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研究生: 周于賢
論文名稱: SUS444不銹鋼薄板應用CO2雷射之銲接性質研究
A Study on the Weldability of SUS444 Stainless Steel thin plate by CO2 Laser Welding
指導教授: 程金保
Cheng, Chin-Pao
學位類別: 碩士
Master
系所名稱: 工業教育學系
Department of Industrial Education
論文出版年: 2010
畢業學年度: 98
語文別: 中文
論文頁數: 77
中文關鍵詞: 柱狀晶結構
論文種類: 學術論文
相關次數: 點閱:164下載:3
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  • 肥粒鐵系不銹鋼具有優異抗高溫氯氣氧化腐蝕性能,近年來常被運在太陽能熱水器面板、熱水槽、水管管路等。本研究針對SUS 444肥粒鐵系不銹鋼薄板施以CO2雷射銲接,利用改變不同銲接走速,探討不同入熱量對SUS 444不銹鋼銲件微觀組織及機械性質之影響。經雷射銲接之試片銲道以XRD分析及顯微鏡觀察組織變化,再分別進行拉伸測試、硬度測試與拉伸破斷面型態觀察,最後再探討銲接試片銲道附近析出物變化情況,與電化學測試做比較,以瞭解材料之抗腐蝕性變化。研究結果發現SUS 444不銹鋼在母材與銲接後之銲道皆為單相肥粒鐵相組織,利用CO2雷射銲接後,若銲接走速越慢,入熱量較高,則在銲道區域會形成粗大柱狀晶結構,導致機械性質較差。隨銲接走速提昇,銲道柱狀晶有細化現象,銲道硬度值越高,延伸率與拉伸強度亦有增加趨勢。此外,銲接走速降低也會影響銲件熱影響區析出物的型態,導致含鈮析出物團聚在晶界附近,降低材料的抗腐蝕性。

    Ferritic stainless steels have recently been received increasing interest for application in the solar water heater panels and hot-water tank, due to the low thermal expansion coefficient, excellent resistance to high-temperature oxidation, and stress corrosion cracking. The objective of this study is to demonstrate the feasibility of CO2 laser welding for joining of SUS 444 ferritic stainless steel by different welding speeds. Microstructures and precipitations of the welds will be examined using optical microscopy (OM) and scanning electron microscopy (SEM). This experiment performs micro-hardness measurement in accordance with welding areas after CO2 laser welding. Moreover, the specimens have been cut vertical to weld pass after welding and then perform tensile test using universal material testing machine in order to explore the joining quality of welding joints. At the same time, SEM has been used to observe the fractured surface of the tensile testing specimens. Finally, electrochemistry experiments were performed in an aqueous solution of 3% NaCl to explore the Pitting corrosion resistance of the welds. The experimental results have found that microstructure of 444 stainless steel welds is completely ferrite single-phase structure, including base metal and welding path. However, the welding fusion zones present coarse columnar structure when the specimens have lower welding speed, which will result in the mechanical properties degradation of weldments. With the increase of welding speed, the solidification zones have fine columnar structure and the weldments show higher microhardness in the welding fusion zone. At the same time, the tensile strength and elongation have been promoted, and the fracture site appears in the base metal. Furthermore, the lower welding speed will result in the aggregation of Nb-contained precipitations in the grain boundaries of heat-affected zone, which will bring the pitting corrosion resistance degradation of weldments.

