다층 FCA 용착금속의 수소취성 저항성 및 확산성 수소 방출 거동

유재석,곽현,이명진,김용덕,강남현,Yoo, Jaeseok,Xian, Guo,Lee, Myungjin,Kim, Yongdeok,Kang, Namhyun 대한용접접합학회 2013 대한용접·접합학회지 Vol.31 No.6

In this study, constant loading test (CLT) was performed to evaluate the hydrogen embrittlement resistance for multipass FCA weld metals of 600MPa tensile strength grade. The microstructures of weld metal-2 having the smallest carbon equivalent (Ceq=0.37) consisted of grain boundary ferrite and widmanstatten ferrite in the acicular ferrite matrix. The weld metal-1 having the largest Ceq=0.47, showed the microstructures of grain boundary ferrite, widmanstatten ferrite and the large amount of bainite (vol.%=19%) in the acicular ferrite matrix. The weld metal-3 having the Ceq=0.41, which was composed of grain boundary ferrite, widmanstatten ferrite, and the small amount of bainite (vol.%=9%) in the acicular ferrite matrix. Hydrogen desorption spectrometry (TDS) used to analyze the amount of diffusible hydrogen and trapping site for the hydrogen pre-charged specimens electrochemically for 24 hours. With increasing the current density of hydrogen pre-charging, the released amount of diffusible hydrogen was increased. Furthermore, as increasing carbon equivalent of weld metals, the released diffusible hydrogen was increased. The main trapping sites of diffusible hydrogen for the weld metal having a low carbon equivalent (Ceq=0.37) were grain boundaries and those of weld metals having a relatively high carbon equivalent (Ceq: 0.41~0.47) were grain boundaries and dislocation. The fracture time for the hydrogen pre-charged specimens in the constant loading test was decreased as the carbon equivalent increased from 0.37 to 0.47. This result is mainly due to the increment of bainite that is vulnerable to hydrogen embrittlement.

Origin of hydrogen embrittlement in vanadium-based hydrogen separation membranes

Ko, W.S.,Jeon, J.B.,Shim, J.H.,Lee, B.J. Pergamon Press ; Elsevier Science Ltd 2012 International journal of hydrogen energy Vol.37 No.18

Hydrogen embrittlement in metals is a challenging technical issue in the proper use of hydrogen energy. Despite extensive investigations, the underlying mechanism has not been clearly understood. Using atomistic simulations, we focused on the hydrogen embrittlement in vanadium-based hydrogen separation membrane. We found that, contrary to the conventional reasoning for the embrittlement of vanadium, the hydrogen-enhanced localized plasticity (HELP) mechanism is the most promising mechanism. Hydrogen enhances the nucleation of dislocations near the crack tip, which leads to the localized plasticity, and eventually enhances the void nucleation that leads to the failure. Those results provide an insight into the complex atomic scale process of hydrogen embrittlement in vanadium and also help us design a new alloy for hydrogen separation membranes.

수소연료전지 자동차의 수소밸브용 알루미늄 합금의 저변형율인장실험에 의한 수소취화특성 연구

김성종,황현규,신동호 한국부식방식학회 2022 Corrosion Science and Technology Vol.21 No.6

As part of eco-friendly policies, interest in hydrogen vehicles is growing in the automotive industry to reduce carbon emissions. In particular, it is necessary to investigate the application of aluminum alloy for light weight hydrogen valves among hydrogen supply systems to improve the fuel efficiency of hydrogen vehicles. In this research, we investigated mechanical characteristics of aluminum alloys after hydrogen embrittlement considering the operating environment of hydrogen valves. In this investigation, experiments were conducted with strain rate, applied voltage, and hydrogen embrittlement time as variables that could affect hydrogen embrittlement. As a result, a brittle behavior was depicted when the strain rate was increased. A strain rate of 0.05 mm/min was selected for hydrogen embrittlement research because it had the greatest effect on fracture time. In addition, when the applied voltage and hydrogen embrittlement time were 5 V and 96 hours, respectively, mechanical characteristics presented dramatic decreases due to hydrogen embrittlement.

