Research On Deep Hole Rolling Technology Of EA4T Hollow Axle

EA4T axle alloy steel is the most widely used material in EMU trains in China.In order to reduce the weight of axle,improve the strength and reduce the error rate of flaw detection,hollow structure is adopted.At present,the rolling processing of EA4 T hollow axle only stays in the rolling processing of the external surface,and the surface of the hollow inner hole has been treated by honing process.Honing process is to polish the surface of the inner hole by using the grinding strip,which can only reduce the surface roughness to a certain extent,but can not change the grain distribution under the surface,and the friction of the grinding strip Relatively large,it will scratch the surface of the inner hole,which will increase the miscalculation of the subsequent ultrasonic flaw detection work,and the key point is that the honing efficiency is too low.In this paper,the deep hole surface rolling of EA4 T axle is analyzed and studied.Firstly,the finishing mechanism of rolling is studied theoretically,that is,the elastic-plastic deformation of rough peak,the surface finishing effect and rolling pressure,residual stress and plastic strain.Then,the effect of rolling parameters on the surface roughness and surface hardness is analyzed by experiments,that is,the corresponding orthogonal array,measurement results and signal-to-noise ratio are obtained by Taguchi method.The optimal combination level of control factors was determined by means of mean value analysis.The relative importance of each control factor is understood by variance analysis.It is found that the roll feed and roll speed have significant effect on reducing the surface roughness,and the contribution rate is(40.13%)and(31.49%)respectively,while the roll pressure and roll times have the least effect on the surface roughness.Rolling times and rolling pressure play an important role in maximizing hardness.The contribution rate is(48.95%)and(19.80%),respectively.On the contrary,the impact of rolling speed and feed rate on hardness is relatively small.Finally,ABAQUS finite element analysis software is used to set the steps ofrolling process,and the rolling parameters combination with the best roughness is selected to analyze the three stages of plastic deformation in the rolling process,as well as the impact on the equivalent residual stress and equivalent plastic strain.The simulation results show that the equivalent residual stress is 1.58 times of the yield strength under the optimal combination of parameters.The relationship between the rolling amount and the equivalent plastic strain depth is discussed.Finally,the range of the best rolling amount is i=(0.17%-0.34%).