Numerical Simulation And Experimental Verification On Multi-wires LSAW Of The X80Pipeline

Longitudinally Submerged Arc Welding (LSAW) can be used in the production of steel pipelines with large diameter, thick wall and high strength, which are often used at trunk line in high pressure oil and gas transportation. The performance of the weld seam is the key factor of welded pipe safety. Most of the welding methods need to adopt different kinds of heat source for heating. When welding the metal is heated and melted under the action of heat source. After the heat source leaving the melting metal begins to cool down. So there would exist heat input, transmission and distribution problems in the whole welding process. The weld have different thermal cycle curves in different processing parameters, and thus different microstructures in welded joints and heat affecting zones are obtained, which would leads to different weld performances. It will take a lot of manpower and material resources to measure this kind of curves in the actual production.Based on ANSYS software, the simulation software for LSAW is developed by using the moving boundary technology for the treatment of moving heat source and using the viscous amplification method considering convection heat transfer. The several modules such as moving ellipsoid heat source, power distribution and solder filling are programed by using APDL, and the pre-processing and post-processing interfaces are also developed in order to meet the requiremnts of enterprise engineers. In these interfaces the specific parameters such as material physical parameters, model dimension and welding parameters can be input conveniently and the appropriate simulation results can be obtained.Based on the developed simulation software, the influences of some single factors such as thermal conductivity, specific heat capacity, plate thickness, line energy, preheating temperature and wire spacing on thermal cycle curve of multi-wires LSAW are studied firstly. And then the coupling influences of plate thickness, line energy, preheating temperature and wire spacing on the thermal cycle curve are researched by using the orthogonal experiments. At the same time, the influences of power and welding speed on thermal cycle curve are analyzed, The results show that the cooling rates of the heat affected zones are very close and the highest temperature of the molten pools is clearly increased with the increase of welding speed when the welding linear energy keep constant. Finally the influences of the power allocation among the wires on welding thermal cycle curve are discussed, and the results show that the power distribution among the wires of multi-wires LSAW will impact the highest temperature of the molten pool. For the four wires LSAW, the highest temperature of the molten pool is relatively low when the energy of the formal two wires takes60percent of the total.The simulation is verified through the cases, from Chu Kong Steel Pipe CO., LTD, of the X80steel with22mm thickness using four wires welding. The simulation results coincide well with the experimental ones, which shows the mathematical model and the numerial method of this paper are right, and the simulation software can be used for the technique optimization of multi-wires LSAW.