Abstract: The effects of the underlayer structure of oriented silicon steel on adhesiveness were studied by comparing the microstructure and composition distribution of oriented silicon steel with better adhesiveness and poorer one. The results showed that the underlayer is mainly divided into phosphate insulating coating and magnesium silicate underlayer (partial magnesium silicate bottom layer is formed into the base material to form pinning), which have no obvious transition layer and fusion area. The main source of adhesive force of oriented silicon steel should be the mechanical action between the magnesium silicate underlayer and the steel base, and the adhesive force is mainly determined by the structure of the magnesium silicate underlayer. Good adhesiveness requires dense a magnesium silicate underlayer with a large pinning particles closing to the bottom layer of magnesium silicate and forming a "peninsula". The magnesiumaluminum spinel in the bottom layer should be distributed into the pinning.

Key words: magnesium silicate under layert（layer）, phosphate insulating coating, pinning, magnesiumaluminum spinel