楔横轧成形25CrMo4厚壁空心轴件的不圆度分析

机械结构轻量化的主要途径是在结构上采用空心轴.近年来, 采用楔横轧带芯棒轧制空心轴类件的工艺得到了较广泛的关注.厚壁空心轴类件在楔横轧轧制过程中易发生“失圆”现象.本文通过热压缩实验研究了25CrMo4合金钢在楔横轧变形条件下热变形行为, 获得其真应力-应变曲线.在此基础上, 基于Deform-3D有限元软件, 建立25CrMo4厚壁空心轴楔横轧有限元仿真模型, 分析厚壁空心轴楔横轧成形机理, 研究得出断面收缩率、成形角、展宽角对轧件不圆度的影响规律: 断面收缩率增大, 不圆度减小; 成形角增大不圆度减小, 轧制温度越高减小趋势越明显; 展宽角增大不圆度增大, 提高轧制温度抑制增大趋势.选取部分工艺参数进行楔横轧验证实验, 对比了有限元仿真结果和实验结果, 表明有限元仿真模型预测精度较高. 

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.