Use of modern tool steel and surface engineering in sheet cold forming

In sheet metal forming, one of the paramount questions to answer is which die matrix properties are required in combination with the necessary properties/conditions on the active die/sheet surfaces to achieve long die life and also increase the time elapsed between maintenance events. Usually, the die steel surface hardness has been the dominant parameter when judging the die performance, while only minor attention has been put on the die matrix ductility. Modern steel making technology enables steel manufacturing of tool steel with much improved toughness when compared with traditional grades. A study has been carried out pertaining to evaluate influence of surface engineered layer properties when stamping EHSS details. Prehardened tool steel was chosen as matrix to simplify die manufacturing. The results show that both a single physical vapour deposition (PVD) layer and a duplex coating (nitriding+PVD) show the desired die life, i.e. 50 000 produced details, when stamping 1·95 mm 600 DP sheet.