Temperature Field Calculation And Hardening Feature Prediction Of Grinding Ball In Different Quenching Conditions

In this paper， the heat transfer equation of grinding ball and jominy quenchingsamples has carried on the finite difference respectively in spherical coordinates andcylindrical coordinate system.In combination with grinding ball and jominy end boundarycondition in quenching process，we make a list of difference scheme by using the principleof conservation of energy and finite volume method. On this basis，temperature fieldcalculation programs of the grinding balls and jominy sample quenching process werecompiled by using Matlab software.The influence on temperature field of diameter ofgrinding ball and quenching temperature in quenching process were calculated，at the sametime，we have calculated the temperature field of grinding ball air cooling after watercooling for a short time and completed end quenching temperature field calculation injominy test.In the same the material and the austenitizing temperature condtion，accordingto the law of the same cooling rate corresponding to the same quenching hardness，weestablished relationship of hardness distribution of grinding ball with end quenching test.Through calculating the average cooling rate of grinding ball， we have predicted thethickness of the grinding ball hardening layer, test has been verificated.The results shows that the grinding ball water cooling in different time，temperature ofsurface rise，it confirmed the validity of the calculation of temperature field in grinding ballquenching process.The data of quenching test is consistent with700℃instantaneous coolingspeed data in documents，it confirmed that the calculation method and the selection ofvarious parameters are in accordance with practical parameter. Along with increasing ofquenching temperature， the influence of quenching temperature on the cooling rate ofgrinding ball surface is small.However，the cooling rate of position inside of grinding ballincrease.Improving the quenching intensity can increase the cooling rate of grinding ball surface，however，it make little effect on the cooling speed of position inside of the grindingball.Diameter of grinding ball have a significant influence on distribution of cooling rate，along with the increase of grinding ball diameter，the position inside of the grinding ballcooling rate reduced significantly.According to distribution of the the cooling rate ofgrinding ball and the martensite transformation critical cooling rate calculation，we canpredict the thickness of hardening layer，the results is corresponded with the test results aswell.This research on technology of the grinding ball water cooling for short time and aircooling，the surface temperature can be calculated after grinding ball is out of the water backto rise，it makes cooling rate in range of martensite transformation temperature slowed downto lower the tendency to cracking.