臺灣博碩士論文加值系統

本研究針對肥粒鐵系之無縫合金鋼管（P11, 1.25 Cr-0.5 Mo）進行高溫潛變與週期潛變實驗。於潛變實驗848 – 923 K溫度範圍中，其應力指數為3.26 – 4.23之間，與真實應力值相符，故潛變機制屬於差排潛變，真實潛變活化能的平均值為365 KJ。
週期潛變實驗溫度873 K中，其應力指數為4.37 – 4.69之間，真實潛變活化能的平均值為431 KJ。由實驗結果得知，週期潛變之應力指數與潛變活化能皆大於固定負載之潛變，並且週期應力作用會縮短潛變破斷時間。由金相與電子顯微鏡的組織變化觀察得知，經由潛變實驗後破斷面主要由延性穿晶潛變破壞所構成。
週期應力作用會出現加工硬化轉變成軟化的現象，隨平均應力提高，會明顯提高最小潛變速率，初期加工硬化之後會快速轉變成軟化，換言之，在硬化轉變成軟化的過程同時也意味著潛變由穩態期進入加速期，相當接近破斷時間。
本研究之鋼管材料以 Larson-Miller 與 Manson-Haferd 參數法所進行的壽命預測，維持管材長期使用15年而不致發生潛變破壞，1.25Cr-0.5Mo合金鋼之安全操作條件為溫度773 K（即500℃）及應力50 MPa以下。

The study of ferritic alloy steel tube (P11, 1.25Cr-0.5Mo) carries out static and cyclic creep tests in tension at elevated temperature. In the temperature range 848 – 923 K, the 1.25Cr- 0.5Mo alloy steel exhibited an apparent stress exponent of 3.26 – 4.23 in conformity with true stress exponent and an apparent activation energy of 365 kJ/mol for static creep. The static creep belongs to dislocation creep.
At the temperature of 873 K, the 1.25Cr- 0.5Mo alloy steel exhibited an apparent stress exponent of 4.37 – 4.69 and an apparent activation energy of 431 kJ/mol for cyclic creep. The values of apparent stress exponent and activation energy for cyclic creep of the 1.25Cr- 0.5Mo alloy steel were higher than those obtained from the static creep measurements. SEM fractograph showing transgranular facture in creep tests and exhibits transgranular facture characterized by dimples.
The work hardening in initial stage is observed and will be changed and softening with increasing the mean stress. While increasing with the stress, will obviously raise the steady state creep rate. On the other hand, cyclic creep enters from steady state creep one and accelerating creep one, quite close to creep rupture time. The cyclic stressing reduces the creep life at high temperature.
The remnant lift of the research was raised parameter methods of Larson-Miller in 1952 and Manson-Haferd in 1953, which aimed at creep of the 1.25Cr- 0.5Mo alloy steel for analysis and assessment, and the suitableness of predictable remnant lift. According with general pipe service life 15 years without creep rupture, the condition of safety in operation of 1.25Cr- 0.5Mo alloy steel is under temperature 773 K and stress 50 MPa.

目 錄
摘 要 i
Abstract ii
誌 謝 iii
目 錄 iv
圖目錄 vii
表目錄 ix
符號說明 x
一、緒論 1
1.1 前言 1
1.2 研究動機 2
1.3 研究目的與流程 3
二、基本理論 5
2.1 鉻鉬合金鋼 5
2.2 潛變 5
2.3 潛變曲線 7
2.3.1 第一階段潛變 7
2.3.2 第二階段潛變 8
2.3.3 第三階段潛變 8
2.4 潛變變形機制 10
2.4.1 差排滑移 10
2.4.2 差排潛變 10
2.4.3 擴散潛變 12
2.4.4 晶界滑移 13
2.5 潛變之應力與溫度函數 15
2.5.1 應力函數 16
2.5.2 溫度函數 17
2.5.3 時間硬化 18
2.5.4 應變硬化理論 18
2.6 參數模式 19
2.6.1 Larson-Miller參數法 20
2.6.2 Manson-Haferd參數法 21
三、實驗方法 25
3.1 金相觀察 25
3.2 材料及規格 25
3.3 潛變實驗 26
3.4 實驗條件 30
3.5 實驗步驟 32
3.6 SEM破斷面觀察 33
四、結果與討論 34
4.1金相觀察 34
4.2 定溫下應力對潛變之影響 35
4.3 定應力下溫度對潛變之影響 37
4.4 定溫下週期應力對潛變之影響 39
4.5 潛變應力指數 43
4.5.1 週期潛變應力指數 44
4.6 潛變活化能 46
4.6.1 週期潛變活化能 49
4.7 Larson-Miller參數法 50
4.7.1 週期潛變壽命評估 57
4.8 Manson-Haferd參數法 60
4.9 SEM破斷面觀察 63
五、結論 69
5.1 結論 69
六、參考文獻 70
自傳 74

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