The influence of nitrogen in shielding gas on the 316LN austenitic stainless steel welded joints

IF 1.9 3区工程技术 Q1 NUCLEAR SCIENCE & TECHNOLOGY

Fusion Engineering and Design Pub Date : 2024-11-19 DOI:10.1016/j.fusengdes.2024.114699

Zhongtao Zhang , Zhihong Liu , Jiefeng Wu , Jianguo Ma

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Abstract

To ensure the stable operation of fusion reactors and synchrotron radiation facilities, the magnetic permeability of the weld joints in 316LN austenitic stainless steel (ASS) must be μ_r ≤ 1.03. Therefore, controlling magnetic permeability during welding is essential. This paper examines the impact of nitrogen in the shielding gas on the magnetic permeability, microstructure, and mechanical properties of 316LN welded joints. This was achieved by using argon-nitrogen mixed shielding gas to weld the test plates. The findings indicate that the primary microstructures of the welded joints consist of austenite and a small amount of ferrite. The magnetic permeabilities are measured at 1.026, 1.015, 1.010, 1.007, 1.004, and 1.005, respectively. The main factor contributing to the decline in magnetic permeability with increased nitrogen content in the shielding gas is the reduction in ferrite content. Additionally, adding nitrogen to the shielding gas improves the mechanical properties of the welded joints at 4.2 K. The ultimate tensile strengths of the welded samples using pure argon gas and argon-nitrogen mixed gas (1 % and 2 % nitrogen) were 1423.73 MPa, 1465.49 MPa, and 1546.45 MPa, respectively. The impact energy of the samples was 38 J, 139 J, and 137 J, respectively. Analysis of the fracture surfaces reveals that the argon-nitrogen mixed gas welded samples exhibit ductile fracture with dimples and micropore morphology. In contrast, the pure argon gas welded samples show the combination of ductile and brittle fracture. It is proposed that fine grain strengthening and the dispersion strengthening effect of N is the main factors in improving strength. This study provides an effective guide for the application of the welded joint of 316LN ASS at cryogenic temperature.

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保护气体中的氮对 316LN 奥氏体不锈钢焊接接头的影响

为确保聚变反应堆和同步辐射设施的稳定运行，316LN 奥氏体不锈钢 (ASS) 焊点的磁导率必须 μr ≤ 1.03。因此，在焊接过程中控制磁导率至关重要。本文研究了保护气体中的氮对 316LN 焊接接头的磁导率、微观结构和机械性能的影响。这是通过使用氩气-氮气混合保护气体焊接测试板实现的。研究结果表明，焊接接头的主要微观结构由奥氏体和少量铁素体组成。测得的磁导率分别为 1.026、1.015、1.010、1.007、1.004 和 1.005。随着屏蔽气体中氮含量的增加，磁导率下降的主要原因是铁氧体含量的减少。使用纯氩气和氩氮混合气体（1 % 和 2 % 氮气）的焊接样品的极限拉伸强度分别为 1423.73 兆帕、1465.49 兆帕和 1546.45 兆帕。样品的冲击能量分别为 38 J、139 J 和 137 J。对断裂表面的分析表明，氩气-氮气混合气体焊接样品呈现出韧性断裂，具有凹陷和微孔形态。相比之下，纯氩气焊接样品则表现出韧性断裂和脆性断裂的结合。研究认为，细晶粒强化和 N 的分散强化效应是提高强度的主要因素。这项研究为 316LN ASS 焊接接头在低温下的应用提供了有效指导。

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来源期刊

Fusion Engineering and Design 工程技术-核科学技术

CiteScore

3.50

自引率

23.50%

发文量

275

审稿时长

3.8 months

期刊介绍： The journal accepts papers about experiments (both plasma and technology), theory, models, methods, and designs in areas relating to technology, engineering, and applied science aspects of magnetic and inertial fusion energy. Specific areas of interest include: MFE and IFE design studies for experiments and reactors; fusion nuclear technologies and materials, including blankets and shields; analysis of reactor plasmas; plasma heating, fuelling, and vacuum systems; drivers, targets, and special technologies for IFE, controls and diagnostics; fuel cycle analysis and tritium reprocessing and handling; operations and remote maintenance of reactors; safety, decommissioning, and waste management; economic and environmental analysis of components and systems.