Method for determining the brittleness of medium alloy steel under vacuum tempering

By analyzing the relationship between gas pressure and cooling rate in a vacuum tempering furnace, the problem of brittleness in medium alloy steel during vacuum tempering was solved, the impact toughness of medium alloy steel was improved, and the standard cooling requirements were met, thus ensuring the production quality of vacuum tempered parts.

CN117344126BActive Publication Date: 2026-03-31JIANGXI HONGDU AVIATION IND GRP
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Patent Information

Application Number
CN202311255771.0
Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
Filing Date
2023-09-27
Publication Date
2026-03-31
Estimated Expiration
2043-09-27

AI Technical Summary

Technical Problem

Medium alloy steel is prone to high-temperature tempering brittleness during vacuum tempering, which can lead to fatigue fracture accidents. Existing technologies are unable to effectively avoid this phenomenon, and the cooling methods of vacuum tempering furnaces are limited and cannot meet the standard requirements.

Method used

By tempering medium alloy steel samples in a vacuum tempering furnace and an air electric furnace, and cooling them with medium gases of different pressures, the microstructure and property changes of the samples were analyzed. The relationship between gas pressure and cooling rate was calculated to determine a reasonable range of vacuum tempering gas pressure, avoid tempering brittleness, and meet the standard requirements.

Benefits of technology

It effectively improves the impact toughness of medium alloy steel, avoids temper brittleness, meets the requirements of standard cooling methods, and ensures the production quality of vacuum tempered parts.

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Abstract

A method for determining vacuum tempering brittleness in medium alloy steel involves dividing selected test samples into test and control groups, and pre-treating the test samples. The pre-treated test samples are then placed in a vacuum furnace for quenching. Subsequently, the test samples from the test and control groups, after heat treatment, are placed in a vacuum furnace and an air furnace, respectively, for tempering. After tempering, the samples are cooled. The test group samples are cooled with gases of different pressures, while the control group samples are cooled to room temperature using air, water, and oil cooling media. By analyzing the performance changes of the control group samples, the relationship between gas pressure and cooling rate in the test group is calculated. Finally, based on the performance changes of the control group samples and the relationship between gas pressure and cooling rate in the test group, the pressure range at which tempering brittleness occurs is determined. Using the relationship between tempering brittleness and cooling rate, the gas pressure inside the vacuum furnace is controlled to prevent the occurrence of type II tempering brittleness.
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