Please use this identifier to cite or link to this item:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/79121
Title: | 硝酸鋁前處理對凝膠溶膠鈍化鍍鋅鋼板高溫氧化行為之影響 The Influence of Aluminum Nitrate Pre-Treatment on High Temperature Oxidation Resistance of Dip-Coated Silica Coating on Galvanized Steel |
Authors: | Tzu-Chin Yang 楊子勤 |
Advisor: | 林招松 |
Keyword: | 熱衝壓,熱浸鍍鋅,矽烷化合物,凝膠-溶膠,前處理, Press hardening steel,Galvanized steel,Silane,Sol-Gel,Pre-treatment, |
Publication Year : | 2018 |
Degree: | 碩士 |
Abstract: | 熱浸鍍鋅鋼板利用表面鍍鋅層,提供鋼材障蔽保護及犧牲陽極保護的效果,為目前鋼鐵材料常見之表面處理。而在熱衝壓製程應用中,於沃斯田體化處理時,熱浸鍍鋅鋼板面臨嚴重的液態鋅脆化及高溫氧化問題,大幅限制其在熱衝壓製程之應用。
本研究將商用熱浸鍍鋅鋼板以硝酸鋁水溶液進行前處理,利用GPTMS及TEOS作為前驅物,化合成凝膠溶膠矽烷化合物,再以沉浸塗佈法進行鈍化處理,提供其一層具有良好抗高溫氧化能力的二氧化矽鈍化皮膜。探討硝酸鋁前處理以及矽烷鈍化處理對於熱浸鍍鋅鋼板抗高溫氧化之效果、構築矽烷鈍化皮膜表面裂紋以及氧化物生成機制並討論其對於後續磷酸鹽處理之影響。 首先,針對硝酸鋁前處理,由AES實驗結果及SEM橫截面影像可以得知,硝酸鋁前處理具有表面均質化及氧化層增厚之效果,並且會在表面生成一層氧化鋁。而另一方面,接觸角量測結果顯示前處理對於鍍鋅鋼板表面氫氧鍵數目並沒有明顯的影響。 針對皮膜抗高溫氧化的部分,SEM表面形貌以及XRD繞射分析結果顯示矽烷鈍化皮膜可以有效抑制高溫氧化行為並保留較多鐵鋅介金屬相於合金層中。而SEM橫截面以及TGA熱重分析結果則是證明AlS皮膜具有最佳的抗高溫氧化效果。此外,由化學剝除法以及ICP成分分析結果可以得知,硝酸鋁前處理對於金屬鋅的保留有明顯助益。 本研究也對AlS鈍化皮膜表面裂紋及氧化物生成機制進行討論。在沃斯田體化處理一開始升溫到500至600℃時,由於金屬液化進而導致矽烷皮膜破裂,而在表面裂紋處會有氧化鋁層生成,該氧化鋁層可以防止底材更進一步的氧化。在後續升溫至900℃的過程中,氧化鋁層受到應力作用而在表面生成特殊成長方向的氧化物。此外,表面裂紋以及矽烷皮膜交界處會提供快速擴散路徑,後續氧化行為會傾向在該區發生。而矽烷皮膜披覆處在表面以及皮膜內部都可以觀測到氧化物顆粒,代表該區域仍有氧化行為發生。最後,磷酸鹽處理後的SEM表面形貌顯示氧化鋁以及二氧化矽皮膜會阻礙磷化反應進行,故磷酸鋅會傾向從表面氧化物顆粒的邊緣開始成長。 Hot-dip galvanizing is one of the common methods for anti-corrosion treatments on steels nowadays. However, liquid metal induced embrittlement and high temperature oxidation occur during the austenitization treatment of hot-dip galvanized press hardening steel. The present study focused on the effect of aluminum nitrate pre-treatment on the properties of the subsequent silica coating formed via sol-gel route. The high temperature oxidation resistance was evaluated using the thermal gravimetric analysis and the microstructural evolution was followed during austenitization. Besides, chemical stripping analysis and ICP were applied to estimate the amount of residual Zn in the intermetallic layer. Experimental results showed that silica coating with pre-treatment had better high temperature oxidation resistance and retained more Zn. The Auger spectroscopy analysis further revealed that the surface of hot-dip Zn coating became chemically homogeneous after the aluminum nitrate pre-treatment, signifying the necessity of a homogeneous aluminum hydroxide surface layer to enhance the adhesion and oxidation resistance of the silica coating on hot-dip galvanized steel during austenitization. In the end, the mechanism of oxidation and crack formation about AlS coating has been built. In addition, the influence of silica coating and surface oxide on subsequent phosphate treatment has been discussed. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/79121 |
DOI: | 10.6342/NTU201802740 |
Fulltext Rights: | 有償授權 |
Appears in Collections: | 材料科學與工程學系 |
Files in This Item:
File | Size | Format | |
---|---|---|---|
ntu-107-R05527054-1.pdf Restricted Access | 6.77 MB | Adobe PDF |
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.