Based on the requirements of 400 km/h high-speed railway for high fatigue properties of axles， the mechanism of ultra-high fatigue performance of axle was analyze， the key to high fatigue performance was the size of fine carbide and martensite lath. The microstructure parameters such as the width of martensitic lath sheaf ， the distribution of precipitated phases were determined as key control units affecting the yield strength of high-speed railway axle steel. The target microstructure of high-speed railway axle steel was designed， and the optimal alloy composition of 400 km/h high-speed railway axle steel was determined by high-throughput calculation. The developed high-speed rail axle with a speed of 400 km/h had good strength and toughness matching after quenching at 850-950 ℃ and high-temperature tempering at 620 ℃， with a tensile strength greater than 880 MPa and an impact energy of 180 J at -40 ℃. At the same time， the grain size and carbide size of the axle treated by this process are fine， and the grain size is refined to 9.0 level. Both high cycle and ultra-high cycle fatigue performance met the standards. After the overall heat treatment of the axle， the ultra-high cycle fatigue test of the small-sized sample was stable to level 3， and the fatigue limit was 517 MPa at 10

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cycles， indicating a high fatigue limit. The overall fatigue performance of the axle was predicted through the sample reduction of the axle， and the predicted values were in good agreement with the actual values. The axle as a whole passed 10

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cycles of fatigue assessment under a test force of 320 MPa.