Laser-arc Hybrid Welding Research Of High Strength Oil And Gas Pipeline Steel

As the growth of demands for gas and oil, people are pursuing high speed transportation of these energy, which accelerates the development of high grade, long distance and large diameter pipeline. In the construction of long distance pipeline, welding quality and speed are key factors of project. Laser-arc hybrid welding is a welding method of high quality and efficiency. With its large penetration, strong adaptability and fast welding speed, etc, it has obvious advantages in pipeline welding.In this paper, we use laser-MIG hybrid welding to research and discuss the effects of main technological parameters like laser power, laser arc distance and defocusing amount in welding process. Suitable hybrid welding parameters are obtained by experiments, when the laser power is 3 kW, welding speed is 0.5 m/min and welding current is 140 A, we can get relatively good weld forming. Not only the coupling effect of laser heat source and arc heat source is the best, but electrical signal waveform is also stable.In order to improve the welding efficiency and reduce the possibility of crack, we select suitable hybrid welding parameters and obtain qualified weld joints of five kinds blunt edges(3.5,4,4.5,5,5.5 mm) by different heat inputs. Through analyzing the microstructure of heat affected zone, we get the grain size and number's change rule of lath bainite and granular bainite by different heat inputs. By analyzing the results of tensile test, bend test, impact test, hardness test, five kinds of welding joints all meet the pipeline route specification of west-to-east gas transmission second line project, the welding joint with heat input of 16.1 kJ/cm has good toughness and comprehensive performance.This paper simulates the temperature field and stress field distribution of 10 mm thickness X80 pipeline steel welded by laser-arc hybrid welding. We establish double ellipsoid heat source model and compare the weld cross section shape and weld width of simulation and actual experiment to verify the rationality of welding heat source model. By simulating analyzing and calculating laser-arc hybrid welding of X80 pipeline steel stress field, we get the distribution of longitudinal residual tensile stress field. Compared with the experiment result, the simulative results are in good agreement with the actual situation.