Cross wedge rolling is an effective process for producing shaft parts, but it will produce&nbsp; concave heart during the production process, resulting in waste of materials. The closed-open cross wedge rolling process is improved on the basis of the original cross wedge rolling technology, which can effectively inhibit the deformation of concave heart and greatly improve the utilization rate of materials. Experts have done a very complete study on the macroscopic aspects, but there is still a lack of research on micro-quality control.In order to improve the comprehensive mechanical properties of the rolled piece, it is necessary to obtain a finer and more uniform microstructure of the rolled piece in closed-open cross wedge rolling. In this paper, the microstructure has been obtained by exploring the evolution law of the internal microstructure under different process parameters. Firstly, an automobile oil pump axle made of 42Crmo is considered as a research object, and a 3D thermal-mechanical-microstructure coupled finite element model of closed-open cross wedge rolling is established by adopting software DEFORM. Secondly, three points are uniformly selected along the central axis of the rolled piece as observation points, and the variation law of the average grain size at different positions with time is studied. Thirdly, the effects of the reduction of area, the diameter of the rolled piece, the forming angle of the wedge section and the stretching section on the average grain size of the rolled piece and the uniformity of the grain distribution are studied separately.Finally, according to closed-open cross wedge rolling experiments, the average grain size and its distribution in the axial direction of the rolled piece under different process parameters were obtained.The simulation results show that the grain size refinement is the most obvious near 1/4 and 3/4 along the axis of the blank, on both sides of the two positions, the grain size gradually increases, especially in the direction of the axle end.&nbsp;In addition, the average grain size decreases with increasing the reduction of area ψ, and the more uniform of the average grain size. The average grain size increases with increasing the diameter of the rolled piece D, but the less uniform of the average grain size will become. As forming angles of the wedge section θ1 and the widening section θ3 increases, the variations of average grain size and the uniformity of the average grain size are not obvious.&nbsp;In summary, the blank diameter D has the greatest influence on the average grain size and microstructure uniformity, reduction of area ψ is the second, and wedge section wedge angle θ1 and stretching stage wedge angle θ3 have less influence on them.&nbsp;Combined with the closed-open cross wedge rolling experiment, the variations of average grain size in the experiment are consistent with the simulation results, which verifies the reliability of the model.

Effect of Process Parameters on the Microstructure of Closed-Open Cross Wedge Rolling

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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