Einfluss unterschiedlicher Gefügezustände auf den Werkzeugverschleiß bei der Feinbearbeitung von ein

FKM 1998
Booklet No. 233
Project No. 212

Abstract:

The machining of hardened steels with a defined cutting edge is an alternative to grinding processes. In contrast to grinding, hard finishing with a defined cutting edge offers the advantage of a higher specific cutting performance in the simultaneously possible dry cut. A disadvantage of machining processes with a geometrically defined cutting edge for machining hard surfaces is the great influence of the machinability of the material on tool wear. Thus, under apparently constant boundary conditions of the cutting process (workpiece, cutting material, technology), the service life of carbide tools often varies considerably. The aim of the research project was therefore to determine the influence of the microstructural conditions of the workpiece on tool wear during hard machining with a defined cutting edge. For this purpose, different microstructural states in the form of different retained austenite contents and surface layer hardnesses were machined with uncoated carbide tools in a process analogous to skiving. The heat treatment was carried out on the case-hardening steel 16MnCr5, which is widely used in gear manufacturing. To classify different heat treatment batches, the case hardening of the components was repeated with a time delay on a second group of samples. A staggered repetition of the heat treatment leads to the same surface hardness of 57 and 61 HRC and a reproducible case hardening depth. However, the microstructure formation is not constant. Furthermore, differences in the proportions of retained austenite and martensite produced by the heat treatment were found. This statement is supported by X-ray analyses of the machined and unmachined workpiece surface layer. The tool wear is characterized by a uniform formation of a wear mark width independent of both the retained austenite content and the surface layer hardness. Local cutting edge defects as a result of cutting edge chipping were not observed depending on the microstructure variant. Stochastically occurring cutting edge fractures can therefore not be attributed to the RA content of the microstructure. The tool wear on the cutting surface in the form of a cutting edge offset amounts to SV a 4 IJm when the tool life criterion is reached on the flank face in all analyzed cutting tests and thus has no dominant influence on the tool life behavior of the tools. The same applies to the cutting edge rounding that occurs during machining, which is relatively constant over the tool life and is reduced when the tool life criterion is reached p Scope of report:
68 pages Start of work:
01.05.1996 End of work:
31.08.1997 Funding body:
AiF-Nr. 10671 Research Center Laboratory for Machine Tools and Production Engineering at RWTH Aachen University, Prof. Dr.-lng. F. Klocke Editor and author:
J. Becker Chairman of the Advisory Board:
Prof. Dr.-lng. H. Kipphan, Heidelberger Druckmaschinen