Welding Technology Study And Welding Tooling Design Of Underwater Friction Stud For X65 Submarine Pipeline

Submarine pipelines are usually protected against corrosion by the addition of sacrificial anodes,which are easily worn or lost in the marine.The traditional method of installing sacrificial anodes underwater in China is pipe clamp installation,but its connection reliability is low.Friction stud welding can achieve high efficiency of stud welding on components,and is not sensitive to water depth as a solid phase welding method.It has outstanding technical superiority when used for sacrificial anode replacement of submarine pipelines.At present,a large number of underwater anode installation projects in China are monopolized by foreign companies using friction stud welding technology,which has high installation cost and long cycle.In order to break the monopoly of foreign technology.In this paper,the underwater friction stud welding process of X65 submarine pipeline is studied,and a set of welding tool is designed and manufactured for underwater anode installation.The main research contents of this paper are as follows:(1)Experimental study on weldability of underwater friction stud welding.The weldability test of the friction stud welding in the conventional underwater environment is carried out,and the process parameter interval in which the welding can be carried out smoothly is obtained.The morphology analysis of the welded joint is carried out.The results show that the joint between the stud and the pipe is good,and no macroscopic defects are found in the bonded area..The mechanical properties of the welded joints were tested.The results show that the tensile strength of some welded joints is better than that of the base metal.The inclination of the studs and pipes in the bending test can reach 45° without fracture.In the torsion test,the torque can reach 300 N·m and the torsion angle is around 300°.Impact toughness meets the requirements for Class B welds in AWS D3.6.The hardness distribution trend is low on both sides and high in the middle.The corrosion resistance test was carried out.Theresults show that the corrosion resistance is the best in the weld zone,the heat affected zone on both sides is slightly worse,the pipe base material zone is the third,and the stud base metal zone is the smallest.(2)Study on the influence of process parameters and welding environment on the property of welded joints.Experiment on the influence of process parameters and welding environment on joint properties.The results show that the tensile strength of the joint is inversely proportional to the spindle speed at a feed rate of5 mm/min.When the spindle speed is 8000 rpm,the tensile strength of the joint is proportional to the feed rate.When the welding pressure is mentioned to 7 MPa,the welding quality of the joint can be improved.When the water temperature is 5°C,it is necessary to increase the spindle speed or reduce the feed rate to obtain a welded joint with excellent mechanical properties.The tensile strength of the welded joint under3 MPa water pressure(300m water depth)decreased slightly.There is no significant difference in the tensile strength of the 6-inch,12-inch,and16-inch pipe joints.(3)Design of underwater friction stud welding and welding tooling for submarine pipeline.In order to realize the installation of the underwater sacrificial anode of the submarine pipeline,the underwater friction stud welding tooling was designed and manufactured,and the installation test was carried out.The mechanical body reduces the spindle mass from approximately 80 kg to 25 kg through material upgrade and structural optimization.The armed grip fixing scheme was selected and subjected to force analysis,and the anode mounting block was designed in conjunction with the pipe.The main improvement of the hydraulic system and control system is to adapt the hydraulic circuit with the Remote Operated Vehicle(ROV)system,and design the potential of the control element to automatically weld with the control potential.In the welding tooling test,the underwater friction stud welding and Tungsten Inert Gas(TIG)Welding are compared.The results show that the tensile strength of the welded joint is about 10 kN,which is higher than that of TIG welding,which meets the requirements of underwater sacrificial anode installation.