A Process of Notch Wavy Rolling for Strengthening Metal Sheets

Wavy roll design was employed for strengthening 1mm thin austenitic stainless steel coil sheet by cold rolling without further reduction in thickness. This steel possesses high corrosion resistance and high ductility. Initially, the sheets were rolled into sine wave shape (wave amplitude <2mm) and then flattened using conventional cold rolling mill. Such a process cycle was repeated for four times successfully and the mechanical properties were measured after each cycle. The yield strength increased from 255 to 931MPa with corresponding decrease in elongation from 45% to only 17% after the fourth cycle of severe cold working. Tensile strength and hardness values increased from 753MPa and 185 HV to 973MPa and 371 HV, respectively. The micro-to-nano-scale resolution structures, obtained by optical and atomic force microscope (AFM), were used to explain the variation in properties during this manufacturing process and to propose schematically the deformation mechanism.