Transfer layer and friction in cold metal strip rolling processes

Mechanically mixed layers (MMLs) and transfer layers (TLs) are present in t he metal forming industry, in rolling processes among others, just as in ot her fields of Materials and Mechanical science and engineering. Due to the asymmetry of mechanical properties between workpieces and tools, however, T Ls are much more frequent - indeed, almost systematic - and the present pap er focuses on them. A review is given of experiments performed both on an e xperimental rolling mill and on a tribological simulation test, the plane s train compression test (PSCT). Various metals and alloys have been investig ated under a range of deformation conditions. As in other systems, the orig in is abrasive wear followed by adhesion, or adhesive wear. Constant exchan ges between the tool surface, the workpiece and the re-circulating lubrican t lead to a steady state TL, the characteristics of which (density and size of transferred particles, hardness and roughness of the TL) depend on the tool-workpiece contact conditions. Tribological consequences, in terms of f riction and formed piece surface aspect, vary with the TL properties. (C) 2 000 Published by Elsevier Science S.A.