Study On Action Mechanism And Experiment With Water Vapor As Coolants And Lubricants In Green Cutting

Cutting fluid is usually used to reduce cutting force, lower cutting temperature, extend tool life and enhance machining efficiency and surface finish quality during machining. In general, the better the performance of cutting fluid, the more pollutant it is to environment, the higher its cost is enpended. With environment protection awareness enhanced and laws enforced, the negative influence that the cutting fluid application brought has become a great barrier for mechanical industry development. Green cutting has become focus of attention in manufacture field in the 21th century. The investigation of pollution-free and eco-friendly green cutting technique has been predominant emphasis in each country. Because water vapor is cheap, pollution-free, eco-frindly and no recovery, the cutting technoloy that water vapor is used as coolants and lubricants is a new green cutting technique. According above, we issued a study on action mechanism and experiment with water vapor as coolant and lubricant in green cutting, which is a frontier project in the world. Some researching results of theory significance and application value have been drawn. Firstly, through experiment of transparent acryl glass material cutted, the fact of capillary existence is proved. The necessary condition that cutting fluid has effective lubricating action is that the cutting fluid penetration capillary time is less than capillary life time. The Langmiuer single molecular physical absorption theory is used to discuss the effect that cutting fluid physical properties influence on boundary lubrication layer forming. The friction force model of tool-chip contact is proposed, and the friction force is reduced by the penetration porformence enhanced and the shear strength of boundary lubrication layer lowered with cutting fluid application. Secondly, the investigation of action mechanism is researched with water vapor as coolants and lubricants. Water vapor fills up capillary in cutting zone with gaesous state because of canceling infiltration and evaporation explosion of liquid phese, and water vapor penetrates capillary time less than liquid phase cutting fluids. As water molecular and oxygen atoms will gentrate absorption and chemical reaction that water vapor forms boundary lubrication layer in capillary because of severe tool-chip contact friction mechanical action and clear metal surface catalysis. Water and oxygen will react to metal surface to genetrate metal oxidation, and meatl oxidation can weaken the interactivity between tool bulk material and chip. Water vapor jet flow has high force-convection heat transfer coefficient and directly reduces cutting temperature, and water vapor has direct cooling action, the stress and length of tool-chip interface are reduced by water vapor lubricating action, and the cutting thermal is decreased, and water vapor has indirect cooling action. Under the conditions of indirect and direct cooling action, the cutting temperature is reduced obviously. Thirdly, the vapor generator and vapor feeding system developed, and the research on experiment with water vapor as coolant and lubricant is taken as important problem to research. With water vapor as coolants and lubricants, the main cutting force is reduced respectively by about 25~30%, 15~20% and 10~15% as compared with dry cutting,compressed air and oil water emulsion; the friction coefficient, the deformation coefficient and surface roughness value are decreased. The influence laws are found that water vapor jet flow parameters influence on main cutting force, chip deformation and metamorphic zone thickness of finished surface. With orthogonal test, the optimization parameters of water vapor jet flow are obtained for main cutting force reduced or cutting temperature lowered. So that it provides fundamental theory for green cutting technoloy application of water vapor as coolant and lubricant. Lastly, the tool wear configuration and influence laws are researched with water vapor as coolants and lubricants. It is obtained that the cutter wear is reduced about 50~75 percent than dry cutting. Through rake face SEM pictures and EDS analyzed, the reason is investigated that tool wear is reduced with water vapor as coolant and lubricant. It is discussed that carbon dioxide gas and oxygen gas influence on water vapor lubricating action, and carbon dioxide gas can enhance water vapor lubricating action at higher cutting speed, and carbon dioxide gas has few effect on water vapor at lower cutting speed. Oxygen gas will lower water vapor lubricating action, which gives evidence that oxidation wear is increased because of oxygen quantity higher.