304不锈钢水下激光焊接排水装置设计及焊接工艺研究

发布时间：2018-04-02 02:10

本文选题：水下激光焊接　切入点：激光/水/金属相互作用机理　出处：《哈尔滨工业大学》2017年硕士论文

【摘要】：随着人类的活动范围向更深、更广的海洋领域扩展,以及新材料的大量使用,传统水下焊接方法受到了越来越多的限制。另外,在核电修复领域,高压、高辐射的水下环境也对水下焊接技术提出了更高的要求。与水下电弧焊接相比,水下激光焊接具有受水压影响小,焊接材料广泛,热输入量低,冷却速度快,热影响区小,残余应力低等优点。然而,由于技术封锁等原因,我国的水下激光焊接技术仍然处于十分落后的地位,尤其是在高功率激光与水中金属相互作用机理以及水下激光焊接排水装置设计等方面尚未取得实质性突破。本文首先对高功率激光与水中金属相互作用机理进行了研究,采用传统可见光成像系统,获得了不同水深下水下湿法激光焊接过程视频序列及焊接等离子体形态图片,建立了水下湿法激光焊接过程中“光束通道”形成、长大、关闭的力平衡和能量平衡模型。研究发现,随着水深的增加,水下湿法激光焊接过程稳定性和焊接质量逐渐变差,在激光功率6.0 k W,焊接速度0.1 m/min,离焦量0 mm时,水下湿法激光焊接的可焊接水深超过了20 mm。在此基础上,从进气方式设计以及内部流体动力学模拟计算入手,利用Solid Works和ANSYS Workbench 14.5,自主设计了两套水下激光焊接排水装置——单层气体辅助排水装置和双层气体辅助排水装置。针对所设计的排水装置分别进行了气液两相流的流场数值模拟计算,通过对流体流线图、速度矢量图、速度云图和压力云图的分析,验证了排水装置设计的可靠性。其中,单层气体辅助排水装置采用带等距离出气孔的环向进气方式,双层气体辅助排水装置外层筒体采用侧切向进气方式,内层筒体采用斜切向进气方式。最后搭建了局部干法水下激光焊接试验系统。利用所设计的两套水下激光焊接排水装置分别进行了304不锈钢水下激光焊接工艺研究。试验结果表明,本文所设计的两套水下激光焊接排水装置均能够得到外观成形良好、内部无缺陷、性能优异的水下焊接接头。其中,利用单层气体辅助排水装置得到的水下焊缝抗拉强度和冲击韧性分别为665 MPa和107 J/cm2;利用双层气体辅助排水装置得到的水下焊缝抗拉强度和冲击韧性分别为620 MPa和152 J/cm2。与陆上焊接相比,水下焊缝中铁素体除了以树枝状形态存在外,还能够以板条状形态存在,焊缝强度满足要求,韧性有所降低,微观硬度相差不大。
[Abstract]:Traditional underwater welding methods are more and more limited with the extension of human activities to deeper and wider ocean fields and the extensive use of new materials.In addition, in the field of nuclear power restoration, high pressure, high radiation underwater environment also put forward higher requirements for underwater welding technology.Compared with underwater arc welding, underwater laser welding has the advantages of less influence by water pressure, wide range of welding materials, low heat input, fast cooling rate, small heat affected zone and low residual stress.However, due to the technical blockade and other reasons, the underwater laser welding technology in China is still in a very backward position.Especially the mechanism of interaction between high power laser and metal in water and the design of underwater laser welding drainage device have not made substantial breakthrough.In this paper, the mechanism of interaction between high power laser and metal in water is studied. The video sequence of underwater wet laser welding process and the shape picture of welding plasma are obtained by using traditional visible light imaging system.The model of force balance and energy balance for forming, growing and closing of "beam channel" in underwater wet laser welding is established.It is found that with the increase of water depth, the process stability and welding quality of underwater wet laser welding become worse. When the laser power is 6.0 kW, the welding speed is 0.1 m / min, and the defocus is 0 mm, the weldable water depth of underwater wet laser welding exceeds 20 mm.On this basis, starting with the design of intake mode and the internal hydrodynamic simulation calculation,Using Solid Works and ANSYS Workbench 14.5, two sets of underwater laser welding drainage devices, single-layer gas-assisted drainage device and double-layer gas-assisted drainage device, are designed.The flow field of gas-liquid two-phase flow was simulated and calculated respectively for the designed drainage device. The reliability of the design of the drainage device was verified by the analysis of the flow line diagram, velocity vector diagram, velocity cloud diagram and pressure cloud diagram.The single-layer gas-assisted drainage device adopts the annular air intake mode with equal distance air outlet, the bilayer gas-assisted drainage device adopts the lateral tangential air intake mode, and the inner layer adopts the oblique tangential air intake mode.Finally, a local dry underwater laser welding test system is built.The underwater laser welding process of 304 stainless steel was studied by using two sets of underwater laser welding drainage devices designed in this paper.The experimental results show that the two underwater laser welding drainage devices designed in this paper can obtain underwater welded joints with good appearance, no internal defects and excellent performance.The tensile strength and impact toughness of underwater weld are 665 MPa and 107J / cm ~ 2, respectively, and the tensile strength and impact toughness of underwater weld are 620 MPa and 152J / cm ~ 2, respectively.Compared with onshore welding, the ferrite in underwater weld exists not only in dendritic shape, but also in strip shape. The strength of weld meets the requirement, the toughness is reduced, and the microhardness is not different.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG456.7;TG439.4

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