Design strength, reliability, and life of heat-treated railroad rails

Abstract

1. Heat treatment of rails to a hardness of BHN 340–400 is an effective method of increasing their reliability and life in service, especially their resistance to contact fatigue damages. 2. High-frequency induction surface-hardened rails with a water-air mixture in the elastically stressed condition have, in comparison with rails heat-treated by other methods, higher values of fatigue limit and life, a lower rate of fatigue crack growth, lower sensitivity to stress concentrators, and higher resistance to the formation of transverse fatigue cracks in the head. 3. The high design strength and reliability of high-temperature induction-hardened rails using the method of the “Azovstal' ” plant may be explained primarily by the favorable distribution of residual stresses (compressive stresses on the rolling surface) and the character of the hardened metal structure, which is related to features of the phase transformations in rapid induction heating. 4. To increase the resistance of high-frequency induction-hardened rails to the formation of surface contact fatigue defects, it is necessary to increase the lower hardness level and primarily to maintain a high hardness over the whole depth of the hardened layer.