複雜中空截面鋁擠型成形模擬分析與表面條紋缺陷研究

Abstract

隨著全球暖化效應的加劇，輕量化技術成為減少碳排放的重要途徑之一。鋁合金因其重量輕、強度高、延展性好、耐腐蝕性優異、導熱性和導電性良好及易於加工的特性，廣泛應用於多個領域。然而，鋁合金材料在生產擠型材的過程中經常發生條紋缺陷，這是目前業界難以控制的問題之一。 本論文旨在建立複雜中空截面鋁擠型模具的擠製模擬模型，透過電腦模擬分析擠製過程中型材的受力情況與溫度分布，並結合材料分析性質實驗，探討型材表面出現條紋缺陷的可能因素。本研究使用DEFORM-3D 有限元素分析軟體對鋁合金擠製成形製程進行分析，觀察擠製過程中擠型如何產生表面條紋缺陷，並依據材料實驗發現的現象，找出擠製成形中的可能導致條紋發生之關鍵因素。 在模擬模型建立方面，經過測試發現，採用雙曲線正弦函數方程式來建立材料卡，並選擇絕對網格做為生成網格的設定，更適用於擠製成形的模擬分析，能使模擬時間更高效且結果更準確。 分析結果顯示，模擬結果與實際成形過程中的擠壓負荷、型材料頭的成形趨勢，以及焊合線位置幾乎相符，證明 DEFORM-3D 在預測型材變形方面具有一定的可信度且分析數值具有一定的準確性。 在材料分析實驗方面，透過電子背向散射繞射技術(EBSD)分析發現，沒有條紋缺陷位置的低角度晶界 (2°~10°) 比例較高且晶粒方位具有極強的方向性；經由粗糙度實驗測試發現，在條紋缺陷處使用較高目數砂紙再次研磨微量深度可以消除條紋缺陷；而在硬度檢測顯示，正常區域的硬度明顯高於有條紋缺陷的區域。 在模型分析方面，在型材肉厚變化區存在較高溫現象，推論條紋可能與 Mg2Si 析出相顆粒尺寸較大有關，而肋骨區的條紋可能與表面受力情況有關。本論文透過製程參數調整與模具設計修改，發現型材在擠製過程中之等效應力與溫度呈現規律性的變化，當盛錠筒溫度較低時，型材於出口端溫度分布較為平均，能使肉厚變化區條紋較高溫的現象獲得改善。 本研究有助於改善產品外觀，提高生產效率，降低成本，同時提升產品品質，研究成果兼具學術研究與產業應用的價值。

As the effects of global warming intensify, lightweight has become an important approach to reducing carbon emissions. Aluminum alloys, due to their lightweight, high strength, good ductility, excellent corrosion resistance, good thermal and electrical conductivity, and ease of processing, are widely used in various fields. However, aluminum alloy materials often encounter streak defects during the production of extruded profiles, which is currently one of the most uncontrollable issues in the industry. This thesis aims to establish a finite element simulation model for the extrusion process with complex-shaped hollow cross-section aluminum extrusion dies. Through simulation, the study analyzes the stress conditions and temperature distribution during the extrusion process and, combined with material analysis experiments, investigates the possible factors causing surface streak defects on the profiles. This research employs DEFORM-3D finite element analysis software to analyze the aluminum alloy extrusion process, observing how streak defects are formed on the surface during extrusion, and identifying key factors that may lead to the occurrence of streaks based on the phenomena observed in material properties experiments. In the finite element model development, testing has shown that using a hyperbolic sine function equation to create material lists and selecting an absolute mesh for mesh generation is more suitable for extrusion simulation. This approach makes the simulation results more efficient and accurate. The analysis results show that the simulation results closely match the actual forming process in terms of extrusion load, the forming trend of the profile head, and the location of weld lines. This proves that DEFORM-3D has a certain degree of reliability in predicting profile deformation and the numerical accuracy of its analyses. In terms of material properties experiments, Electron Back Scatter Diffraction (EBSD) analysis reveals that the proportion of small-angle grain boundaries (2°~10°) is higher and the grain orientation is strongly directional in areas without streak defects. Roughness tests indicate that re-grinding with higher grit sandpaper at the streak defect locations can eliminate the defects. Hardness tests show that the hardness of normal areas is significantly higher than that of areas with streak defects. As to model analysis, it is observed that the high-temperature phenomenon in the thickness variation zone of the profile might be related to the larger particle size of the Mg2Si precipitates, while the streaks in the rib area might be related to the surface stress conditions. This thesis, through process parameter adjustments and die design modifications, found that the equivalent stress and temperature of the profile show regular changes during the extrusion process. When the container temperature is lower, the temperature distribution at the profile exit becomes more uniform, which helps to improve streaks caused by high-temperature in the thickness variation zone. This research helps to improve product appearance, increase production efficiency, reduce costs, and enhance product quality, providing both academic research contribution and industrial application value.