低温氮气射流对钛合金高速铣削加工性能的影响

在钛合金的高速切削过程中，切削区温度很高，加速了刀具的磨损，限制了切削速度的进一步提高。为降低切削区温度、防止刀具的氧化磨损，提出在低温氮气射流条件下进行钛合金的高速铣削加工。在干铣削、浇注切削液、常温氮气油雾、低温氮气射流和低温氮气射流结合微量润滑等冷却润滑条件下进行了钛合金的高速铣削对比试验。试验结果表明，低温氮气射流结合微量润滑能够最有效地降低铣削力，抑制刀具磨损。借助扫描电镜的检测手段，研究了不同冷却润滑条件下刀具的失效形式。指出在低温氮气射流条件下高速铣削钛合金时，只要热裂纹的形成与扩展未引起刀具的崩刃及刀面的剥落，进一步降低低温氮气的温度将提高刀具的使用寿命。

Effects of Cryogenic Nitrogen Gas Jet on Machinability of Ti-Alloy in High Speed Milling

In the course of high speed cutting of titanium alloy, the temperature of cutting zone is very high, which accelerates tool wear so that cutting speed is more restricted. The use of cryogenic nitrogen gas jet to reduce the temperature of cutting zone and to avoid oxidation wear of tool in high speed milling titanium alloy was presented. The experiments of high speed milling of titanium alloy were conducted under different cooling and lubricating modes, i.e. dry milling, flood coolant, oil mist with nitrogen gas, cryogenic nitrogen gas jet, and cryogenic nitrogen gas jet with minimal quantities of lubricant. The experimental results indicate that cryogenic nitrogen gas jet with minimal quantities of lubricant is the most effective cooling and lubricating mode to reduce milling force and to retard tool wear. Through analyses carried out with SEM,tool failure patterns under different cooling and lubricating modes were studied. It has been pointed out that for the application of cryogenic nitrogen gas jet in high speed milling of titanium alloy, unless the chipping and fracture caused by thermal cracks take place, the reduced temperature of cryogenic nitrogen gas will prolong the tool life.