Study Of The Friction Stud Welding Process

Friction stud welding is one of the friction welding technologies.With the continuously strengthening exploiting of offshore oil&gas resources in the worldwide scale,connection technologies and related safety ensuring technologies of underwater structures is got more and more attention.Friction stud welding technology has many advantages such as its excellent performance and being unaffected by the ambient pressure,so it has attracted extensive attention in the field of underwater connection,and many countries such as European Union,America,Brazil,and Japan have conducted a series of related research work and gradually applied it to the unimportant structures such as sacrificial anode connections,but domestic concern is very few currently.The dissertation is carried out based on foreign literatures and the problem extracted in engineering practice,and study of the friction stud welding process and safety in construction has been conducted.In this paper,the influence of main process parameters on the forming process has been studied by the procedure orthogonal test and procedure qualification test,and the results show that rotational speed is the most important parameters of affecting joint forming process,too low rotational speed is will lead to the welding suspension,and too high rotational speed is will cause excessive softening of the heat affected zone resulting in that axial pressure is difficult to build up.Feed speed affects the time to build up axial pressure.Rotational speed and feed speed together determine the heat input,and the heat input should be reduced in the weldable case as soon as possible.It is favorable for joint forming to set the axial pressure as “low-medium – high”,that is to say that using low axial pressure in the initial friction stage and using medium axial pressure in the stable friction stage while using high axial pressure in the upsetting stage.Besides,high levels of axial pressure should be set in the weldable case.The welding adaptability of friction stud welding has been analyzed through the welding tests on the plate and pipe,and the results show that the quality of welding on the pipe has a certain degree of reduction relative to the welding on the plate.Influence of welding ambient on the forming quality of welding joints has been analyzed through the welding tests in different welding ambient,and the results show that high quality welding joints can be obtained as long as the rotational speed matches with feed speed appropriately under the air condition.Rotation speed should be increased appropriately under the condition of underwater welding,and the scope of optimum technological parameters combination has widened,that is to say that high quality welding joints can be obtained easier under the condition of underwater welding.When the welding is done underwater using shielded studs,the protective layer on the stud may cause heat accumulating and that may be negative for forming joints.Besides,exploratory research on safety of friction stud welding in construction has been conducted by the method of tests,and it can be initially inferred that the technology has no risk of explosion when used for the welding of underwater pipeline in service.The significance of this paper can be seen as follows.It is the first time to briefly introduce and discuss the appearance,research status,engineering application and development prospect of friction stud welding,and the related research work has been conducted.Research production obtained in this study can provide technical reserves for China's marine engineering,and provide reference for further study in the future.