A full-sectional microstructure characterization method was developed to investigate the formation of coarse slag rims during the continuous casting of hypo-peritectic steel.The cross-sectional microstructural analysi...A full-sectional microstructure characterization method was developed to investigate the formation of coarse slag rims during the continuous casting of hypo-peritectic steel.The cross-sectional microstructural analysis of typical slag rims for two highly crystalline powders revealed that their formation was primarily driven by the solidification of the liquid slag.Distinct differences were observed in the microstructures of slag rims from the two powders.Powder A(characterized by a higher breaking temperature and viscosity)displayed alternating lamellar microstructures of coarse and fine phases,with the coarse phases composed of akermanite-gehlenite transition phases.In contrast,powder B(with a lower breaking temperature and viscosity)predominantly comprised regular akermanite-gehlenite crystals interspersed with a certain amount of glassy phases.Numerical simulations of a three-phase fluid flow coupled with heat transfer indicate that slag rim formation correlates with mold oscillation.Solidification of the liquid slag at the slag rim front predominantly occurs during the negative stroke of the mold oscillation.The average heating rate during the ascending stage of the mold reaches approximately 100 K·s^(−1),whereas the average cooling rate during the descending stage attains 400 K·s^(−1).This temperature variation leads to the formation of lamellar microstructures,whereas the ascending stage promotes the formation of coarse structures and thicker slag rims.Based on the powder properties,two distinct formation pathways exist for highly crystalline mold powders.For the powders with a higher breaking temperature,higher viscosity,and narrower solidification range(powder A),coarse microstructures and thicker slag rims were preferentially formed.For powders with lower breaking temperature and viscosity and wider solidification ranges(powder B),the liquid slag resisted rapid solidification,and the extended mushy zone allowed the partial liquid slag to persist at the slag rim front,promoting the formation of a thin slag rim.This study enhances the understanding of slag rim formation in highly crystalline mold powders and provides critical insights into the control of longitudinal surface cracks in hypo-peritectic steel.展开更多
To develop a suitable production process for fiber reinforced investment casting shell mold,three methods were studied:the traditional method(M_(1)),the method of adding fiber into silica sol with mechanical stirring ...To develop a suitable production process for fiber reinforced investment casting shell mold,three methods were studied:the traditional method(M_(1)),the method of adding fiber into silica sol with mechanical stirring and ultrasonic agitation(M_(2)),and the method of adding fiber into slurry with mechanical stirring and ultrasonic agitation for durations of 3,15,30,and 45 min(M_(3)).The bending strength,high-temperature self-load deformation,and thermal conductivity of the shell molds were investigated.The results reveal that the enhancement of fiber dispersion through ultrasonic agitation improves the comprehensive performance of the shell molds.The maximum green bending strength of the shell mold by M_(2) reaches 3.29 MPa,which is 29% higher than that of the shell mold prepared by M_(1).Moreover,the high-temperature self-load deformation of the shell mold is reduced from 0.62% to 0.44%.In addition,simultaneous ultrasonic agitation and mechanical stirring effectively shorten the slurry preparation time while maintaining comparable levels of fiber dispersion.With the process M_(3)-45 min,the fillers are uniformly dispersed in the slurry,and the fired bending strength and the high-temperature self-load deformation reach 6.25 MPa and 0.41%,respectively.Therefore,the proposed ultrasonic agitation route is promising for the fabrication of fiber-reinforced shell molds with excellent fibers dispersion.展开更多
The modified precipitation theory was employed to directly predict the multi-variantε-carbide precipitation from thermodynamics and growing and ripening kinetics.Three distinct variants were identified:Variants 1 and...The modified precipitation theory was employed to directly predict the multi-variantε-carbide precipitation from thermodynamics and growing and ripening kinetics.Three distinct variants were identified:Variants 1 and 2 were the perpendicular plate-likeε-carbides,while the granularε-carbides were Variant 3.The particle sizes of Variants 1 and 2 were usually larger than those of Variant 3.The mean aspect ratios of Variants 1 and 2 were 4.96,4.62 and 4.35 larger than those(1.72,1.63 and 1.56)for the granularε-carbides when coiled at 140,200 and 250℃,respectively.Thermodynamic analysis indicated that Variants 1 and 2 are easier to nucleate than Variant 3.The growing kinetic analysis implied that the relative nucleation time and precipitation time for Variants 1 and 2 were about 8 and 5 orders of magnitude less than those for Variant 3,respectively.The ripening kinetics further displayed that the ripening rate was similar for Variants 1,2 and 3.In addition,the dislocation density has weak influence onε-carbide nucleation.These findings suggest that the precipitation thermodynamic and kinetic models could be extended to second phase precipitation in other materials systems.Besides,nano-scaleε-carbides,fine block size and nano-twins,as well as medium-density dislocations,jointly caused the optimal match between strength and total elongation when coiled at 140℃.展开更多
High temperature tensile were performed by using a thermo-mechanical GW1600 to simulate the deformation of Ti microalloy steels at high temperatures and low deformation rates similar to those during continuous casting...High temperature tensile were performed by using a thermo-mechanical GW1600 to simulate the deformation of Ti microalloy steels at high temperatures and low deformation rates similar to those during continuous casting.An equivalent austenite diameter was proposed,taking into account the weakening effects of proeutectoid ferrite films and Ti carbonitride precipitation.Based on this,a hot ductility prediction model for the slab was established to investigated hot ductility.The results show that as Ti content increases,the hot ductility of Ti microalloy steel initially increases and then decreases.At low Ti content,the pinning effect of Ti carbonitrides increases with the increase in Ti content,which inhibits grain coarsening for improving hot ductility.As Ti content increases,the size of carbonitrides grows,weakening the pinning effect and leading to austenite grain coarsening.Simultaneously,the formation of Ti carbonitrides inhibits proeutectoid ferrite film formation,leading to a reduction in its thickness.These combined factors reduce the hot ductility of the continuous casting steel.According to the hot ductility prediction model,in order of severity,the factors affecting hot ductility are:proeutectoid ferrite film,chain-like nanoscale Ti carbonitrides,austenite grain size,and dispersed nanoscale Ti carbonitrides.An accuracy error of less than 10%is shown by the model.展开更多
