CONTRIBUTION TO TURNING HARDENED STEEL
Published: 2 Jun 2014
Abstract: The article discusses the issue of finish turning of hardened materials in the production of bearing rings. In this area grinding technology is commonly used, what has several advantages. This technique ensures mass production in tolerance grade IT 4 to IT5 and the average arithmetical mean deviation of the profile in the range of Ra = 0.4μm and Ra = 0.8μm. Possible cross cut further improves the tribological properties of friction surfaces. Certain disadvantage is at increased internal stress in the surface layer, what is a consequence of grinding technology. Alternative technologies may be turning wits tools of cubic boron nitride, which may replace to some extent grinding technology. The article further discusses the technological experiment with the tools of cubic boron nitride and describes in detail the results and analysis of experiments. The experiment was conducted on turning machines with CNC control, where in the cutting conditions such as cutting speed, feed rate, cutting width of the blade can be accurately set and at the same time it is possible to watch the cut of the tool. The necessary condition is also sufficient rigidity of the system - machine tool, cutting tool and workpiece. On the tools the face and flank wear were evaluated and from partial graphical representations wear curves were compiled. These diagrams are the basis for the compilation dependency of tool life vs. cutting speed for each size of the wear. The article presents the basic results that have been achieved. The data of arithmetic mean deviation of Ra profile, which was statistically processed, was also obtained during the experiment.
Keywords: hardened steel, bearing ring, turning, removable insert, cutting speed, feed
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