【作者】 史琦；

【导师】 何宁；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2013， 博士

【摘要】 钛合金在加工中切削效率低、刀具磨损严重、尺寸精度和表面质量差。因此，在保证刀具耐用度和加工质量的前提下，发展高材料去除率的机械加工技术迫在眉睫。高性能切削工艺可以根据加工对象的不同，以最高的加工效率获得具有良好经济效益并满足加工质量要求的零件产品，然而高性能切削工艺的发展起步较晚，缺乏充分的理论依据和数据支持。为此，本文致力于寻求提高钛合金加工效率和改善已加工表面质量的工艺方法，将以新型损伤容限型钛合金TC21作为研究对象，开展高性能铣削钛合金的工艺基础研究。主要研究工作包括：（1）通过在常规速度和高速下铣削钛合金TC21的切削试验，分析了铣削用量、刀具磨损和刀具材料等对铣削力和铣削温度的影响，讨论了刀具的磨损机理，并从表面粗糙度、加工硬化层和金相组织等方面研究了加工表面完整性，对TC21钛合金的铣削加工性进行了综合性评估。获取了较优的精加工铣削参数范围，并揭示了铣削时的刀具磨损机理。（2）分析了大进给铣削工艺的特点，通过研究铣削速度和每齿进给量对铣削力的影响进一步明确了大进给铣削工艺的特点，利用夹丝热电偶测温方法对大进给铣刀刃口切削区的温度进行了测量。采用扫描电镜和能谱仪对两种典型的大进给铣刀的刀具磨损形态进行了分析，并探讨了大进给铣削钛合金时的刀具磨损机理，为优化大进给铣刀奠定了基础。（3）通过大进给铣削TC21钛合金试验，重点研究了采用三角形大进给铣刀切削钛合金时铣削用量对切屑宏观和微观形貌的影响及其成因。借助金相试样的显微分析方法，研究了铣削速度和每齿进给量对切屑变形的影响，并从大进给铣削时的锯齿状切屑成因、锯齿化程度等方面探究了切屑的变形过程，进一步明确了大进给铣削工艺特点。（4）分别设计了具有倒棱刃口和倒圆刃口两种刃口结构硬质合金刀具，并采用高速和高进给量的方式进行铣削加工钛合金，探究了这两种刃口结构对刀具耐用度、刀具磨损和已加工表面质量的影响，重点讨论了刀具几何角度、倒棱宽度、刃口钝圆半径大小与铣削力、刀具耐用度和已加工表面质量之间的关系。另外，探讨了硬质合金晶粒大小与两种刃口结构之间的相互关系与影响。试验结果表明合理的倒棱宽度和刃口钝圆半径都能延长刀具耐用度和改善已加工表面质量，而且可以采用较高的每齿进给量。（5）根据大进给铣削的工艺特点，结合考虑航空典型零件的结构特征，从程序执行的水平进刀、垂直进刀、行间过渡和层间过渡等几个方面探讨了大进给铣削程序编制的特点，并给出了合理的优化解决方案，从而保证了大进给铣削高材料去除率能力的充分发挥。应用大进给铣削工艺加工飞机典型零件结构的试验和生产验证，发现在粗加工和精加工中材料去除率均可以提高50%以上。更多还原

【Abstract】 Titanium alloy has poor machinability no matter what techniques are employed. Lots of problemsare brought such as low cutting efficiency, severe tool wear, poor dimensional accuracy and surfacequality. Therefore, to develop mechanical manufacturing technology of high material removal rate isextremely urgent in the guarantee of tool life and surface quality. High performance cuttingtechnology can obtain good economic benefits and satisfy parts quality according to the specificmachined object. But high performance cutting technology starts late and lack of sufficienttheoretical basis and experimental data support. To devote to the machining technology which canimprove the cutting efficiency and surface quality, basic research work in high performance millingof titanium alloy is conducted and a new damage-tolerant titanium alloy (TC21) is as the researchobject. The major research works are as follows:(1) The influence of cutting parameters, tool wear, and tool material on cutting force and cuttingtemperature is analyzed through milling experiment of TC21at regular speed and high speed. Andtool wear mechanism is discussed as well. Then surface integrity is studied by investigating surfaceroughness, machining hardening of surface and metallurgical structure of surface. Finally, themachinability of TC21is evaluated comprehensively based on the experimental results. Bettercutting parameters in finish milling are obtained, and tool wear mechanism in milling is revealed.(2) The characteristics of high feed milling are analyzed. For further understanding it, theinfluences of cutting speed and feed per tooth on cutting forces are investigated. And the cuttingtemperature in the machining area is as well measured applying Semi-artificial thermocoupletechnique. Then the tool wear morphology and tool wear mechanism of two typical cutting toolsused in high feed milling of titanium alloy is observed by SEM (scanning electron microscope). Allthe results establish the foundation for optimizing cutting tools used in high feed milling.(3) The effects of cutting parameters on chip morphology in macro and micro scale in high feedmilling TC21are studied only when the cutting tool in triangular shape is used. By means ofmicroanalysis on chip metallurgical specimen, the influence of cutting speed and feed per tooth onchip formation is investigated. Then the chip formation theory is explored in high feed millingtitanium alloy. The characteristics of high feed milling are further understood.(4) The carbide cutting tools with chamfered and honed edge geometry are designed to cuttingtitanium alloy apply high speed and large feed. Tool life, tool wear and surface integrity are analyzed when using these cutting tools. And the effects of cutting tool geometry, width of chamfered edgeand radius size of honed edge on cutting forces, tool life and surface quality are studied. Additionally,the interrelationship between carbide grain size and cutting edge shape is also discussed.Experimental results show that proper width of chamfered edge and radius size of honed edge canprolong tool life and improve surface quality, even higher feed per tooth is adopted.(5)According to the characteristics of high feed milling process, making NC program for highfeed milling is discussed from the aspects of horizontal feed, vertical feed, leading transition andtransition between layers after considering the typical aviation structure. And the reasonableoptimization solution is given to make sure that high feed milling can fully play its high materialremoval rate ability. Then high feed milling is applied to machining typical structure of plane parts.Production results show that material removal rate can be increased more than50%both in roughcutting and in finish cutting.更多还原