覆蓋劑對Al-7Si和A356合金品質之影響; Effect of fluxing treatment on the quality of Al-7Si and A356 alloys

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Title:	覆蓋劑對Al-7Si和A356合金品質之影響;Effect of fluxing treatment on the quality of Al-7Si and A356 alloys
Authors:	詹益鎮;Yi-Chen Tsan
Contributors:	機械工程研究所
Keywords:	石墨棒;除氣處理;覆蓋劑處理;冰晶石;微孔;介在物;fluxing treatment;micro bubble;pore;lance;degassing treatment;inclusion;cryolite
Date:	2004-07-06
Issue Date:	2009-09-21 11:45:55 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本研究以Al-7Si、A356.2含鍶或不含鍶合金為實驗材料，使用石墨除氣棒進行除氣，並選用KCl、NaCl (44%-56%)及Na3AlF6、KCl、NaCl (30%-35% -35%)兩種混合物做為鋁合金熔煉時的覆蓋劑。分別備製有無添加覆蓋劑施予除氣處理的鋁合金冷激片、減壓片、船型水平模試棒。將冷激片拋光處理後，調查除氣與兩種覆蓋劑製程處理對於不同成份鋁合金的冷激片中微孔(介在物)數量、尺寸分布及超音波振蕩處理後，霧化區(氧化膜)分布型態、面積率的影響。接著觀察減壓片孔洞型態並探討介在物與鑄件中氣孔形成的關聯。最後將船型水平模試棒車削成標準疲勞試棒以比較兩種覆蓋劑處理後對鋁合金疲勞性質的相關影響。實驗結果顯示： @覆蓋劑處理可以有效降低冷激片上霧化區(氧化膜)面積率，使用氯化物鹽類效用較佳，氟-氯化物鹽類使氧化膜更加碎裂，但霧化區(氧化膜)面積率的降低幅度較氯化物鹽類來的少。 @鋁液中的氣泡可能由介在物表面異質成核、成長，若介在物表面附著氣袋，或鋁湯中存有懸浮微氣泡，這些位置將更利於氣體分子擴散進入，進而成長。 @覆蓋劑處理與除氣處理會增加微孔(介在物)數量，而使用氟-氯化物覆蓋劑可明顯降低Al-7Si合金中微孔(介在物)尺寸。 @氟-氯化物覆蓋劑使用於含鎂的鋁液時，可能導入微氣泡於鋁湯中，劣化鑄件機械性質。 @疲勞壽命因使用覆蓋劑處理而降低，以使用氟-氯化物覆蓋劑疲勞性質最差，原因為鑄件中縮孔面積比例增加。 The alloys studied include Al-7Si alloys and A356.2 alloys with or without strontium. A lance type diffuser was used for degassing treatment. Two types of cover fluxes are used: (1) mixture of KCl and NaCl (44%-56%). (2) mixture of Na3AlF6, KCl and NaCl (30%-35%-35%). This study is aimed at investigating effect of fluxing treatment on the pore count and foggy mark area of chilled samples in different aluminum melts. The chilled samples and reduced pressure test samples were polished and observed to analysis pore counts and their shape along with distribution. Experimental results indicated that fluxing treatment resulted in increasing pore counts but decreasing pore size and foggy mark area. Fluorine added in the fluxes reacted with magnesium to get more micro bubbles. Micro bubble and inclusion attaching with air pocket suspend in the melt provide potential size for forming micro bubble traped in the samples and/or forming pores. All of these micro-bubble or pore (attaching air-pocket) deteriorated the quality of alloys and remarkably decreased their fatigue life.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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