A study of the optimum process parameters for Radial Forging of DIN21 CrMoV 511 alloy steel tubes

[[abstract]]本文在探討DIN21鉻鉬釩511合金鋼管徑向鍛造成形後鍛件直度品質的最佳化參數，實驗的方式是以兩種不同調質的胚料進行鍛製，在徑向鍛造機上設定轉速、進給率、兩頂間力、彈簧桿數等四個製程參數及水準，並配合田口實驗法之 直交表配置9種組合進行實驗。實驗獲得的數據應用田口博士的累積分析法加以分析。結果顯示硬度較均勻的第一組胚料獲得合格品的機率為96.30﹪，高於第二組胚料的74.07﹪。接下來利用Omega﹙Ω﹚轉換公式來預測最佳組合，結果第一組胚料可達100%的合格品，第二組胚料最多達94.90%。除此之外，胚料硬度均勻性對於實驗的結果及最佳組合有明顯的影響。硬度均勻性好的胚料，徑向鍛造後的直度品質變異小，只要找出製程參數最佳組合，即可大幅降低廢品率；若使用不穩定的胚料進行鍛造，即使製程參數組合已達「最佳組合」，仍無法獲得好的直度品質。[[abstract]]The purpose of this paper is to find the optimum process parameters for straightness of the DIN21 CrMoV 511 alloy steel tubes after radial forging. Two kinds of tubes, Group A&B, with different hardness were forged. Taguchi’s accumulation analysis method are employed in this study. An orthogonal array allocating four control factors such as rotation、feedrate、axial force、springs are applied in this experiment . The probability of eligible forged tubes for Group A is 96.30﹪,and 74.07% for Group B. Finally, Oemga（Ω）transfer method is applied to reach an optimal solution. The results shows that the probability of eligible forged tubes for Group A raise from 96.30﹪to 100﹪,and from 74.07﹪to 94.90﹪for Group B. Besides,the homogeneity of the hardness of tube has the evident effect on the experiment’s results and the optimum solution. The tube of homogeneous hardness has small variation on the quality of straightness after radial forging. The ineligible group can be great reduced as long as the optimum parameters combination are found. But if that of inhomogenous hardness is used, the good straightness can not be obtained even though using the optimum parameters combination