The Systematic Study On The Evaluation Technology Of Grinding Wheel For Rail Grinding

At present,the rail profile grinding owners used in our country should have GMC-96X rail grinder,GMC-96B rail grinder and CMC-20 turnout grinder.The grinding wheel end face is used for cutting,which has the advantages of high primary grinding quantity and high degree of automation.It has become an important means for railway departments to maintain the line.The grinding wheel for rail grinding car is the terminal component of grinding,but there is no special and reliable inspection method for a long time,which has become an important reason that restricts the technological progress of grinding wheel in China.The standard of grinding wheel for rail grinding car in China was formally promulgated and implemented at the end of 2014,and the testing work began in the past two years,and there is no domestic and foreign experience to be used for reference.In the process of initial detection,some test conditions and environmental factors that are not mentioned in some standards and have certain influence on the test results are found,so it is urgent to carry out systematic research and discussion..In this paper,the rail grinding simulation test-bed is used to study the problems and influencing factors found in the grinding wheel test process,and the evaluation indexes of grinding performance?grinding pressure,workpiece grinding quantity,grinding wheel wear,grinding ratio,workpiece and grinding wheel final temperature?under different test conditions are analyzed.The effects of grinding wheel wear,grinding ratio,final temperature of workpiece and grinding wheel are analyzed.The main work and conclusions can be summarized as follows:?1?The evaluation methods of grinding wheel used in rail grinding wheel at home and abroad are introduced and compared.The evaluation methods abroad are mainly EN 12413:2007+A1:2011 and ISO 525:2013.According to all grinding wheel types,the emphasis is placed on the requirements for classification and shape dimensions.In the two standards,the static balance,rotary strength and limit deviation are regulated,but the grinding performance is almost not required.The domestic standard is mainly enterprise standard Q/CR 1-2014.In this standard,the grinding wheel shape size,limit deviation,conventional performance?static balance and rotary strength?and grinding performance are stipulated,which are systematic and comprehensive.?2?The influence of workpiece initial height is studied.It is found that when the workpiece height is too high or too low will affect grinding performance parameters of grinding wheel to a certain extent.If the workpiece height is too high,the grinding quantity,grinding wheel wear and grinding ratio increase obviously because of the resonance of the workpiece,while the final temperature of the workpiece and the grinding wheel decreases slightly.If the workpiece height is too low,the loading system will be out of balance and the grinding head will vibrate,which will cause the workpiece grinding quantity and grinding wheel temperature rise to increase.The simulation results of the workpiece harmonic response verify this conjecture.The most reasonable test condition is that the starting height of the workpiece is in the range of50²10mm.?3?Under the condition that the initial height of the workpiece is 50²10mm,the influence of grinding power is studied.It is found that the grinding pressure increases rapidly when the actual grinding power increases from 20%to 30%of the motor power.When the interface temperature and contact stress of the friction pair are increased,the grinding quantity,grinding wheel wear and grinding ratio of the qualified grinding wheel increase steadily,and the final temperature of the workpiece and the grinding wheel increase slowly.However,the grinding quantity,grinding wheel wear and grinding ratio of the unqualified grinding wheel increase exponentially,and the final temperature of the workpiece and the grinding wheel decrease slightly.When the grinding power is 30%,the grinding performance of the grinding wheel can be distinguished well,while the unqualified grinding wheel does not meet the requirements of the heavy load grinding wheel.?4?The wear chips of qualified grinding wheel and unqualified grinding wheel are collected,and their composition,content,morphology,thermogravimetric,infrared and thermal ablation properties are comprehensively analyzed.The main composition of the wear debris is Fe and its oxides?Fe₃O₄ and FeO?.The higher the power,the higher the temperature rise of the workpiece,the less Fe content,and the more and wider the strip wear chips are.The shape of the unqualified grinding wheel is not uniform,but narrow and short.And the weight of the powder under heat loses as well.Therefore,the grinding process of the unqualified grinding wheel is unsTab.,the heat resistance of the grinding wheel is poor,and the grinding ability of the grinding grain is weak.