Multi-scale roughness transfer in cold metal rolling

We report on a comparative Atomic Force Microscope (AFM) multi-scale roughn ess analysis of cold rolled Al alloy and steel roll, in order to characteri ze the roughness transfer from the steel roll to the workpiece in cold stri p rolling processes. More than three orders of length-scale magnitudes were investigated from 100 microns to 50 nanometers on both types of surfaces. The analysis reveals that both types of surfaces are anisotropic self-affin e surfaces. Transverse and longitudinal height profiles exhibit a different roughness exponent (Hurst exponent) zeta(perpendicular to)=0.93+/-0.03 and zeta(parallel to)=0.5+/-0.05 Different length-scale cut-offs are obtained in each direction l(perpendicular to)(sup)=50 mu m, l(parallel to)(sup)grea ter than or equal to 100 mu m. Height and slope distributions are also comp uted to complement this study. The above mentionned self-affine characteres itics are found to be very similar for the roll and the strip surfaces, whi ch suggest that roughness transfer takes place from the macroscopic (100 mu m) to the very small scale (50 nm). (C) 1999 Elsevier Science Ltd. All rig hts reserved.