Effect of Some Thermodynamic Properties of Cutting Fluids on Machinability of Carbon Steel

Abstract

Cutting fluids are used to reduce heat generated during machining, however some have been discovered to pose health challenges hence the search for viable alternatives. In this paper, three machining conditions (dry machining, wet machining with soluble oil and wet machining with used-engine oil) were conducted on high carbon steel, with a sole aim of investigating the suitability of engine oil as an alternative to soluble oil. Measurements related to effective use of oil as metal cutting fluids were determined and the machining parameters used were cutting speed (750 – 1750 rpm), feed rate (40 – 120 mm/rev), and depth of cut (0.1 – 0.3 mm). The experimental procedure was formulated using Minitab software version 18 and the machining responses investigated were maximum temperature at the cutting interface, surface roughness, and tool wear rate (TWR). Thermodynamic properties investigated include, flashpoint, specific heat capacity, viscosity and density. The experimental results showed that cutting temperature reduced from an average of 440oK during dry machining to 369.8oK (16% improvement) during machining with used-engine oil and 362.6oK (18% improvement) during machining with soluble oil. The surface roughness produced was generally higher while machining with used-engine oil with an average improvement of 39% in surface integrity. However, when soluble oil was used as cutting fluid, average improvement in surface integrity increased to 70%. Hence, used-engine oil offered impressive lubricating and cooling properties and could replace soluble oil as a cutting fluid during machining.