A feedforward controller for the automatic regulation of chemical composition of molten steel in the tundish of a continuous casting machine is proposed in this work. The flow of molten steel inside the tundish is mod...A feedforward controller for the automatic regulation of chemical composition of molten steel in the tundish of a continuous casting machine is proposed in this work. The flow of molten steel inside the tundish is modeled as a distributed parameter system, and the resulting partial differential equation is transformed into a set of ordinary differential equations by means of the finite differences technique. From the above set and using a proper boundary condition, a feedforward control law is synthesized. No experimental tests are reported, however, the dynamic performance of the controller is illustrated by means of numerical simulations.展开更多
Fields of fluid flow and temperature, and residence time distribution(RTD) curves were investigated by mathematical simulation in a one-strand tundish for continuous casting. It was known from the investigation that a...Fields of fluid flow and temperature, and residence time distribution(RTD) curves were investigated by mathematical simulation in a one-strand tundish for continuous casting. It was known from the investigation that a big "spring uprush" formed on surface around the long shroud when molten steel flowed into a turbulence inhibitor(TI) with extending lips and rushed up reversely out of the TI, while four small "spring uprushes" existed on surface when a TI without extending lips because the liquid steel flowed mainly out of the 4 corners of the TI. The flow of liquid steel in the former tundish configuration was not reasonable and the height of an area where temperature was less than 1819 K was about half of liquid surface height on the right side of the stopper, which meant that big dead zone existed in the former tundish configuration. In the optimal one, the height of such area was only seventh of the liquid surface height. The RTD curves obtained from the mathematical simulation basically agreed with those from the physical modeling and the flow characteristics obtained from these two methods agreed with each other.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
The horizontal and vertical velocity components of molten steel in a slab continuous casting mold produced by three different two-port Submerged Entry Nozzle (SEN) designs are monitored and compared using Computationa...The horizontal and vertical velocity components of molten steel in a slab continuous casting mold produced by three different two-port Submerged Entry Nozzle (SEN) designs are monitored and compared using Computational Fluid Dynamics (CFD) simulations. These two ports designs correspond to a conventional cylindrical SEN, a plate SEN and an anchor-shaped SEN. Four monitoring points at the molten steel in the centered vertical plane were selected to track the horizontal and the vertical component of the velocity vector. Two of them are located near the free surface and the remaining two are located in the vicinity of the SEN discharge nozzles. Some statistical values of the time series of above the velocity components are analyzed and correlated with the Kelvin-Helmholtz instability and the Karman vortex streets, which cause mold powder entrapment in the molten steel.展开更多
A three-dimensional mathematical model was established to investigate the behavior of molten steel flow and steel/slag interface with different processes and electromagnetic parameters under two different static magne...A three-dimensional mathematical model was established to investigate the behavior of molten steel flow and steel/slag interface with different processes and electromagnetic parameters under two different static magnetic field configurations [ruler-type electromagnetic brake （EMBr ruler） and vertical electromagnetic brake （V-EMBr）] in a continuous casting mold. The results showed that the brake effect of EMBr ruler is significantly influenced by its configuration parameters, the distance between the pole and bottom of the submerged entry nozzle （SEN）, and the port angle of the SEN outlet; therefore, it is not helpful to depress the diffusion of jet flow along the thickness direction of mold. For a constant SEN depth and port angle, there is a reasonable pole position （P = 0 mm） where the pole simultaneously covers three key zones, i.e., the jet flow impact zone and the upward and downward backflow zones. For V-EMBr, the magnetic field can simultaneously cover the three key zones and depress the diffusion of jet flow along the casting and thickness directions of the mold. Both the meniscus height and the impact intensity of the jet flow can be obviously depressed by V-EMBr even if the SEN depth and port angle have changed in the continuous casting process.展开更多
