Abstract
It is well known that the fatigue strength of steels is decreased by oxygen and/or humidity in the atmospheres. Only few reports have been published, however, on the effect of impurities such as SO2 gas on the fatigue strength of steels. In order to study the effect of SO2 gas on fatigue strengths of steels, rotating bending fatigue tests of a mild steel, a 60 kg/mm2 and an 80 kg/mm2 high strength steels and an 18-8 stainless steel have been corned out in various atmospheres. The employed atmospheres are air, humidified a'r, dry SO2 gas, mixed gas of dry SO2 and humidified air, mixed gas of dry H2S and humidified air, H2O, and H2SO4.
On the fatigue strength of the mild steel the influence of dry SO2 gas is not recognized, but the influence of mixed gas of dry SO2 gas and humidified air is detected. The degree of the influence, however, is almost the same as that in humidified air. Therefore the influence of SO2 gas on fatigue strength of the mild steel seems to be little, but some influences of SO2 gas can be surmised from the characteristic aspect of fractured surfaces. On the 60 kg/mm2 and 80 kg/mm2 high strength steels and the 18-8 stainless steel the influence of SO2 gas is not observed. For all the steels tested in this experiment, the influence of H2SO4 is very conspicuous.
