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In metal cutting, the cutting is performed on the fresh surface every time, the speed varies from a few millimeters to hundreds of meters per minute, and the pressure is as high as 2 to 3 GPa.
In addition to friction during cutting, there is also intramolecular friction between the tool and the cut metal. The interface temperature of the cutting zone can reach 600-800℃. Such high temperature and high pressure will reduce the strength and hardness of the tool, so the cutting oil must have the four functions of cooling, lubrication, cleaning and rust prevention.
1. Cooling is
manifested in reducing the temperature of the tool tip, inhibiting the thermal expansion of the material to be cut and the tool, so as to improve the operating performance and machining accuracy. The thermal conductivity and specific heat capacity of water are both larger than that of oil, and its viscosity is also lower than that of oil, so the cooling performance of the emulsion is far better than that of oil.
2. Lubrication
reduces the friction between the rake face and the chip, the flank face and the machined surface, prevents adhesion, buildup, scales or cold welding, so as to reduce power consumption and tool wear, and obtain a better surface finish.
3. Anti-rust In
order to prevent the water and oxygen in the atmosphere from rusting the newly processed surface, an anti-rust agent should be added to the cutting oil to improve the anti-rust performance of the cutting oil to meet the needs of short-term protection of the workpiece during the processing.
4. Cleaning
uses liquid flow to wash away fine chips and powders to prevent sticking, so as to ensure continuous processing of tools and workpieces. In the grinding process, cutting oil with poor cleaning properties can cause blockage of the grinding wheel, increase the temperature in the grinding area and burn the workpiece. The use of low-viscosity oil and the addition of surfactants can improve the cleanability of cutting.
In addition to the above properties, the cutting fluid should also have the stability of the emulsion during processing, no delamination, resistance to hard water and anti-bacterial contamination and deterioration.