    目錄 中文摘要……………………………………………………………. I Abstract………………………………............................................... II 目錄…………………………………………………………………. III 表目錄………………………………………………………………. VI 圖目錄………………………………………………………………. VII 第一章 前言………………………………………………………. 1 1.1 研究背景……………………………………………………….. 1 1.2 研究動機與目的……………………………………………….. 2 第二章 文獻探討………………………………………………….. 4 2.1雷射與雷射銲接介紹…………………………………………… 4 2.1.1 雷射器的基本構造………………………………………… 4 2.1.2 雷射光的特性……………………………………………… 4 2.1.3 二氧化碳雷射銲接………………………………………… 8 2.1.4 雷射銲接參數設定………………………………………… 10 2.2 肥粒鐵不銹鋼介紹……………………………………………... 13 2.2.1 鋼鐵物理與機械冶晶學…………………………………… 13 2.2.2 肥粒鐵脆性現象…………………………………………… 15 2.3 肥粒鐵不銹鋼銲接性…………………………………………... 21 2.4 腐蝕與電化學腐蝕……………………………………………... 22 2.4.1 電化學腐蝕原理…………………………………………… 23 2.4.2 鈍化與鈍化膜特性與理論………………………………… 25 2.4.3 元素Cr、Mo 對孔蝕的影響……………………………… 26 第三章 研究設計與實施…………………………………………. 27 3.1 實驗流程設計…………………………………………………... 27 3.2 實驗前置作業…………………………………………………... 29 3.2.1 實驗材料…………………………………………………… 29 3.2.2 銲接方式…………………………………………………… 30 3.3 銲接製程參數設計……………………………………………... 32 3.4 金相顯微組織觀察……………………………………………... 33 3.5 微硬度試驗……………………………………………............... 34 3.6 拉伸試驗………………………………………………………... 35 3.7 SEM顯微觀察及EDS分析……………………………………. 38 3.8 X光繞射分析(XRD)…………………………………………… 39 3.9 恆電位儀實驗…………………………………………………... 40 第四章 實驗結果與討論…………………………………………. 42 4.1 銲接製程參數對SUS444不銹鋼銲道外觀形貌影響………… 42 4.2 顯微組織觀察………………………………………………....... 44 4.3 微硬度試驗…………………………………………………....... 46 4.3.1 硬度分析…………………………………………………… 54 4.3.2 銲接製程對銲道微硬度之影響…………………………… 55 4.4 微拉伸試驗……………………………………………………... 49 4.4.1 抗拉強度分析……………………………………………… 49 4.4.2 拉伸破斷位置分析………………………………………… 51 4.5 觀察與EDS分析……………………………………………. 52 4.5.1 破斷面顯微組織觀察……………………………………… 52 4.5.2母材與不同銲接走速銲件析出物情況……………………. 54 4.5.3析出物成份分析……………………………………………. 63 4.6 X光繞射分析(XRD)……………………………………………. 66 4.7 孔蝕電位實驗………………………………………………....... 67 4.7.1 不同銲接走速孔蝕電化比較……………………………… 77 第五章 結果與建議……………………………………………….. 69 5.1 結論……………………………………………………………... 69 5.2 建議……………………………………………………………... 70 參考文獻…………………………………………………………….. 71 表目錄 表2-1 雷射四種特殊性質之應用…………………………………....... 7 表2-2 鐵鉻合金添加物對475℃脆性影響……………………………. 16 表2-3 成份與微結構對高溫脆化的影響…………………………....... 19 表3-1 SUS 444不銹鋼化學成分表…………………………………… 29 表3-2 LBW銲接製程參數設定………………………………………. 32 表3-3 X-Ray繞射分析試驗條件……………………………………… 39 表4-1 SUS 444不銹鋼母材未經銲接析出物半定量分析…………… 64 表4-2 SUS 444不銹鋼母材銲接過後析出物半定量分析…………… 65 圖目錄 圖2-1 雷射器的基本結構示意圖【16】……………………………… 4 圖2-2 譜線寬度【17】………………………………………………… 6 圖2-3 雷射加工製程之功率密度與作用時間關係圖【25】………… 8 圖2-4 鑰孔(Keyhole)示意圖【25】…………………………………… 9 圖2-5 雷射光在鑰孔(Keyhole)內發生連續多重反射【26】………… 9 圖2-6 銲接不同厚度之低碳鋼的雷射功率與走速的關係【27】…… 11 圖2-7 雷射銲接之銲道橫截面【27】………………………………… 11 圖2-8 電漿雲暮之生成過程示意圖【32】…………………………… 12 圖2-9 Fe-Cr-C三相平衡圖【33】……………………………………. 14 圖2-10 退火409不銹鋼板材金相組織【34】…………………………. 14 圖2-11 430熱滾壓鋼板金相組織【34】……………………………… 15 圖2-12 鉻含量與時間對Sigma phase形成相對關係圖【38】……… 17 圖2-13 不同氮與碳含量對材料韌性的影響【40】…………………… 18 圖2-14 Type436冷加工破裂於HAZ【40】…………………………… 19 圖2-15 Type436冷加工破裂破斷面SEM觀察……………………… 20 圖2-16 一些商業用鋼利用Varestraint test 銲接凝固裂縫敏感度【44】………………………………………………………… 22 圖2-17 孔洞在鹽水中自行催化原理【52】…………………………… 24 圖2-18 金屬從活性到鈍化的曲線轉變【54】………………………… 25 圖3-1 論文架構圖…………………………………………………… 28 圖3-2 SUS 444不銹鋼對接銲示意圖……………………………….. 30 圖3-3 LBW銲接製程示意圖………………………………………... 31 圖3-4 Future-Tech FM-700型微硬度試驗機……………………….. 34 圖3-5 CHMER CW640S1 CNC線切割放電加工機……………….. 35 圖3-6 萬能材料試驗機MODEL:UH-1系列………………………... 36 圖3-7 試片規格取樣位置…………………………………………… 36 圖3-8 CNC線切割加工拉伸試片實體圗…………………………... 37 圖3-9 JEOL JSM6360電子顯微鏡………………………………….. 38 圖3-10 X-Ray繞射儀…………………………………………………. 39 圖3-11 三電極體系恆電位儀………………………………………… 41 圖3-12 電化學試片採樣位置…………………………………………. 41 圖4-1 銲接走速600 mm/min銲件與銲接走速2000 mm/min銲件外觀圖………………………………………………………… 43 圖4-2 未銲母材與不同銲接走速銲件金相圖……………………… 45 圖4-3 SUS 444不銹鋼微硬度之取樣示意………………………….. 46 圖4-4 微硬度量測示意圖…………………………………………… 46 圖4-5 母材硬度分佈曲線圖………………………………………… 48 圖4-6 三種銲接走速銲件之銲道附近硬度值分布………………… 48 圖4-7 不同銲接走速銲件之拉伸強度比較………………………… 50 圖4-8 不同銲接走速銲件之伸長率比較…………………………… 50 圖4-9 不同銲接走速銲件破斷位置…………………………………. 51 圖4-10 不同銲接走速銲件之拉伸破斷面顯微組織………………… 53 圖4-11 SUS444不銹鋼母材未經銲接析出物情況………………….. 56 圖4-12 SUS444不銹鋼經銲接走速1500mm/min銲後析出物分佈情況………………………………………………………………. 57 圖4-13 SUS444不銹鋼經銲接走速800mm/min銲後析出物分佈情況………………………………………………………………. 59 圖4-14 SUS444不銹鋼經銲接走速600mm/min銲後析出物分佈情況………………………………………………………………. 61 圖4-15 SUS444不銹鋼母材未經銲接析出物半定性分析…………... 64 圖4-16 SUS444不銹鋼母材經銲接過後析出物半定性分析………... 65 圖4-17 SUS444不銹鋼基材與不同銲接走速之XRD分析………… 66 圖4-18 母材與不同銲接走速極化曲線圖……………………………. 68 圖4-19 母材與不同銲接走速Pitting曲線圖………………………… 68

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