掺氢天然气输送用X65管线钢的氢脆行为

中海石油气电集团有限责任公司技术研发中心

管线钢;氢脆;气相原位充氢;慢应变速率拉伸;断裂韧性

Hydrogen embrittlement behavior of X65 pipeline steel for transmitting hydrogen-enriched compressed natural gas
LIU Fang,YANG Hongwei,DENG Fujie

Technology R&D Center, CNOOC Gas & Power Group

pipeline steel, hydrogen embrittlement, gas-phase in-situ hydrogen charging, slow strain rate tension, fracture toughness

DOI: 10.6047/j.issn.1000-8241.2024.03.005

备注

【目的】将氢气以一定比例掺入现有天然气管网进行大规模长距离输送是氢能储运最为高效和经济的方式之一,但在氢气环境中管线钢可能发生氢脆现象,导致其力学性能发生退化,为管道的安全运行带来隐患。天然气管道掺氢输送工程的应用实施关键需要对掺氢输送管线钢进行力学性能评价,明确掺氢比对管线钢氢脆敏感性的影响规律。【方法】基于ASTMG142-2016《高压、高温或高压高温含氢环境中测定金属脆化敏感性的标准试验方法》,采用自行设计的带有压力容器的慢应变速率拉伸试验系统进行高压气相原位充氢慢应变速率拉伸试验,并借助Instron8801伺服液压疲劳测试系统开展高压气相原位充氢准静态断裂韧性试验,从而开展不同氢气压力环境条件下X65管线钢的氢脆行为研究,并结合断口形貌分析研究不同掺氢比对管线钢力学性能的影响。【结果】X65管线钢在总压为9MPa,掺氢比分别为3%、5%、10%的条件下,与无氢环境相比,其断后总延伸率下降程度在11.5%以内,而断裂韧性在掺氢比为3%、10%氢气环境中分别下降23.5%、43.1%,氢脆程度随掺氢比的增加而加剧。断口形貌表明在掺氢比小于10%的条件下,试样断口主要均以韧性断裂为主,没有典型脆性断口形貌。【结论】对于X65管线钢,尤其是在役运行多年的管道,如需开展掺氢输送,建议开展相关管线钢氢脆敏感力学性能评价分析工作,以确保管道的安全运行。(图8表1,参[21]
[Objective] One of the most efficient and economical approaches for storing and transporting hydrogen energy is to blend hydrogen at a certain ratio into the existing natural gas pipeline network for large-scale long-distance transmission. However, the exposure of pipeline steel to hydrogen environments can lead to hydrogen embrittlement, which undermines its mechanical properties and poses potential risks to pipeline safety. Consequently, it is crucial to evaluate the mechanical properties of pipeline steel used for hydrogen-enriched compressed natural gas (HCNG) transmission and understand the influence rules of hydrogen blending ratios on the steel’s susceptibility to hydrogen embrittlement. [Methods] Slow strain rate tensile experiments were conducted with in-situ hydrogen charging under high-pressure gas-phase conditions using a self-designed experimental system adhering to the requirements of Standard Test Method for Determination of Susceptibility of Metals to Embrittlement in Hydrogen Containing Environments at High Pressure, High Temperature, or Both (ASTM G142-2016). Additionally, quasi-static fracture toughness experiments with in-situ hydrogen charging under high-pressure gas-phase conditions were performed using an Instron 8801 servo hydraulic fatigue test system. These experiments investigated the hydrogen embrittlement behavior of X65 pipeline steel, considering varying hydrogen pressure conditions. Moreover, the influence of different hydrogen blending ratios on the mechanical properties of the pipeline steel was analyzed, taking into account fracture morphology characteristics. [Results] The X65 pipeline steel exhibited a decrease in total percentage elongation after fracture by up to 11.5% when hydrogen was charged at 3%, 5%, and 10% under a total pressure of 9 MPa, compared to hydrogen-free environments. The fracture toughness decreased by 23.5% and 43.1%, respectively, when hydrogen was charged at 3% and 10%. The severity of hydrogen embrittlement increased with higher hydrogen ratios. Concerning fracture morphology, specimens with hydrogen ratios below 10% displayed ductile fractures without typical brittle fracture morphology. [Conclusion] To ensure the safe operation of X65 pipelines, particularly those that have been in service for several years, it is recommended to conduct evaluations and analyses of the mechanical properties, focusing on the steel’s susceptibility to hydrogen embrittlement before introducing HCNG transmission. (8 Figures, 1 Table, 21 References)
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