KC of molten steel at low-carbon stage is improved.
基金Item Sponsored by National Natural Science Foundation of China(50934009)
文摘The effect of nitrogen content on primary recrystallization microstructure,texture and magnetic property of Hi-B steel was studied by means of optical microscopy(OM),scanning electron microscopy(SEM),and electron backscatter diffraction(EBSD).When nitrogen content increased gradually from 0.005 5% to 0.031 0%,the primary grain size and variation coefficient of nitrided sheet reduced from 26.85μm,0.590 to 18.87μm,0.525-0.565,respectively.Meanwhile,the primary recrystallization texture style of nitrided sheet was nearly identical to the texture style of decarburized sheet before nitriding treatment,but exhibiting a certain change on texture intensity.The variation of average magnetic induction value(B_8)and core loss value(P_(17/50))were manifested to be Mshaped and W-shaped curves,respectively.When nitrogen content reached 0.016 0%,the best value of the average magnetic property of the final product was obtained as follows:the B_8 and P_(17/50) were 1.921 Tand 0.968W/kg,respectively.Meanwhile,the best performance,B_8 and P_(17/50),of single sheet was 1.964 Tand 0.854 W/kg.
基金Item Sponsored by National Natural Science Foundation of China and Baosteel Group Corporation of China(51074206)Fundamental Research Funds for Central Universities of China(N120402011)
文摘The reaction of CO_2 gas with hot metal was investigated based on the thermodynamic analysis and experimental results.It shows that both silicon and carbon in hot metal can be oxidized by CO_2 gas in the temperature range of 1 300-1 500 ℃.When using graphite crucible,temperature has little influence on final mass percent of carbon w[C]because of the carburization effect.Decarburization degree rises significantly with increasing gas injection rate and w[C]can be reduced to 3.2% at most when using MgO crucible.Lower temperature or higher gas injection rate is propitious to promote desilication reaction,but only 5%-10% of desilication ratio could be obtained in 20 min.The final mass percent of silicon w[Si]when using MgO crucible is lower than that when using graphite crucible.Experimental results also demonstrate that CO_2 injection has no effect on the concentration of manganese,sulfur and phosphorus in hot metal.In view of the weak oxidation ability and temperature drop of hot metal,CO_2 gas is suggested to be used as carrier gas in desilication process rather than oxidizing agent.
基金financially supported by the Shandong Taishan Industry Leading Talents Project(SF1503302301)
文摘In this research,2205/Q235 B clad plates were prepared by a vacuum hot rolling composite process.The effects of adding Fe,Ni,and Nb interlayers on the bonding interface structures and the shear strengths of the clad steel plates were studied.The results showed that 2205 duplex stainless steel and the three interlayers produced a large amount of plastic deformation and low-angle boundaries,and the main structures were the recrystallized and deformed grains.There were many recrystallized grains in the microstructure of the Q235 B low-carbon steel due to the low deformation in the rolling process.The Fe interlayer had better wettability with the two kinds of steel,but the lower strength led to the reduction of shear strength by about14 MPa compared with the original clad steel plate.The C element in the Q235 B low-carbon steel easily diffused into the Fe interlayer,and the clad steel plate attained a poor corrosion resistance because a large decarburization area was formed.The Nb interlayer reacted with the Mo element in the 2205 duplex stainless steel to form an Nb-Mo binary alloy,which generated long-banded ferrite.The decarburization area was also produced because the Nb reacted with the C element in the Q235 B to form hard and brittle NbCx.As a result,the shear strength was significantly reduced by about 282 MPa,and the corrosion resistance of the bonding surface was deteriorated.The Ni interlayer did not react with the alloy elements in both sides,and therefore effectively prevented element diffusion and improved the corrosion resistance of the bonding surface.Due to the low strength of the Ni interlayer and the increased number of bonding surfaces of the clad steel plates,the shear strength was reduced to some extent(about 40 MPa),but it still met the engineering application standards.
基金Item Sponsored by National Natural Science Foundation of China[50804009,50834010]National High Technology Research and Development Program 863[2012AA03A503]the Fundamental Research Funds for the Central Universities(N110402013)
文摘The clean steel refining tests carried out in a 100 kg plasma ladle furnace(PLF)were to show the metallurgical effects of the different plasma gases such as Ar-H_2 and Ar-CO_2.The variations of carbon,nitrogen contents in steels and the mechanism of denitrogenation were studied.Compared with the conventional ladle furnace,when the plasma gases were injected into the ladle furnace,there was a decarburization process,the carburetion rates were reduced obviously.The carburetion rate is 3.6×10^(-6)per minute for the steel heated by conventional LF,and is 2.20 and 1.35 times of the heats blown 85%Ar-15%H_2 and 85%Ar-15%CO_2,respectively.When the plasma ladle furnace operated with Ar-H_2 plasma gas,the denitrogenation of the molten steel occurs.The lowest denitrogenation rate is 0.30×10^(-6)per minute when Ar-H_2 gas mixtures were used.The main reactant gas is monatomic hydrogen and the main product of denitrogenation is NH_3 for Ar-H_2 injection.
基金the support by Shandong Taishan Industry Leading Talents Project(SF1503302301)the help of Shandong Iron&Steel Group Co.,Ltd.,in the experiment of raw materials and thermal simulation.
文摘2205/Q235B clad steel plates were fabricated using a thermal simulator.The metallographic microscope,scanning electron microscope,energy-dispersive spectrometer,shear test,electrochemical corrosion test and acid immersion test were used to study the influence of the pass reduction ratio on the microstructure and properties of 2205/Q235B clad steel plate.The results show that the clad steel plates had a good bonding surface when the pass reduction ratios were between 16.3%and 36.0%.There existed the mutual diffusion effect of elements near the bonding surface,which caused the long austenite strip on the side of 2205 stainless steel and the decarburization layer on the side of Q235B low-carbon steel.The transformation ofδferrite toγaustenite and the generation of the decarburization layer were promoted because of the lower pass reduction ratio.The corrosio n resista nee of 2205 duplex-phases stainless steel worse ned by the decrease in 8 ferrite con tent.The increase in the decarburization layer thickness made the shear strength of the clad steel plates reduce from 453 to 390 MPa.The potential of the decarburization layer was lower than that of 2205 stainless steel and Q235B low-carb on steel,which was easily corroded in the corrosive medium.
