WELDING FEASIBILITY STUDY OF A THICK WALLED, CARBON STEEL PRESSURE VESSEL

To assess the problems involved in the fabrication of a 0.35% C steel reactor vessel shell of thickness up to 8 in., full-scale tests on weld details were undertaken. Branches set in and on the shell with weld thickness up to 5 1/ 2 in., welded manually using low-hydrogen electrodes, showed sound welds with 100 deg C preheat. Butt welds in 4, 5 1/2, and 8 in. plate, using the submerged-arc method, showed sound welds provided that a balanced welding sequence and preheat of up to 150 deg C was maintained. Four submerged-arc deposit compositions were investigated. Destructive examination showed that cold cracking in the weld metal or heat-affected zone was found where preheat was inadequate or when a weld deposit over-matching the tensile strength of the plate was used. The deposit most suitably matching the plate properties and giving no welding difficulty contained 0.09% C and 2.09% Mn. A test using the electro-slag process showed no apparent difficulty when welding this steel, and demonstrated the large economic savings to be obtained with the process. (auth)