A new flow control technology in continuous casting process named permanent magnet flow control-mold(PMFC-Mold)was proposed,in which the permanent magnets are arranged in Halbach array near the narrow region of the mo...A new flow control technology in continuous casting process named permanent magnet flow control-mold(PMFC-Mold)was proposed,in which the permanent magnets are arranged in Halbach array near the narrow region of the mold.The behavior of molten steel flow and the fluctuation of molten steel/slag interface in the PMFC-Mold under different continuous casting speeds were investigated.Firstly,a physical experiment of liquid Ga-In-Sn alloy circulating flow was carried out in Perspex mold with Halbach’s permanent magnets(HPMs)to investigate the magnetic field distribution of HPMs and its impactful electromagnetic braking effect.The numerical simulation of 1450 mm×230 mm slab shows that a stronger magnetic field over 0.3-0.625 T is formed at the wide surface and the narrow surface of the mold,which provides an effective electromagnetic braking for controlling the impingement of molten steel jet and suppressing the fluctuation of molten steel/slag interface.The numerical simulation results show that in the PMFC-Mold,the region with the turbulent kinetic energy greater than 0.01 and 0.04 m^(2)s^(-2)on the upper backflow zone and near the narrow surface of the mold are significantly reduced.The maximum turbulent kinetic energy of the submerged entry nozzle(SEN)jet in front of the narrow surface is significantly reduced,and the SEN jet moves downward before impacting the narrow surface of the mold.In the PMFC-Mold,the region with the surface velocity greater than 0.2 m s^(-1)on the steel/slag interface is eliminated,the flow pattern and fluctuation profiles on the molten steel/slag interface become regular on both sides of SEN,and the vortex near SEN disappears.The maximum fluctuation height of molten steel/slag interface is controlled below 2.59 and 5.40 mm corresponding to the casting speed of 1.6 and 2.0 m min-1,respectively.展开更多
Al/steel bimetallic composites were prepared by compound casting,and the effects of the rotating magnetic field on the interfacial microstructure and shear property of bimetallic composite was investigated.The applica...Al/steel bimetallic composites were prepared by compound casting,and the effects of the rotating magnetic field on the interfacial microstructure and shear property of bimetallic composite was investigated.The application of rotating magnetic field refined the grain structure of the Al alloy matrix,changed the eutectic Si morphology from coarse lath to needle-like.The rotating magnetic field improved the temperature field and solute distribution of the Al alloy melt,enriched a layer of Si at the interface,and suppressed the growth of intermetallic compounds,the thickness of the interface layer decreased from 44.9μm to 22.8μm.The interfacial intermetallic compounds consisted ofη-Al_(5)Fe_(2),θ-Al_(13)Fe_(4),τ6-Al_(4.5)FeSi,τ_(5)-Al_(8)Fe_(2)Si andτ_(3)-Al_(2)FeSi,and the addition of the rotating magnetic field did not change phase composition.The rotating magnetic field improved the stress distribution within the interfacial intermetallic compounds,the presence of high-angle grain boundaries retarded crack extension,and the shear strength was enhanced from 31.27±3 MPa to 52.70±4 MPa.This work provides a feasible method for preparing Al/steel bimetallic composite with good bonding property.展开更多
The microstructural characteristics of austenite in Ti microalloyed steel during continuous casting significantly influence thethermoplasticity,thereby affecting the quality of the slab.In this work,a prediction model...The microstructural characteristics of austenite in Ti microalloyed steel during continuous casting significantly influence thethermoplasticity,thereby affecting the quality of the slab.In this work,a prediction model for two-stage austenite growth under varyingcooling rates was established by incorporating the effect of second-phase pinning and high-temperature ferrite-austenite phase transform-ation and growth theory.The results indicate that with 0.02wt%Ti,the high-temperature ferrite growth exhibits typical parabolic growthcharacteristics.When the Ti content increases to 0.04wt%,the high-temperature ferrite grain boundary migration rate significantly slowsduring the initial solidification stage.The predicted austenite grain sizes for 0.02wt%Ti microalloyed steel at the center,quarter,and sur-face of the slab are 5592,3529,and 1524μm,respectively.For 0.04wt%Ti microalloyed steel,the austenite grain sizes are 4074,2942,and 1179μm at the same positions.The average error is within 5%.As the Ti content increases from 0.02wt% to 0.04wt%,the austenitegrain refinement at the center is most significant,with an average grain size reduction of 27.14%.展开更多
To address the current issues with the conventional slide gate system utilized in the steel teeming process,a unique electromagnetic induction controlled automated steel teeming(EICAST)technology has been developed.Co...To address the current issues with the conventional slide gate system utilized in the steel teeming process,a unique electromagnetic induction controlled automated steel teeming(EICAST)technology has been developed.Cooling means of spiral coil in this technology is directly related to its service life.Firstly,heat transfer processes of air cooling and spray cooling were compared and analyzed.Secondly,the impacts of water temperature,water flow rate and air flow rate were examined in order to maximize the spray cooling effect.To maintain coil temperature at a low value consistently throughout the entire thermal cycle process of the ladle,a combined cooling mode was finally employed.Numerical simulation was applied to examine the coil temperature variation with different cooling systems and characteristics.Before coil operation,spray cooling is said to be more effective.By controlling the water flow rate and air flow rate,the spray cooling effect is enhanced.However,water temperature has little or no impact when using spray cooling.Air cooling during the secondary refining process and spray cooling prior to coil operation are combined to further lower coil temperature.When the direction of the spray cooling is from bottom to top,the coil temperature is lowered below 165℃.A practical induction coil cooling plan was provided for the EICAST technology’s production process.展开更多
