Optimization of machining processes of high resistant steels for the automotive industry

The developments in the automotive industry are mainly motivated by the demand for more resource efficient vehicles. Besides this, there are high strength requirements for the used construction materials in order to implement efficient engines. As a consequence of the described requirements in the automotive field there exists a continuous trend towards the development of more resistant steels to realize lighter and more rigid and safer structures. Against the benefits of the application the workability of these steels is challenging. Due to a directive of the European Union from year 2005 the max. percent by weight of lead, which is allowed to alloy to heat-treated steels, is up to 0,35 wt% [1]. According to this, experimental investigation on the machining of lead-free heattreated steels that combine the demand for high strength requirements and reliable chip breaking processes have been carried out. For deep hole drilling processes a reliable and safety chip breakage is necessary to avoid sudden tool failure. The effect of the element lead to influence the chip breakage positively is known [2]. Due to that, machining a lead-free heat-treated steel efficiently by high feed rates an optimized tool geometry which supports the chip breakage is required. According to the experimental investigations a safety and reliable deep hole drilling process of a lead-free modified C45 was established. Although the basic hardness is up to 20% in comparison to a conventional lead-free C45, the chip breakage and the influence on the sub surface zone are similar between all three modifications. Regarding to the resulting surface quality of the bore hole, machining the modified C45 achieves the best results in comparison to the lead-free C45 or conventional lead-alloyed C45Pb.