Investigation On The Radial Friction Welding Process Of Steel Pipe

Oil and gas pipeline welding method is still conventional fusion welding technologybased now, existing problems such like high production costs, low productivity and difficultyto guarantee welding quality. As a new type of pipeline butt welding method, radial frictionwelding has a broad application prospect in future pipeline construction for its efficient,high-quality technological features.According to radial friction welding process requirements, the HSMZ-80hybrid axialfriction welder’s mechanical system, hydraulic system and control systems were modified,successfully achieved radial friction welding function on the axial friction welder.The radial friction welding technology research of open radial ring to45steel bars, closedradial ring to45steel bars and closed radial ring to37CrMnMo steel tube have beenconducted successively for the realization of joining radial ring to steel pipe by radial frictionwelding. Radial ring structure parameters are designed based on radial ring’s force analysis,deformation analysis and friction torque analysis. The reasonable radial ring structure size aredetermined by welding process test. In order to explore radial friction welding parameters,orthogonal tests of open radial ring to45steel bars, closed radial ring to45steel bars andclosed radial ring to37CrMnMo steel tube have been conducted and optimal weldingparameters have been obtained. On the basis of time and displacement control, peak torquecontrol has been adopted in the radial friction welding process test and succeeded in solvingthe problem of motor rotation blockage. Expansion bolt was adopted to support steel pipewhen joining closed radial ring to steel pipe, which effectively prevent the steel pipe radialcontraction deformation and improved the quality of welding joint.In this study, macrographic examination, shear test, microhardness test, scanningelectron microscopy test and microstructure test have been conducted to analyze the radialfriction welded joint of45steel radial ring to37CrMnMo steel pipe. Test results showed that:Radial friction welding joint formed well under appropriate welding parameters; The averageshear strength of the weld is up to400MPa, which is higher than45steel base metal;Microhardness of the joint showes a gradually rising trend from both sides of the base metalto heat affected zone to the center of the weld; The grains refine gradually from both sides ofthe base metal to heat affected zone to the center of the weld; Metallurgical structure of thewelding joint is good, and there is no defects such as welding pores, welding slag and weldingcrack.Research results show that joining radial ring to Steel pipe by radial friction welding canbe realized successfully under appropriate welding parameters. The microstructure andmechanical properties of the welding joint are good. This study enriches the basic data ofradial friction welding processes and further reveals the mechanism and regularity of radial friction welding process which help to expand radial friction welding processe to oil and gaspipeline welding.