| The rapid increase of the operating speed of the EMU puts high demands on the safe operation of the railway,and also makes the quality requirements of the key components of the locomotive such as axles higher and higher.Among them,improving the forging quality of axles has become the main goal of domestic axle manufacturers.EA4T steel for axles has excellent toughness and is one of the main materials for manufacturing axles.In this paper,the EA4T steel axle is studied,and the high temperature rheological behavior of EA4T axle steel is studied.Based on this,the microstructure evolution model is constructed and coupled into the finite element software.Subsequently,the macro-micro integration simulation of the axle forging process is carried out to guide the forging process design of the axle.The main results of this paper are as follows:(1)The Hansel-Spittel model,Arrhenius model and coupled strain Arrhenius model of high temperature deformation of EA4T steel for axles were constructed.The Gleeble single pass thermal compression experiment with T=900°C?1200°C and??=0.1s-1?20s-1 was completed.The predicted values and experimental values of the three constitutive equations were compared.It was found that the coupled strain Arrhenius model predicts the stress-strain relationship of the entire deformation process more accurately and can characterize the stress drop caused by dynamic recrystallization softening.(2)Construction of a grain growth model.According to the characteristics of long-term high-temperature heating of the axle before hot forging,the grain growth law of EA4T steel at different temperatures and different holding time was studied,and the grain growth model of the steel was established,which provides a reference for the development of a reasonable heating process(3)Based on the single and double pass hot compression experiments,the effects of different deformation parameters on the recrystallization softening of EA4T steel were studied,and a mathematical model reflecting the softening characteristics of EA4T steel was established.Axle forging is a multi-pass,multi-step hot forging.During the forming process,the material will undergo varieties of softening behaviors,including dynamic recrystallization softening behavior,meta-dynamic recrystallization and static recrystallization softening occurring during the interval.(4)Carry out macro and micro integration simulation of EA4T steel hot forging.The established rheological model,recrystallization model and grain growth model are combined with the user subroutine and EA4T steel material file,and implanted into the finite element software to realize the macro-micro integrated simulation of the axle forging process.(5)A process design flow for fast forging forming of a certain type of axle was established.The relationship between the radius of the circular anvil and the reduction of chamfering and the constraint of the rotation angle and step of the billet during forging are studied,which can be used to determine the geometry of the circular anvil and the process parameters of each forging step.In this way,the dimensional accuracy of the axle during the forging process can be ensured,and the forging quality can be improved. |
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