Research On Residual Stress In Grinding Surface Of Gear Material(20CrMnTi)

Carbon steel material 20CrMnTi,which has a good performance and mainly used in gear,shaft,piston parts and automobile parts,aircraft and various special parts.However,the material in the processing and use of process often produces cracks and premature failure.Research shows that the reason of inner crack and premature failure is high residual tensile stress on the surface.To explore the relation between 20CrMnTi residual stress and the grinding parameters and do some research on how to reduce the residual stress of the material,this article based on grinding experiment,pulse electric processing experiment and thermoelectric complex legal experiment,carried out a series of 20CrMnTi material research,the main contents are as follows:(1)Introduce the choice of experimental parameters,analyzes the different grinding depth and table speed of grinding forces and grinding temperature,combined with the microstructure,hardness and residual stress measurement analysis,the grinding workpiece burn even crack condition.(2)Research the influence of the different electric pulse parameters on residual stress,and poor by orthogonal experiments and analysis,the influence of residual stress pulse current parameters are analyzed in weight.(3)Propose a method to reduce the residual stress-thermoelectric complex legal,through the analysis of the feasibility of theory,formulates the thermoelectric compound experiment scheme,and through the thermoelectric compound experiment verifies the correctness of the method.The results show that:(1)With the increase of grinding wheel table speed and grinding depth,grinding force and grinding temperature has emerged as a rising trend;Grinding burn the workpiece surface hardness value is higher than normal grinding workpiece hardness with surface microstructure changing and the emergence of secondary quenching martensite;With the increase of grinding depth,the workpiece surface compressive stress gradually transform into tensile stress.(2)With the increase of pulse frequency,the residual stress first decreased and then increased;with the increase of the number of pulse intervals,the residual stress decreased first and then gradually stabilized;With the pulse duty cycle increases,reducing the residual stress the greater the degree;pulse processing time increases,the greater the degree of reducing the residual stress,arrived at a certain time limit,the residual stress becomes stable;the residual stress tends to be stable;With the increase of pulse current density,the greater the extent of residual stress reduction.(3)Weight analysis results show that:in addition to the current density,the most important factor which influences residual stress is the pulse frequency,after pulse frequency pulse are the pulse duty cycle and processing time,the processing interval number has the minimal influence on residual stress.(4)The experiment of reducing residual stress through thermoelectric composite method shows that:a single short heat treatment does not change the basic distribution of surface residual stress,a single electrical treatment on the surface residual stress has a reduced role,on the basis of the treatment,the thermoelectric composite processing has a further effect of reducing the residual stress of the workpiece surface.