複合式冷卻與潤滑用於Ti-6Al-4V車削之研究

Abstract

Titanium alloy is well known as one of the typical difficult-to-cut materials. This thesis focuses on the effect of various cooling and lubricating methods on machinability in turning Ti-6Al-4V titanium alloy. The appropriate cutting fluid and its associated flow rate of the minimum quantity lubrication (MQL) applied in the cutting process are determined first. Thereafter, four types of cooling and lubrication methods during cutting are compared. They are machining with the MQL technique, machining with flooded cutting fluid, machining with a heat pipe embedded beneath the insert for heat removal, and machining with the MQL technique together with the assistance of a heat pipe. The most appropriate cooling and lubrication method is determined based on the analysis of the resulting tool wear, cutting force, tool temperature, surface finish and the chip morphology in cutting. It is found that 20% water-based cutting fluid and a flow rate of 20ml/hr are the proper combination of MQL. The use of MQL incorporates with a heat pipe assisting heat removal results in minimum tool wear. The cutting speed in turning Ti-6Al-4V titanium alloy can be increased from the normally recommended 50-70 m/min to 90m/min. Hence improvement of machining efficiency is expected.