| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 100 === Titanium alloy (Ti-6Al-4V) has superior physical properties, mechanical properties and biocompatibility. It is an attractive material in many engineering fields. In machining Ti-6Al-4V, due to low thermal conductivity of the material the generated heat during machining cannot be conducted through the work piece and chips effectively, which is resulted in rapid tool wear. It has been reported that cutting speed of Ti-6Al-4V is limited to 30 m/min and 60 m/min. Cutting fluids have been used in machining operations in order to reduce cutting temperature.
In this study, a heat pipe cooling system was used in turning of Ti-6Al-4V at different cutting speeds (60 m/min, 90 m/min, 120 m/min). The tool temperature and tool wear of uncoated carbide inserts, the cutting force and surface roughness have been compared to dry, wet, compressed cold air at 0℃ and minimum quantity lubrication (MQL) cooling environments . The results show that the heat pipe cooling system can effectively remove the heat generated at the tool-chip interface in machining. The flank wear values of the cutting tool with the combination of heat pipe cooling system and MQL is lower than which with flood coolant at the cutting speed of 60 m/min and 90 m/min. Compare to conventional wet cutting, tool life extension of using a heat pipe of larger diameter and MQL is 30% at a cutting speed of 90 m/min. With the use of larger diameter heat pipe cooling system and MQL, flank wear values of the cutting tool is lower than wet cutting at a cutting speed of 120 m/min. Therefore, the combination of heat pipe cooling system and minimum quantity lubrication is a technique which can reduce the use of conventional cutting fluids in turning of Ti-6Al-4V.
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