Numerical Simulation Of Multi-layer And Multi-pass Welding Deformation At Turbine Diaphragm Outer Ring

Turbine plays an irreplaceable role in the power plant equipment, which isthe heart of the electric power industry. Diaphragm is one of the maincomponents of nuclear power unit flow passage, which acts the role of fixingstatic blade and preventing interstage leakage, to ensure unit’s economy andsecurity. Taking into account the diaphragm’s running environment, processdesign requires surfacing stainless steel corrosion resistance layer at the innerand outer circle of outer ring, in order to improve the ability of anti-water erosionof diaphragm outer ring. Harbin Turbine Company limited makes a small piece ofphysical experiment surface which can characterize the typical structure ofdiaphragm outer ring. In this paper, finite element analysis software MARC,firstly is used to simulate test piece by adjusting parameters to narrow the gapbetween the results of the experiment, and then apply the adjusted parametersto simulate welding process of diaphragm outer ring.Simulation results of test piece’s welding deformation show that the basemetal’s displacement is small, while the liner’s is big and has obvious gradientdistribution after welding. With the increasing distance from weld, thedisplacement increases, and the maximum displacement is located at the outeredge of the liner on the side of crater, which is17.1mm and mainly reflected inthe Y-displacement. Comparing experimental data with simulation results finds,there is a certain deviation in terms of angular distortion’s specific values, but thedeviation is within the allowable range(under10%). In addition, the paper alsodesigns using the welding sequence from both ends to the middle to weld the testpiece. In this case, the maximum displacement is located at the middle of testpiece, which is12.8mm. Compared to welding sequence from beginning to end,the maximum displacement is reduced25.1%. This is because welding from both ends to the middle, temperature field overlaps each other, temperature gradient issmall, and thus welding deformation is reduced. By comparing with the angledata of test piece’s starting and ending under two welding sequences, finds thatthe use of welding sequence from both ends toward the middle affects onlyangular distortion of test piece’s ending, but has no effect on angular distortion ofthe starting.Simulation results of diaphragm outer ring’s welding deformation show thatwhen firstly welding the inner circle and then outer circle, the total nodaldisplacement is7.8mm and the total equivalent residual plastic strain is13.3%.when welding the inner and outer circle simultaneously, the total nodaldisplacement is3.8mm and the total equivalent residual plastic strain is8.6%.Displacement and equivalent residual plastic strain are respectively reduced by51.3%and35.3%. This is because welding deformation inhibits mutually whenwelding the inner and outer circle simultaneously. In addition, when backstepwelding the inner and outer circle simultaneously, the total nodal displacementand total equivalent residual plastic strain are respectively3.7mm and8.2%. Itis little different from welding the inner and outer circle simultaneously, whichmay be caused by excessive subsection’s length.