【作者】 陈海军；

【导师】 张华；

【作者基本信息】 南昌大学 ， 机械电子工程， 2011， 硕士

【摘要】 随着海洋开发、核电工业的发展以及港口工程的大量建设,水下焊接技术在这些项目中起到了非常重要的作用,急待提高和发展。局部干法水下焊接同时具有高质量焊缝和操作技术简便易行的优点。基于旋转电弧传感器的局部干法水下焊接有利于水下焊接质量和自动化水平的提高,是非常值得研究的一种水下焊接技术。论文针对改善水下焊接质量和提高焊接自动化的目的,结合实验室现有旋转电弧传感器的部分结构,研制了一种适用于水下局部干法焊接的气幕式旋转电弧传感器。该焊炬的排水工作原理是利用高压气体通过排水罩将焊接区域的水排开,在工件表面形成一个局部高压气罩,从而达到局部干法焊接的目的。排水罩采用了收缩喷管加速气流来达到排水的目的。针对所设计的排水罩进行了气液两相流的流场数值模拟,通过对压力场、速度场及速度矢量场的分析,验证了排水装置设计的可行性。利用所建立的气幕式旋转电弧传感器水下焊接的电弧数值仿真模型,研究了局部高压气罩内焊接电弧特性的变化趋势。在空气中的最优焊接参数下(电流260A、电压24V),以氩气为保护气,弧长12mam,直流反接等条件下,分别在环境压力为0.1MPa、0.4MPa和0.6MPa下,对氩弧等离子体的温度、电流密度进行了数值仿真。仿真结果表明：随着环境压力的升高,电弧温度有所下降、电流密度有所增大,电弧形状呈收缩趋势,电弧直径变小,电弧变得不稳定呈现短路过渡现象。适当升高电弧电压可有效解决弧长被压缩问题。故通过电弧仿真,在进行气幕式旋转电弧传感器的水下焊接正交试验时,可以大致预测正交试验中电流电压因子的水平值的范围。搭建了水下基于气幕式旋转电弧传感器的焊接实验平台。然后针对气幕式旋转电弧传感器的水下局部干法焊接的6个影响因素设计了正交试验表,通过正交试验,得出了该焊接方法最优工艺参数。通过与陆地焊接焊缝和水下湿法焊接焊缝的外观对比,以及对焊缝进行X射线探伤对比分析和焊缝截面质量对比分析,可知气幕式旋转电弧传感器水下局部干法焊接所取得焊缝质量相对于湿法焊接有很大的提高。更多还原

【Abstract】 With the marine development, the nuclear power industry development and a lot of port project construction, underwater welding technology plays a very important role in these aspects, arid improve and develop and need to great improvement and development. Local dry underwater welding has the high quality welding seam of dry underwater welding and easy and simple technology of wet underwater welding. the local dry underwater welding Based on rotating arc sensor is to benefit of raising the level of underwater welding automation,the welding technology is worth researching.Thesis aims to the purpose of improve the underwater welding quality and improve the underwater welding automatic tracking, combining with part of the structure of laboratory existing rotating arc sensor, and developed a kind of air curtain rotating arc sensor applied in underwater local dry welding of to improving underwater welding quality. The sensor’s working principle is to use high-pressure air through drainage device to drain off the watet of welding areas, so as to achieve the purpose of local dry welding. The sensor combined drainage device and sensor with an organic whole, and integrated high-pressure air pipe and protection gas pipeline into arc sensor; The drainage device adopted the contraction nozzle to speed up air currents, thus reach drainage purposes. Aims to the designed drainage device, the gas-liquid two phase flow numerical simulation of flow field has been done. Through the analysis of pressure field, velocity field and velocity vector field, verified the feasibility of the drainage device designing.With established air curtain rotating arc sensor of underwater welding arc argon plasma numerical simulation model, study changing trend of welding arc characteristic in the local high-pressure gas cover. Under the optimal welding parameters in the air(current 260A, voltage 24V), under the conditions of argon as the protection of the gas, arc length 12mm, straight polarity direct current, respectively in environmental pressure 0.1 MPa,0.4 MPa and 0.6 MPa,with the help of numerical simulation, plasma temperature, current density has been researched.The simulation results show that, with the environmental pressure increasing, arc temperature has dropped and arc current density has increased somewhat, arc has a shrinking trend, arc diameter decreased, arc became unstable and present short-circuit transition phenomenon. Appropriate elevated arc voltage can effectively solve the problem the arc length is compressed. when make the orthogonal test with air curtain rotating arc underwater welding, we can roughly predict the level value of current and voltage factor in orthogonal test by the arc simulation.Established the underwater welding hardware platform and software system. With six influencing factors for air curtain rotating arc sensor underwater local dry welding, the orthogonal experiment table was designed. By the test,the optimum process parameters of local dry welding is obtained. Through comparing the land welding effect and underwater wet welding effect and the contrastive analysis of X-ray detection of welding seam and the contrastive analysis weld section, we can get that local dry welding seam quality relative to wet welding has greatly improved.更多还原