A three-dimensional finite-element model has been established to investigate the thermal behavior of the medium-thick slab copper casting mold with different cooling water slot designs. The mold wall temperatures meas...A three-dimensional finite-element model has been established to investigate the thermal behavior of the medium-thick slab copper casting mold with different cooling water slot designs. The mold wall temperatures measured using thermocouples buried in different positions of the mold with the original designed cooling system were analyzed to determine the corresponding heat flux profile. This profile was then used for simulation to predict the temperature distribution and the thermal stress distribution of the molds. The predicted temperatures during operation matched the plant measurements. The results showed that the maximum temperature, about 635 K in the wide hot surface, was found about 60 mm below the meniscus and 226 mm from the center of the mold. For the mold with the type I modified design, there was an insignificant decrease in temperature of about 5 K, and for the mold with the type II modified design, the maximum temperature was decreased by about 15 K and the temperature of the hot surface was distributed more uniformly along the length of the mold. The corresponding maximum thermal stress at the hot surface of the mold was reduced from 408 MPa to 386 MPa with the type II modified design. The results indicated that the modified design II is beneficial to the increase of mold life and the quality of casting slabs.展开更多
The segregation of solute elements at solidification front could be greatly improved by application of electromagnetic stirring(SEM)in secondary cooling zone.The location of SEM in secondary cooling zone affects the o...The segregation of solute elements at solidification front could be greatly improved by application of electromagnetic stirring(SEM)in secondary cooling zone.The location of SEM in secondary cooling zone affects the operational effect.In the present study,based on the application of SEM in Ultra-thick slab continuous casting,the shell thickness was calculated by self-programming code and the results were verified by nail-shooting test.A numerical model was established to calculate the fluid flow of molten steel under shell to determine the suitable SEM location in secondary cooling zone.The results shows that the velocity of molten steel increases with increase of stirring current which enhance the circulatory flow of unset steel at solidification front.Whereas,in order to fully develop ability of SEM it is necessary to select suitable stirring current and mode for ultra-thick slab casting.This calculation provides theoretical base for application of SEM in secondary cooling zone during ultra-thick slab casting process.展开更多
The key to reduce shell breakout in the continuous casting process is to control shell thickness in the mold. A numerical simulation on the turbulent flow and heat transfer coupled with solidification in the slab mold...The key to reduce shell breakout in the continuous casting process is to control shell thickness in the mold. A numerical simulation on the turbulent flow and heat transfer coupled with solidification in the slab mold using the volume of fluid （VOF） model and the enthalpy-porosity scheme was conducted and the emphasis was put upon the flow effect on the shell thickness profiles in longitudinal and transverse directions. The results show that the jet acts a stronger impingement on the shell of narrow face, which causes a zero-increase of shell thickness in a certain range near the impingement point. The thinnest shell on the slab cross-section locates primarily in the center of the narrow face, and secondly near the comer of the wide face. Nozzle optimization can obviously increase the shell thickness and make it more uniform.展开更多
After the heavy reduction(HR)process was carried out at the solidification end of the continuous casting slab,the austenite grains were refined by recrystallization,which improved the thermoplasticity of the slab.Howe...After the heavy reduction(HR)process was carried out at the solidification end of the continuous casting slab,the austenite grains were refined by recrystallization,which improved the thermoplasticity of the slab.However,the reduction in deformation during the HR process initiated stress concentration at the slab surface,and the crack risk increased.To effectively evaluate the risk of slab surface cracks under these complex conditions,the effect of the HR on the austenite recrystallization and thermoplasticity of a microalloyed slab surface was investigated by 15-pass reduction thermal simulation according to the wide and thick slab continuous casting process.The softening fraction was introduced as a global internal variable to quantitatively analyze various recrystallized re-refined grains.After the critical strain reaches the critical strain of dynamic recrystallization,a variety of recrystallization modes alternately occur.Among them,the contribution rate of dynamic crystallization to the later refinement reaches more than 50%.The contribution rates of static recrystallization and metadynamic recrystallization to grain refinement are almost the same.The thermoplasticity of the slab surface first increases and then decreases with increasing reduction pass.It was verified by transmission electron microscopy that the main reason for the decrease in thermoplasticity is that the dislocation multiplication rate increases,resulting in a sharp increase in stress and a decrease in thermoplasticity.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.51525401,51274054,U1332115,51401044)the Science and Technology Planning Project of Dalian(No.2013A16GX110)+1 种基金the China Postdoctoral Science Foundation(2015M581331)the Fundamental Research Funds for the Central Universities
文摘A three-dimensional finite-element model has been established to investigate the thermal behavior of the medium-thick slab copper casting mold with different cooling water slot designs. The mold wall temperatures measured using thermocouples buried in different positions of the mold with the original designed cooling system were analyzed to determine the corresponding heat flux profile. This profile was then used for simulation to predict the temperature distribution and the thermal stress distribution of the molds. The predicted temperatures during operation matched the plant measurements. The results showed that the maximum temperature, about 635 K in the wide hot surface, was found about 60 mm below the meniscus and 226 mm from the center of the mold. For the mold with the type I modified design, there was an insignificant decrease in temperature of about 5 K, and for the mold with the type II modified design, the maximum temperature was decreased by about 15 K and the temperature of the hot surface was distributed more uniformly along the length of the mold. The corresponding maximum thermal stress at the hot surface of the mold was reduced from 408 MPa to 386 MPa with the type II modified design. The results indicated that the modified design II is beneficial to the increase of mold life and the quality of casting slabs.
