Performance of Different Tool Steels for the Cutting of an CP1000 Advanced High Strength Steel

Abstract

During the last decade, AHSS (Advanced High Strength Steels) have received growing attention in the construction of light-weight car bodies with excellent crash-performance. With the rising strength of these materials, the requirements for forming and cutting tools are also increasing permanently. To investigate the tool performance for such conditions, four different cold work tool steels (1.2379 – Sverker21, Sleipner, 1.2358 – Carmo and Caldie), one of them (1.2379 – Sverker21) additionally PVD-coated, were used in their typical heat treatment condition to compare the wear behavior and the cutting performance. The tests were performed on semi-industrial forming and cutting press under industrial process parameters on partially preformed test pieces of the steel CP1000. The measurement methods applied include optical as well as tactile measurement methods to measure the tool wear, optical methods to investigate the cutting zone and the burr formation at the workpiece as well as scanning electron-microscopy to characterize the tool surface regarding wear, fracture and adhesion of the zinc coating. Except for the lower alloyed surface hardened and nitride tool steel (1.2358 – Carmo), which showed early failure, all other tooling solutions easily reached 100,000 test pieces with good workpiece quality. Nevertheless, small partial fracturing at the cutting edge was found at all tools. Best results regarding wear, but especially lowest zinc adhesion were found at the PVD-coated tools.