Austenitization and Tempering Temperatures Effects on EUROFER 97 Steel

Abstract

EUROFER 97 is considered as standard steel for the nuclear applications in the case of high radiation density for first wall of a fast breeder reactors. Based on such consideration the microstructural behaviour of EUROFER 97 after thermo-mechanical processing is fundamental, since such materials properties are interesting also for innovative solar plants. In this paper the effect of thermo-mechanical behavior on the mechanical properties of EUROFER 97 has been analyzed by hot rolling followed by heat treatment on laboratory scale.A strong effect of reheating conditions before rolling on the material strength, due to an increase of hardenability following the austenite grain growth is found. A limited effect of the hot reduction and of the following tempering behavior is found in the considered deformation-range investigated. A loss of impact toughness is detected together with the hardness improvement.Mechanical properties are depending on the tempering temperature and an improvement of tensile yield stress (YS) and ultimate stress (UTS) was determined in tensile test carried on at T=550°C and T=650°C, e.g.: YS increase from about 400 MPa for standard EUROFER 97 [1] to about 550 MPa in samples treated by a tempering temperature of 720°C instead of the standard 760°C for EUROFER 97. Same trend has been found for UTS results.