The strip casts of cobalt-free maraging steel were fabricated using a twin-roll strip casting simulator,and its characteristics of sub-rapid solidification were studied.Subsequently,the confocal laser scanning microsc...The strip casts of cobalt-free maraging steel were fabricated using a twin-roll strip casting simulator,and its characteristics of sub-rapid solidification were studied.Subsequently,the confocal laser scanning microscope(CLSM)was employed to in situ observe the phase transformation during the heat treatment of maraging steel strip cast such as austenitization,solution treatment,and aging processes.It was found that due to the high cooling rate during the twin-roll strip casting process,the sub-rapid solidified strip cast possessed a full lath martensitic structure,weak macrosegregation,and evident microsegregation with a dendritic morphology.During austenitization of strip cast,the austenite grain size increased with the austenitization temperature.After holding at 1250℃for 250 s,the austenite grain size at the high temperature owned a high similarity to the prior austenite grain size of the strip cast,which effectively duplicates the microstructure of the strip cast after sub-rapid solidification.During the solution treatment process,the martensitic structure of the strip cast also underwent austenitic transformation,subsequently transformed into martensite again after quenching.Due to the low reheating temperature during solution treatment,the austenite grain size was refined,resulting in the fine martensitic microstructure after quenching.During the aging process of strip cast,some of martensite transformed into fine austenite,which was located in the interdendritic region and remained stable after air cooling,resulting in the dual-phase microstructure of martensite and austenite.The solute segregation of Ni and Mo elements during the sub-rapid solidification of strip cast caused the enrichment of Ni and Mo elements in the interdendritic region,which can expand the austenite phase region and thus enhance the stability of austenite,leading to the formation of austenite in the interdendritic region after aging treatment.展开更多
Renovation design of wasteland on the original Quarter A of Panzhihua Nongnongping Steelcasting Factory was taken for example in this study, natural conditions and biological landscapes in the study area were investig...Renovation design of wasteland on the original Quarter A of Panzhihua Nongnongping Steelcasting Factory was taken for example in this study, natural conditions and biological landscapes in the study area were investigated. Principles and theories of the renovation design were introduced, it was proposed that protection and landscape renovation of industrial heritage had to be insisted to make regular and unique overall spatial layouts. On this basis, design approaches for the wasteland landscape renovation of the steel-casting factory were proposed as "maintaining original images, realizing the functional substitution; optimizing spatial structure; updating seriously-damaged industrial facilities with insignificant functionality; improving and recovering landscape soil; recovering and reconstructing vegetation".展开更多
Because of the addition of significant quantities of aluminum and manganese, the great challenge of casting 20Mn23Al nonmagnetic steel is to design a mold slag that is chemically compatible with this steel composition...Because of the addition of significant quantities of aluminum and manganese, the great challenge of casting 20Mn23Al nonmagnetic steel is to design a mold slag that is chemically compatible with this steel composition. A new mold slag with low melting point and low basicity was proposed. The initial slag （the base mold slag） and two corresponding mold slags sampled after 8 min and 15 min were investigated, and the changes of mold slag composition and properties of molten slag were discussed. The results showed that the slag quickly changed in chemical composition to a slag that contained a small quantity of silica and a larger quantity of alumina, and the basieity increased obviously; the heat flux density through the slag film decreased slightly compared with the slag film at 0 min, 8 min and 15 min; the mold slag used for nonmagnetic steel was precipitated as CaF2 crystals. The casting experi- ment shows that the slab has good surface quality without longitudinal face cracks and slag inclusions; the Al2O3 content in the molten slag pool increased with time at the beginning stage, and it can approach equilibrium state after about 600 s.展开更多
In steel squeeze casting process, the working condition of a punch was very rigorous. The abnormal failure models of an H13 punch, such as plastic rubbed damnification, could not be avoided easily. Based on the analys...In steel squeeze casting process, the working condition of a punch was very rigorous. The abnormal failure models of an H13 punch, such as plastic rubbed damnification, could not be avoided easily. Based on the analysis of the flow stress and the friction-shearing stress of an H13 punch in steel squeeze casting process, the following results were obtained： if the flow stress of an H13 punch was smaller than its friction-shearing stress, these abnormal failures could not be avoided; and if there were some protection measures that enable the flow stress to have a greater value than its friction-shearing one, the abnormal failures would not occur. In the production of 45^# steel valves and catenary system components, the flow stress of a lateral H13 punch without any protection measure was about 29 MPa and its friction-shearing stress was about 51 MPa, then, the abnormal failures occurred; however, when the protection measures of the punch enabled its working temperature to have a value below 682 ℃ its flow stress was greater than its friction-shearing stress, and the abnormal failures were avoided.展开更多
The grain refinement and macrosegregation control of GCrl5 bearing steel were investigated under a type of rarely-used electromagnetic stirring, vertical electromagnetic stirring （V-EMS）, in continuous casting. V-EM...The grain refinement and macrosegregation control of GCrl5 bearing steel were investigated under a type of rarely-used electromagnetic stirring, vertical electromagnetic stirring （V-EMS）, in continuous casting. V-EMS can create an upward electromagnetic force and generate longitudinal loop convection, which ena- bles the better mixing of the upper part with the lower part of the liquid steel. The results showed that ap- plying V-EMS can enlarge the region of the equiaxed grain, decrease the secondary dendrite arm spacing （SDAS） and reduce the segregation of both carbon and sulfur. After applying V-EMS, liquid steel with a high solute concentration is brought to the dendrite tips, making the dendrite arms partially melt. The length of the dendrite fragment is approximately 1.8 mm, 10 to 12 times the SDAS. Upon increasing the amount of cooling water from 2.0 to 3.5 m3/h, the dendrite fragments exhibit an obvious aggregation fol- lowing V-EMS. Finally, a criterion for dendrite fragmentation under V-EMS was derived based on the dendrite fragmentation theory of Campanella et al.展开更多
