高频磁场下连铸保护渣渣膜特性研究

Study on the crystallization characteristics of continuous casting mold flux under high frequency magnetic field

结晶器保护渣是连铸过程中非常重要的功能材料。随着电磁技术在连铸中应用的不断发展,保护渣受其影响的相关理论日益受到冶金工作者的关注。利用渣膜制取装置分别在管式炉、高频加热炉中制取了无磁场和高频电磁场作用下的保护渣渣膜,运用磁场下保护渣热力学和动力学理论,结合XRD衍射、偏光显微镜和拉曼光谱仪分析保护渣渣膜特性的变化规律。结果发现:高频磁场下,保护渣渣膜厚度增加,没有新的矿相生成。渣膜气孔率由原来的5%~10%降低至2%~4%,结晶率由原来的70%~77%增加至83%~88%,但晶体尺寸由原来的0.16~0.58mm减小至0.15~0.29mm。这是由于电磁场的作用下,保护渣熔体离子碰撞加剧,临界吉布斯自由能降低,加快形核进程,保护渣渣膜结晶率增加。但同时,保护渣网络化程度增加,黏度增大,抑制了晶体的进一步发育长大,渣膜析出晶体尺寸明显减小。

Mold flux is very important functional material in the continuous casting process. With the continuous development of electromagnetic technology in continuous casting, the theory of the influence of mold flux has been paid more and more attention by the metallurgical workers. In this paper, the slag film was made in a tubular furnace and a high-frequency heating furnace by using a slag film-making device. Using the thermodynamics and kinetic theory of the mold flux under the magnetic field, the change law of the crystallization characteristics of the mold powder was analyzed by XRD, polarizing microscope and Raman spectroscopy. The results showed that the flux film thickness increased and there was no new phase formation under high frequency magnetic field. The flux film porosity reduced from 5 % - 10 % to 2 % - 4 %, crystallization rate increased from 70 % - 77 % to 83 % - 88 %, but crystal size decreasd from 0.16 - 0.58 mm to 0.15 - 0.29 ram. Under the action of the electromagnetic fields, the ion collision of the melted slag was aggravated, the critical Gibbs free energy was reduced, the nucleation process was accelerated and the crystallization rate was increased. However, the network of slag increased, the viscosity increased, and the crystal growth was inhibited and the crystal size of slag film decreased obviously.