Fractured Electric Flash Butt Welded Rail - Ledeburite Formation

Electric Flash Butt Welding (EFBW) has proven to be a safe and reliable method of joining rail. When EFBW rail does fail, it is commonly due to the presence of a defect referred to as "innie/outie" or "nipple/dimple." Caused by the formation of ledeburite in the center of the rail, these defects are not possible to detect prior to fracture. A fractured EFB weld may be one of hundreds of welds produced using the same equipment and parameters. What causes the formation of these defects, and why is the rate of occurrence so seemingly unpredictable?

The mechanism of ledeburite formation in the EFB weld is not well understood. The author gives examples of fractured EFBW rails containing these defects, lists useful methods of forensic analysis, discusses contributing factors to ledeburite formation, and recommends methods to minimize EFBW rail fractures.