本文選題：激光焊接 + C-276薄板��； 參考：《大連理工大學(xué)》2016年碩士論文

【摘要】：核電作為新型清潔能源而得到世界各國青睞,為加快核電發(fā)展,我國引進(jìn)了第三代核電站AP1000制造技術(shù)。屏蔽套是AP1000核主泵的關(guān)鍵部件,材料為Hastelloy C-276,通常采用氬弧焊工藝進(jìn)行制造。相對于氬弧焊,激光焊具有焊縫窄、熱變形小等優(yōu)點(diǎn),有利于保證屏蔽套的制造精度和可靠性。屏蔽套處于周期變化的電機(jī)旋轉(zhuǎn)磁場和冷卻劑流場中,在循環(huán)交變載荷下易發(fā)生疲勞破壞,因此研究屏蔽套焊接接頭疲勞性能對于保證核主泵的長期使役具有重要意義。本文采用Nd:YAG脈沖激光對Hastelloy C-276薄板進(jìn)行焊接,通過疲勞實(shí)驗(yàn)和斷口形貌分析激光焊接C-276疲勞性能和斷裂機(jī)理,利用數(shù)值模擬方法研究不同焊縫形貌下焊接接頭應(yīng)力分布和疲勞壽命,為屏蔽套的安全服役提供理論指導(dǎo)。主要研究內(nèi)容如下：(1)對接間隙對焊縫形貌的影響規(guī)律。在合理的工藝參數(shù)下,研究對接間隙對焊縫形貌(上下表面寬度和負(fù)余高)的影響規(guī)律,為數(shù)值模擬提供實(shí)驗(yàn)?zāi)Ｐ汀?2)疲勞性能和斷口形貌研究。通過疲勞實(shí)驗(yàn)分別得到母材和焊接接頭S-N曲線,利用SEM觀察母材和焊接接頭疲勞斷口形貌,利用EDS檢測斷面化學(xué)元素成分,分析不同應(yīng)力下母材和焊接接頭疲勞斷口形貌特征和元素分布。(3)疲勞性能和斷裂機(jī)理對比分析。通過S-N曲線對比母材和焊接接頭疲勞性能,從應(yīng)力集中、表面狀態(tài)、微觀組織、殘余應(yīng)力、焊接缺陷等方面分析激光焊接對C-276薄板疲勞性能的影響規(guī)律,對比同應(yīng)力下母材和焊接接頭疲勞斷口形貌特征,分析兩者斷裂機(jī)理的差異性。(4)焊縫形貌對焊接接頭疲勞性能的影響規(guī)律。根據(jù)對接間隙對焊縫形貌的影響規(guī)律,建立焊接接頭有限元模型,并通過疲勞試驗(yàn)進(jìn)行驗(yàn)證,利用數(shù)值模擬方法分析焊縫形貌對焊接接頭應(yīng)力分布和疲勞壽命的影響規(guī)律,揭示對接間隙對焊接接頭疲勞壽命的影響規(guī)律,為利用激光焊接方法制造屏蔽套提供理論指導(dǎo)。
[Abstract]:Nuclear power, as a new clean energy, has been favored by many countries all over the world. In order to speed up the development of nuclear power, the third generation AP1000 manufacturing technology has been introduced in China. Shielding sleeve is the key component of AP1000 nuclear pump. The material is Hastelloy C-276. it is usually manufactured by argon arc welding. Compared with argon arc welding, laser welding has the advantages of narrow weld seam and small thermal deformation, which is helpful to ensure the manufacturing accuracy and reliability of shield sleeve. In the rotating magnetic field and coolant flow field of the motor with periodic variation the fatigue failure is easy to occur under cyclic alternating load so it is important to study the fatigue performance of the welded joint of the shield sleeve for ensuring the long-term service of the nuclear main pump. In this paper, Nd:YAG pulsed laser is used to weld Hastelloy C-276 thin plate. The fatigue properties and fracture mechanism of laser welding C-276 are analyzed by fatigue test and fracture morphology. The stress distribution and fatigue life of welded joints under different weld morphology are studied by numerical simulation method, which provides theoretical guidance for the safe service of shield sleeve. The main contents are as follows: 1) the effect of butt clearance on weld morphology. Under reasonable process parameters, the influence of butt clearance on weld morphology (upper and lower surface width and negative residual height) was studied. The S-N curves of base metal and welded joint were obtained by fatigue test, the fatigue fracture morphology of base metal and welded joint was observed by SEM, and the chemical composition of cross section was detected by EDS. The fatigue properties and fracture mechanism of base metal and welded joint under different stresses were analyzed. The effects of laser welding on fatigue properties of C-276 thin plate were analyzed from the aspects of stress concentration, surface state, microstructure, residual stress, welding defects and so on, by comparing the fatigue properties of base metal and welded joints with S-N curves. By comparing the fatigue fracture characteristics of base metal and welded joint under the same stress, the effect of weld morphology on the fatigue properties of welded joint is analyzed. According to the influence of butt clearance on weld morphology, the finite element model of welded joint is established and verified by fatigue test. The effect of weld shape on stress distribution and fatigue life of welded joint is analyzed by numerical simulation. The effect of butt clearance on fatigue life of welded joints is revealed, which provides theoretical guidance for manufacturing shield sleeve by laser welding.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TG407

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