Electric Flash Butt Rail Weld Failure Called “Concave–Convex”

Abstract

Sporadically, electric flash butt (EFB) rail welds fracture vertically through the cross section of the rail. A particular type of vertical transverse weld failure exhibits a protruding and recessed area in the center of the web and coincides with the maximum centerline segregation within a given rail. This failure will herein be called “concave–convex.” The failures initiate in the web near the middle of the cross section of the rail where iron carbide networks, also called grain boundary cementite (GBC), were found. Hard and brittle iron carbide networks create stress concentrations and, in general, the weld fails prematurely, sometimes as early as the first train that passes over it. There have been numerous discussions and different opinions within the rail industry regarding whether this type of weld failure is due to the EFB weld process, or if the iron carbide networks were present in the as-rolled rail, or a combination of both. In this study, using metallographic methods, the authors showed that iron carbide networks, which caused the failure were, in fact, present in the as-rolled rail, specifically the rail with the post-fracture concavity.