1977 年 26 巻 280 号 p. 38-43
It is well known that delayed fracture (sometimes called delayed failure, or static fatigue) is a serious problem when high tension steels having the yield strength of more than 120kg/mm2 are used as pre-stressed concrete steel bars, hexagon bolts, members of aircraft etc. Hydrogen embrittlement is considered the main cause of delayed fracture.
In this investigation, the notched specimens of Cr-Mo steels SCM2 and AISI 4150 dipped in 5% H2SO4 solution to charge hydrogen were used to examine the change in their mechanical properties and the effect of hydrogen by means of static bending tests, residual stress measurements by X-ray diffraction technique and delayed fracture tests. The experimental results show that the compressive residual stress near the surface caused by heat treatment seems to be released by dissolution of hydrogen and the intrinsic strength level has a close relation to the sensitivity of hydrogen embrittlement. The variation of maximum stress with hydrogen charged time in static bending tests seems to be similar to the curve of delayed fracture diagram.
Therefore, it is considered that the static tests or residual stress measurements by X-ray is a useful tool to study the delayed fracture phenomenon due to hydrogen embrittlement.