Study On The Deformation And Group Welding Conditions To GMAW Multi-Pass Welding Of The Symmetric Units Of Membrane Wall

The symmetric units of membrane wall made up of light pipe and fin is the key structural parts of boiler wall. The correction of welding deformation needs a lot of time, because the welding deformation decreases its strength capability and makes the assembly and welding of next step become more difficult. Therefore, developing a method to predict and control the deformation is essential. In this paper, the heating-elastic-plastic FEM of ANSYS is used to simulate thewelding process of the symmetric units of membrane, with the GMAW welding conditions to the actual production process. Heating-elastic-plastic analysis of large structure, which faces with the problems as simulation to Weld pool and filling no-balanced, large scale computing time and convergence difficulty, can be solved by using moving heat source which combines double ellipsoidal shaped model with the life-death element technique. At first, the welding process was studied from the temperature field, stress field and deformation in three areas. Then, the relation between the group welding conditions to multi-welding-pass and the deformation is researched. Conclusions are as follows:(1) The temperature distribution is symmetrical; the cooling rate of both sides is higher than the central region.(2) Residual stress increases with the further distance between nodes to the arc-starting face, but decreases with the higher heat-input. (3) The heat input inconsistent of the single flat welding pass is insensitive to the total deformation. There are some contributive sections which cause the decrease to the total deformation in the heat input of overhead welding pass, when the flat welding pass heat input is a certain section.On the base, the method of controlling the unit's deformation and computation model of the heat-input to each welding pass are brought up along with the experimental verification.