Research On The Green High Speed Machining Of Titanium Alloy

The machining of difficult-to-machine materials represents one of the very complicated and urgent problems in aircraft, spacecraft and other manufacturing industries. In order to realize high speed and green cutting of difficult-to-machine materials, high speed cutting of titanium alloy utilizing nitrogen gas as coolant is selected as the object studied, and the action mechanism of nitrogen gas on the cutting process is studied emphasizedly. Theoretical analysis, numerical simulation and experimental verification are applied in this research. The major research works are included as follows:1. Rotating pin-on-disc friction tests were carried out on a pin-on-disc type wear test machine. The friction and wear behavior of WC-Co cemented carbide sliding against Ti6Al4V alloy were investigated at high sliding speeds, which were helpful to deeply analyze the action mechanism of nitrogen gas on the high speed cutting process of titanium alloy.2. High speed cutting experiments were carried out to investigate the cutting forces and cutting temperature under nitrogen gas and air and also in dry machining. It was discovered that nitrogen gas provided good anti-attrition and cooling effects on the high speed cutting process of titanium alloy.3. Based on the finite element analysis of orthogonal machining, high speed cutting tests were carried out to investigate the mechanism of chip formation. It was found that the catastrophic failure, within the primary shear zone during the saw-tooth chip formation in machining Ti6Al4V alloy, could be attributed to both the occurrence of thermo-plastic instability and workpiece material embrittlement. Finite element analysis was also used to investigate the cooling and anti-attrition influences of cutting media on the serrated chip formation processes, and to verify the cutting experimental results. A new method to get the chip root from milling process has been described in this dissertation, which supports a new way to investigate the chip formation in milling process.4. The tool wear forms and tool life of cemented carbide tools in high speed cutting of titanium alloys were analyzed. The brittle fracture and wear mechanism of high speed cutting titanium alloy under nitrogen gas and air were investigated along with the main elements, which influence the tool life. An element analysis model of orthogonal metal cutting was combined with the tool diffusion wear model to discuss the diffusion rates distribution on the rake face, and to predict the effect of cutting media on the diffusion rates on the rake face.5. Rotating pin-on-disc friction tests,experiments on cutting force and cutting temperature, and investigation on chip formation and tool wear were carried out to scrutinize the anti-attrition feature of nitrogen gas in the high speed machining of titanium alloy. This was found as the key to improve the cutting performance and tool life of cemented carbide tools.