The failure behavior of ultra-high cycle fatigue of a 2 000 MPa grade high strength steel (0.45C
2. OSi
0.9Cr
0.001S
0. 005P
0.026A1
0.001 50
0.002 8N) melted by 500 kg vacuum induction furnace + electro-slag remelting has been studied by USF-2000 ultrasonic fatigue test machine with resonant frequency 20 kHz
load ratio R = -1
resonant gap 150 ms. Results found that the fatigue crack originated mosdy from non-metallic inclusions (inclusion average size 12.3μm ) ; with increasing inclusion size both fatigue strength and fatigue life of steel decreased; fatigue failure area caused by inner inclusion presented fish-eye shape ; and with decreasing the stress intensity factor range ΔK