Method of mechanical surface treatment of a blank metal sheet

DETAILED DESCRIPTION We claim: 1.
A method of mechanically structuring a blank surface of a sheet metal workpiece, comprising the steps of: (a) applying to said blank surface of said sheet metal workpiece an adherent but non-adhesively bonded foil; (b) pressing said foil against said surface with a roll, thereby deforming said surface and impressing a texture of said foil in a deformed state into said surface; (c) during said pressing of said foil against said surface in step (b) varying a ratio of peripheral speed of said roll to speed of advance of said workpiece and varying a pressure of said roll against said workpiece to control said deformation of said foil and said sheet metal, said varying of ratio and pressure being performed during said pressing step; and (d) recovering the sheet metal with a deformed and textured surface.
2.
The method defined in claim 1 wherein said foil is formed with a side thereof confronting said surface with a surface texture which is at least partially imparted to said sheet metal surface.
3.
The method defined in claim 2 wherein said at least partially imparted surface texture arises from wrinkling of said foil.
4.
The method defined in claim 1 wherein said sheet metal is composed of soft pure aluminum or a soft aluminum alloy.
5.
The method defined in claim 1, further comprising the step of removing said foil from said sheet metal.
6.
A method of mechanically structuring a blank surface of a sheet metal workpiece, comprising steps of: (a) applying to said blank surface of said sheet metal workpiece an adherent but non-adhesively bonded foil; (b) pressing said foil against said surface with a roll, thereby deforming said surface and impressing a texture of said foil in a deformed state into said surface; (c) varying a ratio of peripheral speed of said roll of speed of advance of said workpiece and varying a pressure of said roll against said workpiece to cause wrinkling of said foil and thereby control of the deformation of said foil and said sheet metal, said varying of ratio and pressure being performed during said pressing step; and (d) recovering the sheet metal with a deformed and textured surface covered by said foil as a protective layer