Research On Electric Slag Cladding Technology Of Inconel690for Nuclear Power Steam Generator Tube-Sheet

The cladding technology of Inconel690tube-sheet is one of the key technology tomanufacture nuclear steam generator main equipment. Because a Inconel690electroslagcladding has many welding difficulties, thermal crack, bite edge, slag inclusion,combining surface crack defects such as poor fusion and heat affected zone are easy toappear. In order to ensure the safety operation of plant, ASME specification, threegenerations of new engineering standards and localization of technical standards haveput forward higher requirements about tube sheet welding materials, weldingparameters, welding corrosion properties, the mechanical properties, the mothermaterials quality evaluation in heat affected zone and so on.Based on ASME Code, engineering standards on three generations of new nuclearpower plant steam generator and standards of localization technology, the surfacingwelding of Inconel690was realized. By welding parameters matching test, electroslagwelding method to evaluate the base crack in heat affected zone test and simulationapplication test, the optimum parameters of the welding process is determined. Thewelding current was1050±30a. The welding voltage was23to25v. The welding speedwas180-220mm/min. The overwhelming amount was7-8mm.For the electroslag cladding of Inconel690tube plate, LAF1600DC power and125-ESI-300type special welding head for electroslag cladding were chosen. Thecombination of Inconel Weldstrip52M welding belt and Incoflux ESS2flux were used.Weld forming was regular and beautiful. No defects such as crack, bite edge, slaginclusion and so on were appeared. After heat treatment, non-destructive testing,welding layer of metal under normal temperature and high temperature mechanicalproperties test, chemical analysis and corrosion test showed that results meet the nuclearpower product technical standard requirements.Crack evaluation experiment about samples of SA-508Gr3CL2steel electroslagwelding Inconel690, MT test and bending test of combining with the surface showedthat the toughness of cladding layer metal is good. And the fusion is good in thejunction surface of weld and parent metal. And no defects such as cracks exist. Bycladding layer surface and the lateral metallographic test for100times and500timesrespectively to multiple profiles of metallographic testing, no cracks and other welddefects were found. These series of crack evaluation test proved crack was not exited inthe junction surface between welding layer combined with parent metal and parentmetal heat affected zone.The products welding procedure qualification test and the ring to the simulation experiment were also made. The results of procedure qualification test and simulationproducts for annular electroslag welding test plate of PT, UT NDT, side bend test wereall qualified. Research data and results showed that using electroslag weldingtechnology to achieve large area surfacing for Inconel690alloy tube sheet of threegenerations of new nuclear power plant steam generator is feasible.