A new process for forging shafts with convex dies. Research into the stressed state

A new manufacturing approach has been developed, which applies energy-saving processes for forging parts from ingots with convex dies without the need for upsetting the ingots. A new forging process provides a complete closing of an ingot’s axial defects. It has been established that an increase in convex die wedge angle and an increase in the degree of reduction result in the linear growth of (a) the level of compressive stress and (b) the intensity of the axial defect closure. The rounding of a “four-beam” workpiece with concave cross-section using flat dies leads to a decrease in deformation force by a factor of 1.5–3.0 times in comparison with rounding using cut dies. The effective geometric shapes of die tooling and efficient process parameters have been determined. The convex die angle has to be in the range of 160–170°. The depth of the concavity faces has to be on the order of 25 %. The tool for rounding has to be in the shape of flat dies. The method of workpiece positioning in the dies has to be “edgeways.” A new process for forging large shafts with a 2000-mm diameter using convex dies without an upsetting operation has been proposed, reported, verified, and industrially implemented. Industrial implementation of this new technology resulted in an increase in forging process productivity of 15–20 % and a decrease in heating number from 8 to 6 during the forging of large parts. Research results in the form of process and design recommendations have been successfully validated and implemented at a metal forming industrial workplace.