AZ91D壓鑄鎂合金之熱間鍛造性及手機外殼混合成形之應用研究

Study on the Hot Forgability for AZ91D Magnesium Die Casting Alloy and Hybrid Forming Process for Shell Frame of Cellular Phone

林文樹(w.s.Lin) ； 黃文星(w.S.Huang) ； 吳春甫(Chuen-Fuu Wu)

《鍛造》 11卷3期 (2002/10) Pp. 4-22

https://doi.org/10.29791/Forging.200210.0002

摘要

本研究主要探討AZ91D壓鑄鎂合金在壓鑄薄片狀態下，其熱間鍛造性質。並由鍛造性研究過程中所獲得鍛造參數，利用DEFORM鍛造模擬軟體，來模擬手機外殼完成鍛胚(Finisher)的最佳預成形壓鑄件外殼外形及厚度。最後依模擬結果得預成形壓鑄胚料，實際進行壓鑄模及熱間鍛造模之設計製作及實際壓鑄鍛造實驗，結果由完成鍛件表面觀之，證實AZ91D壓鑄薄板件在熱間300°C~400°C鍛造流動性很好。
AZ9AD壓鑄鎂合金熱間鍛造性研究方面為：
在0.3m/s、0.5m/s、0.7m/s等不同壓鑄、速度條件下，AZ91D不同階梯厚度之壓鑄試片各不同厚度(15mm、10mm、5mm)部位之總平均密度隨壓鑄試片厚度增加而降低，而不同厚度之孔隙率則隨壓鑄試片厚度增加而增加。不同階梯厚度之壓鑄試片，於不同壓鑄速度下，相同厚度之密度變化隨壓鑄速度增加而增加。利用650T肘節壓床鍛造，鍛模預熱溫度200°C情況下，鎂合金壓鑄試片加熱到300°C再進行鍛造，可以大幅增加壓縮率，其最大壓縮率可達60%以上，而其密度亦可達到1.81g/cm3之理論密度。
手機外殼鍛件之預成形壓鑄胚模擬方面為：
利用300°C鍛造下，由不同厚度(15mm、10mm、5mm)之密度與壓縮率趨勢，並利用外插法，可求得2mm(外插)，1.2mm(外插)之壓縮率與密度之關係值，由此值以做為DEFORM模擬時所需的下料尺寸厚度之參數。由成形品之實體圖形，經橫斷面之體積分配，預估預成形品之形狀設計，而由此預成形品設計可經由DEFORM模擬最佳狀況並做局部修正，最後可得到鍛造成形件之壓鑄預成形鑄件，此即為鍛造之預成形鑄胚。
手機外殼之壓鑄鍛造實體成形試驗方面為：
預成形鑄胚密度為1.778g/cm3，先披覆一層水性石墨，胚料之爐體加熱溫度400°C，保溫約20分，利用1600T之曲柄式鍛造壓床(Crank Press)進行手機外殼鍛造，上/下模溫度控約(200°C~300°C)及成形負荷約為700噸左右，完成鍛件毛胚密度為1.8079g/cm3，其外觀表面甚光滑且平坦。

並列摘要

This study aims to investigate the hot forging behaviors of the slabs AZ91D magnesium alloy, fabricated by die casting process. Through forging package DEFORM, the parameters obtained from this experiment are used to simulate the shell frame and thickness of optimum die casting in the shell frame of cellular phone after the completion of finisher. To verify the results got from simulation, the solid hybrid die casting (performer part of shell frame) and hot die forging (finisher part of shell frame) process are proceeded. The finisher surface roughness for the shell frame of cellular phone shows much better than fabricated by die casting method.
The Hot Forging Behaviors For The AZ91D Die Cast Magnesium Alloy:
Three kinds of thickness are manufactured by hot chamber die cast method and are used as blanking of hot upsetting test. When the material AZ9lD is at the different die casting velocities (0.3m/s, 0.5m/s, 0.7m/s), the average density for the stepped thickness of test pieces (l5mm, l0mm, 5mm) decreases along with the increase of thickness. It means the porosity percentage for die casting increases along with the increase of thickness for the same stepped test piece at the same die casting velocity. It also shows that the same thickness for the different stepped thickness test pieces, the density increases as soon as the die cast velocity increases. In the experiment of hot upsetting behaviors for the hybrid die cast and forging process, the forging machine capacity used in this test is 650T knuckle joint press. When the forging temperature is up to 300°C, the forge ability increases rapidly, meanwhile the density can be 1.8lg/cm3, the theoretical density of AZ9ID, upon hot upsetting ratio reaching 60%.
The Simulation On The Die Cast Rougher For The Finisher in the Forging Shell Frame Of Cellular Phone:
Under the condition of hot die forging temperature at 300°C, the relationship between density and hot upsetting ratio for the initial thickness (2mm, 1.2mm) of pre former can be obtained by the extrapolation method through the trend between density and hot upsetting ratio at different thickness (l5mm, l0mm, 5mm). The relationship can be used as parameters of blanking material thickness required by DEFORM simulation. The profile of the performer can be estimated from the volume distribution of the cross section of the forging finisher. The best performer design for forging finisher can be obtained by means of the simulation and modifying the parameter data. Experiment On The Shell Frame Of Cellular Phone Manufactured By The Hybrid Die Cast And Hot Die Forging:
In the hybrid die casting and hot die forging processes, the performer density is measured at 1.778g/cm3, the performer is lubricated with aqueous graphite solution and the heating temperature of furnace and heating time is set at 400°C for 20minutes, the forging on shell frame of cellular phone is conducted by 1600T crank press. Besides the forging die temperature for the upper die / lower die is preheating about 200°C / 300°C, while the forging load required is measured about 700T by load cell. The density of finished shell frame is 1.8079g/cm3 with smooth and flat surface. In addition, the cavity filling is much better than that formed by hot chamber die casting method.