극저온 사용 소재 스테인레스강 316L의 수소취화 저항성 평가

황재식,Nguyen Le Thanh Hung,김명성,이제명 한국마린엔지니어링학회 2019 한국마린엔지니어링학회지 Vol.43 No.4

Hydrogen is currently attracting attention as a next-generation energy source. However, the phenomenon of hydrogen embrittlement is the biggest problem related to hydrogen energy. In this study, the mechanical strength of stainless steel 316L with hydrogen embrittlement (HE) conditions was analyzed. To establish an HE environment, a cathodic electrolytic method was performed with hydrogen charging time (0, 24, and 48 h) as a parameter, and a tensile test was conducted at 25, -110, and -195°C. Zinc plating was applied to prevent hydrogen from being released during the tensile test for mechanical strength analysis. To analyze hydrogen charging of hydrogen-charged stainless steel 316L, a sample taken from the specimen was melted to release hydrogen gas. The experiment confirmed that different amounts of hydrogen were charged into the stainless steel 316L particles according to the hydrogen charging time, but the decrease in the mechanical strength based on the hydrogen loading amount was very small. The study thus showed that stainless steel 316L exhibits resistance to hydrogen embrittlement in a cryogenic environment. 차세대 에너지원으로 수소가 각광받고 있는 현재, 수소에너지로 인한 가장 큰 문제점인 수소취화 현상이 주목받고 있다. 이에 따라 본 연구에서는 수소취화(Hydrogen Embrittlement, HE)조건을 적용한 스테인레스강 316L의 기계적 성능을 분석하였다. 수소취화 환경을 조성하기 위하여 수소장입시간(0h, 24h, 48h)을 변수로 음극전기분해법(Cathodic Electrolytic Method)을 수행하였으며, 온도(25℃, -110℃, -195℃)에 따른 인장시험을 진행하였다. 기계적 강도 분석을 위한 인장시험 중 수소가 방출되는 것을 방지하기 위하여 전기아연도금을 시행하였다. 수소 장입된 스테인레스강 316L의 수소 장입량을 분석하기 위하여, 시편에서 채취한 시료를 용융시켜 수소가스를 방출시켰다. 실험 결과, 수소장입시간에 따라 서로 다른 양의 수소가 스테인레스강 316L의 입자 속에 장입되었지만, 수소장입량에 따른 기계적 성능의 감소가 매우 미미함을 확인할 수 있었다. 이에 따라 스테인레스강 316L이 극저온 환경에서 수소취화에 대한 뛰어난 저항성을 확인할 수 있었다.

수소 주입 방식에 따른 세 고망간강의 수소 취화 거동 비교

이승용 ( Seung-yong Lee ),황병철 ( Byoungchul Hwang ) 대한금속ㆍ재료학회 2017 대한금속·재료학회지 Vol.55 No.10

In this study the hydrogen embrittlement characteristics of three high-manganese steels were tested using different hydrogen charging methods, and the results were compared with various Mn-containing steels. The results showed that the hydrogen embrittlement susceptibility of the high-manganese steels increased with increasing inherent strength because deformation mechanisms, such as deformation twinning, ε-martensite transformation, and shear- or micro-band formation, enhanced their sensitivity to hydrogen-induced cracking. The different hydrogen charging methods also affected their ability to achieve the critical hydrogen concentration needed for hydrogen-induced cracking under the stress fields of each microstructure. The relative reduction in ductility for different charging methods usually increased in the order of ex-situ electrochemically-charged, ex-situ high-pressure thermally-charged, and in-situ environment tensile testing, although it was somewhat dependent on the charging, testing and specimen conditions. Based on the results of the three high-manganese steels, it was found that the high-pressure thermally-charged steel specimens had higher relative reductions in ductility because a larger amount of hydrogen was uniformly injected into the steel specimens, which promoted hydrogen-induced cracking under smaller strain than that of the electrochemically-charged steel specimens. (Received May 18, 2017; Accepted June 20, 2017)

