Analysis of white-stripe defects of non-oriented silicon steel rolled surface with emulsion

School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, P.R. China
e-mail: sjl@ustb.edu.cn

Received: 14 April 2015
Accepted: 8 September 2015

Abstract

For non-oriented cold-rolled silicon steel lubricated with oil-in-water (O/W) emulsion, the typical white-stripe defects can always be found on the rolled strip surface. The white-stripe defects are parallel to the rolling direction. In this paper, an experimental investigation and mechanical analysis were carried out to study the white-stripe defect formation during cold strip rolling using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The emulsion lubricating properties and surface topography of wear scars are discussed. It is considered that the poor lubricating properties of the emulsion are a key factor for surface defect formation on the rolled strip surface. The surface roughness R_a of the white-stripe area is 31.2% larger than that of the normal area. The results show that when the tribological properties of commercial emulsion are poor; it will lead to generate surface defects on the rolled non-oriented silicon steel surface. Furthermore, emulsions were embedded into the surface defects of the rolled strip. When the emulsion residue agglomerates together, white-stripe defects appear on the rolled strip surface.