Simulation Of Stiffness Controlling On Welding Distortion Of Large Annulus Structure

Because of steam turbine diaphragms serving in special environment, itrequired to weld stainless steel on outer annulus of diaphragms. Due to the largeamount of welding, the welding distortion affected the assembly quality. Tocontrol the welding distortion of the diaphragm outer annulus and solve theproblem of the high test cost of large welded structure, numerical simulation isused to predict the welding process. Moreover, aiming at the problems that arelarge simulative component, large amount of data and long computing time insimulating large welded structures, welding temperature field based on similaritytheory is analyzed to define the relationship of residual stress and weldingdistortion between the simulative component and practical structure in order toreduce the elements and nodes. Instead of double-ellipsoid heat source model,using the segmented moving heat source model can reduce the time incrementsand iterative operations. Moreover, to ensure the accuracy, similarity structurephysical test is designed to verify the accuracy of simplify method. Therefore,the study about the simulation of stiffness controlling on welding distortion oflarge annulus structure has the meaning of practical engineering.The welding distortion of diaphragm outer annulus is controlled by weldingthe stiffness fixing, the stiffness fixing is the welding reinforcing. Two types ofwelding reinforcing are designed and the reinforcing’s ability of controlling thewelding distortion is compared by simulation. The result is that both of the twotypes can control the welding distortion and the ability of type A is better thantype B’s. When the reinforcing of type A is used, the distortion of reinforcing islarger than diaphragm’s. When the reinforcing of type B is used, the result isopposite. Especially in controlling the axial distortion and circumferentialdistortion, the reinforcing of type A can ensure the perpendicularity and reducethe influence of heating expansion. On welding technology, it optimized thewelding speed and fixtures. The better welding speed is6mm/s, the better numbers of fixtures is6. The simulation of welding is finished by using clusterbanding and the time of the simulation is about50hours. Basing on therelationship of residual stress between practical structure and simulativecomponent, the residual stress peak value of practical structure is calculate about86MPa.