抄録
High strength Cr-Mo steels are useful for high performance machinery and equipment. Factors that affect hydrogen susceptibility of fatigue lives have been explored and analyzed quantitatively by using SCM435 steel of various purities. Logarithm of fatigue life ratio log (RNf) , which means the fatigue life of hydrogen charged specimen normalized by that of non-charged one, is proportional to H (450K) that means the amount of hydrogen evolved up to 450K in thermal desorption spectroscopy (TDS) measurement. The proportional coefficient is negative and changes in accordance with the square of phosphorous content of the specimen. The intercept of log (RNf) is zero for soaking in FIP solution, but it becomes log (0. 2) to log (0. 4) for cathodic hydrogen charging. The log (RNf) is lowered by increase in tensile strength. Supposing that the degradation be independent with hydrogen and phosphorous contents, this term could be proportional to tensile strength. Within the experimental range, the fatigue life ratio RNf can be expressed by the following equation,
log RNf(est) =log (rpit) -1500•H(450K) •P2-0. 0045•TS+4. 8
Here rpit is the correction factor for corrosion pit, P is phosphorous content, TS is tensile strength in MPa
