Research On Narrow Groove Welding Technology Of Full Position Rotating Arc In Pipeline

With the rapid development of economy and society,the scale of long oil and gas pipeline is increasing,and the pipeline is developing to large diameter,large wall thickness and high pressure,which puts forward higher requirements for the field welding construction.For thick plate welding,rotating arc narrow gap welding technology can not only ensure the welding quality,but also improve the welding efficiency.In order to study the practicability of the utilization of the rotating arc narrow gap welding technology in the pipeline laying construction,the influence of droplet transfer and process parameters on weld formation of typical position rotary arc in pipeline all position welding process was studied.Based on the analysis of the pool forming characteristics of different positions,the parameters are optimized to realize the full position automatic welding of the rotary arc narrow groove pipe.In the flat welding position,the droplet transition behavior was observed and analyzed by using the high-speed camera system.At different positions of the groove,the droplet transition forms have periodic changes: the droplet transition occurs near the middle of the groove,and the jet transition occurs near the lateral wall.The wire feeding speed is matched with the welding speed through the theoretical calculation,and a set of theoretical parameters can be referred to.The influences of wire feeding speed,welding speed and rotation frequency on weld forming quality were studied.In vertical and overhead welding position through the orthogonal experiment design,establish experimental results classification standard and scoring criteria,compared with the result of the experiment,calculation of rotational frequency,welding speed and wire feed speed,the mean square value of the three process parameters on the result of the experiment the influence degree of the sort,for welding speed > wire feeding speed >rotating frequency,and choose the optimal parameter combination of vertical position is rotating frequency of 10 Hz,welding speed is 32 cm/min,wire feed speed 8.5 m/min,the optimal parameter combination in overhead welding position for rotating frequency for 15 Hz,the welding speed is 24cm/min,and the wire feeding speed is 7.5m/min.The optimized parameters were used for single multilayer welding,and the well-formed and defect-free welded joints were obtained in both vertical and overhead welding positions.The influence of gravity,arc force and surface tension on the weld formation is analyzed.The mechanical properties of the welded joints were tested,and the tensile strength was up to 610 Mpa.The fractures of the specimens were all in the base material,and the tensile strength was higher than that of the base material.When the positive bending and the back bending reached 180°,no cracks appeared in the weld specimens.The rotating arc welding gun is integrated into the self-developed automatic welding equipment for laying sea pipes,and the obtained process parameters of typical spatial position are used to carry out the rotating arc full position welding experiment for the sea pipes with the specification of ? 457 × 15.9mm and the material of X65,and the all position welding joints with good appearance and qualified ut detection are obtained.