The development of continuous casting technology of electrical steel was analyzed. The technologies and products characteristics of conventional continuous casting, thin slab continuous casting and rolling, middle thi...The development of continuous casting technology of electrical steel was analyzed. The technologies and products characteristics of conventional continuous casting, thin slab continuous casting and rolling, middle thin slab continuous casting and rolling and twin-roll thin strip were compared. Conventional continuous casting technology was widely adopted in producing electrical steel, thin slab continuous casting and rolling and middle thin slab contin- uous casting and roiling technology industrialized electrical steel~ and study of twin-roll thin strip casting technology was focused on fundamental experiments.展开更多
In this study, the effect of melting temperature on the microstructural evolutions, behavior, and corrosion morphology of Hadfield steel in the casting process is investigated. The mold was prepared by the sodium sili...In this study, the effect of melting temperature on the microstructural evolutions, behavior, and corrosion morphology of Hadfield steel in the casting process is investigated. The mold was prepared by the sodium silicate/CO_2 method, using a blind riser, and then the desired molten steel was obtained using a coreless induction furnace. The casting was performed at melting temperatures of 1350, 1400, 1450, and 1500°C, and the cast blocks were immediately quenched in water. Optical microscopy was used to analyze the microstructure, and scanning electron microscopy(SEM) and X-ray diffractrometry(XRD) were used to analyze the corrosion morphology and phase formation in the microstructure, respectively. The corrosion behavior of the samples was analyzed using a potentiodynamic polarization test and electrochemical impedance spectroscopy(EIS) in 3.5 wt% NaCl. The optical microscopy observations and XRD patterns show that the increase in melting temperature led to a decrease of carbides and an increase in the austenite grain size in the Hadfield steel microstructure. The corrosion tests results show that with increasing melting temperature in the casting process, Hadfield steel shows a higher corrosion resistance. The SEM images of the corrosion morphologies show that the reduction of melting temperature in the Hadfield steel casting process induced micro-galvanic corrosion conditions.展开更多
In the present paper, low carbon steel strips with different phosphorus contents were produced using a twin roll strip casting process. The solidification structure was studied and its features were analyzed in detail...In the present paper, low carbon steel strips with different phosphorus contents were produced using a twin roll strip casting process. The solidification structure was studied and its features were analyzed in detail. It was found that the strips possessed a fine microstructure compared with the mould cast steels. With increasing phosphorus content more ferrite has been formed with finer grains.展开更多
A three-dimensional heat transfer model for continuous steel slab casting has been developed with realistic spray cooling patterns and a coupled microsegregation solidification model that calculates the solidification...A three-dimensional heat transfer model for continuous steel slab casting has been developed with realistic spray cooling patterns and a coupled microsegregation solidification model that calculates the solidification path for multi-component steels. Temperature and composition dependent properties are implemented in a database for 15 chemical species. Considerable effort is made to accurately model the spray cooling heat transfer. Each spray nozzle position and distribution is considered, including variations of the spray patterns with flow rate, and spray overlap. Nozzle type, layout, nozzle-to-slab distance, and spray span and flux are variable. Natural convection, thermal radiation and contact cooling of individual rolls are computed. The present model provides more comprehensive information and realistic slab surface temperatures than results from a model using the 'averaged' treatment of boundary conditions. Cooling operating conditions and parameters of individual spray nozzles can be analyzed to optimize nozzle spray distribution, improve product quality, and troubleshoot issues such as nozzle clogging that may arise during production. One spray cooling correlation is used for the entire machine, achieving as good or better agreement with surface temperature measurements than was found previously for the model using an 'averaged' treatment of boundary conditions and using three machine-segment-dependent correlations.展开更多
Fe-3Si steel strip was produced by thin slab casting and rolling （TSCR） process in the laboratory. The microstructure and texture of hot rolled strip by different total reduction and rolling schedules were observed ...Fe-3Si steel strip was produced by thin slab casting and rolling （TSCR） process in the laboratory. The microstructure and texture of hot rolled strip by different total reduction and rolling schedules were observed through EBSD technique and X-ray diffraction method. The rule of texture density for the a,ε and γ fibers was analyzed. When the total reduction was increased from 82.9% to 97.1%, the gradient of microstrueture and texture for A steel surface layer and center layer was found, {001}〈110〉 texture had higher intensity, and {001}〈110〉texture was changed to { 110 } 〈 001 〉 and { 112 } 〈 111 〉. The texture distribution with different reduction schedules for B steel was basically similar, but the Goss texture orientation density and volume fraction for B steel were higher, the hot rolling reduction schedule of C1 was effective for the formation of Goss texture. The research work was useful theoretical basis and reference data to develop electrical steel by thin slab continuous casting and direct rolling technology.展开更多
Solidification cracking that occurs during continuous casting of 1Cr13 stainless steel was investigated with and without final elec- tromagnetic stirring （F-EMS）. The results show that cracks initiates and propagate...Solidification cracking that occurs during continuous casting of 1Cr13 stainless steel was investigated with and without final elec- tromagnetic stirring （F-EMS）. The results show that cracks initiates and propagates along the grain boundaries where the elements of carbon and sulfur are enriched. The final stirrer should be appropriately placed at a location that is 7.5 m away from the meniscus, and the appropri- ate thickness of the liquid core in the stirring zone is 50 ram. As a stirring current of 250 A is imposed, it can promote colurnnar-equiaxed transition, decrease the secondary dendrite arm spacing, and reduce the segregation of both carbon and sulfur. F-EMS can effectively de- crease the amount of cracks in 1Cr13 stainless steel.展开更多
基金supported by the National Natural Science Foundation of China(No.52274318).
