A model of the heat transfer between molten steel and the ladle lining was established for the strip casting process,which involves a series of different operations. These operations include preheating,ladle tapping,l...A model of the heat transfer between molten steel and the ladle lining was established for the strip casting process,which involves a series of different operations. These operations include preheating,ladle tapping,ladle waiting,blowing of argon gas,and ladle pouring. To simulate the process of pouring molten steel,the geometric deformation( moving grid) technique was used in the model. Moreover,the model considers the heat absorption effect of argon gas and the formation of open eyes during argon blowing. Note that the model was used to compare the effect of different parameter values,including different preheating temperatures,tapping temperature,and argon blowing rates. The results indicate that the argon blowing rate has considerable influence on the decrease in the temperature of molten steel.展开更多
The metal spray forming process was examined using mathematical simulation and verified through the prototyping evaluation at Baosteel＇ s test and development facilities. The mathematical model comprised of four sect...The metal spray forming process was examined using mathematical simulation and verified through the prototyping evaluation at Baosteel＇ s test and development facilities. The mathematical model comprised of four sections, including jet gas flow in the deposition chamber;single droplet behavior along its trajectory path;probability and statistical analysis of droplet mass behavior, and forecast of the shape and temperature distribution of the billet during the spray forming process.展开更多
M42 high speed steel （HSS）, a high grade alloy, was produced using the spray forming technology. Optical metallography （OM）,X-ray diffraction （XRD） and scanning electron microscope （SEM） were used to investiga...M42 high speed steel （HSS）, a high grade alloy, was produced using the spray forming technology. Optical metallography （OM）,X-ray diffraction （XRD） and scanning electron microscope （SEM） were used to investigate the microstructures of the as-sprayed M42 HSS and the as-atomized powders. It is found that as-sprayed M42 HSS is composed of martensite, retained austenite and carbides. The grain size, as well as the morphology, size and distribution of the carbides have been greatly improved compared with those of the as-cast M42 steel （ a traditional process）. The size of the powder obtained at a high cold speed was ranged from 50 μm to 100μm in diameter. Its representative microstructures include dendrite, dendritic fragments, a mixture of dendrites, equiaxed grains and dendritic fragments,and equiaxed grains. The rapid solidification in the spray forming is a key factor to cause the refinement of the M42 HSS.展开更多
An unsteady mathematical thermal model was developed for predicting the time,molten-steel weight,induction heating power,and temperature changes of the steel from the end of ladle refining to the end of the continuous...An unsteady mathematical thermal model was developed for predicting the time,molten-steel weight,induction heating power,and temperature changes of the steel from the end of ladle refining to the end of the continuous-casting process of a tundish. The calculations revealed that for a specific strip-casting process,the ladle tonnage should be controlled to about 90 t. If the ladle capacity reaches 130 t,the provision of a 1 500-kW tundish induction heating device is recommended. By comparing the measured and predicted molten-steel temperature values in the Ningbosteel-Baosteel strip casting industrialization demo project( NBS) of a tundish,it was determined that the prediction accuracy of the model could meet the forecasting accuracy requirements for the molten-steel temperature in the tundish during mass production. Simultaneously,the heat flux density on each surface of the tundish was found at about 50 min,which is entirely consistent with the values reported in the related literature,and the tundish had not reached a heat balance during the casting test period. This model can also be applied to calculate the suitable size of a tundish for a specific continuous-casting process,thereby providing a theoretical basis for the design of the continuous-casting tundish.展开更多
A 3D coupling mathematical simulation program of the fluid flow, thermal transfer and solidification was developed based on the slab continuous casting process. Some characteristics such as fluid flow, solidification ...A 3D coupling mathematical simulation program of the fluid flow, thermal transfer and solidification was developed based on the slab continuous casting process. Some characteristics such as fluid flow, solidification and temperature distribution near the submerged entry nozzle （SEN） and the corner of the mold were simulated and analyzed. The result of the calculation indicates that the flow of molten metal forms two big cycling zones in the mold after it flows out of the SEN, and the temperature at the center of the two zones is relatively low. Moreover, there is a small narrow cycling zone near the narrow side of the mold due to casting. The velocity of the surface flow, the turbulent kinetic energy and the F value might reveal the relationship between the fluctuation of meniscus and the quality of the slab to some degree.展开更多
