Study Of Friction Stitch Welding Test Device And Welding Process

Friction stitch welding is a kind of friction welding technology, which belongs to a new type of solid-phase connection technology. With the reinforcement of worldwide offshore oil and gas resource developing, the exploiting depth of underwater oil and gas field increase continually, the connection and repair technology of deepwater engineering steel structure have been paid more attentions day by day. Because the performance of friction stitch welding joint is excellent and there is less effect resulting from environmental pressure on the welding quality, friction stitch welding technology develops rapidly in the repairmen areas of deepwater steel structure. In recent years, friction stitch welding technology has received great attention in the offshore oil countries. They have carried out a series of research and development work for the friction stitch welding equipment, welding process and the application of the technology in underwater connection engineering. In our country, as the strengthening of offshore oil exploitation and the developing of underwater engineering, the requirements of research on friction stitch welding are very urgent. At present, the studies of friction stitch welding equipment and welding process are still non-existent in China. Therefore, in this paper, the study on friction stitch welding test device and welding process has important engineering value and theoretical significance.Firstly, in this paper, the friction stitch welding test device design requirements have been proposed based on the friction stitch welding process and the parameters affecting the welding quality provided by the data from foreign research related. The first set of friction stitch welding test device has been designed meeting the technical requirements. Design work can be divided into mechanical system design, hydraulic system design and electrical control system design. Finite element analysis results show that the design of mechanical system is reasonable, safe and reliable. During the test of friction stitch welding process for LY12 aluminum alloy, the hydraulic system can provide adequate welding speed, welding pressure and welding torque to meet the requirements of process test. The design of electronic control system structure is reasonable; it can achieve the control of welding process.In the friction stitch welding process test, in order to monitor and acquire the parameters, a set of friction stitch welding test data acquisition system has been designed and developed for the process parameters. The data acquisition system can capture and store the test data. Its man-machine interface is simple and easy to learn. All test data can be stored directly as Excel format, which is easy to be researched and analyzed.Secondly, on the basis of friction stitch welding test equipment and friction stitch welding test data acquisition system, a series of LY12 aluminum ally welding process test have been designed and carried out, in order to study the influence of the several key process parameters on the welding quality. The main contents include:influence of argon gas protection on welding quality, influence of rotational speed on welding quality and influence of feed speed on welding quality The results show that:In the welding process, the use of argon gas protection can reduce the production of alumina and improve the welding quality of unit forming. Welding speed is the most important welding parameters for the welding process. The welding quality can be improved through increase the welding speed. The influence of feed speed on welding quality is restricted by the welding speed. Under the condition of high rotational speed, the increase of feed speed will help improve the welding quality. But, under the condition of lower rotational speed, the increase of feed speed can not improve the welding quality. Through a lot of test, a reasonable range of welding parameters have been determined, and a perfect FHPP weld has been acquired.In the study, after test of unit weld process, the experiment of friction stitch welding for LY12 aluminum alloy have been carried out further. The perfect weld of friction stitch welding has been acquired in the experiment. The results show that:the jump continued method is reasonable for friction stitch welding, which can avoid the unbalanced force on both sides of the drill in drilling. Other, the preheating of workpiece for friction stitch welding can help reduce the welding residual stress and improve the weld quality.Then, in the study, based on heat transfer, tribology, contact mechanics and other related theories, the thermal coupled simulation model of FHPP has been established by the finite element analysis software MSC.Marc. And the model Q235 steel material is also simulated. The computed results show that:the influence of welding process parameters is the same as that for LY12 aluminum alloy. It means that the influence variation of welding process parameters on friction unit welding do not change with changes in the material. Just, the different thermal properties and mechanical properties of materials lead to the numerical size requirement of welding process parameters are different. That will lay the foundation for the study of steel material welding process test in the future.Finally, the design requirements of the new pipeline friction stitch welding test equipment have been proposed based on the shortcomings and deficiencies of friction stitch welding test equipment reflected in the welding process experiments. The new test device adapts the bus communication. In addition to the spindle rotation and axial feed, the other movements are driven by AC servo motor, that have improved the control precision and equipment response speed. The equipment performance is improved greatly.The studies in this paper have great significance for the study of friction stitch welding equipment and welding process in our country.