Modification of the surface integrity of powder metallurgically produced S390 via deep rolling

Fine blanking is an economical process for manufacturing sheet metal workpieces with high sheared surface quality. When machining high-strength steels, material fatigue leads to increased punch wear, which reduces the economic efficiency of the process. This fatigue of the cutting edge and lateral punch surface can be counteracted by mechanical surface treatments. Deep rolling has proved particularly useful for such surface modification, as it allows both: machining of the lateral punch surface and the application of the cutting edge rounding required for fine blanking. For the precise design of the fine blanking punch contour especially the macroscopic deformation of the workpiece is decisive. In this paper, the possibility of specifically modifying the surface integrity of hardened and powder metallurgically produced S390 by means of the incremental surface treatment process deep rolling is investigated. By varying the decisive process parameters rolling pressure, ball diameter and step over distance, their influence on surface integrity is determined. The surface integrity is afterwards characterized by macro hardness, surface topography and residual stress state and microstructural images.