RIDGING AND THE STRIPE PATTERN CAUSED BY THE DIFFERENCE OF CORROSION IN 18%Cr STAINLESS STEEL SHEETS.

An investigation of the origin of ridging in 18% Cr ferritic stainless steel is reported. A pattern of macroscopic stripes composed of many dark and bright microscopic stripes in the rolling direction was observed on the surface of sheet when it was severely etched. The macroscopic and microscopic stripes corresponded to large and small undulations of ridging, respectively, which appeared after stretching of the sheet. Electron probe microanalysis across the dark and bright zones in the stripe pattern showed clear segregation of chromium and carbon. This segregation was inherited from the austenite-ferrite two-phase structure in hot rolled sheet and was preserved in cold rolled and annealed sheet. Each segregation zone was extended by cold rolling and made a stripe pattern on the sheet surface.