取向硅钢成品板中点状硌印的检测与成因分析

Examination and analysis of point indentations in grain oriented silicon steels

表面质量问题是影响取向硅钢最终产品质量的一个关键要素.磁性能达标并稳定后,表面质量出现问题,同样会造成成品降级处理甚至报废.露晶、水印、硌印、花斑等都是较为典型的现场表面质量问题.本文以取向硅钢成品板中点状硌印为例,通过激光共聚焦显微镜、扫描电镜、能谱仪、电子背散射衍射EBSD系统检测其特点并分析其可能的成因,为现场解决此类问题提供理论依据.检测表明,硌印凹坑内存有较厚的完整绝缘层成分,而硌印凹坑边部却是Fe含量很高的区域,两个位置成分都不同于正常绝缘层的成分.鉴于硌印下方钢板基体内没有后期形变留下的痕迹,初步认为硌印主要是氧化层点状不均匀或涂覆氧化镁不均匀并经高温退火时烧结出现的硬颗粒物造成的塑性变形所致.

The surface quality of grain oriented silicon steels is another most important key factor that controls the final qualities of steel products.When the magnetic properties are checked to be satisfactory,the poor surface quality could lead to the degrading or even abandonment of products.Bare grains,water marks,indentations,etc,are all typical surface defects of grain oriented silicon steels during their developments.This paper aims to examine and analyze the point indentations occurred in the final surface sheets of grain oriented silicon steel so as to provide basic features of point indentations and possible reasons of their formation.For this purpose,laser confocal microscopy,scanning electron microscopy,energy dispersive spectroscopy and electron backscatter diffraction technique are used.It is shown that the holes of indentations contain mainly insulating materials,whereas their surroundings are much rich in Fe element of sheet matrix.The compositions of both positions are different to those of normal insulating layers away from them.Based on these features and the facts that the no trace of deformation or recrystallization with fine grains are observed in the interior steel matrix directly located below indentation hole,it is suggested that the investigated indentations should be caused by either the inhomogeneous point defects of oxide layer or inhomogeneous MgO layer which form as hard particle obj ects and induce a strong plastic deformation in the soft steel sheets during high temperature annealing.