Study On Key Issues Of Diamond-cutting Steels

It is a bottleneck in manufacturing field about how to reduce the diamond tools wear in ultra-precision machining of steel materials. This thesis has conducted an in-depth study on the two potential approaches, i.e., ultrasonic vibration assisted cutting and surface modification.(1) Given the limitations of traditional thinking in horn design and the characteristics of ultra-precision machining, it was proposed that modal analysis should be replaced by harmonic analysis to do finite element aided design without considering amplitude in the field of ultra-precision machining.(2) The design of the new curved horn structure was optimized through combining finite element analysis with three-dimensional modeling. The result of variation of the horn revealed that the operating frequency range to meet the processing requirements is about 62 KHz ~ 72 KHz.(3) The overall design of ultrasonic vibration assisted cutting device was completed. A laser interferometer was used to detect vibration characteristics of the tool tip. Normal direction rake tip amplitude curve with the input ultrasonic voltage and frequency of the device has been drawn, which would provide a reference for setting the parameters of subsequent experiments.(4) Cutting experiments were implemented in an ultra-precision machine to verify the practicability of the new device. Elliptical vibration results obtained by finite element analysis were confirmed by machining AL6061. Surface roughness Ra value was reduced to about 10 nm with the help of optimized processing parameters, thus the plane mirror with a diameter of 20 mm was processed successfully in cutting STAVAX experiments. It was also proved that the new device can be applied to diamond ultra-precision machining.(5) Nitriding deformation effects on ultra-precision machining were analyzed and method for iron nitriding was proposed. Sample preparation was achieved by using gas nitriding combined with annealing and quenching. Nitriding layer composition analysis showed that iron material obtained a nitriding layer with a thickness of 140?m through gas nitriding process, which was divided into four sub-layers in accordance with the metallographic structure. Annealing and quenching process changed the surface of metallographic structure.(6) The experimental results of cutting the nitriding layer showed that subsequent thermal treatment of annealing and quenching could eliminate the layer where diamond tool is not capable of cutting. 140?m diamond cutting layer was obtained with surface roughness Ra value of 6 ~ 8nm. No significant wear was found on diamond cutting tools. It meant that nitriding deformation could be controlled by iron nitriding technology.