Ultra-fine-grain ultra-high-obdurability high-speed axle steel and heat treatment method thereof

Abstract

Provided is ultra-fine-grain ultra-high-obdurability high-speed axle steel. The axle steel comprises uniform fine-grained austenite grains and an Nb micro-alloyed nanometer second-phase-enhanced martensite structure. The average grain size of the austenite grains is below 10 micrometers. The axle steel comprises, by mass percentage, 0.00-0.06% of Nb and 0.16-0.30% of V. The invention further provides a heat treatment method for the steel. The method comprises the steps that the functions of each element in the axle steel are fully played, two-time quenching and high-temperature tempering heattreatment is adopted, and finally a high-speed axle has good serviceability such as impact resistance and fatigue resistance, excellent obdurability matching and good hardenability. The average grainsize of the austenite grains in the structure of the axle steel is below 10 micrometers, the yield strength Rp0.2 is larger than or equal to 900 MPa, the tensile strength Rm is larger than or equal to1,000 MPa, the elongation rate A is larger than or equal to 15%, the 5-mm gap longitudinal impact absorbing energy KU2 at the room temperature is larger than or equal to 100 J, and the ductile-brittle transformation temperature is lower than negative 80 DEG C.

Description

Technical field [0001] The invention relates to the technical field of steel for railway axles, in particular to a high-speed axle steel with ultra-fine grains and ultra-high strength and toughness and a heat treatment method thereof. Background technique [0002] The axle is one of the most demanding parts of rail transit trains, and bears almost all of the train's own weight and load. At present, the maximum operating speed of high-speed trains in my country has exceeded 350 kilometers per hour, and is developing towards the goal of speeds above 400 kilometers per hour. Further speeding up to a speed of more than 400 kilometers per hour will put higher performance requirements on axle materials, which must ensure sufficient safety, reliability and long service life. Fatigue fracture is the main form of axle failure. Therefore, axle materials need to have high strength, high toughness, and excellent matching between the two, which can effectively prevent the initiation and prop...

AI Technical Summary

Problems solved by technology

For example, the axles of Shinkansen high-speed railways in Japan are generally made of carbon steel (S38C), and the surface intermediate frequency quenching heat treatment process is adopted. The process is complex and requires a high level of process control for equipment and personnel; European high-speed railway axle materials are mostly low-alloy Structural steel (such as EA4T), the corresponding microstructure and properties can be obtained through traditional quenching and tempering heat treatment, but due to the low alloy content of this steel, there is a problem of insufficient hardenability of the large-section axle, and the microstructure and properties of the axle section are not uniform , affecting its overall performance; a small part of European high-speed rail axle materials use 30NiCrMoV12 alloy structural steel, the steel contains Cr 0.60~1.00wt.%, Ni 2.70~3.30wt.%, Mo 0.40~0.60wt.%, V 0.08~0.13 wt.%, this type of steel has good hardenability, oil quenching, high hardness and good corrosion resistance

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