Regularities of the influence of strength and ductility of steels on the embrittlement effect of stress raisers (SR) as fatigue cracks in standard specimens for determining the fracture toughness of metals and alloys are ascertained. Special indices proposed in Pt. 1 of this report are used for this analysis, namely: strength margin, $B_{r}$, and the effective coefficient of stress raise, $\alpha_{ef}$. As shown, an excess of $\alpha_{ef}$ over $B_{r}$ is the condition for mechanical instability of metal (brittleness) under the SR influence; this means fracture of the specimen with SR at the average stress that does not exceed the yield strength of metal, $\sigma_{0.2}$.Regularities are found for the effect of strength, $\sigma_{0.2}$, on indices of strength margin, $B_{r}$, and the value of the effective stress raise coefficient, $\alpha_{ef}$, due to an increase in strength of steels, $\sigma_{0.2}$, within the range 140-500 MPa (as a result of decrease in temperature) and within the range 140-2200 MPa at room temperature (as a result of changing the chemical composition of steel and heat treatment). As established, the SR destructive effect, $\alpha_{ef}$, is governed directly by the value of strength margin, $B_{r}$, which, in turn, is related to the strength characteristic, $\sigma_{0.2}$. Thus, ductility reduces SR embrittlement effect, $\alpha_{ef}$, not by itself, but against the background of yield strength, $\sigma_{0.2}$, more strongly for low-strength steels and less strongly for high-strength steels.