Tensile and impact properties of thick-section plate and weldments

Abstract Most nuclear pressure vessels have been fabricated from ASTM A533, grade B, class 1 steel plate. This steel is quenched and tempered in order to obtain its optimum properties in section sizes from 6 to 12 in. in thickness. The quench-and-temper heat treatment results in a variation in mechanical properties through the thickness of the plate. The room-temperature ultimate tensile strength varies from nearly 97 000 psi at the plate surface to about 89 500 psi at the midsection ( 1 2 T ). The greatest effect of the quench is observed in the nil ductility transition temperature. The 30 ft lb Charpy V-notch temperature varies from −150°F at the surface to + 10°F at the 1 8 T location. Anisotropy due to the rolling is reflected in the upper shelf values of the longitudinal, transverse, and through-the-thickness properties of the plate, These values are 115, 100, and 80 ft lb, respectively, for the three directions. Three welding processes are employed in the fabrication of the pressure vessels. These are the submerged arc (subarc) process, the shielded metal-arc process, and the electroslag process. The subarc and shielded metal-arc processes employ multipass welding techniques and the weldments resulting from these processes are only stress relieved after welding. The electroslag weld consists of a coarse-grained (ingot-like) structure which is unacceptable in the as-welded condition. The electroslag weldment is quenched and tempered after welding. The ultimate tensile strength of the welds is uniform through their thicknesses. Their ultimate tensile strengths are all similar, about 80 000 to 85 000 psi. The impact properties of the electroslag and multipass weldments are not similar. The electroslag weld metal has an upper shelf Charpy V-notch energy of about 80 ft lb, whereas the multipass welds (subarc and shielded metal-arc) have shelf values of from 120 to 150 ft lb. Further, the 30 ft lb C v temperature of the subarc and shielded metal-arc welds are near −50 to −70°F. The temperature for the electroslag weld metal for the same energy value is −20°F.