Effect of Thermal Ageing on the Mechanical Properties of PWR Pressure Vessel Steels and Weldments

摘要

The effects on mechanical properties of aging treatments in the temperature range 300 to 550 C for durations up to 2 x 10 to the 4 and their significance to PWR operational conditions are discussed. The materials investigated include A533B plate and A508 forging materials, simulated heat-affected-zone-microstructures and actual weldments. Changes in hardness, tensile properties, the ductile-brittle-transition-temperature (DBTT) and upper-shelf crack growth resistance was assessed, together with associated changes in fracture mode and grain boundary chemistry. The results indicate little or no change in mechanical properties other than DBTT. Three separate embrittlement mechanisms have been identified: strain-aging at 300 C, grain boundary segregation at 400 to 500 C and matrix softening at 500 C and above.