Fatigue testing has been performed according to
the staircase method and the results have been
treated statistically (30 specimens). The fatigue
limit, af, is the impact intensity l~vel at which 50o/o
of the specimens can withstand 10 1 cycles. The
result of the fatigue testing is shown ir: table 2 ..
There is a considerable range £o,· the fatigue lin'lit,
the highest being af = l. 6, and the lowest ar = l. o.
The standard deviation is 0. 3. Test of significance
shows that the steels can. be divided into two groups
with respect to impact fatigue streng'[h: A-C and
D-H. The impact fatigue limits of the steels A-C
are significantly (95o/o confidence level) superior to
those of the steels D-I-I. Thus, the stainless
chromium valve steel, A, belongs to the group
with high in1pact fatigue strength and the carbon
valve steels, D and F, to che other group. Thereis
no significant difference between the fatigue limits
within each group.