Morphology and metallurgical factors of line defects on surface of cold rolled 304 austenitic stainless steel sheet

摘要

The morphology and line defects on the surface of cold rolled 304 austenitic stainless steel sheets were studied in this paper. The microstructures of continuous casting slab, hot rolled strip and cold rolled sheet were observed by optical microscope and scanning electron microscope. The deformation behaviour of casting billet was studied by Gleeble 1500 thermal simulator. The results show that the line defect of cold rolled 304 stainless steel sheets is a microscopic 'groove'. The bottom and edge of the line defect are relatively rougher than the normal surface. The three dimensions of the most line defects are about 5-8 mm in length, 30-1000 mu m in width and 5-20 mu m in depth. On the edge of some line defects, oxidation film composed of chrome oxide, iron oxide and some oxide film in multilayer exists. Other elements, such as Mg, Ca and Al, were also found in some regions of line defects. Chromium segregation and inclusions at the junction region of the columnar dendrites that are growing are the main reasons for the formation of the line defect formation.