The study of cutting fluids has grown into a vast research area in recent years due to the importance of these fluids in the machining process and their vital role in extending tool life, reducing costs, and improving cutting performance. Cutting fluids are complex mixtures involved in lubrication, cooling, chip evacuation, and protection from corrosion of the workpiece, tool, and machine components. In particular, water-soluble cutting fluids have gained much attention due to their high cooling efficiency, easy-to-handle nature, and environmental acceptability. These fluids are complex mixtures of components, including surfactants, corrosion-inhibiting agents, wetting agents, and oil-soluble components.
The performance of water-soluble cutting fluids is greatly affected by the choice of its components. Surfactants are an essential component of water-soluble cutting fluids, since they reduce surface tension and increase wettability. They are typically ethoxylated fatty amines. Corrosion-inhibiting agents protect the workpiece, tool, and machine components from corrosion, and are typically complex organic inhibitors composed of sulfur, nitrogen, phosphorus, and oxygen atoms. Antifoam agents, wetting agents, and oil-soluble components reduce foam formation, improve the drying characteristics, and increase the cutting fluid’s lubricity. Oil-soluble components are typically oil-soluble sulphonates, which are very effective in providing lubrication and coolant properties.
The performance of a water-soluble cutting fluid can be evaluated by measuring its surface tension, kinematic viscosity, flash point, and cutting power. The surface tension is a measure of the forces holding the fluid in a thin film and is determined by a Tensiometer. Kinematic viscosity is an indication of the fluid’s ability to lubricate, and is measured by using a Kinematic viscometer. The flash point indicates the temperature at which the fluid can ignite, and is determined by a Flashpoint tester. The cutting power is a measure of the cutting performance of the fluid, and is determined by a cutting-force tester.
In addition to performance testing, the selection of the right type of cutting fluids is also important. Generally, water-soluble cutting fluids are divided into two main categories: oil-free and oil-in-water emulsions. The selection of the right type of cutting fluid depends on the operations to be performed, the materials being machined, and the machine tool specifications. For example, oil-free cutting fluids are ideal for materials with low heat sensitivity, while oil-in-water emulsions are used for materials with higher heat sensitivity.
In conclusion, the selection and performance of water-soluble cutting fluids play a major role in cutting processes, and are an important factor to consider when working with modern tools and materials. The components selected for a cutting fluid, as well as the performance parameters, are the key elements to consider when choosing the best cutting fluid for a given application. Thus, a comprehensive understanding of the components, selection criteria, and performance evaluation is essential for successful machining operations.
