In this report,the microstructure,mechanical properties,and textures of warm rolled interstitial-free steel annealed at four different temperatures(730,760,790,and 820°C)were studied.The overall structural featur...In this report,the microstructure,mechanical properties,and textures of warm rolled interstitial-free steel annealed at four different temperatures(730,760,790,and 820°C)were studied.The overall structural features of specimens were investigated by optical microscopy,and the textures were measured by X-ray diffraction(XRD).Nano-sized precipitates were then observed by a transmission electron microscope(TEM)on carbon extraction replicas.According to the results,with increased annealing temperatures,the ferrite grains grew;in addition,the sizes of Ti_4C_2S_2 and Ti C precipitates also increased.Additionally,the sizes of Ti N and Ti S precipitates slightly changed.When the annealing temperature increased from 730 to 820°C,the yield strength(YS)and the ultimate tensile strength(UTS)showed a decreasing trend.Meanwhile,elongation and the strain harden exponent(n value)increased to 49.6%and 0.34,respectively.By comparing textures annealed at different temperatures,the intensity of{111}texture annealed at 820°C was the largest,while the difference between the intensity of{111}<110>and{111}<112>was the smallest when the annealing temperature was 820°C.Therefore,the plastic strain ratio(r value)annealed at 820°C was the highest.展开更多
Since the production of tinplate with non-earing properties is difficult, especially when it is produced via the double-reduction process, the optimal degree of second cold reduction is particularly important for achi...Since the production of tinplate with non-earing properties is difficult, especially when it is produced via the double-reduction process, the optimal degree of second cold reduction is particularly important for achieving desirable drawing properties. The evolution of texture and the earing propensity of double-reduction tinplate with different extents of second reduction were investigated in this study. Optical microscopy and scanning electron microscopy were used to observe the changes in the microstructure at various extents of reduction. Two common testing methods, X-ray diffraction(XRD) and electron backscatter diffraction, were used to investigate the texture of the specimens, which revealed the effects of deformation percentage on the final texture development and the change in the grain boundary. The earing rate was determined via earing tests involving measurement of the height of any ear. The results obtained from both XRD analyses and earing tests revealed the same ideal value for the second cold reduction on the basis of the relationship between crystallographic texture and the degree of earing.展开更多
The dissolution kinetics of Al_(2)O_(3) in CaO-Al_(2)O_(3) SiOslags was studied using a high-temperature confocal scanning laser microscope at 1773 to 1873 K.The results show that the controlling step during the Al_(2...The dissolution kinetics of Al_(2)O_(3) in CaO-Al_(2)O_(3) SiOslags was studied using a high-temperature confocal scanning laser microscope at 1773 to 1873 K.The results show that the controlling step during the Al_(2)O_(3) dissolution was the diffusionin molten slag.It was found that the dissolution curves of Al_(2)O_(3) particles were hardly agreed with the traditional boundary layer diffusion model with the increase of the CaO/Al_(2)O_(3) ratio of slag.A modified diffusion equation considering slag viscosity was developed to study the dissolution mechanism of Al_(2)O_(3) in slag.Diffusion coefficients of Al_(2)O_(3) in slag were calculated as 2.8×10to 4.1×10m~2/s at the temperature of 1773-1873 K.The dissolution rate of Al_(2)O_(3) increased with higher temperature,CaO/Al_(2)O_(3),and particle size.A new model was shown to be v_(Al_(2)O_(3))=0.16×r_(0)^(1.58)×x^(3.52)×(T-T_(mp))^(1.11)to predict the dissolution rate and the total dissolution time of Al_(2)O_(3) inclusions with various sizes,where vAl_(2)O_(3) is the dissolution rate of Al_(2)O_(3) in volume,μm^(3)/s;x is the value of CaO/Al_(2)O_(3) mass ratio;R_(0) is the initial radius of Al_(2)O_(3),μm;T is the temperature,K;T_(mp) is the melting point of slag,K.展开更多
