NATURE OF THE SLOW-FRACTURE PHENOMENON IN QUENCHED STEELS

One of the most dangerous kinds of brittle fracture is the slow variet y. After more than a hundred years, researchers have offered some hypo theses regarding causes for explaining this phenomenon: vacancies, sur face-active media, etc. The most commonly used hypothesis at present i s one of local internal stresses concentrated in the martensitic struc ture at grain boundaries. In this paper, we have presented results of investigations of slow fracture of quenched steels in the untempered s tate and have offered a mechanism for it, according to which, the main role in this process is played by the diffusionally mobile hydrogen w hich is formed in small amounts during the quenching of the steel.