文摘A full-sectional microstructure characterization method was developed to investigate the formation of coarse slag rims during the continuous casting of hypo-peritectic steel.The cross-sectional microstructural analysis of typical slag rims for two highly crystalline powders revealed that their formation was primarily driven by the solidification of the liquid slag.Distinct differences were observed in the microstructures of slag rims from the two powders.Powder A(characterized by a higher breaking temperature and viscosity)displayed alternating lamellar microstructures of coarse and fine phases,with the coarse phases composed of akermanite-gehlenite transition phases.In contrast,powder B(with a lower breaking temperature and viscosity)predominantly comprised regular akermanite-gehlenite crystals interspersed with a certain amount of glassy phases.Numerical simulations of a three-phase fluid flow coupled with heat transfer indicate that slag rim formation correlates with mold oscillation.Solidification of the liquid slag at the slag rim front predominantly occurs during the negative stroke of the mold oscillation.The average heating rate during the ascending stage of the mold reaches approximately 100 K·s^(−1),whereas the average cooling rate during the descending stage attains 400 K·s^(−1).This temperature variation leads to the formation of lamellar microstructures,whereas the ascending stage promotes the formation of coarse structures and thicker slag rims.Based on the powder properties,two distinct formation pathways exist for highly crystalline mold powders.For the powders with a higher breaking temperature,higher viscosity,and narrower solidification range(powder A),coarse microstructures and thicker slag rims were preferentially formed.For powders with lower breaking temperature and viscosity and wider solidification ranges(powder B),the liquid slag resisted rapid solidification,and the extended mushy zone allowed the partial liquid slag to persist at the slag rim front,promoting the formation of a thin slag rim.This study enhances the understanding of slag rim formation in highly crystalline mold powders and provides critical insights into the control of longitudinal surface cracks in hypo-peritectic steel.
基金supported by the National Natural Science Foundation of China (Grant No. 5186504)the University Science Foundation for Young Science and Technology Talents in Inner Mongolia Autonomous Region of China (Grant No. NJYT22078)+2 种基金the Basic Scientific Research Expenses Program of Universities directly under Inner Mongolia Autonomous Region (Grant No. JY20220059)the Inner Mongolia Autonomous Region ‘Grassland Talent’ project Young Innovative Talent Training Program Level ⅠBasic Research Expenses of Universities directly under the Inner Mongolia Autonomous Region (Grant No. ZTY2023040)。
文摘To develop a suitable production process for fiber reinforced investment casting shell mold,three methods were studied:the traditional method(M_(1)),the method of adding fiber into silica sol with mechanical stirring and ultrasonic agitation(M_(2)),and the method of adding fiber into slurry with mechanical stirring and ultrasonic agitation for durations of 3,15,30,and 45 min(M_(3)).The bending strength,high-temperature self-load deformation,and thermal conductivity of the shell molds were investigated.The results reveal that the enhancement of fiber dispersion through ultrasonic agitation improves the comprehensive performance of the shell molds.The maximum green bending strength of the shell mold by M_(2) reaches 3.29 MPa,which is 29% higher than that of the shell mold prepared by M_(1).Moreover,the high-temperature self-load deformation of the shell mold is reduced from 0.62% to 0.44%.In addition,simultaneous ultrasonic agitation and mechanical stirring effectively shorten the slurry preparation time while maintaining comparable levels of fiber dispersion.With the process M_(3)-45 min,the fillers are uniformly dispersed in the slurry,and the fired bending strength and the high-temperature self-load deformation reach 6.25 MPa and 0.41%,respectively.Therefore,the proposed ultrasonic agitation route is promising for the fabrication of fiber-reinforced shell molds with excellent fibers dispersion.
基金financially supported by the Central Government Guiding Local Science and Technology Development Fund of Henan Province(Z20241471091)the Independent R&D Funds of State Key Laboratory of Advanced Metallurgy(41624025).
基金supported by the National Natural Science Foundation of China(No.52293395)National Key R&D Program of China(No.2021YFB3702403).
文摘The modified precipitation theory was employed to directly predict the multi-variantε-carbide precipitation from thermodynamics and growing and ripening kinetics.Three distinct variants were identified:Variants 1 and 2 were the perpendicular plate-likeε-carbides,while the granularε-carbides were Variant 3.The particle sizes of Variants 1 and 2 were usually larger than those of Variant 3.The mean aspect ratios of Variants 1 and 2 were 4.96,4.62 and 4.35 larger than those(1.72,1.63 and 1.56)for the granularε-carbides when coiled at 140,200 and 250℃,respectively.Thermodynamic analysis indicated that Variants 1 and 2 are easier to nucleate than Variant 3.The growing kinetic analysis implied that the relative nucleation time and precipitation time for Variants 1 and 2 were about 8 and 5 orders of magnitude less than those for Variant 3,respectively.The ripening kinetics further displayed that the ripening rate was similar for Variants 1,2 and 3.In addition,the dislocation density has weak influence onε-carbide nucleation.These findings suggest that the precipitation thermodynamic and kinetic models could be extended to second phase precipitation in other materials systems.Besides,nano-scaleε-carbides,fine block size and nano-twins,as well as medium-density dislocations,jointly caused the optimal match between strength and total elongation when coiled at 140℃.
基金financially supported by the National Natural Science Foundation of China(No.51974078)the Liaoning Province Science and Technology Plan Joint Program(Key Research and Development Program Project,Nos.2022 JH25/10200003 and 2023 JH2/101800058)the Fundamental Research Funds for the Central Universities(No.N25YJS003).
