高钛钢液面温度及“结鱼”形成的控制

Control of temperature of high-Ti steel on top surface and"floater"formation

在高钛钢的生产过程中,由于钢中的钛与氮容易生成TiN夹杂物,并部分在结晶器内钢渣界面处聚集,这容易在钢液面低温区诱发“结鱼”的形成而导致高钛钢难以顺利连铸。针对高钛钢连铸“结鱼”产生的问题,采用数值模拟的方法,讨论了不同电磁搅拌强度、拉速和过热度等连铸参数对钢液面温度的影响,并对保护渣的碱度进行了优化,以通过提高钢液面温度来降低结晶器内“结鱼”的形成。通过建立的数学模型模拟发现,在浇铸拉速为0.85m/s和1.05m/s时,在结晶器内施加电磁搅拌均能引起钢液面温度的升高,且当搅拌电流为200A时钢液面的温度最高;在电磁搅拌强度一定时,提高拉速和浇铸过热度均能提高结晶内钢液面的温度,并能减小结晶器角部低温区域的大小;现场试验发现,除拉速外,在其他连铸参数一定时,浇铸过热度由25K提高到60K后,连铸结晶器内未发现“结鱼”物的形成,且连铸坯表面的夹渣缺陷明显降低;将连铸保护渣碱度由0.60提高到0.88后,保护渣的结晶性能增强,控制传热能力改善,在高过热度浇铸过程中结晶器内液渣层的厚度由6mm增加到为8mm,这说明钢液面的温度升高,但该保护渣在低过热度浇铸(40K)时也未发现“结鱼”的发生。因此,高钛钢连铸过程中的“结鱼”形成受钢液面的温度的影响,通过提高浇铸过热度和改善连铸保护渣控制传热的能力均能控制结晶器内“结鱼”的形成,优化渣可用于高钛钢的低过热度浇铸生产,为改善高钛钢的可浇性提供理论指导。

During the production of the high-Ti steel,TiN inclusions formed under the reaction of the tatinium and nitrogen in the liquid steel,and aggregated near the steel-slag interface,which easily resulted in the formation of the"floater"on the steel-slag interface at the low-temperature zone and then the troubled continuous casting.The numerical simulation was established and used to solve the problem of the"floater"formation in the continuous casting mold during the casting of high-Ti steel.In order to reduce the formation of"floater"in the mold by increasing the temperature of the steel on the surface,the influence of the current by the electromagnetic stirring,casting speed and casting superheat on temperature of the steel on the surface was discussed,and the adjustment of the basicity of the mold slag was conducted.Through mathematical simulation,it is found that the temperature of the steel on the surface can be raised by the application of the electromagnetic stirring equipment in the mold with the casting speed of 0.85m/s and 1.05m/s,and the temperature is the highest with the stirring current of 200A.With the current of the electromagnetic stirring constant,the increase of the casting speed and casting superheat can result in the increase of the steel temperature on the surface and the decrease of the size of the low temperature zone at the corner of the mold.Through the trial in the steel plant,it is found that with the casting superheat increasing from 25Kto 60K,the formation of"floater"did not occur in the mold,and the slag-entrapment defects on the surface of continuous casting billet were significantly reduced when the continuous casting parameters except the casting speed were constant.With the basicity of continuous casting mold slag increasing from 0.60to 0.88,the ability of crystallization and the heat-transfer control increased,and during the trial in the steel plant the thickness of liquid slag increased from 6mm to 8mm,which indicates that the temperature of liquid steel on the surface increased.Besides,the"floater"also did not occur with the application of the optimized slag during the low-superheat casting(40K).Hence,the formation of"floater"in the continuous casting process of high-titanium steel was affected by the temperature of the liquid steel at the surface,and the formation of"floater"in the mold could be reduced by increasing the casting superheat and improving the control ability of the heat transfer of the continuous casting slag.The optimized slag could be used for the casting of high-titanium steel with low superheat,and would provide theoretical guidance for improving the casting ability of high-itanium steel.