An assessment of the embrittling effects of certain residual elements in two nuclear pressure vessel steels (A533B, A508)

Abstract

The intergranular embrittlement caused by such impurity elements as P, As, Sn and Sb in ferritic steels can be manifested in several ways: (1) an impairment of toughness or impact transition behaviour (temper embrittlement); (2) a reduction in high temperature ductility and resistance to intergranular failure (creep embrittlement); and (3) degradation in properties at the operating temperature caused by the accumulation of creep damage during a post-weld stress relieving heat treatment (stress relief embrittlement). A detailed study of stress relief embrittlement (s.r.e.) and temper embrittlement (t.e.) in bainitic microstructures representative of those found in weld h.a.zs has been carried out on a number of casts of A533B class 1 (MnMoNi) and A508 class 2 (NiMoCr) steel.