文摘High temperature tensile were performed by using a thermo-mechanical GW1600 to simulate the deformation of Ti microalloy steels at high temperatures and low deformation rates similar to those during continuous casting.An equivalent austenite diameter was proposed,taking into account the weakening effects of proeutectoid ferrite films and Ti carbonitride precipitation.Based on this,a hot ductility prediction model for the slab was established to investigated hot ductility.The results show that as Ti content increases,the hot ductility of Ti microalloy steel initially increases and then decreases.At low Ti content,the pinning effect of Ti carbonitrides increases with the increase in Ti content,which inhibits grain coarsening for improving hot ductility.As Ti content increases,the size of carbonitrides grows,weakening the pinning effect and leading to austenite grain coarsening.Simultaneously,the formation of Ti carbonitrides inhibits proeutectoid ferrite film formation,leading to a reduction in its thickness.These combined factors reduce the hot ductility of the continuous casting steel.According to the hot ductility prediction model,in order of severity,the factors affecting hot ductility are:proeutectoid ferrite film,chain-like nanoscale Ti carbonitrides,austenite grain size,and dispersed nanoscale Ti carbonitrides.An accuracy error of less than 10%is shown by the model.
基金the National Natural Science Foundation of China(Grant No.U1760206 and Grant No.51574083)the 111 Project(2.0)of China(No.BP0719037)for the financial support.
文摘A new flow control technology in continuous casting process named permanent magnet flow control-mold(PMFC-Mold)was proposed,in which the permanent magnets are arranged in Halbach array near the narrow region of the mold.The behavior of molten steel flow and the fluctuation of molten steel/slag interface in the PMFC-Mold under different continuous casting speeds were investigated.Firstly,a physical experiment of liquid Ga-In-Sn alloy circulating flow was carried out in Perspex mold with Halbach’s permanent magnets(HPMs)to investigate the magnetic field distribution of HPMs and its impactful electromagnetic braking effect.The numerical simulation of 1450 mm×230 mm slab shows that a stronger magnetic field over 0.3-0.625 T is formed at the wide surface and the narrow surface of the mold,which provides an effective electromagnetic braking for controlling the impingement of molten steel jet and suppressing the fluctuation of molten steel/slag interface.The numerical simulation results show that in the PMFC-Mold,the region with the turbulent kinetic energy greater than 0.01 and 0.04 m^(2)s^(-2)on the upper backflow zone and near the narrow surface of the mold are significantly reduced.The maximum turbulent kinetic energy of the submerged entry nozzle(SEN)jet in front of the narrow surface is significantly reduced,and the SEN jet moves downward before impacting the narrow surface of the mold.In the PMFC-Mold,the region with the surface velocity greater than 0.2 m s^(-1)on the steel/slag interface is eliminated,the flow pattern and fluctuation profiles on the molten steel/slag interface become regular on both sides of SEN,and the vortex near SEN disappears.The maximum fluctuation height of molten steel/slag interface is controlled below 2.59 and 5.40 mm corresponding to the casting speed of 1.6 and 2.0 m min-1,respectively.
基金supported by the Natural Science Foundation of Shanxi Province(202103021224193).
文摘Al/steel bimetallic composites were prepared by compound casting,and the effects of the rotating magnetic field on the interfacial microstructure and shear property of bimetallic composite was investigated.The application of rotating magnetic field refined the grain structure of the Al alloy matrix,changed the eutectic Si morphology from coarse lath to needle-like.The rotating magnetic field improved the temperature field and solute distribution of the Al alloy melt,enriched a layer of Si at the interface,and suppressed the growth of intermetallic compounds,the thickness of the interface layer decreased from 44.9μm to 22.8μm.The interfacial intermetallic compounds consisted ofη-Al_(5)Fe_(2),θ-Al_(13)Fe_(4),τ6-Al_(4.5)FeSi,τ_(5)-Al_(8)Fe_(2)Si andτ_(3)-Al_(2)FeSi,and the addition of the rotating magnetic field did not change phase composition.The rotating magnetic field improved the stress distribution within the interfacial intermetallic compounds,the presence of high-angle grain boundaries retarded crack extension,and the shear strength was enhanced from 31.27±3 MPa to 52.70±4 MPa.This work provides a feasible method for preparing Al/steel bimetallic composite with good bonding property.
基金financially supported by the National Natural Science Foundation of China(No.52474355)the Liaoning Province Science and Technology Plan Joint Program(Key Research and Development Program Project,Nos.2022JH25/10200003 and 2023JH2/101800058)the Fundamental Research Funds for the Central Universities(Nos.N25YJS003 and N25DCG006)。
文摘The microstructural characteristics of austenite in Ti microalloyed steel during continuous casting significantly influence thethermoplasticity,thereby affecting the quality of the slab.In this work,a prediction model for two-stage austenite growth under varyingcooling rates was established by incorporating the effect of second-phase pinning and high-temperature ferrite-austenite phase transform-ation and growth theory.The results indicate that with 0.02wt%Ti,the high-temperature ferrite growth exhibits typical parabolic growthcharacteristics.When the Ti content increases to 0.04wt%,the high-temperature ferrite grain boundary migration rate significantly slowsduring the initial solidification stage.The predicted austenite grain sizes for 0.02wt%Ti microalloyed steel at the center,quarter,and sur-face of the slab are 5592,3529,and 1524μm,respectively.For 0.04wt%Ti microalloyed steel,the austenite grain sizes are 4074,2942,and 1179μm at the same positions.The average error is within 5%.As the Ti content increases from 0.02wt% to 0.04wt%,the austenitegrain refinement at the center is most significant,with an average grain size reduction of 27.14%.
基金supported by the Startup Foundation of Shenyang Agriculture University(No.X2023050)the Fundamental Research Funds for the Central Universities(No.N2209006)the National Natural Science Foundation of China(No.U22A20173).