A 1：1 water model of a twin-roll strip caster was set up based on the Froude number（Fr） and Reynolds number （Re） similarity criteria. Fluctuation and the mixing effect in the molten pool of twin-roll strip castin...A 1：1 water model of a twin-roll strip caster was set up based on the Froude number（Fr） and Reynolds number （Re） similarity criteria. Fluctuation and the mixing effect in the molten pool of twin-roll strip casting process were analyzed through hydraulic simulation. The height of the fluctuation of the liquid pool surface and the residence time were measured by DJ800 multifunctional monitor under different process conditions. The results show that the casting velocity, the insertion depth and the pool level have a great effect on the fluctuation.展开更多
The feeding system used in the strip casting process delivers molten metal from the tundish to the pool that is bordered by side dams and rolls and is one of the key units in the production of high quality strip metal...The feeding system used in the strip casting process delivers molten metal from the tundish to the pool that is bordered by side dams and rolls and is one of the key units in the production of high quality strip metal. The traditional method for studying this key unit is to use a combination of a water model and a mathematical model. However,the relations in the model with and without roll rotation have not been clearly revealed in previous studies. A 2D transient model based on a continuity equation, momentum equation, turbulent equations, and a VOF equation was established in this study and used to simulate the meniscus fluctuation. A half model with a structured grid was used for the reported simulation. The simulation showed that significant differences existed in the fluctuation in the flow fields and wave length with or without the roll rotation. The wave fluctuation exhibited uncertainty and an unstable character in the roll rotation condition. The level fluctuation employing different process parameters such as rotating speed and immersion depth of tip angle was simulated and compared with and without roll rotation. The study results showed that the meniscus fluctuation of twin-roll strip casting was primarily affected by the roll rotation, and the level fluctuation increased with the increase in rotation velocity and decreased with immersion depth.展开更多
Targeting the single tuyere and double tuyere methods of argon blowing for Baosteel＇ s 300 t ladle furnace, the 3D continuity equation, the N-S equation and the turbulent k-ε double-equation were used to model the f...Targeting the single tuyere and double tuyere methods of argon blowing for Baosteel＇ s 300 t ladle furnace, the 3D continuity equation, the N-S equation and the turbulent k-ε double-equation were used to model the form of the molten steel flow and the dead areas under six different argon blowing conditions. The different flow field forms and the degree of mixing under different argon blowing methods were compared. The results demonstrate that when large ladles are operated via different methods of argon blowing, the spray from the centre of a single tuyere forms a symmetrical vortex, while when a double tuyere sprays, there is basically no clear vortex. In regards to the amount of argon blowing that will produce the best blend of molten steel, the amount of dead area reduction will not be clearly noticeable if there is an excessive argon blowing amount.展开更多
The material selected for this work was the spray formed Vanadis4 high alloy cold working mould steel （abbreviated to V4 steel）. Its microstructure, hot rolling process, and annealing treatment have been investigate...The material selected for this work was the spray formed Vanadis4 high alloy cold working mould steel （abbreviated to V4 steel）. Its microstructure, hot rolling process, and annealing treatment have been investigated. Observed from the optical and electron microscopes, the as-sprayed V4 steel had the finer microstructure of uniform and equiaxial grains ,while after hot rolling for densification and spheroidized annealing, the V4 steel obtained an excellent spheroidized structure that is favorable to subsequent quenching and tempering treatment. The spheroidized structure and level of annealed hardness of the V4 steel are almost the same as expensive imported powder metallurgy the V4 steel. It is difficult to produce V4 steel with the conventional ingot metallurgical technique, so the multi-step and high-cost powder metallurgy method is generally used at present. Compared to the powder metallurgy technique, using the spray forming technique to produce the V4 steel has obvious advantages and potential market competitiveness in reducing production costs, simplifying working process, and shortening the production cycle.展开更多
