Performance evaluation of vegetable-based cutting fluids in turning of AISI 1050 steel

In most machining operations, cutting fluids are essential to ensure the economical profitability of the process. Turning of common plain carbon and low alloy steels is an example of manufacturing process widely used in several branches of the manufacturing industry, were the use of cutting fluids plays a key role in minimizing tool wear, machining forces and surface roughness, and improving overall process performance. Unfortunately, the cutting fluids, particularly those mineral-based, are considered harmful to the environment and therefore a source of pollution in production lines, as well as being a threat to the health of the operators. An attempt of minimizing environmental pollution is to use cutting fluids which are vegetable-based instead of mineral-based, with many producers offering this option in their portfolios. Doubts though arise on how vegetable-based cutting fluids perform compared with the mineral-based fluids. The present work compares the performance of three concentrations (3%, 7%, and 10%) of two vegetable-based cutting fluids (an emulsion and a synthetic) with one mineral-based fluid (semi-synthetic). The comparisons are made through reciprocating sliding tests, wettability, cooling capacity, viscosity, and cutting force measurement in turning of an AISI 1050 steel. All non-machining tests (friction coefficients, droplet contact angles (wettability), heat exchange coefficient by convection and viscosity) and machining tests (machining forces) were performed with all cutting fluids. This set of rheological and tribological tests performed allowed better understanding of the differences in machinability, regarding the cutting forces, of the cutting fluids evaluated. The results showed that, despite the better thermal and tribological properties of the mineral-based cutting fluids, the vegetable-based emulsion had an overall better performance in relation to the wettability angle and machining forces. These results, together with the greater sustainable appeal of vegetable-based cutting fluids, point to their clear feasibility in the machining of AISI 1050 steel.