A metallurgical analysis was made of 33 carbon-steel rail samples selected from service, 31 of which had service-developed defects. The program was formulated to attempt to establish the metallurgical characteristics that promoted the defects and to establish possible interrelationships among these characteristics, the in-location service stresses, and the defects. This paper describes the results of chemical analyses, hardness and tension tests, and the results of wear, deformation, metallographic, and fractographic analyses. A companion paper in this symposium describes the results of Charpy V-notch impact toughness tests, fracture toughness tests, and fatigue tests.

The results of this investigation showed that (a) all the service-developed defects in the rail samples examined were fatigue cracks, (b) all these fatigue cracks initiated at sharp internal notches such as inclusions, and (c) a correlation between the metallurgical properties of the rail samples and defect formation could not be made.

Overall, it is reasonable to conclude that the service lives of the rails investigated would have been longer if the inclusions responsible for crack initiation had not been present. However, it should be noted that most of these rails had service lives lasting 16 years—454 million metric tons (MMT) (500 million gross tons (MGT)) with one sample lasting 22 years—685 MMT (755 MGT). Furthermore, the service stresses, although unknown, were apparently severe as evidenced in the deformation of the rail-heads.

It appears that of greater importance and interest with respect to the effect of steel quality and properties on defect formation in rails would be a study of defects that form early in the rail life. It is recommended that such studies be conducted.