Influence of normalising temperature on MX precipitation behaviour in high-chromium steel

Obara, Satoshi; Onizawa, Takashi  ; Wakai, Takashi ; Asayama, Tai 

This study investigates the influence of normalising temperature on metal carbonitride (MX) precipitation behavior and mechanical property of high chromium (Cr) ferritic steel for sodium cooled fast reactor (SFR) structures. Generally, mechanical strength in high Cr steel is increased addition of vanadium (V) and niobium (Nb), because V and Nb play a role of precipitation strengthening elements as metal carbonitride (MX) particles. However, precipitation behavior depends not only on the amount of V and Nb but also on the heat treatment conditions. In this presentation, in order to investigate the optimum heat treatment conditions for FBR structural materials, several kinds of high Cr steels with different heat treatments were produced and a series of mechanical tests and metallurgical examinations were conducted.