文摘The segregation of solute elements at solidification front could be greatly improved by application of electromagnetic stirring(SEM)in secondary cooling zone.The location of SEM in secondary cooling zone affects the operational effect.In the present study,based on the application of SEM in Ultra-thick slab continuous casting,the shell thickness was calculated by self-programming code and the results were verified by nail-shooting test.A numerical model was established to calculate the fluid flow of molten steel under shell to determine the suitable SEM location in secondary cooling zone.The results shows that the velocity of molten steel increases with increase of stirring current which enhance the circulatory flow of unset steel at solidification front.Whereas,in order to fully develop ability of SEM it is necessary to select suitable stirring current and mode for ultra-thick slab casting.This calculation provides theoretical base for application of SEM in secondary cooling zone during ultra-thick slab casting process.
基金supported by the National Natural Science Foundation of China (No.60672145)
文摘The key to reduce shell breakout in the continuous casting process is to control shell thickness in the mold. A numerical simulation on the turbulent flow and heat transfer coupled with solidification in the slab mold using the volume of fluid （VOF） model and the enthalpy-porosity scheme was conducted and the emphasis was put upon the flow effect on the shell thickness profiles in longitudinal and transverse directions. The results show that the jet acts a stronger impingement on the shell of narrow face, which causes a zero-increase of shell thickness in a certain range near the impingement point. The thinnest shell on the slab cross-section locates primarily in the center of the narrow face, and secondly near the comer of the wide face. Nozzle optimization can obviously increase the shell thickness and make it more uniform.
基金supported by the National Natural Science Foundation of China(51974078)the Applied Basic Research Program of Liaoning Province(2022JH2/101300002,2022JH25/10200003)the Applied Basic Research Program of Liaoning Province,and the State Key Laboratory of Metal Material for Marine Equipment and Application Project(SKLMEA-K202204).
文摘After the heavy reduction(HR)process was carried out at the solidification end of the continuous casting slab,the austenite grains were refined by recrystallization,which improved the thermoplasticity of the slab.However,the reduction in deformation during the HR process initiated stress concentration at the slab surface,and the crack risk increased.To effectively evaluate the risk of slab surface cracks under these complex conditions,the effect of the HR on the austenite recrystallization and thermoplasticity of a microalloyed slab surface was investigated by 15-pass reduction thermal simulation according to the wide and thick slab continuous casting process.The softening fraction was introduced as a global internal variable to quantitatively analyze various recrystallized re-refined grains.After the critical strain reaches the critical strain of dynamic recrystallization,a variety of recrystallization modes alternately occur.Among them,the contribution rate of dynamic crystallization to the later refinement reaches more than 50%.The contribution rates of static recrystallization and metadynamic recrystallization to grain refinement are almost the same.The thermoplasticity of the slab surface first increases and then decreases with increasing reduction pass.It was verified by transmission electron microscopy that the main reason for the decrease in thermoplasticity is that the dislocation multiplication rate increases,resulting in a sharp increase in stress and a decrease in thermoplasticity.
