A New Cross Wedge Rolling Process for Producing Rail Axles

Rail axles are large-size parts produced in large batches. Currently, these parts are produced by metal forming techniques such as rotary forging, open die forging with hydraulic presses and open die hammer forging (minimum ram weight: 3 Mg). Nevertheless, not only are the above methods far from being efficient, they also lack accuracy (open die forging). As a result, new techniques for producing rail axles are constantly developed. One of such alternative techniques is based on the use of cross wedge rolling (CWR), which is the subject of the present study. An innovative roll design for producing rail axles by CWR is proposed. The rolls are provided with three pairs of wedge tools that act simultaneously on the workpiece and form the part in one revolution of the rolls, i.e., during 20 s. The numerical modelling of a CWR process with the proposed roll design reveals that the solution can be used to produce railway axles with the desired geometry. This technique, however, requires relatively high loads and torques. To decrease the force parameters, the forming process was modified and ran in two operations. The first operation consists in forming the central step of the workpiece while the other one involves the formation of steps on the ends of the workpiece. The results of the new simulation show a significant decrease in the loads and torques, which is caused, among others, by reducing the nominal diameter of the rolls from 1600 mm to 1200 mm. The numerical findings can be used to design a rolling mill for producing rail axles.