熱管冷卻系統用於車削Ti-6Al-4V之研究

Abstract

Ti-6Al-4V具有優異的物理和機械性質並具生物相容性，被廣泛應用於眾多工業領域，但其特殊的性質會導致切削時產生的熱量累積在刀尖，造成嚴重的刀具磨耗，切削速度亦受限於30 m/min至60m/min間，業界加工時需要使用大量的切削液以降低刀具溫度。 為了達到減少切削液用量但又能減輕刀具磨耗的目的，本研究提出一個結合熱管與冰水循環的冷卻系統，將其架設於刀片上進行Ti-6Al-4V車削實驗，並與乾切削、濕切削、0℃冷空氣切削、最少量潤滑（Minimum quantity lubrication, MQL）等方式比較，分析不同切削速度下（60 m/min、90 m/min、120 m/min），以上切削環境對刀具溫度、刀具磨耗、切削力及表面粗糙度之影響。研究結果顯示，熱管冷卻系統具有將熱量由切削區域傳出的效果，在切削速度60 m/min及90 m/min下同時使用熱管冷卻系統和最少量潤滑可得到比濕切削更少的刀腹磨耗量。使用直徑較大而具有較高熱輸送量的熱管冷卻系統與最少量潤滑車削Ti-6Al-4V時，切削速度90 m/min之刀具壽命比濕切削延長30%，當切削速度提高至120 m/min此冷卻方式的刀腹磨耗量亦比濕切削低。因此並用熱管冷卻系統和最少量潤滑是一種可取代濕切削而較為環保的切削輔助方式。

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.