Technical Reports

Tread Buildup on Railroad Wheels

  • 10
  • Apr
  • 2015
AUTHOR: Federal Railroad Administration
KEYWORDS: Railroad; wheel; slide; flat; tread buildup wheels; Tread Buildup on Railroad Wheels
ABSTRACT: Based on the results of wheel slide tests and an inspection of wheels, the root cause of tread buildup (TBU) was identified as wheel slide caused by excessive brake force. During the tests, TBU accumulated to the greatest heights under dry conditions, at longer slide distances, and under heavier axle loads. Train speeds between 20 and 30 mph appeared to increase TBU height. Chemical analysis of TBU samples indicated that the source of the material is likely a combination of wheel and rail steel. This finding reinforces the conclusion that wheel slides cause TBU. A microstructural evaluation of several TBU samples found no martensite, a microstructure that results when hot steel is rapidly cooled. A relatively slow conductive heat transfer rate from the irregular contact between the hot TBU and the cooler wheel likely does not provide sufficiently rapid cooling for martensite formation.
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