Experiment Investigation On The Lubrication Performance And Grinding Maching Performance Of Cryogenic Nanofluid

Grinding process can obtain better surface accuracy and improve surface quality,which is an indispensable finishing process.However,because of the contact between the abrasive particles of the grinding wheel and the workpiece,abrasive machining is implemented based on negative rake angle,so its grinding temperature and grinding force are greater than other machining techniques.Now pouring lubricating and cooling method is widely used to solve the problem of grinding heat and grinding force in grinding process,whose property is yet not prominent in the high speed and high load machining.And a large number of grinding fluid will cause environmental pollution and increase processing costs.Therefore,the green grinding method is proposed.Dry grinding and low temperature cold air minimum quantity lubrication technology can meet the requirements of environmental protection,but its lubricating and cooling performance is unsatisfactory and it is difficult to obtain better surface quality.Micro jet lubrication technology of low temperature cold air nanoparticles was presented,which combinesd the characteristics of low temperature cold air and nano particle jet lubrication technology.With the addition of nano particles in cryogenic grinding fluid,the heat transfer performance of grinding fluid was improved and grinding temperature in grinding zone was reduced.Moreover,the lubrication performance of grinding fluid was further enhanced due to the physical properties of nano particles and the decrease of grinding temperature.The major content of this dissertation can be concluded as follows:1.Two-steps Method was adopted.The nano molybdenum disulfide particles were added to the low temperature grinding fluid with vegetalitas.After standing for a long time,the height of the gradient layer at the top of the fluid was measured to evaluate the suspension stability of nanofluids with different nanoparticle mass fraction.2.The wet reciprocating friction and wear tests were implemented based on the hardened bearing steel GCr15 by using 8 kinds of low temperature nanofluids with different mass fraction.The lubrication performance of the low temperature nanofluids with different mass fraction was characterized by measuring the friction coefficient in the process of friction and wear,the wear morphology of the grooves and the size of the grinding ball,and the optimum mass fraction of lubrication performance was obtained.3.The grinding experiments of the hardened bearing steel were carried out based on four different grinding conditions of the dry grinding,the pouring grinding,the low temperature cold air micro lubrication grinding and the low temperature cold air nano particle jet micro lubrication grinding.The adaptability of different lubrication cooling modes under different grinding parameters was evaluated based on the analysis of the normal grinding force,specific grinding energy and grinding temperature under different grinding parameters.A better grinding parameter was obtained for micro jet lubrication technology of low temperature cold air nanoparticles.From the results of friction and wear test and the grinding of hardened bearing steel,the Cryogenic nanofluids jet minimum lubrication technology can effectively reduce the grinding force and grinding temperature in the grinding process as well as improve surface quality.Especially under the condition of high speed and heavy load,its superior cooling and lubricating performance is more prominent.