Steel plate cold common （SPCC） is a Al-killed steel with Ca-treatment. The control of Al2O3 inclusion into low melting point liquid region is beneficial for inclusion removal, cast-ability promotion and defects redu...Steel plate cold common （SPCC） is a Al-killed steel with Ca-treatment. The control of Al2O3 inclusion into low melting point liquid region is beneficial for inclusion removal, cast-ability promotion and defects reduction during rolling. Thus it is essential to understand steel-inclusion equilibrium since inclusion composition is determined by composition of liquid steel directly through steel-inclusion reaction. Thermodynamic calculation software FactSage is performed to understand how to control inclusion composition during ladle furnace （LF） refining, and industrial trials are carried out to verify calculated results. Firstly, target region for controlling CaO-Al2O3-MgO ternary inclusion is analyzed on the basis of the ternary phase diagram and the relationship between activities related to pure solid and activities related to pure liquid was fixed by thermodynamic analysis in order to obtain reliable activities for components of inclusions in the target region by FactSage. In addition, inclusions in steel samples are detected by scanning electron microscopy （SEM） combined with energy dispersive spectroscopy （EDS）. It is found that most of Al2O3 inclusions are modified into lower melting point region but a number of them are still located in high melting point region at the end of LF refining after Ca-treatment. Moreover, the composition of liquid steel equilibrating with liquid CaO-Al2O3-MgO inclusion is obtained by steel-inclusion equilibrium calculation when w[Al]s is approximating 0.03% as： a[O] is 1.0×10-6 to 4.0×10-6, w[Ca] is 20×10-6 to 50×10-6 and w[Mg] is 0.1×10-6 to 3.0×10-6. At last, stability diagrams of various calcium aluminates and CaS are established and they show that liquid calcium aluminate inclusions form when w[Ca] is more than 20×10-6, but CaS precipitation is difficult to prevent because sufficiently low w[S] （〈0.003%） is required.展开更多
A there-dimensional unsteady coupled mathematical model has been used to analyze the turbulent flow, temperature fields,magnetic field and macroscopic solidification of molten steel in compact strip production(CSP)thi...A there-dimensional unsteady coupled mathematical model has been used to analyze the turbulent flow, temperature fields,magnetic field and macroscopic solidification of molten steel in compact strip production(CSP)thin slab continuous casting with electromagnetic stirring(EMS)on secondary cooling zone,in which induced current caused both by flow movement and external magnetic field and end effect of stirrer has been considered.Lorenz force and Joule heat contributed by induction current also have been considered.EMS in secondary cooling zone results in the obverse flow changes in molten steel flow pattern,and leads to horizontal recirculation flow within stirrer zone.Degree of superheat is reduced or eliminated rapidly when molten steel is stirred by EMS.The process of EMS makes the temperature in molten steel homogeneous.After a relatively shot period of time when using EMS,the flow pattern and temperature field will reach to a new 'quasi-static-state'.Molten steel could be uniformly stirred by a one-sided stirrer concerned.展开更多
基金Item Sponsored by National Natural Science Foundation of China(61271303)
文摘Steel plate cold common （SPCC） is a Al-killed steel with Ca-treatment. The control of Al2O3 inclusion into low melting point liquid region is beneficial for inclusion removal, cast-ability promotion and defects reduction during rolling. Thus it is essential to understand steel-inclusion equilibrium since inclusion composition is determined by composition of liquid steel directly through steel-inclusion reaction. Thermodynamic calculation software FactSage is performed to understand how to control inclusion composition during ladle furnace （LF） refining, and industrial trials are carried out to verify calculated results. Firstly, target region for controlling CaO-Al2O3-MgO ternary inclusion is analyzed on the basis of the ternary phase diagram and the relationship between activities related to pure solid and activities related to pure liquid was fixed by thermodynamic analysis in order to obtain reliable activities for components of inclusions in the target region by FactSage. In addition, inclusions in steel samples are detected by scanning electron microscopy （SEM） combined with energy dispersive spectroscopy （EDS）. It is found that most of Al2O3 inclusions are modified into lower melting point region but a number of them are still located in high melting point region at the end of LF refining after Ca-treatment. Moreover, the composition of liquid steel equilibrating with liquid CaO-Al2O3-MgO inclusion is obtained by steel-inclusion equilibrium calculation when w[Al]s is approximating 0.03% as： a[O] is 1.0×10-6 to 4.0×10-6, w[Ca] is 20×10-6 to 50×10-6 and w[Mg] is 0.1×10-6 to 3.0×10-6. At last, stability diagrams of various calcium aluminates and CaS are established and they show that liquid calcium aluminate inclusions form when w[Ca] is more than 20×10-6, but CaS precipitation is difficult to prevent because sufficiently low w[S] （〈0.003%） is required.
文摘A there-dimensional unsteady coupled mathematical model has been used to analyze the turbulent flow, temperature fields,magnetic field and macroscopic solidification of molten steel in compact strip production(CSP)thin slab continuous casting with electromagnetic stirring(EMS)on secondary cooling zone,in which induced current caused both by flow movement and external magnetic field and end effect of stirrer has been considered.Lorenz force and Joule heat contributed by induction current also have been considered.EMS in secondary cooling zone results in the obverse flow changes in molten steel flow pattern,and leads to horizontal recirculation flow within stirrer zone.Degree of superheat is reduced or eliminated rapidly when molten steel is stirred by EMS.The process of EMS makes the temperature in molten steel homogeneous.After a relatively shot period of time when using EMS,the flow pattern and temperature field will reach to a new 'quasi-static-state'.Molten steel could be uniformly stirred by a one-sided stirrer concerned.