Mechanical properties and creep behavior of Q460E continuous casting slab were studied by means of uniaxial tensile tests on a Gleeble-3800 thermomechanical simulator from 1000 to 1100 ℃.The high-temperature creep co...Mechanical properties and creep behavior of Q460E continuous casting slab were studied by means of uniaxial tensile tests on a Gleeble-3800 thermomechanical simulator from 1000 to 1100 ℃.The high-temperature creep constitutional equation was derived based on experimental data.The parameters in the equation were calculated by using the regression analysis inverse-estimation method.The experimental curves in the primary and secondary creep stages are fitted well.A three-dimensional elastic-plastic and creep finite element model was proposed in order to investigate the bulging deformation of slab and the bulging deformation at the beginning position of bending segment on the slab continuous casting machine was computed accurately.The results indicate that the maximum bulging deformation appears at the geometric center of the slab.The maximum value of the bulging deformation obtained by the elastic-plastic analysis is 1.301 ram.Consideririg the creep effect,the deformation increases to 1.827 mm which is about 1.4 times the value obtained by the elastic-plastic analysis.The calculation of buleing deformation usin2 the elastic-plastic creed model is more reliable and/iccurate.展开更多
In a continuous casting process,EMLS/EMLA(electromagnetic level stabilizer/accelerator)is applied effectively,which is able to control the surface stream velocity at meniscus in mold.The EMLS are applied to stabilize ...In a continuous casting process,EMLS/EMLA(electromagnetic level stabilizer/accelerator)is applied effectively,which is able to control the surface stream velocity at meniscus in mold.The EMLS are applied to stabilize the molten steel flow and the meniscus fluctuation to prevent powder entrapments on high speed casters.Conversely,the EMLA are applied to activate the molten steel flow to promote heat transfer to the steel meniscus and keep proper temperature at meniscus in mold or wash inclusions off near the solidification front on low speed casters or at the beginning,the ending and during the ladle change of the casting for high speed casters.In this study,the effect of the EMLA on the molten steel flow is investigated.Numerical simulation of the electromagnetic field and the flow field were carried out.The EMLA applies a low frequency alternating magnetic field moving from SEN(submerged entry nozzle)to narrow slab faces below the nozzle exit ports.Simulation results indicate that,due to the electromagnetic force,the molten steel is forced to flow toward the magnetic field traveling direction in the region where the magnetic field is imposed.The molten steel flow is increased in proportion to the imposed accelerating electromagnetic force on the spouting stream from SEN.And excessive accelerating changes the double-roll pattern.However,the magnitude of the electromagnetic force is decided by the current intensity and frequency,a suitable imposed electric current can be chosen to increase the flow velocity properly and also reduce the amount of mold powder entrapments to a minimum.展开更多
文摘A feedforward controller for the automatic regulation of chemical composition of molten steel in the tundish of a continuous casting machine is proposed in this work. The flow of molten steel inside the tundish is modeled as a distributed parameter system, and the resulting partial differential equation is transformed into a set of ordinary differential equations by means of the finite differences technique. From the above set and using a proper boundary condition, a feedforward control law is synthesized. No experimental tests are reported, however, the dynamic performance of the controller is illustrated by means of numerical simulations.
基金Item Sponsored by Key Project of National Natural Science Foundation of China(61333006)
文摘Fields of fluid flow and temperature, and residence time distribution(RTD) curves were investigated by mathematical simulation in a one-strand tundish for continuous casting. It was known from the investigation that a big "spring uprush" formed on surface around the long shroud when molten steel flowed into a turbulence inhibitor(TI) with extending lips and rushed up reversely out of the TI, while four small "spring uprushes" existed on surface when a TI without extending lips because the liquid steel flowed mainly out of the 4 corners of the TI. The flow of liquid steel in the former tundish configuration was not reasonable and the height of an area where temperature was less than 1819 K was about half of liquid surface height on the right side of the stopper, which meant that big dead zone existed in the former tundish configuration. In the optimal one, the height of such area was only seventh of the liquid surface height. The RTD curves obtained from the mathematical simulation basically agreed with those from the physical modeling and the flow characteristics obtained from these two methods agreed with each other.
