Numerical Simulation Of T-tube Welding Deformation And Welding Process Optimization

The improvements of welding technique play significant roles on the industrialdevelopments. Due to the extremely high temperature and unevenly-distributedtemperature field which are generated during welding process, the original materialshave different shrink velocities during cooling, resulting residual stresses around thesurrounding welding area. This can significantly affects the lifetime of welding partsand influences the texture of metal material and mechanical features. Therefore it isnecessary to simulate the temperature field, which can be used to optimize the designof weld elements.In this study the three-dimension finite element analysis softwares (AltairHyperWorks、Visual-Environment, Sysweld, and weld-planner were used to simulatethe appropriate constraints imposed on the classic T-type tube (heading pipes),through which optimal welding design was achieved. The equation of dual-ellipsemoving heat source was solved using SYSWELD, the temperature field and residuestress during cooling were analyzed, and the data describing complicated structures ofwelding model were obtained. Based on the results of simulation of temperaturefield, the clamping-constraint and welding order of integrated welding were optimized.This provides important information for actual welding application.The numerical simulation results of individual T-tube shows that the temperaturewas low at the beginning of welding process. The welding wire and parts did not melt.The area of heat which was influenced was fairly small. The maximum temperature ofT-tube was lower than the stable temperature. The welding parts and welding wirewere welded together at smaller welting area. The heat source showed the ellipseshape. The temperature increase significantly when welding was process further. Thewelding wire and parts were melted at their melting points. The temperature ofheating source of welding area can go as high as the melting point of low-carbon steel. The area of heat which was influenced became greater. At the time of4.32second,the first and second welding stitches were finished and the influenced heat areas havecovered the entire field. The temperature was as high as2200oC. Same phenomenawere observed for the3rd and4th welding stitches except that the temperature andresidue stress were relative greater. After20seconds, each node in welding stitchesstarted cooling down and the temperature deceased accordingly. This would generatelarge residue stress. If multi-vertical tubes were welded in an order then the locationbetween each vertical tube would deformed due to the large concentrated residuestress. Therefore in order to optimize this kind of deformation, a method using ahigher temperature to cool down can be applied. This is helpful to decrease the rate oftemperature decreases and avoid the residue stress concentrated, and hence decreasethe structure deformation.The simulation results of integrated welding showed that clamping-constraintwas applied to integrated structure from x, y and z three directions. The deformationcan be controlled within1mm. The deformation trend was changed to “--”shape,instead of “H”shape. This is helpful for the optimization of T type tube. The weldingorder of1st-3id-5th-2nd-4th was believed an optimized order, which can decrease thedeformation. In addition, the deformations in x, y, and z were distributed to both endsof each vertical tube. The welding was optimized.This study provides important information for future welding process simulation.Understand the distribution of temperature field and residue stress can shorter theduration of trial and error, which can greatly the accuracy of optimization design. Toour knowledge this study is first to optimized the clamping-constraint and weldingorder. This provides accurate guide for actual design.