Heat Treatment and Impact Toughness of the F55-Grade Steel

Low-temperature impact tests are commonly performed to test the quality of industrial forgings in Duplex Stainless Steels (DSS). The F55 grade is a highly alloyed Super DSS characterized by excellent low-temperature toughness in the solution annealed condition. Because of the rich chemical composition, it is very prone to precipitation phenomena during quenching. This research investigates the effect of the material cooling rate on the impact toughness of a water-quenched F55 steel, characterized by the absence of σ-phase. Furthermore, by elaborating the impact test data, the T45J [°C] and the KV−46°C [J] parameters have been identified. They are two indicators based on the austenite/ferrite ratio and the material cooling rate, useful for predicting the material impact behavior prior to testing.