基于Stoney公式适用性分析——取向硅钢绝缘涂层张应力的计算

目的改善涂层张应力状态,进而提升取向硅钢的电磁性能。方法用扫描电镜、辉光光谱仪分析了添加磷酸盐的胶体二氧化硅绝缘涂层的厚度和微观结构,采用静态拉伸试验得到了取向硅钢沿不同位向的力学特性。在此基础上,根据取向硅钢各向异性的特点和绝缘涂层的实际状态,用Stoney公式对取向硅钢涂层应力的适用性进行了讨论。结果取向硅钢的各向异性不满足Stoney公式的适用条件,实际测试的取向硅钢的力学性能结果表明,取向硅钢符合正交对称各向异性材料的一般规律,据此给出了涂层对取向硅钢产生的张应力的计算公式,利用该公式对不同涂覆工艺条件下的胶体二氧化硅绝缘涂层的张应力进行了计算,涂层厚度在1～2μm范围内,双面张应力的计算值为4～11 MPa。结论文中张应力的计算公式不仅适用于取向硅钢,同样适用于其他基体为各向异性的类似情况。通过张应力的计算可知,涂层厚度与张应力呈正相关,张应力的增大将会促使取向硅钢的铁损降低。因此,开发大张力的绝缘涂层,是进一步改善取向硅钢磁性能的有效途径之一。

Based on Applicability Analysis of Stoney Equation: Calculation of Tensile Stress Induced in Grain-oriented Silicon Steel by Insulation Coating

The work aims to optimize the tensile stress of the coating, so as to improve the magnetic properties of grain-oriented silicon steel. The thickness and microstructure of colloidal silica insulation coating with phosphate were analyzed by SEM and GDS and the mechanical properties of substrate along different direction were acquired by tensile test. Based on the anisotropy of grain-oriented silicon steel and the real state of coating, the applicability of Stoney equation to the grain-oriented silicon steel coating was discussed. The anisotropy of grain-oriented silicon steel did not meet the applicable conditions of Stoney equation and the mechanical properties of grain-oriented silicon steel tested in practice showed that the grain-oriented silicon steel conformed to the general law of orthotropic material. Based on that, the equation was given to calculate the tensile stress induced in the substrate of oriented silicon steel by the colloidal silica insulation coating under different technology parameters. The tensile stress was 4~11 MPa when the coating thickness was within 1~2 microns. The equation for calculating the tensile stress is not only applicable to grain-oriented silicon steel, but also applicable to similar cases where other substrates are anisotropic. Through calculation of tensile stress, the stress and thickness of the insulation coating have a positive correlation and the iron loss reduce with increasing of the stress induced in substrate by the coating. Therefore, the research and development of insulation coating with higher tensile stress is the effective method to improve the magnetic properties of grain-oriented silicon steel.