Abstract: The causes of white stripe defects on the surface of grain oriented silicon steel were analyzed. The surface morphology was observed by threedimensional video microscope, the crosssection morphology of the steel and the surface morphology of the defect area after pickling were observed by field emission scanning electron microscope, and the energy spectrum composition was analyzed by energy spectrum analyzer. The analysis result showed that there was elliptical insulation layer falling off in the white stripe defect, and the magnesium silicate substrate in the defect area was abnormal, of which the thickness was much thicker than the normal area. It indicated that the white stripe defect area had been damaged before coating magnesium oxide. After pickling, the spicules with the main composition of O, Al and Si were found in the defect area of white stripe. It was found that the spicules originated from the refractory used in decarburization annealing furnace. The refractory fiber fell and adhered into the surface of the steel strip during decarburization annealing, and was pressed into the strip surface in the process of secondary rolling, which destroyed the oxide film, and affected the formation of the magnesium silicate substrate, and caused the white strip defect on the surface of the steel production after high temperature annealing. This kind of defect has been eliminated by improving the use method of insulating refractory fiber.

Key words: oriented silicon steel, white strip defect,  , refractory fibre