Using the equation of continuity and the double equation of Navier-Stokes and k-ε, numerical modeling on a single outlet continuous casting tundish has been carried out during the process of non-thermal flow coupling...Using the equation of continuity and the double equation of Navier-Stokes and k-ε, numerical modeling on a single outlet continuous casting tundish has been carried out during the process of non-thermal flow coupling. The flow field distribution inside the tundish was calculated and the viscosity response time was calculated with the mass transfer equation based on the flow field distribution. The flow characteristics of the molten steel inside the tundish were analyzed, with the results of the numerical modeling compared to the hydraulic modeling. The results showed that the Resident Time Distribution （RTD） curves in the latter anatomosed comparatively better. This certified the validity established by the mathematical model. Numerical modeling was carried out on both large and small tundishes during the processes of thermal flow coupling and also thermal non-flow coupling. The results showed that in regards to large tundishes with relatively simple flow processes, using numerical modeling for thermal flow coupling is necessary.展开更多
A high alloyed Vanadis4 （V4） steel was produced by spray forming process in Baosteel, and the microstructure of the as-sprayed steel and its evolution during hot rolling and annealing processes were characterized. I...A high alloyed Vanadis4 （V4） steel was produced by spray forming process in Baosteel, and the microstructure of the as-sprayed steel and its evolution during hot rolling and annealing processes were characterized. It was found that the as-sprayed V4 steel has a homogeneous and fine scale rrficrostructure with uniform dispersion of carbides. The hot rolling temperature is the key factor in controlling the evolution of type, morphology and distribution of carbides, as well as the matrix microstructure of the as-rolled steels. The optimized processing parameters for the as-sprayed V4 steel are rolling at 1050℃ and then annealing at 900℃. The microstructural evolution mechanisms during hot rolling and annealing are determined according to the microstructural analyasis of the material at different stages.展开更多
The microstructure of high vanadium and cobalt high speed steel （high-V/Co HSS ） and the morphology of its carbides were analyzed by optical microscope （OM）,scanning electron microscope （SEM） ,electron probe mic...The microstructure of high vanadium and cobalt high speed steel （high-V/Co HSS ） and the morphology of its carbides were analyzed by optical microscope （OM）,scanning electron microscope （SEM） ,electron probe microanalysis （EPMA）, X-ray power diffraction （XRD）, atomic force microscopy （AFM） and single phase erosion （SPE）. The results suggest that the as-sprayed high-V/Co HSS has fine equiaxed grains （about 20 μm in size）, which were homogeneously distributed. The carbides have two classical morphologies- one is fine particles （ about 2 μm in size） distributed along the grain boundaries and the other is needle-like one, distributed on the grain boundaries. There are MC carbides, M2C carbides,M6C carbides and Cr2WC2 carbides in the as-sprayed high-V/Co HSS samples,however,in the as-cast high-V/ Co HSS ,there are MC carbides and CrzWC2 carbides only. The SPE results show that there are two types of MC carbides in the as-sprayed HSS ：the sphere one and the particle-like one. The former is about 2 ixm in size and the latter is less than 1 μm, dispersed inside the grains,quite different from the MC carbides in the as-cast HSS. According to the AFM results, the skeleton-like M6C carbides of the as-sprayed high-V/Co HSS are embedded in the matrix along the grain boundaries. It is found that there are sharp membrane pieces on the carbides. Some small bamboo-shoot-like MC carbides grow from the matrix and are dispersed inside the grain. Those larger MC carbides are spherical particles embedded at the grain boundary junctions.展开更多
基金funded by Shanghai Engineering Research Center of Strip Casting and Rolling(No.11DZ2282300)
文摘A model of the heat transfer between molten steel and the ladle lining was established for the strip casting process,which involves a series of different operations. These operations include preheating,ladle tapping,ladle waiting,blowing of argon gas,and ladle pouring. To simulate the process of pouring molten steel,the geometric deformation( moving grid) technique was used in the model. Moreover,the model considers the heat absorption effect of argon gas and the formation of open eyes during argon blowing. Note that the model was used to compare the effect of different parameter values,including different preheating temperatures,tapping temperature,and argon blowing rates. The results indicate that the argon blowing rate has considerable influence on the decrease in the temperature of molten steel.
文摘The metal spray forming process was examined using mathematical simulation and verified through the prototyping evaluation at Baosteel＇ s test and development facilities. The mathematical model comprised of four sections, including jet gas flow in the deposition chamber;single droplet behavior along its trajectory path;probability and statistical analysis of droplet mass behavior, and forecast of the shape and temperature distribution of the billet during the spray forming process.