The effects of Cr contents(0.3 and 1.0 wt.%)and isothermal holding temperatures(400,440,and 480℃)on the microstructure evolution and properties of complex phase steel with high formability(CH steel)were investigated ...The effects of Cr contents(0.3 and 1.0 wt.%)and isothermal holding temperatures(400,440,and 480℃)on the microstructure evolution and properties of complex phase steel with high formability(CH steel)were investigated using dilatometry,scanning electron microscopy,transmission electron microscopy(TEM),and X-ray diffraction.The results show that the microstructures of CH steel with 0.3 wt.%Cr are ferrite,granular bainite,martensite,and retained austenite,while no ferrite is observed in the microstructure of CH steel with 1.0 wt.%Cr in the same process.Cr promotes the precipitation of(Nb,Ti)C in the high-temperature austenite region through theoretical calculations and TEM observations.Cr retards the bainite transformation and refines the grain size of CH steel.Furthermore,as isothermal holding temperature increases from 400 to 480℃,the bainite and retained austenite fractions of two CH steels decrease,while the martensite fraction increases in the steels after final quenching.Consequently,the strength has an increasing tendency and the total elongation has a decreasing tendency with increasing isothermal temperature.展开更多
The performance of a recycling process for CO_(2) capture and utilization of exhaust gas in the steelmaking plant was reported.A facility capable of capturing CO_(2) at 3200 m^(3)/h was established in the steelmaking ...The performance of a recycling process for CO_(2) capture and utilization of exhaust gas in the steelmaking plant was reported.A facility capable of capturing CO_(2) at 3200 m^(3)/h was established in the steelmaking plant,resulting in the CO_(2) production of 50,000 t/a.The CO_(2) concentration of the exhaust gas from the lime kiln increased from 25.0 to 99.8 vol.%using the comprehensive method of the pressure swing adsorption and cryogenic separation.The captured and purified CO_(2) was successfully applied in the converter process by the top blowing and bottom blowing.The utilization of CO_(2) was 3.5 m^(3)/t through these two modes.After optimizing parameters of CO_(2)-O_(2) mixed top blowing,the value of[C]×[O]and the content of TFe in slag were reduced by 1.33×10-4 and 1.27%,respectively,and the dephosphorization rate of the molten steel increased by 2.31%.For the CO_(2) bottom blowing,the[N]content in the molten steel was significantly reduced by 5.7×10^(-6).展开更多
A mathematical model for simulating the fluid flow,heat transfer and solidification in the conventional mold and the chamfer mold,together with a finite element stress-strain model in the straightening process of both...A mathematical model for simulating the fluid flow,heat transfer and solidification in the conventional mold and the chamfer mold,together with a finite element stress-strain model in the straightening process of both molds,were established for the typical niobium,vanadium,and titanium micro-alloyed steels.On the basis of both numerical analysis,the mold copper plate with an optimum chamfered shape was designed and applied in industrial tests.The predicted results from numerical simulation of fluid flow,heat transfer and solidification in the conventional mold and the chamfer mold show that the increased chamfered angle leads to an approximately linear increase of the slab surface temperature,but it also causes strong flow near the slab corner.Very small chamfered length can lead to a significant increase of the temperature near the slab corner.However,with further increasing the chamfered length,the temperature of the slab corner increased slightly.The calculated results from the finite element analysis of stress-strain during the straightening process show that at the same slope width,the tangential strain on the slab edges and corners is minimum when the chamfered angle is 30°and 45°,which is only 40% to 46% of rectangular slabs with the same cross-section area.At the same chamfered angle of 30°,when the chamfered length is controlled between 65-85 mm,the tangential strain on the part of the slab edges and corners is relatively smaller.Industrial test results show that the slab corner temperature at straightening segment increases about 100 ℃ by using chamfer mold compared to the conventional molds.The slab transverse corner cracks have been reduced more than 95% in comparison with those in the conventional mold.展开更多
