水下高压干式GMAW焊接电弧及熔滴过渡数值模拟

发布时间：2018-10-16 21:30

【摘要】：近年来,由于陆地石油、天然气资源日益匮乏,人们对海洋石油、天然气的开发利用逐渐增多,水下油气管道的投放量和使用量快速增长,受限于服役年限与所处的海洋环境,水下油气管道需要更换和维修。随着开采深度的不断增加,油气管道所处的压力也在不断攀升,焊接环境压力对水下焊接技术提出很高的要求,而水下高压干法焊接因其较强的适应性和较好的焊接质量成为近年来常用的水下焊接手段,有着非常大的应用前景,因此研究和发展高效、高质量的水下高压干法焊接技术意义重大。本文利用数值模拟软件Fluent软件,对水下高压干式GMAW焊接电弧及熔滴过渡进行数学建模,并进行数值模拟和分析。针对焊接电弧进行数值模拟,结果表明:电弧形状为钟罩形,随着环境压力的提升,电弧收缩,电弧径向弧柱尺寸减少,电弧中心最高温度上升,电弧压力上升,电弧电流密度上升。当环境压力一定,随着焊接电流的增大,电弧收缩程度减小,电弧径向弧柱尺寸增大,电弧中心最高温度上升电弧压力下降,电弧电流密度上升。针对熔滴过渡进行数值模拟,结果表明:随着环境压力的提升,熔滴过渡的形式会有不同形式的变化,如射流过渡、射滴过渡、大滴过渡,熔滴过渡的频率会降低,熔滴的尺寸会增大。当环境压力一定,随着焊接电流的增大,熔滴过渡的频率上升,熔滴的尺寸下降。利用水下高压干式焊接实验舱进行焊接试验,试验中采用高速摄像系统将焊接电弧及熔滴过渡过程拍摄下来,通过试验结果与数值模拟结果进行对比验证,二者结果基本一致,试验验证了数值模拟结果的正确性,因此数值模拟的研究成果对水下高压干式焊接研究具有指导意义。
[Abstract]:In recent years, due to the scarcity of land oil and natural gas resources, the exploitation and utilization of offshore oil and natural gas are increasing gradually, and the quantity and usage of underwater oil and gas pipeline are increasing rapidly, which is limited by the service life and the marine environment. Underwater oil and gas pipelines need to be replaced and maintained. With the increasing of mining depth, the pressure of oil and gas pipeline is also rising. The pressure of welding environment puts forward very high requirements for underwater welding technology. Because of its strong adaptability and good welding quality, underwater high-pressure dry welding has become a common method of underwater welding in recent years, and has a great prospect of application. Therefore, the research and development of high efficiency, High quality underwater high pressure dry welding technology is of great significance. In this paper, the numerical simulation software Fluent is used to model the arc and droplet transfer of underwater high-pressure dry GMAW welding, and the numerical simulation and analysis are carried out. The numerical simulation of welding arc shows that the arc shape is bell-shaped. With the increase of ambient pressure, the arc shrinks, the radial arc column size decreases, the maximum temperature of the arc center rises, and the arc pressure rises. The arc current density increases. When the ambient pressure is constant, the arc shrinkage decreases with the increase of welding current, the radial arc column size increases, the arc pressure decreases and the arc current density increases. The numerical simulation of droplet transfer is carried out. The results show that with the increase of environmental pressure, droplet transfer will change in different forms, such as jet transfer, droplet transfer, and the frequency of droplet transfer will decrease. The size of the droplet will increase. With the increase of welding current, the frequency of droplet transfer increases and the size of droplet decreases. The welding experiment was carried out in the underwater high-pressure dry welding laboratory. The welding arc and droplet transfer process were photographed by high-speed camera system in the experiment. The experimental results were compared with the numerical simulation results, and the two results were basically the same. The experimental results verify the correctness of the numerical simulation results, so the research results of the numerical simulation are instructive to the research of underwater high pressure dry welding.
【学位授予单位】：北京石油化工学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE973.3;TG44

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