Heat treatment optimization of China low-activation ferritic/martensitic steel with cerium addition

Abstract

Abstract Chinese Low-activation Ferritic/martensitic steel (CLF-1) with rare earth (RE) cerium (Ce) addition (RE-CLF-1) was prepared by a two-step method: vacuum induction melting (VIM) and vacuum arc re-melting (VAR) processes. The effect of heat treatment parameter on the microstructure and thermal mechanical property of the obtained RE-CLF-1 was studied. The heat treatment process of the RE-CLF-1 was finally optimized as two steps: (1) normalizing at 980 °C for 60 min, (2) tempering at 740 °C for 60 min, to get a complete martensitic structure and maintain its good mechanical property. For the Re-CLF-1 with optimized heat treatment, the elongation under uniaxial tensile test at room temperature was about ∼22 %, which is comparable to that of the CLF-1 steel. The yield strength and maximum tensile strength were up to ∼605 MPa and ∼738 MPa, respectively, which are larger than the CLF-1 steel, indicating its good mechanical property at room temperature. The ductile brittle transition temperature (DBTT) of the RE-CLF-1 steel was about −50 °C, which is higher than the CLF-1 steel. Additionally, Ce segregation around the M23C6 precipitate was observed, indicating that Ce could play an important role on the formation and clustering behavior of precipitates in RE-CLF-1 steel.