| As a new alloy material,titanium alloy has been widely used in various manufacturing fields because of its high strength,good corrosion resistance and cryogenic temperature resistance.However,the machinability performance of titanium alloy is poor,and there will be some phenomena,such as larger cutting force,higher cutting temperature and faster tool failure.To solve the above problems,it is very necessary to choose a suitable processing method when milling titanium alloy.In this paper,combined with capillary dynamic modeling,fluid simulation,and milling titanium alloy experiments,the research on the cooling and lubrication mechanism of supercritical carbon dioxide（scCO2-MQL）in the cryogenic temperature micro-lubrication milling process is carried out.The study contents the following aspects:Firstly,the characteristics of micro-lubrication of supercritical carbon dioxide at low temperature are analyzed,the influence of dry ice particles on the cutting zone is analyzed,and a capillary model is established.The dynamic analysis of the process of tool-chip contact zone infiltrated by supercritical CO2-MQL is proposed;the process of cryogenic temperature gas flow through the capillary is simulated by the Fluent simulation software.The dynamic analysis of boundary lubrication layer during supercritical carbon dioxide micro-lubrication is carried out.By characterizing the friction coefficient of tool-chip contact area,the lubrication mechanism of supercritical carbon dioxide micro-lubrication is described.Secondly,supercritical CO2-MQL injection experiments were carried out,and the cooling rates of cutting tools and workpiece materials under different conditions were measured.The jet structure and the heat transfer between cryogenic fluid and different plates are analyzed by fluid simulation,and the accuracy of the simulation model is verified by comparing the simulation and experimental results.At last,the above simulation model is used to simulate the cooling of cutting tools and workpiece materials at high temperature.Finally,the experiments of milling titanium alloy TC11 under dry and supercritical carbon dioxide micro-lubrication conditions are carried out,the tool wear and breakage under two different conditions are studied,the wear and breakage mechanism of milling titanium alloy TC11 is expounded;by comparing the forms of tool wear and breakage in different wear periods,the effects of different processing conditions on tool wear and breakage during milling are explored,which provides a reference for efficient milling of titanium alloy TC11. |
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