ESSC & DUPLEX 2019

The duplex stainless steel family is widely used in many structural applications due to its high mechanical resistance with a yield stress of about two times the austenitic’s and its outstanding corrosion resistance. An example of this is the grade EN-1.4462 with a yield stress value usually higher than 450 N/mm2 and the tensile strength value between 650 and 880 N/mm2. Another important mechanical property of the duplex is its toughness, which must be higher than 100 J at room temperature and above 40 J at -40º C. The mechanical properties are sensitive to the microstructure, especially the toughness and more this property at low temperature. So the annealing treatment, following the hot rolling stage, must be designed to get the right microstructure and the desired mechanical properties. The present paper describes the investigation carried out to evaluate the influence of the annealing conditions on the microstructure and toughness at low temperature of duplex EN-1.4462. Several commercial hot rolled samples of this grade steel have been treated at lab scale with different temperatures and holding times. After that, the toughness specimens have been machined and tested at -40º C. Finally, the microstructure of the treated samples has been analysed by light and (field emission gun) scanning electron microscopy. The results of the investigation have shown that the impact test results strongly depend on the microstructure, not only on the phase balance and the presence of intermetallic phases but also on the size and recrystallization level of the main phases.