Research On Machining Performance And Experiment In Turning Difficult To Machine Materials With High Pressure Cooling

The applications of high temperature alloy, titanium alloy, alloy steel andother hard processing material are used widely in areas such as aerospace,medical, chemical and oil. Conventional cooling way was adopted to improve thetool life and surface quality, etc., because of the low thermal conductivity, highplasticity and toughness, high chemical activity and high strength of difficult tomachine materials. In recent years, with the constant improvement of themachining efficiency and technical requirements, conventional cooling has notbeen able to meet the manufacturing requirements, and cutting with high pressurecoolant lubrication is gradually recognized by people due to its significant effects,so the cooling and lubrication properties of the high pressure cooling and cuttingtests are carried out to study, in this dissertation, which has important theoreticalsignificance and practical value.Firstly, with the capillary theory, the process which cooling fluid seepinginto the capillary and dynamic model is analyzed under high pressure cooling inthis dissertation. The model of high pressure cooling fluid forming boundarylubrication is established. The influence of cooling fluid injection pressure andshear strength on the frictional force of the rake face are discussed. The variety ofspeed and time of cooling fluid seeping into the capillary with injection pressureare studied, and the MATLAB is applied to calculate and generate curve. Thevary trend of convective heat transfer coefficient is studied under high pressurecooling, and finite element simulation and analysis is carried out based onconvection heat transfer coefficient and thermal conductivity coefficient. Theinfluence of high pressure cooling on temperature on tool, chip and workpiece is discussed.Secondly, the experiment on changing the cutting parameters, coolingconditions and injection pressure of cutting fluid is carried out, studying the toolwear during turning titanium alloys and the chip-breaking form in turningtitanium alloys, high temperature alloys and high strength steel. The forms andinfluencing factors of tool wear are analyzed. And the relationship betweendifferent cooling condition and cooling liquid injection pressure and the tool wearis also analyzed based on tool wear experiments. Compared with the chip shapesunder the condition of conventional cooling and high pressure cooling in cuttinghigh strength steel, the effect of high pressure cooling of chip breaking andseparation is analyzed.At last, the machined surface quality of workpiece in turning process oftitanium alloy and high strength steel was studied. The influence of coolinglubrication conditions on surface roughness, white layer and residual stress isanalyzed, and the effect of cutting with high pressure cooling on the surfacequality of workpiece is discussed.