文摘M42 high speed steel （HSS）, a high grade alloy, was produced using the spray forming technology. Optical metallography （OM）,X-ray diffraction （XRD） and scanning electron microscope （SEM） were used to investigate the microstructures of the as-sprayed M42 HSS and the as-atomized powders. It is found that as-sprayed M42 HSS is composed of martensite, retained austenite and carbides. The grain size, as well as the morphology, size and distribution of the carbides have been greatly improved compared with those of the as-cast M42 steel （ a traditional process）. The size of the powder obtained at a high cold speed was ranged from 50 μm to 100μm in diameter. Its representative microstructures include dendrite, dendritic fragments, a mixture of dendrites, equiaxed grains and dendritic fragments,and equiaxed grains. The rapid solidification in the spray forming is a key factor to cause the refinement of the M42 HSS.
文摘An unsteady mathematical thermal model was developed for predicting the time,molten-steel weight,induction heating power,and temperature changes of the steel from the end of ladle refining to the end of the continuous-casting process of a tundish. The calculations revealed that for a specific strip-casting process,the ladle tonnage should be controlled to about 90 t. If the ladle capacity reaches 130 t,the provision of a 1 500-kW tundish induction heating device is recommended. By comparing the measured and predicted molten-steel temperature values in the Ningbosteel-Baosteel strip casting industrialization demo project( NBS) of a tundish,it was determined that the prediction accuracy of the model could meet the forecasting accuracy requirements for the molten-steel temperature in the tundish during mass production. Simultaneously,the heat flux density on each surface of the tundish was found at about 50 min,which is entirely consistent with the values reported in the related literature,and the tundish had not reached a heat balance during the casting test period. This model can also be applied to calculate the suitable size of a tundish for a specific continuous-casting process,thereby providing a theoretical basis for the design of the continuous-casting tundish.
文摘A 3D coupling mathematical simulation program of the fluid flow, thermal transfer and solidification was developed based on the slab continuous casting process. Some characteristics such as fluid flow, solidification and temperature distribution near the submerged entry nozzle （SEN） and the corner of the mold were simulated and analyzed. The result of the calculation indicates that the flow of molten metal forms two big cycling zones in the mold after it flows out of the SEN, and the temperature at the center of the two zones is relatively low. Moreover, there is a small narrow cycling zone near the narrow side of the mold due to casting. The velocity of the surface flow, the turbulent kinetic energy and the F value might reveal the relationship between the fluctuation of meniscus and the quality of the slab to some degree.
文摘A 1：1 water model of a twin-roll strip caster was set up based on the Froude number（Fr） and Reynolds number （Re） similarity criteria. Fluctuation and the mixing effect in the molten pool of twin-roll strip casting process were analyzed through hydraulic simulation. The height of the fluctuation of the liquid pool surface and the residence time were measured by DJ800 multifunctional monitor under different process conditions. The results show that the casting velocity, the insertion depth and the pool level have a great effect on the fluctuation.
文摘The feeding system used in the strip casting process delivers molten metal from the tundish to the pool that is bordered by side dams and rolls and is one of the key units in the production of high quality strip metal. The traditional method for studying this key unit is to use a combination of a water model and a mathematical model. However,the relations in the model with and without roll rotation have not been clearly revealed in previous studies. A 2D transient model based on a continuity equation, momentum equation, turbulent equations, and a VOF equation was established in this study and used to simulate the meniscus fluctuation. A half model with a structured grid was used for the reported simulation. The simulation showed that significant differences existed in the fluctuation in the flow fields and wave length with or without the roll rotation. The wave fluctuation exhibited uncertainty and an unstable character in the roll rotation condition. The level fluctuation employing different process parameters such as rotating speed and immersion depth of tip angle was simulated and compared with and without roll rotation. The study results showed that the meniscus fluctuation of twin-roll strip casting was primarily affected by the roll rotation, and the level fluctuation increased with the increase in rotation velocity and decreased with immersion depth.
文摘Targeting the single tuyere and double tuyere methods of argon blowing for Baosteel＇ s 300 t ladle furnace, the 3D continuity equation, the N-S equation and the turbulent k-ε double-equation were used to model the form of the molten steel flow and the dead areas under six different argon blowing conditions. The different flow field forms and the degree of mixing under different argon blowing methods were compared. The results demonstrate that when large ladles are operated via different methods of argon blowing, the spray from the centre of a single tuyere forms a symmetrical vortex, while when a double tuyere sprays, there is basically no clear vortex. In regards to the amount of argon blowing that will produce the best blend of molten steel, the amount of dead area reduction will not be clearly noticeable if there is an excessive argon blowing amount.
