第Ⅲ主族、第Ⅴ主族非牛顿流体保护渣的制备与机理研究

For continuous casting process, the mould flux with high viscosity could prevent the slag entrapment; the mould flux with low viscosity could provide adequate lubrication for strand drawing. If the mould flux has these two characteristics of viscosity as non-newtonian fluid, it would have a great effect for strand quality improving and production stabilizing. In this research, two ways for developing mould flux with characters of non-newtonian fluid would be carried out, adding compounds that contain the third main group of elements as B, Al or others into the basic mould flux to develop group Ⅲ, and treating the mould flux as nitriding to develop group Ⅴ series. Through calculating the chemical reaction of non-Newtonian fluid mold flux at molten state by thermodynamic software, the optimum reaction and best conditions would be confirmed, and the preparation technology would also be optimized. For the perspective of microscopic structure and application performance, the shear thinning of non-Newtonian fluid mold flux would be analyzed, and the mechanism would also be revealed. Through application of the non-Newtonian fluid mold flux in lab casting experiment, the strand surface quality and the mould performance would be observed, the usability of non-Newtonian fluid mold flux would be analyzed systematically, and the relationship among mould flux microstructure, shear thinning characters and application for high-speed continuous casting would be established. The results would have a great application value for the stabilizing of continuous casting.

在连铸过程中，非牛顿流体保护渣具有既能防止结晶器卷渣的高黏度又能保证结晶器足够润滑的低黏度等双重特性，对提高铸坯质量和稳定生产有重要的影响。本项目以开发非牛顿流体保护渣为目标，通过向基础保护渣中加入含B、Al等第三主族化合物或者对保护渣进行N化处理，制备Ⅲ-Ⅴ主族系非牛顿流体保护渣。通过热力学软件计算非牛顿流体保护渣在熔融状态下发生的化学反应，确定最优反应及最佳反应条件，进而对其制备工艺进行优化。从微观结构和应用性能角度，对非牛顿流体保护渣体现出的剪切变稀性能进行解析，揭示产生保护渣剪切变稀性质的作用机理。通过将非牛顿流体保护渣用于实验室钢液浇注试验，观察铸坯表面质量及结晶器的运行情况，系统分析保护渣的使用性能，建立非牛顿流体保护渣微观结构-剪切变稀性质-高速连铸应用之间的关系。研究结果对连铸稳定生产有重要的应用价值。

在高拉速连铸生产过程中，较高拉速会带来液面波动增大，导致卷渣风险加剧；同时拉速提高会使液渣流入困难，保护渣消耗量降低，导致渣膜减薄，出现铸坯粘结甚至漏钢的风险增加。如果有一种保护渣能随着剪切速率的增加粘度降低，这样不仅能在剪切速率较小的结晶器钢液面表面区域保持相对较高的粘度从而降低卷渣风险；又能在剪切速率较大的结晶器弯月面区域保持相对较低的粘度，改善保护渣的流动性，增加渣耗量，减少粘结现象的产生。本课题通过向传统连铸保护渣中加入含第Ⅲ或第Ⅴ主族元素的添加剂使保护渣产生剪切变稀特性，从而有效解决上述问题。.1）通过本课题的研究，发现分别向基础保护渣中加入一定量的B2O3、Si3N4或Al2O3可使保护渣产生一定的剪切变稀特性，其中分别当B2O3的含量为9.71%、Si3N4的含量为0.83%或Al2O3的含量为8.61%时，保护渣具有的剪切变稀性质最强。.2）通过对保护渣试样的微观结构进行深入研究，分别掌握了上述三种保护渣产生剪切变稀特性的作用机理。其中含B系或N系非牛顿流体保护渣产生剪切变稀特性的机理属于一种由于施加单向剪切应力造成的临时黏度损失，而含Al系非牛顿流体保护渣是由于渣中的特殊结构单元Q3(1Al)所致。.3）建立连铸结晶器三维模型，分别对基础保护渣和非牛顿流体保护渣作用下的抗卷渣行为进行模拟研究，发现相比于基础保护渣，使用非牛顿流体保护渣不仅能有效降低卷渣现象的发生，而且明显提高结晶器弯月面区域液渣的流入均匀性，从而更好地保证了润滑效果，体现出了较强的剪切变稀特性。.4）通过热试试验发现，相比于基础保护渣，使用非牛顿流体保护渣出现卷渣和铸坯粘结的次数明显减少，铸坯表面光滑，振痕分布均匀，说明该非牛顿流体保护渣实现了剪切变稀特性的作用效果，能够满足高拉速连铸稳定生产的技术需求。.5）成功开发出现场用非牛顿流体保护渣，铸坯质量明显提高，为钢铁企业的高效化连铸生产提供了技术储备。本项目原定计划已全部完成。