Seamless shell course forgings for heavy-wall reactor vessels: A forgemaster's critical review

A review of current international specifications for forged pressure vessel (PV) components has shown that the steelmaking requirements are sometimes in conflict with the reality of worldwide installed facilities. A comparative investigation of three melts of SA-508 Class 3 steel has proven that vacuum carbon deoxidation offers toughness properties, even in the heat-affected zone, that are at least comparable with those obtained with the conventional fine-grain practice. Manufacturing experience with large hollow ingots, up to 181 metric tons, yielded quality results definitely comparable to those achieved with conventional hot pierced ingots. A review of specified post-weld heat treatments (PWHTs) has suggested that during PWHT some zones of a pressure vessel could undergo temperatures never reached either during the previous tempering treatments or during the simulated PWHT of acceptance test coupons. PWHTs at relatively high temperatures, therefore, should be avoided, especially for the 2.25Cr-1Mo steel