Roundness error analysis of 25CrMo4 thick-walled hollow shaft by cross wedge rolling
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摘要: 機械結構輕量化的主要途徑是在結構上采用空心軸.近年來, 采用楔橫軋帶芯棒軋制空心軸類件的工藝得到了較廣泛的關注.厚壁空心軸類件在楔橫軋軋制過程中易發生“失圓”現象.本文通過熱壓縮實驗研究了25CrMo4合金鋼在楔橫軋變形條件下熱變形行為, 獲得其真應力-應變曲線.在此基礎上, 基于Deform-3D有限元軟件, 建立25CrMo4厚壁空心軸楔橫軋有限元仿真模型, 分析厚壁空心軸楔橫軋成形機理, 研究得出斷面收縮率、成形角、展寬角對軋件不圓度的影響規律: 斷面收縮率增大, 不圓度減小; 成形角增大不圓度減小, 軋制溫度越高減小趨勢越明顯; 展寬角增大不圓度增大, 提高軋制溫度抑制增大趨勢.選取部分工藝參數進行楔橫軋驗證實驗, 對比了有限元仿真結果和實驗結果, 表明有限元仿真模型預測精度較高.Abstract: 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.
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Key words:
- 25CrMo4 /
- thick-walled hollow shaft /
- cross-wedge rolling /
- numerical simulation /
- roundness error
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圖 1 熱壓縮實驗流程與試樣. (a) 實驗流程; (b) 試樣尺寸(單位: mm); (c) 熱壓縮后試樣
Figure 1. Procedure and specimen of hot compression test: (a) test program; (b) dimension of a specimen (unit: mm); (c) specimens by hot com-pression
圖 2 25CrMo4鋼真應力-應變曲線. (a) 應變速率1 s-1; (b) 應變速率10 s-1
Figure 2. True stress-strain curves of 25CrMo4 steel: (a) strain rate 1 s-1; (b) strain rate 10 s-1
圖 4 厚壁空心軸楔橫軋有限元仿真模型
Figure 4. Finite element simulation model of cross wedge rolling for thick-walled hollow axle
圖 5 厚壁空心軸楔橫軋成形過程
Figure 5. Forming procedure of cross wedge rolling for thick-walled hollow axle
圖 6 成形過程應變分布. (a) 楔入段; (b) 展寬段; (c) 精整段
Figure 6. Effective strain distribution during the formation process: (a) knifing zone; (b) stretching zone; (c) sizing zone
圖 7 成形過程應力分布. (a) 楔入段; (b) 展寬段; (c) 精整段
Figure 7. Effective stress distribution during the formation process: (a) knifing zone; (b) stretching zone; (c) sizing zone
圖 8 軋件軋前(a) 和軋后(b) 追蹤點分布
Figure 8. Distribution of trace points on workpiece: (a) before rolling; (b) after rolling
圖 9 軋件追蹤點徑向(a) 和軸向(b) 位移
Figure 9. Radial (a) and axial displacement (b) of trace points on workpiece
圖 10 斷面收縮率對不圓度的影響. (a) 影響規律曲線; (b) 特定工況軋件的不圓度對比
Figure 10. Effect of the reduction of section area on roundness error: (a) curve of influence rule; (b) roundness error at different parameters
圖 11 成形角對不圓度的影響. (a) 影響規律曲線; (b) 特定工況軋件的不圓度對比
Figure 11. Effect of forming angle on roundness error: (a) curve of influence rule; (b) roundness error at different parameters
圖 12 展寬角對不圓度的影響. (a) 影響規律曲線; (b) 特定工況軋件的不圓度對比
Figure 12. Effect of stretch angle on roundness error: (a) curves of influence rule; (b) roundness error at different parameters
圖 14 驗證實驗獲得的軋件. (a) 部分軋件; (b) 軋件縱向剖開視圖
Figure 14. Workpieces obtained from the rolling experiment: (a) part of workpieces; (b) vertical dissection of a workpiece
表 1 軋制驗證實驗工藝參數
Table 1. Process parameters of the verification rolling experiment
成形角，
α/(°)展寬角，
β/(°)斷面收縮率，
ψ/%軋制溫度，
T/℃50，60 3，4 35，50，65 1050，1100 
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中文字幕在线观看表 2 最大尺寸Dmax和不圓度e實驗值與仿真值對比
Table 2. Comparison of the Dmaxand e values obtained by experiment and simulation
工況 α/
(°)β/
(°)Ψ/
%T/
℃最大尺寸，Dmax/mm 不圓度，e/mm 實驗值 仿真值 相對誤差/% 實驗值 仿真值 相對誤差/% 1 50 3 35 1050 44.13 44.28 0.34 2.63 2.78 5.7 2 50 3 35 1100 43.19 42.77 0.97 1.69 1.27 24.9 3 60 3 35 1050 43.41 43.13 0.64 1.91 1.63 14.7 4 60 3 35 1100 43.20 42.60 1.39 1.70 1.10 35.3 5 50 4 35 1050 45.52 45.60 0.18 4.02 4.10 2.0 6 50 4 35 1100 43.70 43.88 0.41 2.20 2.38 8.2 7 50 4 50 1050 36.75 36.53 0.60 0.11 0.10 9.1 8 50 4 50 1100 36.61 36.52 0.25 0.11 0.08 27.3 9 50 4 65 1050 31.70 31.52 0.57 0.10 0.05 50.0 10 50 4 65 1100 31.60 31.52 0.25 0.05 0.05 0
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