Heat treatment process of high-speed train axle containing niobium

The invention provides a heat treatment process of a high-speed train axle containing niobium. The axle contains the following chemical components: 0.25-0.32 wt% of C, 0.15-0.40 wt% of Si, 0.60-0.90 wt% of Mn, no more than 0.015 wt% of P, no more than 0.010 wt% of S, 1.00-1.20 wt% of Cr, 0.20-0.35 wt% of Mo, 0.15-0.30 wt% of Ni, 0.015-0.060 wt% of Nb, 0.10-0.30 wt% of Cu, 0.0008-0.0050 wt% of B, 0.010-0.050 wt% of Als, and the balance of iron and residual trace impurities. The heat treatment process of the axle is as below: (1) normalizing at 900-950 DEG; (2) quenching at 880-930 DEG; and (3) tempering at 620-680 DEG C.