Effect of roll surface topography on microstructure and mechanical properties of 304 stainless steel ultra-thin strip

Abstract

Since the thickness of ultra-thin strips of stainless steel is usually only at the micron level, the ratio of surface asperities to thickness significantly increases, the role of the material surface is prominent; thus, the influences of the working roll surface topography on the microstructure and mechanical properties of ultra-thin strips cannot be ignored. In this work, three kinds of rolls with different surface topographies obtained by grinding, polishing and sandblasting are used in a 20-high Sendzimir mill to roll ultra-thin strips of 304 stainless steel with thickness of 70 μm at different reduction rates. The surface morphology, microstructure, texture and mechanical properties of the steel strip are investigated. The results show that at the same reduction rate, the strip has the highest dislocation density, the smallest grain size and the highest tensile strength when rolled with a sandblasted roll; A polished roll can improve the mechanical strength while obtaining stainless steel ultra-thin strips with high elongation. In terms of roughness anisotropy, the surface roughness of steel strips rolled by a ground roll has obvious anisotropy. A sandblasted roll has the strongest influence on the diminution of the surface roughness anisotropy of steel strips. A polished roll also has a weakening function on surface roughness anisotropy, and the larger the reduction rate is, the more obvious the action. The texture intensity can be effectively minimized by weakening the surface roughness anisotropy, thus reducing the anisotropy index of mechanical properties of the ultra-thin strip, which is prominent at a small reduction rate. The tensile strength and elongation anisotropy index (IPA) of the ultra-thin strip rolled by a sandblasted roll are 55.68 % and 56.28 % of the strip rolled by a ground roll at a reduction rate of 5 %, respectively. It is suggested that the surface features, microstructure and mechanical properties of the strip can be modified by polishing and sandblasting the roll surface during the rolling process, which provides a reference for obtaining high-quality stainless steel ultra-thin strips in industrial production.