Roundness error analysis of 25CrMo4 thick-walled hollow shaft by cross wedge rolling

It is important for mechanical structures to be lightweight, and this is mainly realized by using hollow parts in structures. Presently, hollow shaft parts are used in vehicles, machine tools, and other equipment. Traditional hollow shaft parts are mainly manufactured by cutting, die forging, which have low production efficiency and low material utilization. With the increasing demand for hollow shafts, it is necessary to replace traditional processes with an efficient and advanced technology. Cross wedge rolling (CWR) has been widely used to produce shafts because of its advantages of higher productivity, better product quality, and lower material and energy consumption. Manufacturing of hollow shafts using cross wedge rolling with mandrel has received much attention. Phenomenon of roundness error often occurs in the formation of thick-walled hollow shafts using cross wedge rolling. Hot compression tests were conducted to investigate hot deformation behavior of alloy steel 25 CrMo4 in cross wedge rolling forming conditions, and true stress-strain curves were obtained. Based on the results, a finite element (FE) simulation model of cross wedge rolling for thick-walled hollow shafts was established using Deform-3 D, and formation mechanism and effects of area reduction, forming angle, and stretch angle on roundness error were analyzed. The simulation results indicate that the greater the area reduction, the smaller the roundness error; the greater the forming angle, the smaller the roundness error (where decrease in roundness error is facilitated by increasing rolling temperature); and the greater the stretch angle, the greater the roundness error (which is restrained by increasing the rolling temperature).Some process parameters were investigated by verifying the cross wedge rolling experiment, and the experimental results and simulation results were compared. The results show that the prediction accuracy of the FE model is high.