无取向硅钢中镁铝尖晶石的变性机理

对无取向硅钢钙处理过程中镁铝尖晶石夹杂的变性机理进行了研究,重点考察了钙处理前期和中期MgO-Al2 O3的变性过程.钙处理前,钢中除了发现单纯的MgO- Al2 O3外,还发现少量被AlN包裹的MgO- Al2 O3.钙处理1.5 min后,在MgO-Al2 O3表面有中间产物CaS或CaO形成；钙处理4.5 min后,生成由内到外依次为MgO-Al2 O3、CaO-MgO-Al2 O3和CaO-Al2 O3的夹杂物；钙处理10 min后,未反应的MgO-Al2 O3消失,CaO-MgO-Al2 O3和CaO-Al2 O3的成分趋于均匀.通过热力学计算得到了Al2 O3/MgO-Al2 O3/MgO和MgO-Al2 O3/xCaO·yAl2 O3的稳定相图,发现在含铝越高的钢中,镁铝尖晶石变性越困难.结合夹杂物的扫描电镜观察、能谱分析和面扫描图分析结果,提出了夹杂物的变性路径：MgO或Al2 O3→MgO- Al2 O3→CaO-MgO-Al2 O3→CaO-Al2 O3；在产物的中间层CaO-MgO-Al2 O3中,Al2 O3含量除了一般情况下的逐渐降低外,偶尔还存在突然升高的情况.

Evolution mechanisms of MgO--Al2 O3 in non-oriented silicon steel

The evolution mechanisms of MgO-Al2 O3 in the process of calcium treatment in non-oriented silicon steel were studied by laboratory experiments, with focus on the evolution process in the early and middle of calcium treatment. A small amount of MgO-Al2 O3 surrounded by AlN was occasionally detected besides many pure spinels before calcium treatment. CaS or CaO formed as a tran-sient inclusion in the MgO-Al2 O3 surface 1. 5 min after calcium treatment. The composition from the inner part to outer part of inclu-sions was MgO-Al2 O3 , CaO-MgO-Al2 O3 and CaO-Al2 O3 in order 4. 5 min after calcium treatment. 10 min after calcium treatment, unreacted MgO-Al2 O3 spinels disappeared, and simultaneously CaO-MgO-Al2 O3 and CaO-Al2 O3 inclusions became homogeneous in composition. The phase stability diagrams of Al2 O3/MgO-Al2 O3/MgO and MgO-Al2 O3/xCaO·yAl2 O3 were calculated using thermo-dynamic data. The result showed that it was difficult to modify MgO-Al2 O3 spinels with very high aluminum content. In combination with the scanning electron microscopy images, energy-dispersive spectra and element mappings of typical inclusions, the evolution route of an inclusion was described as MgO or Al2 O3→MgO-Al2 O3→CaO-MgO-Al2 O3→CaO-Al2 O3 , and the alumina content occa-sionally showed a sudden increase besides a common decrease in the middle part of the product.