文摘To address the current issues with the conventional slide gate system utilized in the steel teeming process,a unique electromagnetic induction controlled automated steel teeming(EICAST)technology has been developed.Cooling means of spiral coil in this technology is directly related to its service life.Firstly,heat transfer processes of air cooling and spray cooling were compared and analyzed.Secondly,the impacts of water temperature,water flow rate and air flow rate were examined in order to maximize the spray cooling effect.To maintain coil temperature at a low value consistently throughout the entire thermal cycle process of the ladle,a combined cooling mode was finally employed.Numerical simulation was applied to examine the coil temperature variation with different cooling systems and characteristics.Before coil operation,spray cooling is said to be more effective.By controlling the water flow rate and air flow rate,the spray cooling effect is enhanced.However,water temperature has little or no impact when using spray cooling.Air cooling during the secondary refining process and spray cooling prior to coil operation are combined to further lower coil temperature.When the direction of the spray cooling is from bottom to top,the coil temperature is lowered below 165℃.A practical induction coil cooling plan was provided for the EICAST technology’s production process.
基金supported by National Natural Science Foundation of China(Nos.52130408 and 52304361)Natural Science Foundation of Hunan Province(No.2023JJ40737)the Open Project Program of Anhui Province Key Laboratory of Metallurgical Engineering&Resources Recycling(No.SKF23-02).
文摘The strip casts of cobalt-free maraging steel were fabricated using a twin-roll strip casting simulator,and its characteristics of sub-rapid solidification were studied.Subsequently,the confocal laser scanning microscope(CLSM)was employed to in situ observe the phase transformation during the heat treatment of maraging steel strip cast such as austenitization,solution treatment,and aging processes.It was found that due to the high cooling rate during the twin-roll strip casting process,the sub-rapid solidified strip cast possessed a full lath martensitic structure,weak macrosegregation,and evident microsegregation with a dendritic morphology.During austenitization of strip cast,the austenite grain size increased with the austenitization temperature.After holding at 1250℃for 250 s,the austenite grain size at the high temperature owned a high similarity to the prior austenite grain size of the strip cast,which effectively duplicates the microstructure of the strip cast after sub-rapid solidification.During the solution treatment process,the martensitic structure of the strip cast also underwent austenitic transformation,subsequently transformed into martensite again after quenching.Due to the low reheating temperature during solution treatment,the austenite grain size was refined,resulting in the fine martensitic microstructure after quenching.During the aging process of strip cast,some of martensite transformed into fine austenite,which was located in the interdendritic region and remained stable after air cooling,resulting in the dual-phase microstructure of martensite and austenite.The solute segregation of Ni and Mo elements during the sub-rapid solidification of strip cast caused the enrichment of Ni and Mo elements in the interdendritic region,which can expand the austenite phase region and thus enhance the stability of austenite,leading to the formation of austenite in the interdendritic region after aging treatment.
文摘Renovation design of wasteland on the original Quarter A of Panzhihua Nongnongping Steelcasting Factory was taken for example in this study, natural conditions and biological landscapes in the study area were investigated. Principles and theories of the renovation design were introduced, it was proposed that protection and landscape renovation of industrial heritage had to be insisted to make regular and unique overall spatial layouts. On this basis, design approaches for the wasteland landscape renovation of the steel-casting factory were proposed as "maintaining original images, realizing the functional substitution; optimizing spatial structure; updating seriously-damaged industrial facilities with insignificant functionality; improving and recovering landscape soil; recovering and reconstructing vegetation".
基金Item Sponsored by National Natural Science Foundation of China(50874125)
文摘Because of the addition of significant quantities of aluminum and manganese, the great challenge of casting 20Mn23Al nonmagnetic steel is to design a mold slag that is chemically compatible with this steel composition. A new mold slag with low melting point and low basicity was proposed. The initial slag （the base mold slag） and two corresponding mold slags sampled after 8 min and 15 min were investigated, and the changes of mold slag composition and properties of molten slag were discussed. The results showed that the slag quickly changed in chemical composition to a slag that contained a small quantity of silica and a larger quantity of alumina, and the basieity increased obviously; the heat flux density through the slag film decreased slightly compared with the slag film at 0 min, 8 min and 15 min; the mold slag used for nonmagnetic steel was precipitated as CaF2 crystals. The casting experi- ment shows that the slab has good surface quality without longitudinal face cracks and slag inclusions; the Al2O3 content in the molten slag pool increased with time at the beginning stage, and it can approach equilibrium state after about 600 s.
文摘In steel squeeze casting process, the working condition of a punch was very rigorous. The abnormal failure models of an H13 punch, such as plastic rubbed damnification, could not be avoided easily. Based on the analysis of the flow stress and the friction-shearing stress of an H13 punch in steel squeeze casting process, the following results were obtained： if the flow stress of an H13 punch was smaller than its friction-shearing stress, these abnormal failures could not be avoided; and if there were some protection measures that enable the flow stress to have a greater value than its friction-shearing one, the abnormal failures would not occur. In the production of 45^# steel valves and catenary system components, the flow stress of a lateral H13 punch without any protection measure was about 29 MPa and its friction-shearing stress was about 51 MPa, then, the abnormal failures occurred; however, when the protection measures of the punch enabled its working temperature to have a value below 682 ℃ its flow stress was greater than its friction-shearing stress, and the abnormal failures were avoided.
基金supported by the National Natural Science Foundation of China(No.50834009)the Key Project of the Ministry of Education of China(No.311014)the 111 Project of China(No.B07015)
文摘The grain refinement and macrosegregation control of GCrl5 bearing steel were investigated under a type of rarely-used electromagnetic stirring, vertical electromagnetic stirring （V-EMS）, in continuous casting. V-EMS can create an upward electromagnetic force and generate longitudinal loop convection, which ena- bles the better mixing of the upper part with the lower part of the liquid steel. The results showed that ap- plying V-EMS can enlarge the region of the equiaxed grain, decrease the secondary dendrite arm spacing （SDAS） and reduce the segregation of both carbon and sulfur. After applying V-EMS, liquid steel with a high solute concentration is brought to the dendrite tips, making the dendrite arms partially melt. The length of the dendrite fragment is approximately 1.8 mm, 10 to 12 times the SDAS. Upon increasing the amount of cooling water from 2.0 to 3.5 m3/h, the dendrite fragments exhibit an obvious aggregation fol- lowing V-EMS. Finally, a criterion for dendrite fragmentation under V-EMS was derived based on the dendrite fragmentation theory of Campanella et al.
