Effect of phase composition on the micromechanism of fracture of strength class K70 pipe steel

The effect of the structural features of a high-strength (strength class K70) main pipeline steel with a ferritic-bainitic structure after thermomechanical treatment and quenching from rolling heating on the fracture micromechanism during static and dynamic loading is studied. These structural features are shown to affect the ductility margin, the fracture rate, and the crack nucleation and propagation energies. The fracture micromechanisms detected during static tension of samples in the column of an electron microscope agree with the results of bending impact tests and dynamic tests of full-scale technological specimens.