The surface oxide layer of grain-oriented electrical steels was investigated by scanning electron microscopy. The formation mechanism and the influence on the glass film of the surface oxide layer were analyzed by the calculation of thermodynamics and kinetics. The surface oxide layer with 2.3 μm in thickness is mainly composed of SiO₂, a small amount of FeO and Fe₂SiO₄. During the formation of surface oxide layer, the restriction factor was the diffusion of O in the oxide layer. At the initial stage of the decarburization annealing, FeO would be formed on the surface layer. SiO₂ and silicate particles rapidly nucleated, grew and formed a granular oxide layer in the subsurface. As the oxidation layer thickens, the nucleation of new particles decreases, and the growth of oxide particles would be dominant. A lamellar oxide layer was formed between the surface oxide layer and the steel matrix, and eventually formed a typical three-layer structure. During the high temperature annealing, MgO mainly reacted with SiO₂ and Fe₂SiO₄ in the surface oxide layer to form Mg₂SiO₄ and Fe₂SiO₄ would respond first, thus forming the glass film with average thickness of 4.87 μm.

通过扫描电子显微镜研究了方向性电工钢的表面氧化层。通过热力学和动力学计算，分析了表面氧化层的形成机理及其对玻璃膜的影响。厚度为2.3μm的表面氧化物层主要由SiO ₂，少量的FeO和Fe ₂ SiO _4组成。在形成表面氧化物层的过程中，限制因素是O在氧化物层中的扩散。在脱碳退火的初始阶段，FeO将在表面层上形成。二氧化硅₂硅酸盐颗粒迅速成核，生长并在地下形成颗粒状氧化物层。随着氧化层增厚，新颗粒的成核减少，并且氧化物颗粒的生长将占主导地位。在表面氧化物层和钢基质之间形成层状氧化物层，并最终形成典型的三层结构。在高温退火过程中，MgO主要与表面氧化物层中的SiO ₂和Fe ₂ SiO ₄反应形成Mg ₂ SiO ₄，Fe ₂ SiO ₄首先反应，从而形成平均厚度为4.87μm的玻璃膜。