Mix Welding Process Research And Its Application On Robot Multi-pass Vertical Welding For Thick Plate

Shield tunneling machine is a kind of large engineering equipment,which integrates mechanical,electrical and other technologies.In order to make it work normally,it is necessary to ensure the welding quality of shield tunneling machine.In the welding process of heavy machinery like shield tunneling machine,it is difficult to substitute the vertical welding operation because the installation position is not easy to change due to the huge weight.With the large structure of shield tunneling machine,multi-pass welding is needed and the welding situation is more complex.The research on robot multi-pass vertical welding technology can provide some theoretical basis for practical production.Firstly,based on high-speed camera and electrical signal acquisition system,combined with simulation of temperature field and welding test,characteristics of Mix and Universal process were compared and analyzed.The results show that Mix process has two stages,thermal process(with a high current)and cold process(with a low current).There are many peaks on the welding thermal cycle curve and the cooling rate is faster,which is conducive to the solidification of the molten pool,so Mix process is more suitable for vertical welding.Secondly,when Mix process was used in vertical welding,the influences of welding parameters on weld morphology and weld characteristic parameters were studied.It is found that larger welding current and slower welding speed will lead to poor weld formation.Finally,the root pass,filler pass and cap pass of multi-pass vertical welding were studied respectively,and the welding parameters were optimized.The results show that: Increasing groove gap and welding current properly can enhance the effect of penetration during root pass welding.In the filling passes,weld bead arrangement is carried out successfully based on the relationship between weld cross sectional area and welding parameters.Weaving welding can effectively increase weld width and reduce weld reinforcement during cap pass welding.In the process of multi-pass vertical welding,Mix process is used in root and filling passes process and the cap is welded by weaving Universal process,a well-shaped weld joint can be obtained.