Low-temperature cyclic crack resistance of steels of railroad wheels

Abstract

We have established that the steels of high-and medium-strength railroad wheels in the presence of fatigue-crack-type defects are susceptible to low-temperature (up to −60°C) embrittlement only for high amplitudes of cyclic loading, when the growth rate of a fatigue crack exceeds 10−7 m/cycle. Here, the temperature of cyclic ductile-brittle transition for these steels constitutes −20 and −40°C, respectively. We have shown that the permissible and temperature-independent (within the range from 20 to −60°C ) size of a fatigue crack on the rim surface of the wheels under study does not exceed 1.9–2.5 mm for a hoop stress range of 400 MPa and 0.6–0.8 mm for 700 MPa. These results enable us to conclude that, for high-strength railroad wheels working at low climatic temperatures, it is necessary to carry out their flaw inspection with sensitivity to surface cracks of millimeter size.