Influence of gaseous components and pressures on hydrogen embrittlement of natural gas pipeline

김철만,김영표,김우식 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.8

Hydrogen usually penetrates metals through defects such as dislocations, vacancies, and crystalline imperfections and causes embrittlement, leading to cleavage fracture and intergranular fracture. Synthetic natural gas produced by coal gasification, biogas, and landfill gas inevitably contain hydrogen. Therefore, hydrogen embrittlement of pipeline materials should be considered when they are mixed with conventional natural gas and supplied to customers. To analyze hydrogen embrittlement of base metals and girth weld metals of API 5L X70 and X65 gas pipelines, a specimen was treated in 100 % hydrogen environment at 10 MPa to determine the hydrogen concentration in it. Small punch (SP) tests were performed under various gaseous components and pressures. When SP tests were performed at very low speed, hydrogen embrittlement could be observed. Specimens became very susceptible to hydrogen embrittlement with increasing hydrogen partial pressure in the hydrogen/methane gas mixture, and the SP energy also decreased dramatically.

Evaluation of hydrogen embrittlement behaviors of steel welds for pipelines in practical hydrogen environments using in-situ SP tests

Hyung-Seop Shin(신형섭),Juho Yeo(여주호),Jaewon Cho(조재원),Eunsu Min(민은수),Un-Bong Baek(백운봉) 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.5

Recently, ANU group has established a simple screening technique for hydrogen embrittlement compatibility of steels, which is adopting an in-situ small-punch (SP) test method and corresponding to the ‘external hydrogen’ condition, and proposed a characterizing factor which is suitable for the SP test. The technique is based on the quantitative evaluation of the hydrogen embrittlement (HE) behaviors of various structural steels for hydrogen energy facilities. To investigate the HE compatibility of metallic materials, the in-situ SP tests were carried out under a high-pressure hydrogen gas environment and at the temperature ranges sensitive to HE. Through the measurement of the reduction of thickness (ROT) at the fractured part of the specimen after SP tests under both H2 and inert gas environments, the relative reduction of thickness (RRT) due to HE can be obtained. The RRT has a similar physical meaning to the relative reduction of area (RRA) obtained by the conventional slow strain-rate tensile test (SSRT), since both factors are based on the ductility induced under hydrogen environments. In this study, it is tried to investigate the hydrogen embrittlement (HE) behaviors of pipeline steels and welds by the in-situ SP test. The ductility-based RRT obtained by in-situ SP tests was used to quantify the HE sensitivity of the base metal and welds under various test conditions corresponding to practical use environments of hydrogen devices. This study will contribute to confirm the validity of in-situ SP tests as a simple test method for the quantitative evaluation of the HE susceptibility of pipeline steel welds.