文摘The material selected for this work was the spray formed Vanadis4 high alloy cold working mould steel （abbreviated to V4 steel）. Its microstructure, hot rolling process, and annealing treatment have been investigated. Observed from the optical and electron microscopes, the as-sprayed V4 steel had the finer microstructure of uniform and equiaxial grains ,while after hot rolling for densification and spheroidized annealing, the V4 steel obtained an excellent spheroidized structure that is favorable to subsequent quenching and tempering treatment. The spheroidized structure and level of annealed hardness of the V4 steel are almost the same as expensive imported powder metallurgy the V4 steel. It is difficult to produce V4 steel with the conventional ingot metallurgical technique, so the multi-step and high-cost powder metallurgy method is generally used at present. Compared to the powder metallurgy technique, using the spray forming technique to produce the V4 steel has obvious advantages and potential market competitiveness in reducing production costs, simplifying working process, and shortening the production cycle.
文摘Using the equation of continuity and the double equation of Navier-Stokes and k-ε, numerical modeling on a single outlet continuous casting tundish has been carried out during the process of non-thermal flow coupling. The flow field distribution inside the tundish was calculated and the viscosity response time was calculated with the mass transfer equation based on the flow field distribution. The flow characteristics of the molten steel inside the tundish were analyzed, with the results of the numerical modeling compared to the hydraulic modeling. The results showed that the Resident Time Distribution （RTD） curves in the latter anatomosed comparatively better. This certified the validity established by the mathematical model. Numerical modeling was carried out on both large and small tundishes during the processes of thermal flow coupling and also thermal non-flow coupling. The results showed that in regards to large tundishes with relatively simple flow processes, using numerical modeling for thermal flow coupling is necessary.
文摘A high alloyed Vanadis4 （V4） steel was produced by spray forming process in Baosteel, and the microstructure of the as-sprayed steel and its evolution during hot rolling and annealing processes were characterized. It was found that the as-sprayed V4 steel has a homogeneous and fine scale rrficrostructure with uniform dispersion of carbides. The hot rolling temperature is the key factor in controlling the evolution of type, morphology and distribution of carbides, as well as the matrix microstructure of the as-rolled steels. The optimized processing parameters for the as-sprayed V4 steel are rolling at 1050℃ and then annealing at 900℃. The microstructural evolution mechanisms during hot rolling and annealing are determined according to the microstructural analyasis of the material at different stages.
基金Spray forming,an advanced processing technique,isa key project of Baoshan Iron & Steel Co.,Ltd. (No.BG010102)
文摘The microstructure of high vanadium and cobalt high speed steel （high-V/Co HSS ） and the morphology of its carbides were analyzed by optical microscope （OM）,scanning electron microscope （SEM） ,electron probe microanalysis （EPMA）, X-ray power diffraction （XRD）, atomic force microscopy （AFM） and single phase erosion （SPE）. The results suggest that the as-sprayed high-V/Co HSS has fine equiaxed grains （about 20 μm in size）, which were homogeneously distributed. The carbides have two classical morphologies- one is fine particles （ about 2 μm in size） distributed along the grain boundaries and the other is needle-like one, distributed on the grain boundaries. There are MC carbides, M2C carbides,M6C carbides and Cr2WC2 carbides in the as-sprayed high-V/Co HSS samples,however,in the as-cast high-V/ Co HSS ,there are MC carbides and CrzWC2 carbides only. The SPE results show that there are two types of MC carbides in the as-sprayed HSS ：the sphere one and the particle-like one. The former is about 2 ixm in size and the latter is less than 1 μm, dispersed inside the grains,quite different from the MC carbides in the as-cast HSS. According to the AFM results, the skeleton-like M6C carbides of the as-sprayed high-V/Co HSS are embedded in the matrix along the grain boundaries. It is found that there are sharp membrane pieces on the carbides. Some small bamboo-shoot-like MC carbides grow from the matrix and are dispersed inside the grain. Those larger MC carbides are spherical particles embedded at the grain boundary junctions.
