本文選題：Z3CN20-09M鋼　切入點：模擬工況　出處：《西安工業(yè)大學》2017年碩士論文

【摘要】：鑄造雙相不銹鋼(CDSSs)因兼具有高強度、優(yōu)異的可鑄造性和焊接性以及良好的抗應力腐蝕開裂等性能,而廣泛用于制造核電站壓水堆一回路主冷卻劑管道等壓力邊界部件。但是在反應堆運行溫度(一般范圍為288~327℃)下長期工作,鑄造雙相不銹鋼會產生熱老化脆化,導致管道鋼性能下降,進而威脅一回路壓力邊界的完整性和核電站的運行安全。因此,有必要對長時間熱老化后的鑄造雙相不銹鋼組織結構和力學性能進行研究,揭示其熱老化機理,為核電站老化和壽命管理以及延壽工作提供技術支持。基于Z3CN20-09M鑄造雙相不銹鋼的服役條件,本文在350℃和400℃兩種溫度及空氣和模擬工況兩種環(huán)境條件下對國產離心鑄造Z3CN20-09M雙相不銹鋼進行了加速熱老化試驗,然后采用透射電鏡、維氏硬度試驗、微型杯突試驗對不同時長熱老化后Z3CN20-09M鑄造雙相不銹鋼顯微組織結構、顯微硬度、室溫(25℃)及高溫(290℃)微型杯突力學性能進行了研究;通過掃描電鏡對該鋼的微型杯突試樣的斷口形貌進行觀察,分析熱老化對其斷裂機理的影響。獲得了以下主要結論:Z3CN20-09M鋼長期熱老化后奧氏體中全位錯的密度大幅降低,全位錯之間、擴展位錯之間以及全位錯和擴展位錯之間會發(fā)生相互交割而形成位錯網絡、亞晶界和不可動位錯,造成擴展位錯的密度下降。350℃熱老化1000h和400℃熱老化300h后,在基體上有細小的顆粒狀第二相析出;400℃熱老化3000h后鐵素體內可以觀察到調幅分解產生的富Fe的α相及富Cr的α′相,隨熱老化時間的延長,雙相不銹鋼中的調幅分解程度逐漸增大,熱老化10000h后,調幅分解逐漸達到平衡。顯微維氏硬度測試表明:在不同的熱老化環(huán)境與溫度下,Z3CN20-09M鋼奧氏體相的硬度值隨熱老化時間延長變化并不明顯。350℃不同環(huán)境熱老化,鐵素體相硬度有少量的增長。在400℃不同環(huán)境熱老化,鐵素體相的硬度在2000h前增長緩慢,3000h后硬度值迅速增長。維氏硬度值變化與熱老化溫度及其熱老化時長有關,統(tǒng)計學分析表明不同熱老化環(huán)境對顯微維氏硬度值影響不顯著。室溫(25℃)微型杯突試驗表明:350℃兩種不同環(huán)境條件下,隨著熱老化時間的延長,Z3CN20-09M鋼的最大強度Pu/t02有小幅度的增加;比斷裂能Esp有小幅度的減少,比屈服Py/t02均變化幅度不大。400℃兩種不同環(huán)境條件下,隨著熱老化時間的延長,Z3CN20-09M鋼的比強度Pu/t02和比屈服Py/t02均有少量增長,比斷裂能Esp均持續(xù)減少。微型杯突力學性能數(shù)值變化與熱老化溫度及其熱老化時長有關,熱老化環(huán)境的對力學性能影響不顯著。斷口分析表明:微型杯突試驗宏觀斷口沒有明顯的區(qū)別。在熱老化初期材料的微型杯突斷口主要以微孔聚集型斷裂為主,表現(xiàn)為較好的韌性斷裂;隨著熱老化時間延長,出現(xiàn)準解理斷裂形式與微孔聚集型斷裂的結合。隨著熱老化時間延長,材料的韌性下降,逐漸轉化為脆性材料。高溫(290℃)微型杯突試驗表明:在不同的熱老化溫度和環(huán)境條件下,隨著熱老化時間的延長,Z3CN20-09M鋼的最大強度和比屈服都有著小幅度的增加;比斷裂能逐漸減少。高溫微型杯突力學性能數(shù)值變化與熱老化溫度及其熱老化時長有關,熱老化環(huán)境對其的影響不顯著。
[Abstract]:Casting Duplex Stainless Steel (CDSSs) by and has high strength, excellent castability and weldability and good resistance to stress corrosion cracking performance, and is widely used in the manufacture of nuclear power plant primary coolant piping in PWR pressure boundary components. But in the reactor operating temperature (generally in the range of 288~327 DEG C) under work for a long time, the casting will produce thermal aging embrittlement of duplex stainless steel, resulting in a decline in performance and threatens the safe operation of pipeline steel, a loop pressure boundary integrity and nuclear power plant. Therefore, it is necessary to study the long time after thermal aging of cast duplex stainless steel structure and mechanical properties, the thermal aging mechanism and provide technical support for the nuclear power plant aging and life management and life extension. The service condition of double phase stainless steel casting based on Z3CN20-09M, the 350 degrees and 400 degrees two kinds of temperature and air and simulated conditions The two conditions of domestic centrifugal casting of Z3CN20-09M duplex stainless steel was studied by accelerated thermal aging test, and then by transmission electron microscopy, Vivtorinox micro hardness test, Erichsen test on different time after thermal aging of Z3CN20-09M cast duplex stainless steel microstructure, hardness, room temperature (25 DEG C) and high temperature (290 DEG C) the mechanical properties of micro cup were studied; to observe fracture morphology of the steel micro cup samples by scanning electron microscopy, the effects of aging on the fracture mechanism of thermal analysis. The main conclusions are as follows: the aging of Z3CN20-09M steel after long term