This paper is concerned with the question of the brittle cracking of spring steel, which can occur already in the early stages of steel processing, i.e. during rolling, during the mechanical cutting of rolled profiles, or during any other type of mechanical manipulation where the harmful effect of remaining hydrogen has been observed. In order to investigate this question in greater depth, mechanical tests and fractographic analyses of the fracture surfaces were performed on cathodically hydrogenated test specimens of two types of spring steel, with and without alloyed nitrogen, in order to determine the critical concentration of hydrogen below which a relatively ductile fracture surface occurs, with good resistance to brittle cracking, and above which hydrogen embrittlement occurs.Ovaj rad odnosi se na problematiku krtog pucanja čelika za opruge već u njegovoj ranoj fazi prerade: pri valjanju, strojnom rezanju valjanih profila, ili kod neke druge mehaničke obrade, gdje je bio uočen škodljiv utjecaj zaostalog vodika. Pomoću uzoraka koji su bili katodno vodičeni, mehaničkog ispitivanja tih uzoraka i fraktografske analize prelomnih površina, bila je definirana kritična količina vodika. Ispod te kritične količine prisutna je još relativno žilava prelomna površina i dobra otpornost prema krhkom pucanju radi vodikove krhkosti. Iznad te vrijednosti, manifestira se vodikova krhkost
