This study confirmed the hydrogen embrittlement characteristics of API 5L X52, a natural gas pipeline material, and confirmed whether it is a suitable material for hydrogen gas use. In order to confirm the in-situ hydrogen embrittlement characteristics under a high-pressure hydrogen gas atmosphere, a slow strain rate test was conducted under a high-pressure hydrogen gas and nitrogen gas atmosphere. The thickness of the material used for evaluation was 15.9mm and a pipeline welded to 20 inch through submerged arc welding was used. The evaluation was carried out by processing specimens in the transverse direction at the base metal / weld metal part and processing it as a notch specimen based on ASTM G142-98 [1]. The evaluation was carried out when the temperature was stabilized at room temperature and pressure of 8 MPa for 10 minutes and the extension rate was carried out at a rate of 0.02mm/s ± 10%, which is the value shown in ASTM G142-98 [1]. As a result of the evaluation, in a high-pressure hydrogen gas atmosphere the tensile strength and elongation decreased due to hydrogen penetration through cracks during deformation of the material.
Recently, Countries around the world are taking steps to reduce carbon, which is considered a major cause of environmental pollution and the hydrogen market, an eco-friendly energy, is growing rapidly. Major countries such as the United States, Japan and the European Union (EU) are strengthening policies for the use of hydrogen energy and hydrogen-related projects in various fields, from materials to chemistry, energy and mobility, are being actively carried out. In order to use hydrogen energy, it is the most efficient and currently the most reasonable method to transport the produced hydrogen as high-pressure gas through a pipeline. When transporting high-pressure hydrogen gas through a pipeline, the most important part is the hydrogen embrittlement of the pipeline material. Research on hydrogen embrittlement has been conducted for many years and accordingly, a number of evaluation methods and mechanisms for confirming hydrogen embrittlement are also in progress. As a pipeline for transporting hydrogen gas, API 5L grade material, which is a material used for natural gas pipelines, will be used and hydrogen embrittlement evaluation of the existing natural gas pipeline material is required [2].
