Microstructure and Mechanical Properties of Imported EA4T Steel Axle for High-Speed Railway

Microstructure and mechanical properties of imported EA4T steel axle for high-speed railway were investigated, and uniformity of the microstructure and mechanical properties was analyzed. The results show that non-metallic inclusions, including CaS, Al₂O₃ and a small amount of silicate, were found in the axle, and the number of inclusions increased from the surface to the core. The microstructures at different positions in the axle all consisted of tempered martensite, bainite and a small amount of proeutectoid ferrite; the size and number of the proeutectoid ferrite increased from the surface to the core. The microstructure was uneven. The tensile properties and hardness of the axle met the standard requirements. The tensile strength at the core was obviously lower due to higher content of the proeutectoid ferrite. Banded structure was observed in the longitudinal direction of the axle, and therefore the transverse impact toughness was relatively low. The tensile fracture of the axle sample showed relatively small and deep dimples, indicating good plasticity; the tensile fracture mode was ductile fracture. The impact fracture had obvious river patterns and dimples, and the fracture mode was brittle-ductile mixed fracture.