Performance evaluation of different types of cutting fluids in Minimum Quantity of Lubrication (MQL) machining of alloy steel by coated carbide insert

Abstract

High Clltting tempenlture is inherent during machining which shortens the tQollife and deteriorates the job ql.llliity. This problcm becomes morc acute when the jobs are difficn1t to machine and are to be used undcr dynamic loading. Cutting flnid application is the most common strutegy to improve the tool life and the product quality. But COllventionalcutting fluids are not that effective in high production machining particularly ill continuous culting of materials like ~teels. More over cutting fluids are the major sOl.lree of environments pollution, soil contamination and inhalation problems. Minimum quantity lubrication (MQL) with vegetable oil or clitting oil is cnvironment friendly machining technique. MQL refers to the use of cutting fluid~ of only u minutc amount-typically of a flow rate of 50 to 500 mLihwhich is about three to four orders of magnitude lowcr thalllhe amount commonly used in flood cooling condition. Effects of MQL on cutting performance of 42CrMo4 steel in respect of chip-too! interface temperature, chip formation, cutting forces, tool wear and prodllct quality have been studied using coatcd carbidc insert (SNMM-TN 2000). Three types of cutting fluids namely soluble oil, vegetable oil and VG 68 cutting oil have been used to compare the relative perfonnance of those culling fluid, with each other as well as with that of dry condition. Compared to dry condition, MQL perfonned better mainly due to sub<;tantial reduction in cutting temperature that enabling favorable chip-tool interaction. This also facilitated the substantial reduction in tool wear, dimensional inaccuracy and surface roughness. The results indicated that the use of minimum quantity lubrication (MQL) by VG 68 cutting oil performed better in comparison to other entting fluids.