EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Progressive die-tools are essential for the production of steel components within the sheet metal industry. Due to increasing demands on component quality and tool life, WC-Co based carbides are increasingly used as material for the cutting elements within the progressive die-tools. The manufacture of cutting elements, consisting of punches and dies, requires a combination of subtractive manufacturing technologies. Due to existing interactions, the coordination of the manufacturing technologies with each other represents a major challenge. Starting with electrical discharge machining, further functionalization usually follows through processes with geometrically undefined cutting edges, such as surface grinding as well as preparation processes for rounding the cutting edges. In addition to the shape accuracy of cutting elements, the conditioning of the subsurface area is a critical target value. Based on spark erosion machining, the subsurface area of cutting elements often exhibits undesirable tensile residual stresses. In this paper, spark-erosive-machining and subsequent manufacturing steps in the form of surface grinding and pressurized air wet abrasive machining (PAWAJM) and their effects on the subsurface area properties in terms of phase formation and residual stress state are analysed. In order to evaluate the different subsurface area states, real-life application tests for punching of spring strip steel 1.4310 are carried out using the example of cutting punches in order to be able to derive the mechanisms of action of the production chain with the resulting tool life. The results show that thermally induced phase transformations in the form of decarburization effects and Eta-carbide formation lead to embrittlement of the subsurface area, which has a negative effect on tool life. The reworking of cutting punches by preparation processes leads to the removal of the damaged edge area and the integration of residual compressive stresses, which have a positive influence on the constitution of the subsurface area.