楊哲人臺灣大學：材料科學與工程學研究所沈志安2007-11-262018-06-282007-11-262018-06-282004http://ntur.lib.ntu.edu.tw//handle/246246/55296改良型9Cr-1Mo合金鋼屬於高合金鉻鉬鋼種，具有相當良好的硬化能，所以一般在連續空冷的熱處理條件下亦可得到麻田散鐵組織。改良型與標準型之9Cr-1Mo合金鋼不同之處在於多添加了0.2 wt%的釩元素，以增進其在高溫下抗潛變的特性。本實驗主要是對於改良型9Cr-1Mo合金鋼進行恆溫與回火兩種不同的熱處理製程來觀察其相變態與顯微組織之改變。 本實驗恆溫於235℃、285℃與335℃分別持溫15分鐘後，緊接著再做450℃持溫15分鐘的up-quench熱處理，而up-quench的作用主要是為了將第一次由高溫沃斯田鐵化冷卻下來的麻田散鐵轉變成回火麻田散鐵，以利於與恆溫過後連續冷卻下來所產生的新生麻田散鐵有所區隔。於TEM顯微組織照片中可以觀察到，因為受到up-quench的作用，自動回火麻田散鐵為主要的組織，相較之下，新生麻田散鐵的量卻比較少，除此之外，板條狀自動回火麻田散鐵內部含有不同指向性（variants）的M3C碳化物，另外還有長條薄膜狀的殘留沃斯田鐵夾藏於兩板條狀麻田散鐵之間，以及少量於兩板條狀麻田散鐵間為了釋放平面應變而產生相互刺穿的雙晶麻田散鐵組織。 在回火650℃持溫30分鐘的熱處理當中，M3C碳化物會於麻田散鐵內部析出，一旦回火於750℃持溫30分鐘時，會有M7C3與M23C6碳化物於晶粒內部與晶界上析出，所以碳化物演化的模式為M3C→M7C3→M23C6，而且只要增加回火的溫度與時間，則碳化物就會有粗大化的現象。 最後於連續緩慢升溫之熱處理條件之下，長條薄膜狀的殘留沃斯田鐵會於675℃迅速地分解，並在附近產生粗大之M3C碳化物。Modified 9Cr-1Mo alloy steel can virtually transform to lath martensite in continuous cooling heat treatment, since a high alloying content leads to a good harden-ability. Modified 9Cr-1Mo alloy steel has better creep resistance than other 9Cr-1Mo steels, because it contains 0.2 wt% V. In this study, we have performed isothermal and tempering heat treatment for the modified 9Cr-1Mo alloy steel, and the microstructural changes due to the phase transformation have been observed. Isothermal heat treatments have been performed at 235℃, 285℃, and 335℃ for 15 minutes, then up-quenching at 450℃ for 15 minutes. The up-quench heat treatment is intended mainly to distinguish the different between the auto-tempered martensite transform from high temperature cooling down and the fresh martensite transform after isothermal heat treatment. In TEM microstructure analysis, it is found the amounts of auto-tempered martensite are majority, but the amounts of fresh martensite are less. Besides, it is observed the lath auto-tempered martensite contains M3C carbides which have different variants, and is also observed a long film morphology of retained austenite between two lath martensites, a few twins which are joined in order to release invariant-plane strain. In tempering heat treatment at 650℃ for 30 minutes, it is found M3C carbides precipitate from martensite. In tempering heat treatment at 750℃ for 30 minutes, it is observed the M7C3 and M23C6 carbides precipitate from grain boundary. The evolution sequence of carbides is suggest to be M3C→M7C3→M23C6. Carbide could coarsen when increasing tempering temperature or time. At a slow heat rate in a continuously heating treatment for tempering martensite, retained austenite could be decomposed quickly from long film morphology at 675℃, and produce the coarse M3C carbides.第一章 前言...............................................1 第二章 文獻回顧...........................................3 2- 1 Cr-Mo合金鋼..........................................3 2-1- 1 簡介...............................................3 2-1- 2 強化機構...........................................3 2- 2 改良型9Cr-1Mo合金鋼..................................8 2-2- 1 簡介...............................................8 2-2- 2 合金元素添加的影響.................................9 2-2- 3 碳化物之演化與成核方式............................16 2-2- 4 碳化物之種類......................................18 2- 3 麻田散鐵相變態......................................23 2-3- 1 簡介..............................................23 2-3- 2 麻田散鐵相變態之特性..............................24 2-3- 3 麻田散鐵之晶體結構................................26 2-3- 4 麻田散鐵之形貌與種類..............................27 2- 4 殘留沃斯田鐵........................................30 第三章 材料準備與實驗流程................................44 3- 1 實驗材料之準備......................................44 3- 2 熱膨脹試驗..........................................45 3- 3 熱處理實驗流程......................................46 3- 4 金相顯微組織觀察....................................48 3- 5 TEM試片製作與顯微組織觀察...........................49 第四章 改良型9Cr-1Mo合金鋼恆溫相變態之研究...............56 4- 1 簡介................................................56 4- 2 恆溫熱處理製程條件..................................57 4- 3 熱膨脹曲線觀察......................................58 4- 4 顯微組織觀察........................................61 4- 5 TEM顯微組織觀察、晶體結構與方位關係之研究分析.......64 4- 6 結論................................................72 第五章 改良型9Cr-1Mo合金鋼回火相變態之研究..............111 5- 1 簡介...............................................111 5- 2 回火熱處理製程條件.................................113 5- 3 熱膨脹曲線觀察.....................................114 5- 4 顯微組織觀察.......................................116 5- 5 TEM顯微組織觀察與晶體結構之研究分析................117 5- 6 結論...............................................123 第六章 總結論...........................................151 第七章 未來工作.........................................155 第八章 參考文獻.........................................15719800695 bytesapplication/pdfen-US自動回火麻田散鐵改良型9Cr-1Mo合金鋼麻田散鐵相變態殘留沃斯田鐵微雙晶retained austeniteauto-tempered martensitemicro-twinsmartensite transformationmodified 9Cr-1Mo alloy steelthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/55296/1/ntu-93-R91527005-1.pdf