大徑薄壁鎂合金管材之熱間擠製之研究

Study on Hot Extrusion of Large-diameter Magnesium Alloy Thin Tubes

黃永茂(Yeong-Maw Hwang) ； 許家銘(Chia-Ming Hsu) ； 許翼鵬(I-Peng Hsu)

《鍛造》 25卷4期 (2016/12) Pp. 15-24

摘要

鎂合金薄板因為具有高比強度，而被廣泛運用在各領域包含運輸業、電子業等。比起用壓延方式來製造鎂合金薄板，擠製方式會具有更好的成形性，一般寬的鎂合金薄板擠製需要使用大型擠製機台，為了降低擠製負載並且使用較小的擠製機，擴孔分流模的設計技術是必須的，先進行管材的擠製再展開為薄板的方式已成為趨勢。本文主旨為以熱間擠製方式製造大徑薄壁管。使用的擠錠材料為MB8鎂合金，並藉由壓縮試驗得到擠錠之塑流應力。文中將以有限元素模擬軟體DEFORM-3D分析擠製過程中，擠錠於模具內的塑性變形模式。擴孔分流模的設計技術將被運用其中，接著討論模具參數變化對於管材銲合壓力的影響為何，藉由田口法針對分流模進行最佳化，並檢驗其擠製負載與模具應力。鎂合金管的熱間實驗將會使用2,100噸的擠製機台配合所選用的7吋擠錠，實驗結果所得到的負載與產品尺寸將與模擬結果比較，以驗證模具設計技術與有限元素模型之適用性。

並列摘要

Thin magnesium alloy sheets are widely used in various fields such as transportation, electronics industries, etc., because of their high specific strength. Thin magnesium thin sheets made by extrusion processes have better formability compared with those made by rolling processes. Manufacturing of wide magnesium thin sheets by extrusion requires a large extrusion machine. To decrease the extrusion load and use a smaller extrusion machine, an extension port-hole die design technique is required. The thin extruded tubes are manufactured at first and then cut apart and expanded to wide sheets. In this study, large-diameter thin tubes are manufactured by hot extrusion processes. Magnesium alloy MB8 is used as the billet material. The flow stress of the billet is obtained by compression tests. A finite element simulation software DEFORM-3D is adopted to analyze the plastic deformation pattern of the billet inside the die during hot extrusion process of magnesium alloy tubes. An extension port-hoe die design technique is proposed. The effects of various die parameters on the welding pressure are discussed. Then the port-hole die can be optimized by using Taguchi method. Afterwards, extrusion load and die stress distributions will also be examined. Experiments of hot magnesium tube extrusion using a 2100-ton extrusion machine for 7-inch billets are conducted. Experimental results of extruded loads and product dimensions are compared with the simulation results to verify the validity of the finite element modelling and the die design technique proposed.