Research On High Performance Milling Of Titanium Alloy TC21

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.