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论文类型：期刊论文

发表时间：2017-10-01

发表刊物：Guangxue Jingmi Gongcheng/Optics and Precision Engineering

收录刊物：EI

卷号：25

页面范围：135-143

ISSN号：1004924X

摘要：In order to realizereliable seal welding at the end of CAP1400 nuclear reactor coolant pimp can, Nd:YAG pulsed laser was adopted to implement overlapping weld of dissimilar materials of Hastelloy C-276 and austenite stainless steel 304. Optical microscope and scanning electron microscope were adopted to observe morphology and microstructure of the weld metal. EDS was used to detect elementary composition in weld, electron probe was used to measure element distribution in weld and mechanical property of welded joint was evaluated by mechanical tearing experiment. Result of mechanical tearing experiment indicates that fracture occurs in weld under different plus energy, and it is tension fracture. When plus energy is 3-4 J, mechanical tearing resistance strength of weld reaches the maximum and is about 78 N/mm. Optimized weld parameter scopes are: pulse energy 3-4 J, welding speed 125-200 mm/min, pulse frequency 30 Hz, pulse width 6-8 ms, and defocusing amount -1-0 mm. The result shows that the effect of pulse energy and pulse frequency on joint width of overlapping weld is relatively large, but excessively large pulse energy and pulse frequency and excessively small pulse width will cause collapse and serious spatter of weld surface. Along with increase of pulse energy, width of incomplete fusion zone in the side of 304 parent material decreases, content of precipitated phase in weld is reduced. Under relatively high pulse energy, columnar crystal and equiaxed structure in weld coarsen, quantity and size of micropore caused by element ablation is relatively large. Along with improvement of dilution rate of 304 parent material in weld, difference between element content and 304 parent material in weld is reduced, and uniformity of element distribution in weld decreases. © 2017, Science Press. All right reserved.