thermal austenite full dislocation density is greatly reduced, the dislocation between the expansion between and around the dislocation and dislocation of extended dislocations has formed the dislocation network delivery, subgrain boundaries and immobile dislocations, dislocation density decrease caused by expansion of.350 thermal aging and thermal 1000h 400 After aging for 300h, a small granular precipitated in the matrix; after aging 3000h ferrite can be observed spinodal decomposition and the resulting Fe rich 400 degrees heat alpha and alpha 'Cr rich phase, with the increase of aging time, duplex stainless steel in spinodal decomposition increases and thermal aging after 10000h, the spinodal decomposition gradually reached equilibrium. Vivtorinox micro hardness test show that the aging environment and temperature in different heat, the hardness of austenite of Z3CN20-09M steel phase value with aging time prolonged.350 did not change significantly at different thermal aging, the ferrite hardness has risen slightly. Aging 400 degrees in different environment the heat, the ferrite phase hardness in the 2000h before the slow growth of 3000h hardness increased rapidly. Vivtorinox change of hardness and thermal aging temperature and thermal aging time, the statistical analysis showed that the aging hardness on the microstructure of different heat environment of Vivtorinox The value is not significantly affected. At room temperature (25 DEG C) shows that the micro cup test: two different environmental conditions of 350 DEG C, with the increase of aging time, the maximum strength of Pu/t02 Z3CN20-09M steel has increased slightly; Esp has little scope to reduce the ratio of fracture energy, than the yield Py/t02 change of two kinds of different environmental conditions modest.400 DEG C, with the increase of aging time. Specific strength of Z3CN20-09M steel Pu/t02 and Py/t02 were less than the yield increase than the fracture energy Esp decreased continuously. The aging temperature and thermal time related numerical changes and thermal properties of micro cup mechanical aging, influence of thermal aging on the mechanical properties of the environment is not significant. Fracture analysis showed that the small punch test macro fracture has no obvious difference. In the beginning of thermal aging material micro cup fracture to microvoid accumulation fracture mainly exhibited ductile fracture with good heat ageing; The extension, combined with quasi cleavage fracture form and micropore aggregation fracture. With the extension of the thermal aging time, decrease the toughness of the material, gradually transformed into brittle materials. High temperature (290 DEG C) showed that the small punch test: aging temperature and environmental conditions in different heat, with the increase of aging time. The maximum intensity Z3CN20-09M steel and yield have a small increase; than fracture energy decreases gradually. The aging temperature and thermal time related numerical changes and thermal performance of high temperature micro cup mechanical aging, thermal aging environment is not significant for its impact.

【學位授予單位】：西安工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM623.91;TG142.1

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