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The horizontal and vertical velocity components of molten steel in a slab continuous casting mold produced by three different two-port Submerged Entry Nozzle (SEN) designs are monitored and compared using Computational Fluid Dynamics (CFD) simulations. These two ports designs correspond to a conventional cylindrical SEN, a plate SEN and an anchor-shaped SEN. Four monitoring points at the molten steel in the centered vertical plane were selected to track the horizontal and the vertical component of the velocity vector. Two of them are located near the free surface and the remaining two are located in the vicinity of the SEN discharge nozzles. Some statistical values of the time series of above the velocity components are analyzed and correlated with the Kelvin-Helmholtz instability and the Karman vortex streets, which cause mold powder entrapment in the molten steel.
基金This work was financially supported by the National Natural Science Foundation of China （No. 51574083） and the Program of Introducing Talents of Discipline to Universities （The 111 Project of China, No. B07015）. The authors would also like to thank the referees for their work which has contributed to this paper.
文摘A three-dimensional mathematical model was established to investigate the behavior of molten steel flow and steel/slag interface with different processes and electromagnetic parameters under two different static magnetic field configurations [ruler-type electromagnetic brake （EMBr ruler） and vertical electromagnetic brake （V-EMBr）] in a continuous casting mold. The results showed that the brake effect of EMBr ruler is significantly influenced by its configuration parameters, the distance between the pole and bottom of the submerged entry nozzle （SEN）, and the port angle of the SEN outlet; therefore, it is not helpful to depress the diffusion of jet flow along the thickness direction of mold. For a constant SEN depth and port angle, there is a reasonable pole position （P = 0 mm） where the pole simultaneously covers three key zones, i.e., the jet flow impact zone and the upward and downward backflow zones. For V-EMBr, the magnetic field can simultaneously cover the three key zones and depress the diffusion of jet flow along the casting and thickness directions of the mold. Both the meniscus height and the impact intensity of the jet flow can be obviously depressed by V-EMBr even if the SEN depth and port angle have changed in the continuous casting process.
基金National Natural Science Foundation of China (51275446)Hebei Provincial Natural Science Foundation of China (E2016203492).
文摘Mechanical properties and creep behavior of Q460E continuous casting slab were studied by means of uniaxial tensile tests on a Gleeble-3800 thermomechanical simulator from 1000 to 1100 ℃.The high-temperature creep constitutional equation was derived based on experimental data.The parameters in the equation were calculated by using the regression analysis inverse-estimation method.The experimental curves in the primary and secondary creep stages are fitted well.A three-dimensional elastic-plastic and creep finite element model was proposed in order to investigate the bulging deformation of slab and the bulging deformation at the beginning position of bending segment on the slab continuous casting machine was computed accurately.The results indicate that the maximum bulging deformation appears at the geometric center of the slab.The maximum value of the bulging deformation obtained by the elastic-plastic analysis is 1.301 ram.Consideririg the creep effect,the deformation increases to 1.827 mm which is about 1.4 times the value obtained by the elastic-plastic analysis.The calculation of buleing deformation usin2 the elastic-plastic creed model is more reliable and/iccurate.
文摘In a continuous casting process,EMLS/EMLA(electromagnetic level stabilizer/accelerator)is applied effectively,which is able to control the surface stream velocity at meniscus in mold.The EMLS are applied to stabilize the molten steel flow and the meniscus fluctuation to prevent powder entrapments on high speed casters.Conversely,the EMLA are applied to activate the molten steel flow to promote heat transfer to the steel meniscus and keep proper temperature at meniscus in mold or wash inclusions off near the solidification front on low speed casters or at the beginning,the ending and during the ladle change of the casting for high speed casters.In this study,the effect of the EMLA on the molten steel flow is investigated.Numerical simulation of the electromagnetic field and the flow field were carried out.The EMLA applies a low frequency alternating magnetic field moving from SEN(submerged entry nozzle)to narrow slab faces below the nozzle exit ports.Simulation results indicate that,due to the electromagnetic force,the molten steel is forced to flow toward the magnetic field traveling direction in the region where the magnetic field is imposed.The molten steel flow is increased in proportion to the imposed accelerating electromagnetic force on the spouting stream from SEN.And excessive accelerating changes the double-roll pattern.However,the magnitude of the electromagnetic force is decided by the current intensity and frequency,a suitable imposed electric current can be chosen to increase the flow velocity properly and also reduce the amount of mold powder entrapments to a minimum.
