The Design And Welding Process Research Of Elastic Rail-type Pipeline Girth Welding Robot

Pulsed gas metal arc welding(P-GMAW)is one of the most widely used processes in pipeline all-position welding,but it has higher demands for the mechanical properties in the welding process.Therefore,an elastic rail-type pipeline girth welding robot is designed in the present paper,then the research of the effect of pulse parameters to the quality of beads in downward welding,vertical position welding and over-head welding is launched under the circumstance of the speed and position demands for the circle walking machine,lateral adjusting machine and welding torch have been met.The field experiment and metallographic structure analysis have illustrated that welding parameters have a significant impact on the mechanical properties of the welding joints.Firstly,the development of rail crawling machine and elastic orbit that correlate the P-GMAW welding process is introduced in this paper.Its key techniques consist of developing a new type of travel unit,lateral adjusting unit,altitude adjusting unit,welding torch swing unit and orbit.The main illustration is about the system’s structure,action principle and key points of design.Then the electronic control systems of the welding machine and welding process are designed,specifically the model selections of motors,motor drivers and encoders,besides the circuits of welding currents and voltage detection are designed.Secondly,in order to study the effect of the welding parameters to the quality of beads in the all-position welding,the pipeline welding is divided into downward welding,vertical position welding and over-head welding.The effect of the pulse parameters to the droplets transfer in different welding positions under the same average currents and voltage is studied through the previous research results,and an empirical formula is established,which can provide the parameter selection basis for the field welding.The analysis of the welding wire dry extension illustrates its auto-regulation can keep the droplets transfer continuously to the welding molten pool.Lastly,in order to preliminary validate the correctness and applicability of the empirical formula mentioned above,the field experiments of downward welding,vertical position welding and over head welding are made.And for the sake of further illustrate the mechanical properties of the welding joints in all-position welding,the metallographicstructures of the three different welding positions are made and analyzed by metallurgical technology.