Critical Stress for Cleavage Fracture in Continuously Cooled Medium Carbon V-microalloyed Steel☆

Abstract Cleavage fracture of the medium carbon V-microalloyed steel with structure consisting of acicular ferrite, pearlite and grain boundary ferrite has been investigated by means of four-point bending of the notched samples at -196 °C. It was found that cleavage fracture initiation has not been related to the coarse second phase particles cracking. Calculated values of the effective surface energy of 49 J/m 2 and critical cleavage fracture stress normalized by yield stress of 1.84 are in agreement with the results for the steels with ferrite-pearlite and bainite structures.