臺灣博碩士論文加值系統

本研究使用兩種填料，如：T23與309L，分別將T91抗潛變合金與T23、304H進行異質鎢極氣體保護電極銲接製程。將通過非破壞性檢測的銲件，以線切割的方式取出適當尺寸的異質銲道，並進行後續熱處理。研究中主要探討鋼材在異質銲接時，在高溫長時間的負載下進行老化實驗，於異質銲道介面處發生碳遷移現象。異質銲道介面處為鉻濃度差異最為明顯之位置，使得不同活度的碳原子在高溫負載下往高合金端進行擴散，為使碳原子的溶解度達一平衡，低合金端的碳化物溶進基地中，造成脫碳區的生成。鑑定脫碳區的生成與否可藉光學顯微鏡與微硬度值的變化來進行驗證。
研究結果指出，在T23與T91的異質銲接當中，異質銲道經過回火後模擬老化十萬小時後，於T23銲道與T91熱影響區的熔融線交界處生成一連續且粗化的脫碳區，且微硬度值明顯下降；在304H與T91的異質銲接當中，異質銲道經過回火後模擬老化二十萬小時後，於309L銲道與T91熱影響區的熔融線交界處生成一連續的脫碳區，造成微硬度值下降，但脫碳區尺寸與微硬度值變化量與前者相比較不顯著。隨著老化時間的拉長，脫碳區的尺寸也隨之加增，降低T91銲件在超超臨界機組負載下應用的可靠性。

In this study, we use two kinds of fillers, such as T23 and 309L, to weld T23/T91 and 304H/T91 by TIG (Tungsten Inert Gas) separately. The quality of the weldment is examined by using NDT (Nondestructive Testing). Heat treatments are performed after specimens selected from wire cutting of the qualified weldments. In this study, during the aging test of dissimilar weldments under high temperature and long time, carbon migration will occur at the fusion line. Because there is the most obvious difference of chromium concentrations at the fusion line, it causes different activities of carbon atoms diffuse from low-alloy to high-alloy. To balance the solubility of carbon, the carbides dissolve into the base at low-alloy. This is the mechanism of formation of decarburization zone. Besides, decarburization zone can be confirmed by optical microscope and the variation of micro-hardness values.
In the T23/T23/T91 part, after PWHT and simulated aging test for 100,000 hours, the continuous and coarse decarburization zone forms at the interface of T23 weldment and T91 HAZ. The micro-hardness of decarburization zone decreases significantly. In 304H/309L/T91 part, after PWHT and simulated aging test for 200,000 hours, the continuous decarburization zone forms at the interface of 309L weldment and T91 HAZ. The micro-hardness of decarburization zone decreases. The change in the values of micro-hardness is not obvious compared with the former. With the longer time period in the aging test, the size of decarburization zone becomes larger. The formation of decarburization zone deteriorates the mechanical properties and reliability of the T91 weldment applied in ultra-supercritical boiler.

誌謝 ii
摘要 iii
Abstract iv
目錄 v
圖目錄 viii
表目錄 xv
第一章 前言 1
第二章 文獻回顧 3
2.1 超超臨界電廠鍋爐機組介紹 3
2.2 接合方式簡介 4
2.2.1 機械連接 4
2.2.2 黏接 4
2.2.3 硬銲與軟銲 5
2.2.4 固態接合 6
2.2.5 銲接 7
2.2.6 鎢極氣體保護電弧銲 9
2.3 鉻鉬合金鋼 10
2.3.1 鉻鉬鋼之介紹 10
2.3.2 鉻鉬鋼之規範 11
2.3.3 鉻鉬鋼之應用與發展 11
2.3.4 鉻鉬鋼之強化機制 12
2.4 T91鉻鉬合金鋼之銲接特性 14
2.4.1 T91鉻鉬合金鋼銲接熱影響區 15
2.4.2 T91鉻鉬合金鋼銲後碳遷移現象 16
2.5 沃斯田鐵系不銹鋼 18
2.5.1 沃斯田鐵系不銹鋼之介紹 18
2.5.2 沃斯田鐵系不銹鋼之凝固反應 19
第三章 實驗方法 41
3.1 實驗流程 41
3.2 爐管材料異質銲接 42
3.3 異質銲接試片銲後熱處理 42
3.4 異質銲接試片老化實驗 43
3.5 異質銲接碳遷移分析 44
3.5.1 銲道組織金相觀察 44
3.5.2 銲道機械性質分析 45
3.5.3 銲道元素定量分析 46
3.5.4 銲道顯微結構分析 47
3.5.5 JMatPro模擬軟體 47
第四章 結果與討論 54
4.1 使用T23填料進行T23/T91異質銲接 54
4.1.1 T23/T23/T91銲道全圖金相組織觀察 54
4.1.2 T23/T23/T91銲道局部金相組織觀察 56
4.1.3 T23/T23/T91銲道橫截面微硬度分析 59
4.1.4 T23/T23/T91銲道橫截面元素定量分析 61
4.1.5 T23/T23/T91銲道介面顯微結構分析 63
4.2 使用309L填料進行304H/T91異質銲接 64
4.2.1 304H/309L/T91銲道全圖金相組織觀察 64
4.2.2 304H/309L/T91銲道局部金相組織觀察 66
4.2.3 304H/309L/T91銲道橫截面微硬度分析 69
4.2.4 304H/309L/T91銲道橫截面元素定量分析 72
4.2.5 304H/309L/T91銲道與介面顯微結構分析 73
第五章 結論 135
參考文獻 137
附錄 147

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