Texture is a pivotal factor for the deep drawability of interstitial free steel (IF steel). The evolution of microstructure and recrystallization texture of Ti-IF steel through the processing of hot rolling, cold roll...Texture is a pivotal factor for the deep drawability of interstitial free steel (IF steel). The evolution of microstructure and recrystallization texture of Ti-IF steel through the processing of hot rolling, cold rolling and annealing have been studied. The mechanical properties including strain hardening index n and plastic strain ratio r are also measured. For comparison, ferrite rolling and austenite rolling are both studied. The results show that the intensity of γ-fiber after ferrite rolling is higher than that after austenite rolling. The great balance between the {111}〈110〉 and {111}〈112〉 leads to low △r value after annealing. The size of precipitates in ferrite rolled sample is generally larger than that in austenite rolled sample. Compared to austenite rolled sample, the ferrite rolled and annealed one has better formability and its r value reaches 2.36. Different from laboratory production, the test steels were acquired from industrial trial, and all the result can be used in industrial production directly.展开更多
Compared with the original GCr15 bearing steel,TiN inclusions are greatly reduced by the effect of Mg addition,and many different types of non-metallic Mg-containing inclusions were observed in Mg-treated GCr15 bearin...Compared with the original GCr15 bearing steel,TiN inclusions are greatly reduced by the effect of Mg addition,and many different types of non-metallic Mg-containing inclusions were observed in Mg-treated GCr15 bearing steel which includes MgO,MgS·MnS,MgO–MgS·MnS,MgAl_(2)O_(4)–MgS·MnS,MgO–TiN,MgS·MnS–TiN,and MgO–MgS·MnS–TiN.The inclusion size distribution based on automatic inclusion analysis software shows that the number of inclusion with the size ranging from 1 to 3μm increases obviously because a large amount of MgO,MgS·MnS,TiN inclusions containing Mg with smaller sizes are massively generated.In situ observation on the experimental steel by high-temperature confocal laser scanning microscopy confirms that MgO can provide nucleation sites for TiN.In addition,the MgS·MnS and MgO–MgS·MnS inclusions can also provide positions for the nucleation of TiN.Thermodynamic calculations indicate that after Mg addition to liquid steel,a large number of fine MgO inclusions are generated in the liquid steel because of the strong reactivity of Mg and O.At the same time,MgS precedes TiN precipitates in the solid–liquid two-phase region;thus,MgO and MgS·MnS can provide sites for TiN nucleation.At last,two possible formation pathways for the above various TiN inclusions containing Mg are discussed.展开更多
文摘In this report,the microstructure,mechanical properties,and textures of warm rolled interstitial-free steel annealed at four different temperatures(730,760,790,and 820°C)were studied.The overall structural features of specimens were investigated by optical microscopy,and the textures were measured by X-ray diffraction(XRD).Nano-sized precipitates were then observed by a transmission electron microscope(TEM)on carbon extraction replicas.According to the results,with increased annealing temperatures,the ferrite grains grew;in addition,the sizes of Ti_4C_2S_2 and Ti C precipitates also increased.Additionally,the sizes of Ti N and Ti S precipitates slightly changed.When the annealing temperature increased from 730 to 820°C,the yield strength(YS)and the ultimate tensile strength(UTS)showed a decreasing trend.Meanwhile,elongation and the strain harden exponent(n value)increased to 49.6%and 0.34,respectively.By comparing textures annealed at different temperatures,the intensity of{111}texture annealed at 820°C was the largest,while the difference between the intensity of{111}<110>and{111}<112>was the smallest when the annealing temperature was 820°C.Therefore,the plastic strain ratio(r value)annealed at 820°C was the highest.
基金financially supported by the National Natural Science Foundation of China (No.U1460101)
文摘Since the production of tinplate with non-earing properties is difficult, especially when it is produced via the double-reduction process, the optimal degree of second cold reduction is particularly important for achieving desirable drawing properties. The evolution of texture and the earing propensity of double-reduction tinplate with different extents of second reduction were investigated in this study. Optical microscopy and scanning electron microscopy were used to observe the changes in the microstructure at various extents of reduction. Two common testing methods, X-ray diffraction(XRD) and electron backscatter diffraction, were used to investigate the texture of the specimens, which revealed the effects of deformation percentage on the final texture development and the change in the grain boundary. The earing rate was determined via earing tests involving measurement of the height of any ear. The results obtained from both XRD analyses and earing tests revealed the same ideal value for the second cold reduction on the basis of the relationship between crystallographic texture and the degree of earing.
