Jens Boos

The Behaviour of Graphitized Steels in Machining Processes

Graphitized steels are claimed to perform excellent in machining processes. They therefore can be considered as environmental friendly alternatives to the widely used Pb-alloyed steels. Due to liquid metal embrittlement and in-situ lubrication Pb improves machinability in a narrow tool-chip interface temperature window corresponding to low machining speeds. Although graphite inclusions are also supposed to generate in-situ lubrication, the mechanism and the corresponding optimum working zone is not very clear. The present work applies a new test methodology (including in-situ tribology, analysis of material flow and chip formation, optimum working zone analysis) to investigate the effects of graphite inclusions on turning and drilling operations. A Pb-alloyed low carbon free-cutting steel and Pb-alloyed case hardening steel were used as reference steels.

Continuously cooled bainitic steels with improved machinability

Bainitic steels as obtained directly from hot-working temperatures by continuously cooling processes can combine high strength levels with good ductility and toughness. For this reason they are attractive alternatives to conventional quench & tempered steels. On the other hand these excellent material properties can make machining very challenging. The optimization of machinability therefore is an essential task to reach economic manufacturing processes with satisfying high productivity. Not only cutting parameters but also steel design has to be considered to reach best results.

CORRELATION OF CUTTING FORCE AND POWER CONSUMPTION FOR ULTRASONIC-VIBRATION-ASSISTED CUTTING OF LABEL PAPER STACKS

Experiments comparing conventional and ultrasonic vibration assisted guillotine cutting of paper stacks have been performed on plain and aluminum coated label paper. It is shown that ultrasonic vibration assisted cutting reduces the cutting force for both paper species. Reduction of the cutting force allows the down holder force to be decreased and lowers the compression of the paper stack necessary to prevent pull-out of the top sheets of paper. Using a higher amplitude setting on the ultrasonic generator further decreases the cutting force for the paper stack. For three different cutting speeds, it is shown that ultrasonic vibration assisted cutting force reduction depends on the average speed of the tool for both paper species. A linear regression with present experimental data is done to obtain an equation for the relation between input generator power and resulting cutting force. Finally, the quality of the cutting edge is examined, quality parameters are defined, and according to these