Study On Microstructure Rule Of Hollow Railway Axle In Multi-wedge Synchrostep Cross Wedge Rolling

The multi-wedge cross wedge rolling (MCWR) is an advanced precise forming technology,which is a process of plastic deformed that multi-dies roll rolled part from radial direction and axialdirection at the same time. It has many advantages，such as significantly saving roll surface,reducing equipment weight, high production efficiency, saving material and reducing costs.Therefore, this process is suitable for specialization and economization rolling long shaft parts. Thehollow railway axle as a key components of the high-speed train, which is a large long axial partshas large axial and radial size, so multi-wedge synchrostep cross wedge rolling technology is thebest way in forming hollow railway axle. While the research on the cold rolling of irregular cross-section rings is still at an early stage. At present the study of multi-wedge cross wedge rolled solidparts and small radial size hollow parts is abundant, while about multi-wedge rolling large hollowshaft parts is in the infancy stage. Therefore, intensive study on forming hollow railway axle withmulti-wedge cross wedge has important theoretical significance and realistic value.The paper used the hollow railway alxe as the research object, does a detailed research intothe key technologies of multi-wedge cross wedge rolling and the microstructure rule of the hollowrailway axle used theory and numerical simulation. The rotated condition of multi-wedgesynchrostep rolling hollow parts were built on the basis of single-wedge forming solid parts; Withthe long shaft section of the hollow alxe as an example, through using single and two wedge rollingthis segment, analysing the ovality phenomenon appear on the cross-section of workpiece in therolling process, finding out the causes of ovality, and obtaining the influence rule of the broadeningangle to hollow parts. Through study the mold design of multi-wedge cross wedge rolling hollowaxle, win the calculation formula and selection principle of the basic technical parameters andinportant process parameters, and also set up the material mictroscopic organization model,obtained the finite element model of hot, force and microscopic with multi-wedge cross wedgerolling. Through the finite element simulation research on the hollow axle of multi-wedge crosswedge rolling, analysis the eauivalent strain rate and temperature change rule in the whole rollingprocess, that is provided theoretical for austenitic dynamic recrystallization behavior and grain sizedistribution. Then study on the initial temperature, forming angle and broadening angle to impact the average grain size influence law, to ensure the workpiece has even small grain size and goodmechanical properties, and also providing a theoretical basis for the optimization of parameters.The result of research on the microstructure rule of hollow railway alxe with multi-wedgecross wedge rolling have great scientific significance on enhancing product quality and productionefficiency, and improving theory of multi-wedge cross wedge rolling.