A study on lubrication and cooling performance and machining characteristics of magnetic field–assisted minimum quantity lubrication using Fe₃O₄ nanofluid as cutting fluid

As an effective alternative to traditional pouring lubrication method, minimum quantity lubrication (MQL) has been recognized by more and more scholars and applied in factories. However, there are still some technical shortcomings in the application of traditional oil-based MQL technology, such as poor cooling capacity and low lubrication efficiency. Aiming at the technical defects of oil-based MQL, a magnetic field–assisted minimum quantity lubrication (mMQL) technology using Fe₃O₄ nanofluid as cutting fluid was proposed. First, MQL equipment with controllable magnetic field was built, and the contact angle, surface tension, and dynamic viscosity of Fe₃O₄ nanofluid droplets were measured under different magnetic induction intensities. Based on these variation parameters of physical properties of the magnetic nanofluid droplets, the influence of magnetic induction on the droplet penetrability was subsequently analyzed. Finally, the heat transfer performance and machining characteristics of the nanofluid droplets under different magnetic inductions were compared and investigated. Results showed that the Fe₃O₄ nanofluid droplets exhibited lower contact angle and higher viscosity under the influence of magnetic field, thus showing better penetrability and heat transfer performance. Compared with traditional vegetable oil MQL, the cutting temperature, tool wear, and cutting force under mMQL were reduced by ~ 35.5%, ~ 52.4%, and ~ 43.2%, respectively. Under the influence of magnetic field, the contact angle of magnetic droplets was decreased, and the contact area between the droplets and heat transfer surface was larger, which led to the improvement of droplet evaporation heat transfer efficiency. In addition, the penetrability of Fe₃O₄ nanofluid assisted by magnetic field was improved, more nanofluid could penetrate into the tool–chip contact area, and finally improved its lubrication and cooling efficiency.