Effect of Retained Austenite Stability on High Temperature Mechanical Properties of Bainitic Railway Wheel Steels

To explore the relationship between mechanical properties and the stability of retained austenite of free-carbide bainitic steel wheel service under the environment of high temperature, the static tensile test of the sample at room temperature to 500 ℃ was tested. The sample from room temperature to 500 ℃ were characterized by SEM, TEM, X-ray diffraction analyzer and electron backscattering. The results show that the microstructure of carbide-free bainitic wheel steels consists of bainitic ferrite and residual austenite. The tensile strength of the samples increases first and then decreases with the increase of deformation temperature. At 300 ℃, the carbide free bainite steel has the best plasticity and strength match, the tensile strength can reach 1305 MPa, and the total elongation is 25.1%. The continuous transformation of residual austenite under high temperature and stress at 300 ℃ makes the material maintain a high work hardening rate under high strain, which can significantly improve the strength and elongation of wheel steel.