热处理对氮强化奥氏体钢低温力学性能影响研究

A Study on the Effect of Heat Treatment on the Low-Temperature Mechanical Properties of Nitrogen-Strengthened Austenitic Steel

摘要

为探究超导材料热处理工艺对聚变磁体用铠甲材料低温力学性能的影响,本文将经过相同冷变形加工的316LN、N50氮强化奥氏体不锈钢用三种不同超导材料热处理工艺处理后,对二者进行低温拉伸测试和低温断裂韧性测试,对比探究不同超导材料热处理工艺对其低温力学性能的影响.结果表明,4.2K温度下,同种工艺处理的N50整体强度显著高于316LN,且工艺敏感性更强,强度在高场 Nb₃Sn热处理工艺下最高,塑性与韧性随工艺协同变化,在Bi-2212热处理工艺下因沿晶脆性断裂而同步劣化;与之不同,316LN 强度整体维持在相近水平,Bi-2212热处理工艺下相比于高场 Nb₃Sn、ITER Nb₃Sn热处理工艺下具有更良好的韧性,且延伸率始终保持在44%左右,呈现塑性稳定、韧性波动的特征.本研究为新一代聚变磁体用超导材料外部铠甲的选型提供理论数据支撑.

Abstract

To investigate the effect of heat treatment processes for superconducting materials on the low-temperature mechanical properties of armor materials used in fusion magnets, this study subjected 316LN and N50 nitrogen-strengthened austenitic stainless steel—both of which had undergone the same cold deformation—to three different heat treatment processes for superconducting materials. Low-temperature tensile tests and low-temperature fracture toughness tests were then conducted on both materials to compare and investigate the impact of different heat treatment processes for superconducting material on their low-temperature mechanical properties. The results indicate that at 4.2 K, the overall strength of N50 treated under the same process is significantly higher than that of 316LN, and it exhibits greater process sensitivity. Its strength peaks under the high-field Nb₃Sn heat treatment process, whilst its ductility and toughness vary in tandem with the process; under the Bi-2212 heat treatment process, both properties deteriorate simultaneously due to intergranular brittle fracture. In contrast, the strength of 316LN remained at a similar level overall; under the Bi-2212 heat treatment process, it exhibited better toughness compared to the high-field Nb₃Sn and ITER Nb₃Sn heat treatment processes, and the elongation consistently remained around 44%, displaying characteristics of stable plasticity and fluctuating toughness. This study provides theoretical data to support the selection of materials for the external armour of superconducting materials used in next-generation fusion magnets.

关键词

316LN铠甲 / N50铠甲 / 热处理 / 低温力学性能

Key words

316LN jacket / N50 jacket / Heat treatment / Low-temperature mechanical properties

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基金资助

REBCO带材的聚变 CS模型线圈研制(22KZZ501)

国家自然科学基金(52477032)