基金financially supported by the National Nature Science Foundation of China(Nos.U1860206,51725402)the Science and Technology Program of Hebei,China(Nos.20311006D,20591001D)。
文摘The dissolution kinetics of Al_(2)O_(3) in CaO-Al_(2)O_(3) SiOslags was studied using a high-temperature confocal scanning laser microscope at 1773 to 1873 K.The results show that the controlling step during the Al_(2)O_(3) dissolution was the diffusionin molten slag.It was found that the dissolution curves of Al_(2)O_(3) particles were hardly agreed with the traditional boundary layer diffusion model with the increase of the CaO/Al_(2)O_(3) ratio of slag.A modified diffusion equation considering slag viscosity was developed to study the dissolution mechanism of Al_(2)O_(3) in slag.Diffusion coefficients of Al_(2)O_(3) in slag were calculated as 2.8×10to 4.1×10m~2/s at the temperature of 1773-1873 K.The dissolution rate of Al_(2)O_(3) increased with higher temperature,CaO/Al_(2)O_(3),and particle size.A new model was shown to be v_(Al_(2)O_(3))=0.16×r_(0)^(1.58)×x^(3.52)×(T-T_(mp))^(1.11)to predict the dissolution rate and the total dissolution time of Al_(2)O_(3) inclusions with various sizes,where vAl_(2)O_(3) is the dissolution rate of Al_(2)O_(3) in volume,μm^(3)/s;x is the value of CaO/Al_(2)O_(3) mass ratio;R_(0) is the initial radius of Al_(2)O_(3),μm;T is the temperature,K;T_(mp) is the melting point of slag,K.
基金The authors gratefully acknowledge the support from the Key Research and Development Plan of Shandong Province(No.2019TSLH0103)the New Energy Automobile Material Production and Application Demonstration Platform Project(No.TC180A6MR-1)Guangxi Innovation-Driven Development Special Fund Project(No.AA18242012).
文摘The effects of Cr contents(0.3 and 1.0 wt.%)and isothermal holding temperatures(400,440,and 480℃)on the microstructure evolution and properties of complex phase steel with high formability(CH steel)were investigated using dilatometry,scanning electron microscopy,transmission electron microscopy(TEM),and X-ray diffraction.The results show that the microstructures of CH steel with 0.3 wt.%Cr are ferrite,granular bainite,martensite,and retained austenite,while no ferrite is observed in the microstructure of CH steel with 1.0 wt.%Cr in the same process.Cr promotes the precipitation of(Nb,Ti)C in the high-temperature austenite region through theoretical calculations and TEM observations.Cr retards the bainite transformation and refines the grain size of CH steel.Furthermore,as isothermal holding temperature increases from 400 to 480℃,the bainite and retained austenite fractions of two CH steels decrease,while the martensite fraction increases in the steels after final quenching.Consequently,the strength has an increasing tendency and the total elongation has a decreasing tendency with increasing isothermal temperature.
文摘The performance of a recycling process for CO_(2) capture and utilization of exhaust gas in the steelmaking plant was reported.A facility capable of capturing CO_(2) at 3200 m^(3)/h was established in the steelmaking plant,resulting in the CO_(2) production of 50,000 t/a.The CO_(2) concentration of the exhaust gas from the lime kiln increased from 25.0 to 99.8 vol.%using the comprehensive method of the pressure swing adsorption and cryogenic separation.The captured and purified CO_(2) was successfully applied in the converter process by the top blowing and bottom blowing.The utilization of CO_(2) was 3.5 m^(3)/t through these two modes.After optimizing parameters of CO_(2)-O_(2) mixed top blowing,the value of[C]×[O]and the content of TFe in slag were reduced by 1.33×10-4 and 1.27%,respectively,and the dephosphorization rate of the molten steel increased by 2.31%.For the CO_(2) bottom blowing,the[N]content in the molten steel was significantly reduced by 5.7×10^(-6).
