Process for ultrafining heat-treatment on crystal grains of axle steel

The invention discloses a process for ultrafining heat-treatment on crystal grains of axle steel. The process comprises the following steps that: a low-medium carbon axle steel component is heated to a temperature close to a critical point Ac3 in a wave heating mode so as to obtain ultrafine austenite crystal and trace fine ferrite, when wave heating is carried out, the wave range of temperature does not exceed Ac3+/-10 DEG C, and the heating time is controlled at 4mm/min according to an effective diameter of the component; after the wave heating is completed, the heating temperature is increased by 5 to 10 DEG C; and when the temperature is kept to be basically in accordance with that of on the section of the whole component, the component is subjected to quenching-tempering treatment according to the conventional heat-treatment process. The process directly quenches the obtained ultrafine austenite crystal and trace fine ferrite through performing wave heating at the temperature close to the critical point Ac3, obtains a duplex structure of an ultrafine martensite structure and the ultrafine ferrite, and can remarkably toughen and plasticize materials.