鎂合金等邊L形型材與圓管擠型之製程分析

Analysis of Extrusion Processes of Magnesium-Alloy L-shaped Products and Circular Tubes

張兆志(Chao-Chih Chang)

指導教授 ： 陳復國

國立臺灣大學/工學院/機械工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.02842

摘要

鎂合金由於具有密度低、比強度高之特點，目前因輕量化方面之運用而快速成長。本論文利用有限元素分析軟體DEFORM研究鎂合金L形型材與無縫圓管之擠製製程。針對L形型材擠製製程研究方面，一般在生產L形實心產品時，有些製程是運用口袋模具(Pocket die)進行生產，而擠製出的產品常常會有彎曲的情形，因此首先針對L形型材之變形機制進行模擬研究，由模擬結果發現型材變形主要是因材料流速不均所造成，導致型材有彎曲之情形發生。接著再針對可能影響材料流動模式之各項參數(孔穴位置、初始溫度、擠壓速度、定剪摩擦因子、口袋角度)進行分析後，可知口袋角度(Pocket angle) 之影響甚鉅。
針對最佳化模具設計研究方面，利用不同口袋角度具有對型材彎曲程度有不同影響的特性，循序漸進地規劃一系列口袋角度組合之模具設計進行模擬研究，成功地改善型材彎曲的情形。最後針對最佳化模具設計進行實際擠製驗證工作，擠製出來之型材變形狀況、擠製噸數及出口溫度與模擬結果趨勢相近，故可暸解DEFORM對於鎂合金L形型材擠製製程之模擬具有相當高的準確性。
針對無縫圓管擠製製程研究方面，探討各製程參數(初始溫度、擠壓速度、定剪摩擦因子、口袋角度)對擠製壓力及出口溫度的影響，以暸解圓管擠製的製程特性，並建立一套防止擠製鎂合金時會燃燒之對策，而本論文之研究成果可供鎂合金擠製成形業者進行製程規劃以及模具設計時的參考。

關鍵字

AZ31鎂合金 ； 擠製 ； 有限元素法 ； 圓管 ； L形型材 ； 口袋模具 ； 彎曲變形

並列摘要

The superior properties of magnesium-alloy draw attention from the light-trend industry recently. In this thesis, the finite element code, DEFORM, is employed to simulate the extrusion processes of L-shape solid profile and hollow tubes of AZ31 magnesium-alloy. The extrusion of L-shape solid profiles was examined first and the pocket die design was applied to the extrusion study. In the extrusion of the L-shape solid profiles, the unbalanced material flow that causes the extruded part being curved usually occurs. The finite element simulation results show that the unbalanced material flow is affected by the process parameters such as the location of L-shape profile, initial temperature, extrusion speed, friction factor (m), and pocket angle. And the pocket angle is found to be the major process parameter that causes the unbalanced material flow. The finite element analysis was performed to examine the effect of pocket angle on the material flow in details and an optimum pocket die design that renders a straight extruded part was determined. The actual extrusion experiments were conducted to validate the finite element analysis and the good agreement between the experimental data and the simulation results confirm the validity of the finite element analysis on the pocket die design.
The extrusion of seamless AZ31 magnesium-alloy circular tubes was also studied in the present study with the use of the finite element analysis. The effects of the process parameters such as initial extrusion temperature, extrusion speed, and m value on the formability of the extruded circular tube were examined. The limited values of the process parameters that yield a temperature at the exit far below the ignition point of the magnesium-alloy were determined. The proposed design values for the process parameters could be used as design guidelines for the extrusion of AZ31 magnesium-alloy circular tubes.

並列關鍵字

AZ31 magnesium-alloy ； extrusion ； L-shape ； circular tube ； pocket die ； process parameters ； finite element analysis ； experimental validation

參考文獻

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