Thermal treatment process of vanadium-niobium-containing steel for motor train unit axle

Abstract

The invention relates to a thermal treatment process of vanadium-niobium-containing steel for a motor train unit axle. The process includes the following steps of firstly, conducting normalizing, wherein the vanadium-niobium-containing steel for the motor train unit axle is heated till the temperature is 870-900 DEG C, heating and heat keeping time of the temperature section is calculated according to the speed of 1.2-1.7 min / mm, and air cooling is conducted; secondly, conducting quenching, wherein vanadium-containing steel for the motor train unit axle is heated till the temperature is 860-890 DEG C, heating and heat keeping time of the temperature section is calculated according to the speed of 1.5-2.0 min / mm, and water quenching and oil cooling are subsequently conducted; thirdly, conducting tempering, wherein the vanadium-containing steel for the motor train unit axle is heated till the temperature is 620-680 DEG C, heating and heat keeping time of the temperature section is calculated according to the speed of 2-2.5 min / mm, and air cooling is then conducted till the room temperature is reached. The treated steel material has the advantages of being high in strength and excellent in fatigue resistant performance compared with the prior art.

Description

Technical field [0001] The present invention relates to the field of alloy steel, in particular to the application of tensile strength 750~900MPa, yield strength ≥600MPa, -40℃KV 2 ≥150J, and requires high-speed EMU axle steel with excellent fatigue resistance and its heat treatment process. Background technique [0002] The axle is one of the most important moving and load-bearing parts related to safety in various vehicles. Due to the dynamic load of the vehicle bearing, the force state is more complex, such as bending load, torsion load, and bending-torsion combined load, and subject to certain impact, especially the high-speed EMU axles, the force state is more complex. Therefore, the axles of high-speed EMUs may break due to fatigue, bending, torsion, or tensile stress during service. Fatigue fracture is a common form of fracture of high-speed axles. To ensure the safe operation of vehicles, the axles of high-speed EMUs must have sufficient reliability and fatigue safety fac...

AI Technical Summary

Problems solved by technology

For example, the anti-fatigue failure axle steel in Chinese patent application 201110417295.9 still adopts the idea of ​​high C content of traditional medium carbon axle steel, and the C content (0.42-0.45%) is relatively high, which makes the toughness of the steel poor and cannot meet the requirements of EMU axles. Requirements for toughness, and the range of improvement in fatigue resistance is limited

A new type of alloy steel for hollow axles in Chinese patent application 201210384581.4, although the carbon content is low, it has good strength and toughness, but the fatigue strength is still low

The EMU axles imported from Europe are mainly made of quenched and tempered alloy steel EA4T. Although the chemical composition and mechanical performance requirements are given, the key heat treatment process parameters are not given. What is more important is the alloy in the steel that affects hardenability. The element content is low, which makes it difficult for the internal structure (ferrite that is not allowed to exist) and performance (low strength, toughness and fatigue performance of the proximal part) of the large-scale EMU axle to meet the standard requirements.

These are all limited in practical application, and more importantly, the range of improvement in fatigue resistance of axle steel is limited, which affects its popularization and application.

Images