哈氏C-276薄板激光焊接接头疲劳性能研究
本文选题:激光焊接 + C-276薄板 ; 参考:《大连理工大学》2016年硕士论文
【摘要】:核电作为新型清洁能源而得到世界各国青睐,为加快核电发展,我国引进了第三代核电站AP1000制造技术。屏蔽套是AP1000核主泵的关键部件,材料为Hastelloy C-276,通常采用氩弧焊工艺进行制造。相对于氩弧焊,激光焊具有焊缝窄、热变形小等优点,有利于保证屏蔽套的制造精度和可靠性。屏蔽套处于周期变化的电机旋转磁场和冷却剂流场中,在循环交变载荷下易发生疲劳破坏,因此研究屏蔽套焊接接头疲劳性能对于保证核主泵的长期使役具有重要意义。本文采用Nd:YAG脉冲激光对Hastelloy C-276薄板进行焊接,通过疲劳实验和断口形貌分析激光焊接C-276疲劳性能和断裂机理,利用数值模拟方法研究不同焊缝形貌下焊接接头应力分布和疲劳寿命,为屏蔽套的安全服役提供理论指导。主要研究内容如下:(1)对接间隙对焊缝形貌的影响规律。在合理的工艺参数下,研究对接间隙对焊缝形貌(上下表面宽度和负余高)的影响规律,为数值模拟提供实验模型。(2)疲劳性能和断口形貌研究。通过疲劳实验分别得到母材和焊接接头S-N曲线,利用SEM观察母材和焊接接头疲劳断口形貌,利用EDS检测断面化学元素成分,分析不同应力下母材和焊接接头疲劳断口形貌特征和元素分布。(3)疲劳性能和断裂机理对比分析。通过S-N曲线对比母材和焊接接头疲劳性能,从应力集中、表面状态、微观组织、残余应力、焊接缺陷等方面分析激光焊接对C-276薄板疲劳性能的影响规律,对比同应力下母材和焊接接头疲劳断口形貌特征,分析两者断裂机理的差异性。(4)焊缝形貌对焊接接头疲劳性能的影响规律。根据对接间隙对焊缝形貌的影响规律,建立焊接接头有限元模型,并通过疲劳试验进行验证,利用数值模拟方法分析焊缝形貌对焊接接头应力分布和疲劳寿命的影响规律,揭示对接间隙对焊接接头疲劳寿命的影响规律,为利用激光焊接方法制造屏蔽套提供理论指导。
[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.
【学位授予单位】:大连理工大学
【学位级别】:硕士
【学位授予年份】:2016
【分类号】:TG407
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