Research On Pipeline All Position Welding Process Of Tandem Double Wire Eutectic Pool

As a result of high efficiency and good quality,pipeline automatic welding has been greatly applied in oil and gas pipeline construction.As pipeline diameter and wall thickness increases,the demand for high-efficiency pipeline automatic welding technology is more and more urgent than ever before.Tandem arc welding is a relatively new technology,which has higher deposition rate and lower line energy.When it comes to conventional arc pipeline welding,tandem pipeline arc welding has the edge of effectively reducing the number of workstations and the input cost of butt welding.In this paper,based on the full investigation of the research status of pipeline all position welding process at home and abroad and the characteristics of tandem double wire welding,the experimental scheme of tandem double wire pipeline all position welding process is proposed.The main work is as follows.In the first place,welding parameters including welding speed as well as wire feeding speed are calculated and the relation equation between both two parameters is analyzed.In addition,the arc force on twin wires,the all position force of two wires on molten pool and the formation of molten pool is under careful analysis.Finally,the best welding process specification is obtained.Three major variables are picked among the various parameters to conduct statistical test,and they are welding speed,wire feeding speed and arc length correction.The purpose of this operation is to research their effect on bead formation parameters of which penetration,width,sidewall penetration and corner angle are included.A mathematical model made by Design-Expert software that describes the effect of welding parameters on weld profile is established at 0°,45°,60°,90° and 180°.According to the influence diagram of design expert factors,the optimal parameter combination of five welding positions of 0°,45°,60°,90° and 180°is analyzed,thereby offering areasonable reference for the application of tandem double wire eutectic pool welding technology in pipeline welding.Experiments show that this technology has practical significance for shortening welding time and improving welding quality.The mechanical properties of the welded joint(tensile,bending,impact and microhardness tests)were tested,and the conclusion was drawn: the tensile samples were fractured at the base metal,and the tensile strength was greater than that of the base metal;the positive bending and back bending of the samples could reach 180 ° without defects;the absorption energy of the sample impact test was greater than 90J,which met the requirements.