Fracture toughness and fracture behavior of SA508-III steel at different temperatures

Abstract

The fracture toughness of SA508-III steel was studied in the temperature range from room temperature to 320°C using the J-integral method. The fracture behavior of the steel was also investigated. It was found that the conditional fracture toughness (J _Q) of the steel first decreased and then increased with increasing test temperature. The maximum and minimum values of J _Q were 517.4 kJ/m² at 25°C and 304.5 kJ/m² at 180°C, respectively. Dynamic strain aging (DSA) was also observed to occur when the temperature exceeded 260°C with a certain strain rate. Both the dislocation density and the number of small dislocation cells effectively increased because of the occurrence of DSA; as a consequence, crack propagation was more strongly inhibited in the steel. Simultaneously, an increasing number of fine carbides precipitated under high stress at temperatures greater than 260°C. Thus, the deformation resistance of the steel was improved and the J _Q was enhanced.

Keywords

low alloyed steel / fracture toughness / fracture behavior / temperature / dynamic strain aging / nuclear power plants

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