다단인발 공정이 SUS316L의 수소취화에 미치는 영향에 관한 분석

최주호,박준홍 사단법인 한국융합기술연구학회 2024 아시아태평양융합연구교류논문지 Vol.10 No.3

전 세계적으로 널리 사용되어온 화석연료는 사용하기 용이하나, 탄소 배출로 인해 지구온난화와 같은 문제를 초래했다. 배출되는 탄소의 양을 줄이기 위해서 각국에선 다양한 친환경에너지를 도입하고자 하는데, 수소에너지도 그중 하나로 각광받고 있다. 수소에너지를 사용하려면 이송 및 저장할 파이프와 탱크가 필요하다. 하지만 기존에 사용되던 설비를 사용하면 수소취화로 인한 파괴가 일어난다. 따라서 이를 방지하기 위해 내식성이 좋은 수소용 소재에 대한 개발 및 적용을 위한 연구가 활발하다. 다양한 수소용 소재의 기계적·재료적 특성을 분석하기 위해 냉간압연된 판재에 관한 연구는 활발히 진행되어 왔으나, 인발된 봉재에 관한 연구는 거의 진행되고 있지 않다. 따라서 본 연구에서는 다단 인발된 SUS316L 봉재에 관해 인발 전후, 수소장입 전후 기계적·재료적 특성변화에 대해 관찰했다. 또한 수소가 장입된 시편, 비장입된 시편의 Micro-Vickers 경도와 항복강도 사이의 관계식을 도출하였다. 수행된 다단 인발 공정을 통해 얻은 실제 경도 값과, 유효 변형률을 경도로 변환한 값을 비교하기 위해 유한요소해석 툴인 ABAQUS와 DEFORM을 사용했다. 두 유한요소해석 툴에 따른 인발재의 유효 변형률 데이터를 비교했고, 이를 경도로 변환하여 실제 측정 데이터와 비교·분석했다. Global warming and other environmental problems have been caused by the use of fossil fuels, which have been widely used worldwide. Fossil fuels are easy to use, but they have the disadvantage of emitting carbon, which leads to problems such as global warming. Several countries are working to implement renewable energy sources, such as hydrogen energy, in order to lower carbon emissions. Hydrogen energy requires pipes and tanks for transportation and storage. However, using the existing facilities causes hydrogen embrittlement. Therefore, research on the development and application hydrogen-resistant materials with good corrosion resistance is actively being conducted to prevent hydrogen embrittlement. Research on the mechanical and material properties of various hydrogen-resistant materials has been actively conducted for cold-rolled sheets, but research on drawn bars is almost non-existent. Thus, on multi-pass drawn SUS316L bars, the changes in mechanical and material properties were studied before and after drawing as well as before and after hydrogen charging. In addition, this study derived a relationship between the Micro-Vickers hardness and yield strength of specimens with and without hydrogen charging. To compare the actual hardness values obtained through the multi-pass drawing process and the values converted to hardness from effective strain, ABAQUS and DEFORM, two programs for finite element analysis, were utilized. This research compared the effectiveness of a strain data of the drawn material from the two FEA tools, converted it to hardness, and compared and analyzed it with the actual measurement data. To increase the safety and dependability of hydrogen energy infrastructure, the study's findings offer insightful information about the mechanical and material characteristics of drawn SUS316L bars.

Effect of prestrain on hydrogen diffusion and trapping in structural steel

Park, Cheolho,Kang, Namhyun,Kim, Myunghyun,Liu, Stephen Elsevier 2019 Materials letters Vol.235 No.-

<P><B>Abstract</B></P> <P>Hydrogen permeation tests were electrochemically performed to measure hydrogen diffusion and trapping in EH 36 steel. Permeation transients were measured through charging and decaying cycles, for specimens prestrained to varying degrees (0–20%). With increasing prestrain, the effective hydrogen diffusivity (<I>D<SUB>eff</SUB> </I>) decreased, while the total/reversible hydrogen content (<I>C<SUB>o</SUB> </I> and <I>C<SUB>r</SUB>, respectively</I>) increased. The immobile dislocation of the 20%-prestrained specimens decreased <I>D<SUB>eff</SUB> </I> by approximately ten times and increased <I>C<SUB>o</SUB> </I> and <I>C<SUB>r</SUB> </I> by approximately three times. The amount of irreversibly trapped hydrogen (<I>C<SUB>irr</SUB> </I>) remained approximately the same, regardless of the prestrain. The dislocations delay the motion of hydrogen and contain more reversible hydrogen.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hydrogen permeation tests successfully measured the hydrogen diffusivity and concentration. </LI> <LI> As the prestrain increased from 0 to 20%, the effective hydrogen diffusivity decreased. </LI> <LI> Total and reversible hydrogen concentrations increased with the prestrain. </LI> <LI> Irreversible hydrogen showed mostly the same value regardless of prestrain. </LI> <LI> The dislocations delay the motion of hydrogen and contain more reversible hydrogen. </LI> </UL> </P>

A Study on the Post-Weld Heat Treatment Effect to Mechanical Properties and Hydrogen Embrittlement for Heating Affected Zone of a RK 36 Steel

( Kyung Man Moon ),( Myung Hoon Lee ),( Ki Joon Kim ),( Jin Gyeong Kim ),( Seong Jong Kim ) 한국부식방식학회 2003 Corrosion Science and Technology Vol.2 No.6