The cutting fluid sprayed by the micro-lubrication system mainly plays two roles in metal cutting, one is lubrication; the other is cooling. Whether the cutting fluid can fully exert its effective lubrication effect, its penetration ability is an important factor. The penetration of conventional pouring cutting fluid in cutting processing is carried out in two ways: liquid penetration and gas penetration: the penetration efficiency of the poured liquid is lower, and the efficiency is even lower during high-speed cutting. The gas penetration is due to the pouring in the cracks on the surface of the chip. The liquid vaporizes as the cutting temperature rises and penetrates into the rake face. Tests have shown that the penetration ability of conventional cutting fluids is not strong, and the amount of liquid that can be vaporized is very small, which limits the lubrication effect. The two-phase fluid composed of zero-jet cooling can compensate for the lack of cutting fluid penetration ability. When the gas-liquid two-phase fluid is sprayed into the cutting zone, it has a higher speed and greater kinetic energy, so it has a stronger penetration ability. In addition, the size of the trace liquid in the gas-liquid two-phase jet is very small, and it is easy to vaporize when encountering metal with higher temperature, and can penetrate into the rake surface of the tool from many aspects. Although the amount of liquid in the jet is very small, the vaporized part is more than when the cutting fluid is poured continuously, so the lubrication effect is better. In metal processing, cutting heat mainly comes from the plastic deformation of the metal. The cooling process in the cutting zone is the heat transfer process between the solid and the fluid. Because of the attraction between fluid and solid molecules and the viscosity of the fluid, there is a fluid stagnant layer on the surface of the solid, which increases the thermal resistance. The thicker the stagnant layer, the greater the thermal resistance, and the thickness of the stagnant layer mainly depends on the fluidity of the fluid, that is, the viscosity. The cooling effect of fluids with low viscosity is better than that of fluids with high viscosity. The dynamic viscosity of the gas-liquid two-phase fluid can be expressed by the following formula: =f-(uf-g)x where uf is the dynamic viscosity of the fluid, 4g is the dynamic viscosity of the gas, x is the mass coefficient, x=Wf/WfWg( W is the liquid phase mass flow rate, Wg is the gas phase mass flow rate). Obviously, u<uf in the formula, that is, the viscosity u of the gas-liquid two-phase mixed fluid is always smaller than the viscosity of the single-phase liquid, that is, the cooling effect of spray cooling is better than that of single-phase cutting fluid. When the gas-liquid two-phase fluid is ejected, the volume suddenly expands and performs external work, dissipating internal energy and lowering the temperature by about 10°C. The two-phase fluid in spray-zero cooling has a higher velocity, which can wash away the iron eyebrows in time and take away a large amount of heat, further enhancing the cooling effect. Therefore, spray cooling actually combines the cooling effects and advantages of both gas and liquid fluids.