基金Sponsored by National Natural Science Foundation of China(51204059)
文摘A mathematical model for simulating the fluid flow,heat transfer and solidification in the conventional mold and the chamfer mold,together with a finite element stress-strain model in the straightening process of both molds,were established for the typical niobium,vanadium,and titanium micro-alloyed steels.On the basis of both numerical analysis,the mold copper plate with an optimum chamfered shape was designed and applied in industrial tests.The predicted results from numerical simulation of fluid flow,heat transfer and solidification in the conventional mold and the chamfer mold show that the increased chamfered angle leads to an approximately linear increase of the slab surface temperature,but it also causes strong flow near the slab corner.Very small chamfered length can lead to a significant increase of the temperature near the slab corner.However,with further increasing the chamfered length,the temperature of the slab corner increased slightly.The calculated results from the finite element analysis of stress-strain during the straightening process show that at the same slope width,the tangential strain on the slab edges and corners is minimum when the chamfered angle is 30°and 45°,which is only 40% to 46% of rectangular slabs with the same cross-section area.At the same chamfered angle of 30°,when the chamfered length is controlled between 65-85 mm,the tangential strain on the part of the slab edges and corners is relatively smaller.Industrial test results show that the slab corner temperature at straightening segment increases about 100 ℃ by using chamfer mold compared to the conventional molds.The slab transverse corner cracks have been reduced more than 95% in comparison with those in the conventional mold.
文摘Texture is a pivotal factor for the deep drawability of interstitial free steel (IF steel). The evolution of microstructure and recrystallization texture of Ti-IF steel through the processing of hot rolling, cold rolling and annealing have been studied. The mechanical properties including strain hardening index n and plastic strain ratio r are also measured. For comparison, ferrite rolling and austenite rolling are both studied. The results show that the intensity of γ-fiber after ferrite rolling is higher than that after austenite rolling. The great balance between the {111}〈110〉 and {111}〈112〉 leads to low △r value after annealing. The size of precipitates in ferrite rolled sample is generally larger than that in austenite rolled sample. Compared to austenite rolled sample, the ferrite rolled and annealed one has better formability and its r value reaches 2.36. Different from laboratory production, the test steels were acquired from industrial trial, and all the result can be used in industrial production directly.
基金The authors are grateful to the National Natural Science Foundation of China(Grant No.51874170)for supporting this work.
文摘Compared with the original GCr15 bearing steel,TiN inclusions are greatly reduced by the effect of Mg addition,and many different types of non-metallic Mg-containing inclusions were observed in Mg-treated GCr15 bearing steel which includes MgO,MgS·MnS,MgO–MgS·MnS,MgAl_(2)O_(4)–MgS·MnS,MgO–TiN,MgS·MnS–TiN,and MgO–MgS·MnS–TiN.The inclusion size distribution based on automatic inclusion analysis software shows that the number of inclusion with the size ranging from 1 to 3μm increases obviously because a large amount of MgO,MgS·MnS,TiN inclusions containing Mg with smaller sizes are massively generated.In situ observation on the experimental steel by high-temperature confocal laser scanning microscopy confirms that MgO can provide nucleation sites for TiN.In addition,the MgS·MnS and MgO–MgS·MnS inclusions can also provide positions for the nucleation of TiN.Thermodynamic calculations indicate that after Mg addition to liquid steel,a large number of fine MgO inclusions are generated in the liquid steel because of the strong reactivity of Mg and O.At the same time,MgS precedes TiN precipitates in the solid–liquid two-phase region;thus,MgO and MgS·MnS can provide sites for TiN nucleation.At last,two possible formation pathways for the above various TiN inclusions containing Mg are discussed.
