Abstract: In view of the line scale defect on the surface of 304 stainless steel cold rolled sheet in a factory, the morphology and composition of the defect surface and cross section were analyzed by scanning electron microscopy, and the factors affecting the line scale defect were discussed. The results show that the linear scale defects of 304 stainless steel are mainly caused by CaO-SiO2-Al2O3-MgO slag inclusions.The melting point of inclusions in 304 stainless steel slab is reduced by using low aluminium ferrosilicon or reducing the basicity of AOD tapping slag in AOD reduction stage, which is beneficial to improving the plastic deformation ability of inclusions.In addition, the tundish changing rhythm is accelerated, the minimum tundish tonnage proportion is increased to more than 85%，and the tundish flow field is stabilized.At the same time, the amount of remaining molten steel in large ladle should be increased to 5－6 t, so as to avoid large ladle slag entering tundish, limit inclusions from the source and improve the purity of molten steel.After the implementation of the above improvement measures, the degradation rate of line scale defect of 304 stainless steel cold rolled sheet can be stably controlled within 0.2%.

Key words: 304 stainless steel, line scale defect, microstructure, inclusion