Tham khảo tài liệu 'lubricants and lubrication part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 438 14 Metalworking Fluids Solvent raffinates Hydrocracked stocks White oils Synthetic ester natural ester Polyalphaolefins Additives to improve wetting and flushing effect Anti mist additives Fig. Composition of neat metalworking oils. oils. The use of zinc- and other heavy metal-based additives in cutting oils is declining due to environmental and waste water considerations. Chlorinated paraffins are still used as universal EP agents throughout the world but combinations of sulfur additives and ester oils are being increasingly used in Germany and Western Europe as substitutes. The reasons for these developments are the considerably higher disposal costs for products containing chlorine in Germany Fig. . Significance of Viscosity on the Selection of Neat Products The viscosity of most metalworking oils is between 2 and 46 mm2 s-1 at 40 C. The very low viscosities are used for spark erosion applications EDM and for honing and super-finishing while the higher viscosities are mostly used for difficult machining work at low cutting speeds such as broaching and gear cutting. In general high cutting forces continuous chips and large chip cross-sections require higher viscosities. These higher viscosities also have a positive effect on the evaporation and misting behavior of the oils. However the disadvantages of higher viscosity oils are higher drag-out losses on chips and components and the resulting increased pollution of washing lines. For this reason the current trend is towards low viscosity products. The disadvantages of low viscosities . lower flashpoints as well as greater evaporation and misting can be compensated for by new hydrocracked base oils or ester oils. Small components also normally require low viscosities because thicker oils can cause parts to stick together and thus cause transport and positioning problems. Thick oil films can also interfere with monitoring of routine manufacturing tolerance and here again low .
