Electrically Assisted Drilling of Usibor 1500 Boron Steel and its Implications for Electrically Assisted Machining

With the increasing demands in the automotive industry for passenger safety and higher structural strength and stiffness, the automotive industry is using more advanced high strength steels. The ability to reduce tool wear and drilling forces in post forming drilling of high strength steel parts is of high importance to the automotive industry. Electrically assisted drilling is a process in which electric current is passed through the drill bit to the workpiece resulting in local softening, and allowing for a reduction in cutting forces and potential increase in tool life. In this paper, tungsten carbide (WC)-tipped drill bits are used to study the effect of varying electrical current on 1500 Usibor^® steel work pieces. The effects of current on the drilling process of high strength steel are investigated in this research by studying the maximum temperature during drilling, the dependence of chip formation, tool wear and the axial force during the drilling operation. It was found that the magnitude of current passed through the workpiece directly influences the axial force that the tool experiences, and thus the tool wear. This effect is modeled through Joule heating, leading to elevated temperature and thermal softening.