Analyzing the formation of oil mist in metal cutting fluids

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In metal processing operations such as turning, milling, drilling, and grinding, the use of metal cutting fluids results in the formation of a large number of oil mist particles in the air. This phenomenon has drawn widespread attention to air quality issues in workers’ breathing areas. Prolonged exposure to this oil mist is highly detrimental to workers’ health, and according to the National Institute for Occupational Safety and Health (NIOSH) in the United States, as many as 1.2 million workers are exposed to metal cutting fluid mist each year. Therefore, the study of phosphating solutions on the oil mist in metal cutting fluids is a highly significant topic. Mechanism of oil mist formation: To achieve effective lubrication, cooling, and cleaning, metal cutting fluids go through processes such as pump circulation, spraying of heat-darkening agents to deal with residual heat from steel, intense impact from high-speed rotating tools or workpieces, and high-temperature evaporation. This results in a very complex set of factors behind the formation of oil mist, with mechanical, physical, and chemical elements interacting with one another. However, not all factors have a decisive impact on the formation of oil mist. The generation of oil mist from metal cutting fluids during processing can be attributed mainly to two mechanisms: atomization and evaporation. Atomization is the process by which mechanical energy is converted into surface energy of liquid droplets; it occurs as a result of the intense impact of the liquid on the fixed and rotating components within the machine tool system, which breaks the liquid into small droplets that float in the working environment ； Evaporation occurs because a large amount of heat is generated in the cutting area; the blackening agent transfers this heat to the cutting fluid, raising its temperature well above the saturation point. Boiling then takes place at the solid-liquid interface, resulting in the production of steam. These vapors then condense around tiny droplets of air or other particles, forming an oil mist.