Influence of Segregation on Fatigue Strength of Rails

Abstract

Segregation is inevitably recognized in structural steels and seemed to be very harmful for thier reliability. Then, some fatigue tests have been performed to investigate the harmfulness of segregation. The main results obtained are as follows;
(1) Carbon, manganese and phosphorous were segregated positively in the segregation band, where the proof stress, tensile strength and hardness became higher but the elongation and reduction of area became lower than the other positions.
(2) The rotating bending fatigue strength varied little irrespective of the presence or absence of segregation, the degree of segregation or the orientation of test specimens in the rail.
(3) The fatigue crack initiated in the position where there is no segregation, and its originating place showed the flat surface which is seemed to be a parallel face along a pearlite lamellar.
(4) The axial pulsating fatigue strength of bolt-holed specimens varied little with the presence or absence of segregation and degree of segragation.
(5) It is considered that the reason why the segregation has no influence on the fatigue strength is due to the high resistance for slip in the segregation band.