文摘The development of continuous casting technology of electrical steel was analyzed. The technologies and products characteristics of conventional continuous casting, thin slab continuous casting and rolling, middle thin slab continuous casting and rolling and twin-roll thin strip were compared. Conventional continuous casting technology was widely adopted in producing electrical steel, thin slab continuous casting and rolling and middle thin slab contin- uous casting and roiling technology industrialized electrical steel~ and study of twin-roll thin strip casting technology was focused on fundamental experiments.
文摘In this study, the effect of melting temperature on the microstructural evolutions, behavior, and corrosion morphology of Hadfield steel in the casting process is investigated. The mold was prepared by the sodium silicate/CO_2 method, using a blind riser, and then the desired molten steel was obtained using a coreless induction furnace. The casting was performed at melting temperatures of 1350, 1400, 1450, and 1500°C, and the cast blocks were immediately quenched in water. Optical microscopy was used to analyze the microstructure, and scanning electron microscopy(SEM) and X-ray diffractrometry(XRD) were used to analyze the corrosion morphology and phase formation in the microstructure, respectively. The corrosion behavior of the samples was analyzed using a potentiodynamic polarization test and electrochemical impedance spectroscopy(EIS) in 3.5 wt% NaCl. The optical microscopy observations and XRD patterns show that the increase in melting temperature led to a decrease of carbides and an increase in the austenite grain size in the Hadfield steel microstructure. The corrosion tests results show that with increasing melting temperature in the casting process, Hadfield steel shows a higher corrosion resistance. The SEM images of the corrosion morphologies show that the reduction of melting temperature in the Hadfield steel casting process induced micro-galvanic corrosion conditions.
基金This work was supported by the Major State Basic Research Development Program of China(973 Program)under the contract number of 2004CB619108the National Natural Science Foundation of China(No.50574018)the NECT-04-0278 Project of the Ministry of Education of China.
文摘In the present paper, low carbon steel strips with different phosphorus contents were produced using a twin roll strip casting process. The solidification structure was studied and its features were analyzed in detail. It was found that the strips possessed a fine microstructure compared with the mould cast steels. With increasing phosphorus content more ferrite has been formed with finer grains.
基金The authors are grateful to IPSCO Inc. for supporting this research program and for providing surface temperature measure-ments, and measurements of the spray nozzle flow characteris-tics. Without the nozzle flow pattern measurements made by Dr. L.K.Chia
文摘A three-dimensional heat transfer model for continuous steel slab casting has been developed with realistic spray cooling patterns and a coupled microsegregation solidification model that calculates the solidification path for multi-component steels. Temperature and composition dependent properties are implemented in a database for 15 chemical species. Considerable effort is made to accurately model the spray cooling heat transfer. Each spray nozzle position and distribution is considered, including variations of the spray patterns with flow rate, and spray overlap. Nozzle type, layout, nozzle-to-slab distance, and spray span and flux are variable. Natural convection, thermal radiation and contact cooling of individual rolls are computed. The present model provides more comprehensive information and realistic slab surface temperatures than results from a model using the 'averaged' treatment of boundary conditions. Cooling operating conditions and parameters of individual spray nozzles can be analyzed to optimize nozzle spray distribution, improve product quality, and troubleshoot issues such as nozzle clogging that may arise during production. One spray cooling correlation is used for the entire machine, achieving as good or better agreement with surface temperature measurements than was found previously for the model using an 'averaged' treatment of boundary conditions and using three machine-segment-dependent correlations.
基金Item Sponsored by National Natural Science Foundation of China(50534020)
文摘Fe-3Si steel strip was produced by thin slab casting and rolling （TSCR） process in the laboratory. The microstructure and texture of hot rolled strip by different total reduction and rolling schedules were observed through EBSD technique and X-ray diffraction method. The rule of texture density for the a,ε and γ fibers was analyzed. When the total reduction was increased from 82.9% to 97.1%, the gradient of microstrueture and texture for A steel surface layer and center layer was found, {001}〈110〉 texture had higher intensity, and {001}〈110〉texture was changed to { 110 } 〈 001 〉 and { 112 } 〈 111 〉. The texture distribution with different reduction schedules for B steel was basically similar, but the Goss texture orientation density and volume fraction for B steel were higher, the hot rolling reduction schedule of C1 was effective for the formation of Goss texture. The research work was useful theoretical basis and reference data to develop electrical steel by thin slab continuous casting and direct rolling technology.
基金financially supported by the National Natural Science Foundation of China (No. 50834009)the Key Project of the Ministry of Education of China (No. 311014)the 111 Project of China (No. B07015)
文摘Solidification cracking that occurs during continuous casting of 1Cr13 stainless steel was investigated with and without final elec- tromagnetic stirring （F-EMS）. The results show that cracks initiates and propagates along the grain boundaries where the elements of carbon and sulfur are enriched. The final stirrer should be appropriately placed at a location that is 7.5 m away from the meniscus, and the appropri- ate thickness of the liquid core in the stirring zone is 50 ram. As a stirring current of 250 A is imposed, it can promote colurnnar-equiaxed transition, decrease the secondary dendrite arm spacing, and reduce the segregation of both carbon and sulfur. F-EMS can effectively de- crease the amount of cracks in 1Cr13 stainless steel.
