Use of the small punch test to determine the ductile‐to‐brittle transition temperature of structural steels

The small punch test (SPT) consists in punching very small square specimens, measuring 10 × 10 mm² and 0.5‐mm thickness, until fracture using a 2.5‐mm‐diameter hemispherical punch. Different specimens of a structural steel were tested from room temperature to cryogenic temperatures in order to determine its ductile‐to‐brittle transition temperature (DBTT). The DBTT obtained in SPT (DBTT_STP) is much lower than the DBTT obtained by means of Charpy specimens (DBTT_CVN). The variation of the mechanical parameters calculated from the SPTs with temperature was also calculated and the operative fracture micromechanisms defined using a scanning electron microscope.