Irradiation Strengthening and Fracture Embrittlement of A533-B Pressure Vessel Steel Plate and Submerged-Arc Weld

Abstract

Plate and weld material of ASTM A533 Grade B, Class 1 steel furnished by the Heavy Section Steel Technology Program was characterized for irradiation strengthening and fracture embrittlement. Plane strain fracture toughness, K Ic, in the longitudinal orientation was determined ftom specimens irradiated at 540 F (282 C) to neutron fluence levels of 2 and 8 × 1019 n/cm2 (E > 1 MeV); longitudinal tension specimens were irradiated at 510 F (265 C) at 2, 4, 6, and 8 × 1019 n/cm2 (E > 1 MeV). Yield strength was more sensitive to irradiation strengthening than the ultimate strength, and the yield strength increase (Δσys, ksi) as a function of fluence (Ф) and temperature (T, deg. F) may be described by: Δσys = 22 [1- exp (-Φ/5 × 1018)] + Φ/1019(4.3−0.0038T) Irradiation levels of 2 and 8 × 1019 produced shifts of 185 F (103 C) and 275 F (153 C) in the 50-ksi√in KIc fracture toughness transition of A533 plate; the measured shifts agree closely with those predicted, 153 F (85 C) and 282 F (157 C), from a proposed correlation of shift in transition and change in yield strength. Fracture toughness KIc and tensile properties of plate material were independent of the orientation. The fracture toughness of ASTM A533-B submerged-arc weldment metal irradiated at 540 F (282 C) to a fluence of 3 × 1019 n/cm2 (E > 1 MeV) exhibited a marked sensitivity for irradiation embrittlement; the indicated shift of the 50-ksi√in KIc fracture toughness transition level was approximately 390 F. The yield and ultimate tensile strengths of ASTM A533-B sub-arc weld were determined for 510 F (265 C) irradiations to fluences of 0.5 × 1019 n/cm2 and 4.0 to 4.6 × 1019 n/cm2 (E > 1 MeV). Irradiation strengthening of weld yield properties is slightly greater than the longitudinal base properties.