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標題: | 熱浸鍍鋅鋼板鐵鋁障蔽層微結構分析 Microstructural Characterization of Fe-Al Inhibition Layer in Hot-Dip Galvanized Sheet Steel |
作者: | Chih-Kai Chen 陳志凱 |
指導教授: | 林招松 |
關鍵字: | 鐵鋁障蔽層,鐵鋅合金相,熱浸鍍鋅,開路電位,化學腐蝕, Fe-Al inhibition layer,Fe-Zn intermetallics,hot-dip galvanized,open circuit potential,chemically color etched, |
出版年 : | 2008 |
學位: | 碩士 |
摘要: | 熱浸純鋅和鐵鋅合金鋼板因具有優異抗蝕性,廣泛應用於汽車車體和相關零組件,熱浸純鋅鋼板同時大量應用於建築、家電與五金工業。在最佳化熱浸鍍鋅製程開發時,必須同時建立有效且快速鑑定熱浸純鋅鍍層微結構的方法。
本研究即在建立一有效熱浸鋅鍍層微結構分析技術,藉以探討鋅浴鋁含量與溫度、鋼板入溫、熱浸時間對熱浸鋅鋼板界面微結構的影響。實驗結果顯示,在化學腐蝕後橫截面OM試片能觀察到Fe-Zn合金相,由鍍鋅層往內依序為ζ相和δ相,受限於解析力,OM下並無法觀察到Γ和Fe-Al相。然而,藉由橫截面TEM以及擇區電子繞射和低掠角XRD分析證實單一Fe2Al5相存在鋼板和純鋅之間,同時TEM/EDAX分析顯示在界面處鋁含量較高,Fe2Al5的形貌有顆粒狀和層狀兩種形式。另外,開路電位作為一個快速分析鐵鋁層是否存在的方法,除此之外,從開路電位曲線也可了解整個腐蝕過程並非均勻。另外,利用開路電位方法將熱浸鍍鋅上的各層用4% 鹽酸剝離後,可用SEM觀察其表面形貌和對各鍍層做低掠角XRD分析。 綜合以上實驗結果,在低鋅浴鋁含量下(0.12wt%),當鋅浴溫度、鋼帶入溫和熱浸時間三者值愈大,Fe-Al相轉換成Fe-Zn相程度愈大。在中、高鋅浴鋁含量 (0.16wt%、0.20wt%),Fe-Al障蔽層尚未合金化成Fe-Zn相下,鋅浴溫度或鋼帶入溫愈高,界面Fe-Al障蔽層厚度愈厚。 Hot-dip galvanized and galvanealed steel sheets have excellent corrosion resistance, and can be found in body panels and related components in the automobile industry. Large amounts of hot-dip galvanized steel plates are also used in structure, home appliances, and tool applications. To optimize the hot-hot dip galvanize process, it is essential to develop a quick and effective microstructural evaluation method. In this study, an effective technique to determine the effect of aluminum content in the zinc bath, bath temperature, strip entry temperature, and dip-time on the interface microstructure has been established. Results showed that Fe-Zn intermetallic compound can be observed in chemically color etched cross-sectional OM samples: ζ and δ were observed from the zinc coating towards the steel substrate. However, Γ and Fe-Al phases were not observed under OM due to its limited resolving power. In contrast, via cross-sectional TEM, selected area diffraction, EDAX, and GA-XRD analyses, higher aluminum content can be found at the zinc-steel interface in the form of granular and lamellar Fe2Al5 intermetallics. Also, open circuit potential can be a time-saving technique to analyze the presence of Fe-Al phase. Furthermore, the non-uniform corrosion behavior can be observed in the open circuit potential curve. Selective layer on the coating can be removed while performing open circuit potential in 4wt% HCl to observe each layer morphology and crystallinity in SEM and GA-XRD. In summary, when bath temperature, strip entry temperature, and hot-dip time increase, the extent of transformation from Fe-Al to Fe-Zn phases increases, in low aluminum content zinc bath (0.12 wt%). In mid-to-high aluminum content zinc bath (0.16 wt%, 0.20 wt%), in the condition that Fe-Al inhibition layer have not transformed to Fe-Zn intermetallics, the higher the bath or strip entry temperature, the higher thickness in the Fe-Al inhibition layer. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/26691 |
全文授權: | 未授權 |
顯示於系所單位: | 材料科學與工程學系 |
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