PWHT effect on the mechanical properties of borated stainless steel GTA weldments for nuclear shield

To improve ductility of the welded joint of B-added austenitic stainless steels, postweld annealing effect has been studied. Gas Tungsten Are (GTA) welds of AISI 304-B3 stainless steel plates were annealed either at 700 similar to 1100 degrees C for 1 hour or at 1100 degrees C and 1200 degrees C, for 1 similar to 7 hours. Bending test of the welds in as-welded and annealed conditions resulted in cracks propagated along the welds' fusion line except the one annealed at 1200 degrees C, which revealed no cracks. Tensile elongations of the as-welded and annealed welds at the temperature up to 1000 degrees C were only a half value of the base metal, whereas the welds annealed at 1200 degrees C had fully recovered the original elongation of the base metal. Charpy impact test result exhibited the same tendency with annealing temperature. Elongated and accicular morphology of Y-(Cr, Fe)(2)B eutectic phase at the Partially Melted Heat Affected Zone (P.M.HAZ) of welds seemed to be responsible for the poor ductility of the welds. The welds annealed at 1200 degrees C for various durations, on the other hand, showed fully spheroidized eutectic phases at the P.M.HAZ with its size increased with annealing durations, suggesting that postweld annealing at the temperature as high as 1200 degrees C is required for the welds to have ductility matching that of base metal.