铝镇静钢钙处理后氧化铝夹杂物变性动力学模型

Kinetic modeling of alumina inclusion modification in Al-killed steel after Ca treatment

将Al2O3以及固态的钙铝酸盐均视为未反应核,确定铝离子在液态钙铝酸盐层的扩散是铝镇静钢钙处理后Al2O3夹杂物变性的限制性环节,由未反应核模型建立了Al2O3夹杂物变性的动力学模型,并且通过热力学分析计算了模型参数.模型结果显示:随着Al2O3夹杂物直径的增大,其完全变性为液态钙铝酸盐的时间大幅延长.钢液中Ca在一定范围内增加,不仅在热力学上有利于Al2O3变性,也使其变性速率迅速增大,但Ca超过一定值时对变性速率促进减弱.温度升高不利于Al2O3夹杂物变性反应,从而使变性的驱动力减小,对夹杂物变性促进作用不很明显.模型结果与工业试验和夹杂观察结果基本相符.

Al2 O3 and solid calcium aluminate were considered as un-reacted cores, the diffusion of aluminum cations in the liquid calcium aluminate layer was confirmed as the rate determining step of Al2 O3 inclusion modification, and further a kinetic model of Al2 O3 inclusion modification was established on the basis of the un-reacted core model. The model parameters were calculated by ther-modynamic analysis. Modelling results show that the time of Al2 O3 inclusion modification to completely liquid calcium aluminate will be much longer when the size of Al2 O3 inclusions increases. Moreover, increasing the Ca content in a reasonable range is beneficial not only to modify Al2 O3 inclusions to liquid calcium aluminate from thermodynamics but also to speed the modification process whereas the enhancement weakens when the Ca content exceeds a critical level. Temperature rise is disadvantageous to Al2 O3 modification chemical reaction so the driving force of Al2 O3 inclusion modification decreases correspondingly, namely temperature rise is not so obvious to speed Al2 O3 inclusion modification. Finally, the kinetic model results were verified by industrial trials and they accord with each other very well.