Abstract: Bare crystal is one of surface quality problems and may show its features in different extents, such as point bare crystal in small scale or large areas of bare crystals. The morphologies and local compositions of some kinds of point bare crystals in low temperature heated and nitriding grain oriented steels were examined in this paper, and the possible reasons for their formation were analyzed and suggested. The results showed that at least three kinds of point bare crystals are observed, namely, the one containing only steel matrix compositions without glass layer and insulating layer, the one that contains insulating layer but without glass layers and the one that contains a Mgrich ring band around it and lose its glass layer or insulating layer in different extents in the center. The reasons of the formation of the point bare crystals should be diverse because of the variety in their morphologies and local composition.

Key words: grain oriented silicon steels, point bare crystals, surface quality