干式高气压环境下脉冲GMAW焊接工艺研究

发布时间：2019-05-26 18:30

【摘要】：随着海洋油气资源的不断开发,海洋金属结构物和海底管道的维修问题变得日益重要,水下干式高压焊接方法排除了水对焊接质量的有害影响,具有焊接质量好,适应深水施工的优点逐渐成为海洋结构物和海底管道维修的常用方法。因此研究高气压环境下脉冲熔化极气体保护焊(GMAW-P)焊接工艺十分必要。首先研究环境压力、工艺参数(电弧电压、峰值电流、脉冲频率、基值电流)和保护气体配比对焊缝成形的影响规律。试验在高压舱内进行,采用Q345钢板进行堆焊试验。研究表明:环境压力越大,焊缝熔宽逐渐变大,焊缝熔深则逐渐减小;高压环境下改变气体配比、焊接平均电压、脉冲峰值电流、脉冲基值电流和脉冲频率均可以影响其焊缝成形质量。采用坡口堆焊研究环境压力、焊接工艺参数和保护气体配比对Q345钢脉冲GMAW焊接接头宏观金相、微观组织及力学性能的影响。在保证其他工艺参数不变的情况下,采取单参数调节进行试验,通过对所得焊接接头质量检验来分析研究其影响规律。高压干法脉冲GMAW拉伸试样均在母材处断裂,焊接接头的拉伸强度大于母材的抗拉强度;环境压力越高,焊缝区维氏硬度越大;电弧电压优化后焊缝区组织优化,维氏硬度变小,金属柔韧性增强;脉冲峰值电流和脉冲基值电流分别提高时焊接接头维氏硬度和冲击韧性变化不大;脉冲频率增加时焊接接头强度、硬度和冲击韧性提高。最后通过正交试验对电弧电压、峰值电流、脉冲频率和基值电流四因素进行优化组合,找出与典型环境压力相符合的最优工艺参数组合。
[Abstract]:With the continuous development of offshore oil and gas resources, the maintenance of marine metal structures and submarine pipelines has become increasingly important. The underwater dry high pressure welding method eliminates the harmful influence of water on welding quality and has good welding quality. Adapting to the advantages of deep water construction has gradually become a common method of marine structure and submarine pipeline maintenance. Therefore, it is necessary to study the welding technology of pulse melting electrode gas shielded welding (GMAW-P) in high pressure environment. Firstly, the effects of environmental pressure, process parameters (arc voltage, peak current, pulse frequency, base current) and protective gas ratio on weld formation are studied. The test was carried out in the high pressure chamber, and the surfacing test of Q345 steel plate was carried out. The results show that the larger the ambient pressure is, the larger the weld melting width is and the lower the weld penetration depth is. The weld forming quality can be affected by changing the gas ratio, welding average voltage, pulse peak current, pulse base current and pulse frequency under high voltage environment. The effects of environmental pressure, welding process parameters and protective gas ratio on the microstructure, microstructure and mechanical properties of pulse GMAW welded joints of Q345 steel were studied by groove surfacing. Under the condition of ensuring that the other process parameters remain unchanged, the single parameter adjustment is adopted to carry out the test, and the influence law of the welded joint is analyzed and studied through the quality inspection of the welded joint. The tensile strength of the welded joint is higher than that of the base metal, and the higher the ambient pressure, the greater the Vickers hardness of the weld zone, and the tensile strength of the welded joint is higher than that of the base metal. After the optimization of arc voltage, the microstructure of weld zone is optimized, the Vickers hardness becomes smaller and the metal flexibility is enhanced, while the Vickers hardness and impact toughness of welded joints do not change much when the pulse peak current and pulse base current are increased respectively. The strength, hardness and impact toughness of welded joints increase with the increase of pulse frequency. Finally, the four factors of arc voltage, peak current, pulse frequency and base current are optimized by orthogonal test, and the optimal combination of process parameters is found out, which is consistent with the typical ambient pressure.
【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】：2016
【分类号】：TG444.72

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