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

Abstract

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.

Description

technical field [0001] The invention relates to an ultra-fine heat treatment process for axle steel crystal grains, belonging to the technical field of metal heat treatment. Background technique [0002] In recent years, with the speed increase of trains, new challenges have been put forward to the performance of locomotives, thus higher requirements have been put forward for the performance of train axles. It is required that the wheels and shafts should have sufficient strength and impact toughness to ensure absolute safety and reliability under the highest speed and load. Wheels and axles are vital components directly related to train safety for high-speed trains. Therefore, all countries in the world attach great importance to the research and development of materials and processes for wheels and shafts. At present, the heat treatment of axles mostly adopts the process route of quenching and tempering heat treatment plus surface strengthening treatment. This method ha...

AI Technical Summary

Problems solved by technology

This method has the following problems. First, the axle has a relatively coarse grain size when it is forged in the early stage, and subsequent heat treatment is prone to tissue inheritance, resulting in a coarse grain size after quenching and tempering heat treatment.

Second, the high temperature in the quenching and tempering heating process leads to the phenomenon of mixed crystals, which reduces the strength and toughness and poses a threat to the safety of train operation.

Therefore, the effect of the existing axle steel heat treatment process is still not ideal enough