A356.0二次鋁合金之除鐵製程開發

Process Development for Iron Reduction in A356.0 Secondary Aluminum Alloy

盧柏佑(Po-Yu Lu) ； 陳貞光(Jhewn-Kuang Chen) ； 吳孟諺(Meng-Yan Wu) ； 陳嘉仁(Chia-Jen Chen) ； 唐乃光(Nai-Kuang Tang)

《鑄造工程學刊》 45卷2期 (2019/06) Pp. 19-26

摘要

為了減少A356.0二次鋁料中的雜質鐵含量，本研究利用初晶富鐵金屬間化合物（或稱污泥相）在液相鋁中晶出及沉降，並以傾鑄分離方式來分離富鐵金屬間化合物與二次鋁湯。本研究首先透過熱力學計算不同元素添加對液相鋁成分之影響，再由凝固曲線分析金屬間化合物的生成溫度，計算沉降速度來設計沉降實驗參數。結果顯示，添加錳及鉻元素最能有效與鐵元素形成污泥相，同時將熔體保持620°C一小時後可顯著沉降分離污泥相。隨著錳及鉻元素在不同添加比例，其污泥相成分包括Al（FeMn）Si、Al（FeCr）Si及Al（FeMnCr）Si；在相同的添加量時，錳元素傾向提高污泥相尺寸，而鉻元素有細化及球化污泥相的效果。另一方面，添加鉻比錳元素能達到較高的除鐵率及較低的元素殘留率，但鉻含量添加過多反而會額外形成Al_(13)Cr_4Si_4相，若兩元素複合添加過高，則會在污泥相中心形成富錳鉻含量的初晶相，表示單獨添加鉻或是複合添加錳與鉻含量過多，皆對除鐵率的提升有限，造成添加效益的下降。根據本研究最佳化結果，其A356.0-0.84Fe二次鋁料複合添加錳及鉻元素各為1 wt.%時，再透過重力分離除鐵法可去除73.8%鐵含量使鐵元素降低到0.22 wt.%，而分離所得的淨化二次鋁則有77.3%的得料率。

關鍵字

A356.0鋁合金 ； 二次鋁 ； 重力分離除鐵法 ； 富鐵金屬間化合物 ； 污泥相

並列摘要

To reduce the iron content in A356.0 secondary aluminum alloy, the formation and sedimentation of proeutectic Fe-rich intermetallic (so-called sludge) in liquid aluminum has been investigated. Effects of alloy addition were first investigated by thermodynamics to evaluate the phase constituents of aluminum melts. The sedimentation temperature and time was designed according to the solidification curves and settlement formula. Mn and Cr were added to the melts by 0 ~ 2 wt.% each before isothermally sedimenting at 620 °C for 1 hour. It is found that Fe-rich sludge can form Al(FeMn)Si, Al(FeCr)Si and Al(FeMnCr)Si compounds with varied Mn and Cr additions. Mn tends to increase the sludge particle size, and Cr addition has the effects of refining and spheroidizing the precipitates. The addition of Cr demonstrates higher iron removal capability and a lower element residual rate than Mn. When Cr is over-added, the Al_(13)Cr_4Si_4 phase forms without removing Fe. When both Mn and Cr additions are excessive, Mn- and Cr-containing segregation phases are formed at the center of the sludge phase. Therefore, excessive Mn and Cr cannot increase iron removal rate. For optimum iron removal conditions, 1 wt.% Mn and 1 wt.% Cr added melts can remove 73.8% of Fe from the A356.0-0.84Fe alloy and recover 77.3% secondary alloy by gravity separation method.

並列關鍵字

A356.0 alloy ； Secondary aluminum ； Gravity separation ； Fe-rich intermetallic compounds ； Sludge phase