Process for quenching-isothermal heat treatment on 50CrVA steel spring for high-speed heavy loading locomotive

Abstract

The invention discloses a process for quenching-isothermal heat treatment on a 50CrVA steel spring for a high-speed heavy loading locomotive. The process comprises the following steps: polishing a 50CrVA steel round bar with diameter less than or equal to 50mm, and inductively heating the steel round bar to a temperature of between 960 and 1,060 DEG C; then, wrapping the round bar into a spring; cooling the wrapped spring to a temperature of between 840 and 920 DEG C, placing the spring into a constant temperature oil-quenching tank below Ms point, namely at a temperature of between 120 and 250 DEG C, and maintaining for 10 to 80 seconds; and quickly placing the spring into liquid salt above the Ms point, namely at a temperature of between 280 and 360 DEG C, maintaining for 100 to 1,000 seconds, and placing the spring into water or oil for cooling; and tempering the spring at a temperature of between 250 and 430 DEG C for 60 to 120 minutes. The method has the advantages that quantity and quality of martensite and size of the bainite substructure thereof can be controlled, a uniform duplex structure and high toughness can be obtained under the condition of different sizes, and the like.

Description

technical field [0001] The invention relates to a 50CrVA steel spring quenching-isothermal heat treatment process for high-speed heavy-duty locomotives, belonging to the technical field of metal heat treatment. Background technique [0002] Springs for high-speed heavy-duty locomotives and traditional locomotives are very important mechanical parts on locomotives, which play various functions such as shock absorption, energy storage, connection, and support. Locomotive springs work under alternating stresses such as periodic bending and torsion, and are subjected to dynamic load conditions such as tension, compression, torsion, and impact, and sometimes extremely high short-term sudden loads. Therefore, spring steel must have High fatigue strength, high tensile strength and yield strength ratio, sufficient plasticity and toughness, good surface quality, easy rolling and forming in hot state, good hardenability, etc. At present, the spring products of high-speed locomotive b...

AI Technical Summary

Problems solved by technology

After austempering, under the same hardness conditions, compared with ordinary quenching and tempering, it has high toughness and small notch sensitivity, but the yield limit and fatigue strength are about reduced

At the same time, for high-speed and heavy-duty locomotives, the spring material diameter is relatively large, and the quenching hardenability is not enough, so it is difficult to use for large-scale springs.