• Journal of the Korean institute of surface engineering
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• v.45 no.5
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• pp.212-217
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• 2012

High strength steel sheets used for automobile outer-panels have been intensively studied for developing a lightweight automobile under a strong pressure of the requirements for enhancing the mileage and energy saving in production of automobile parts. It is known that high strength steels are susceptible to hydrogen embrittlement, The susceptibility to hydrogen embrittlement increases with increasing its strength. However, the effect of hydrogen on the fracture behavior of high strength steels, though investigated extensively, has not been fully understood. In this paper, hydrogen was charged with 590DP steels by electrochemical method and its content was measured by hydrogen determinator with the different charging conditions. It was shown that the SP energy and maximum load decreased with increasing charging time. The results of SEM-fractography investigation for the hydrogen contained samples showed that a small portion of dimples on cleavage-fractured surface were observed and the size of the dimples were decreased with increasing hydrogen charging time.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.4
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• pp.340-345
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• 2010

For the conversion into hydrogen society, not only studying facilities of hydrogen production, storage, transportation and charging system but also developing technique of ensuring safety are essentially needed. Hence, for the first step of that, evaluated the hydrogen embrittlement of Inconel alloy 617, Ni-based super heat-resisting alloy, by small punch test. Prepared the various specimens through changing electrochemical charging time and measured the toughness degradation of the specimens by small-punch test. The analysis of hydrogen embrittlement behavior were carried out by investigating the fractured surface of specimens. This study has significance on revealing mechanism of hydrogen embrittlement behavior and the factor affecting hydrogen embrittlement in the future study.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.3
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• pp.284-292
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• 2020

In this study, hydrogen charging was conducted for API X70 steel by the electro-chemical hydrogen charging method. Right after hydrogen was diffused from the specimen surface to the inside of the X70, the small punch tests and hydrogen concentration analysis was conducted within 5 minutes. Hydrogen was analyzed by melting the whole specimen and detect the gas after melting. Mechanical properties were measured by the small punch (SP) testing. Fracture surface and specimen surface were observed using scanning electron microscope. Three tests were repeated for study sensitivity of the SP test results under a same charging condition. It was observed that the variation of the maximum load, SP displacement at failure, hydrogen concentration as the charging period was not much in the case of X70 as the other steel such as Inconel. It can be argued that X70 base metal may have high hydrogen damage resistance and hydrogen diffusion in the base metal would not cause much embrittlement. Limitations of the SP test with 0.5 mm thickness for hydrogen damage test for X70 were discussed.

• Journal of the Korean Society of Systems Engineering
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• v.18 no.2
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• pp.140-148
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• 2022

Hydrogen is expected to be widely applied in most sectors within the current energy system, such as transportation and logistics, and is expected to be economically and technologically utilized as a power source to achieve vehiclebon emission reduction. In particular, the construction of hydrogen charging station infrastructure will not only support the distribution of hydrogen electric vehicles, but also play an important role in building a hydrogen logistics system. Therefore, This paper suggest additional charging infrastructure areas in Seoul with a focus on supply according to the annual average growth rate (CAGR), centering on Seoul, where hydrogen vehicles are most widely distributed. As of February 2022, hydrogen charging infrastructures were installed in Gangseo-gu, Gangdong-gu, Mapo-gu, Jung-gu, and Seocho-gu in downtown Seoul. Next, looking at the number of hydrogen vehicles by administrative dong in Seoul from 2018 to 2022, Seocho-gu has the most with 246 as of 2022, and Dongjak-gu has the highest average growth rate of 215.4% with a CAGR of 215.4%. Therefore, as a result of CAGR analysis, Dongjak-gu is expected to supply the most hydrogen vehicles in the future, and Seocho-gu currently has the most hydrogen vehicles, so it is likely that additional hydrogen charging infrastructure will be needed between Dongjak-gu and Seocho-gu.

• Corrosion Science and Technology
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• v.16 no.4
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• pp.201-208
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• 2017

A finite element analysis is proposed to study the effect of specimen dimensions on lateral diffusion of hydrogen during hydrogen permeation flux measurements. The error of measurement on thick specimens because of 1D diffusion approximation may be as much as 70%. A critical condition for accurate measurements is to designate the area of hydrogen monitoring/exit surface smaller than the area of hydrogen charging/entry surface. For thin to medium thickness specimens (ratio of thickness to specimen radius of 5:10 and below), the charging surface should be maximized and the monitoring surface should be minimized. In case of relatively thick specimens (ratio of thickness to specimen radius above of 5:10), use of a hydrogen-diffusion barrier on the specimen boundaries is recommended. It would completely eliminate lateral losses of hydrogen, but cannot eliminate the deviation towards 2D diffusion near the side edges. In such a case, the charging surface should be maximized and the monitoring surface should be as closer in dimension as the charging surface. A regression analysis was carried out and an analytical relationship between the maximum measurement error and the specimen dimensions is proposed.

• Journal of the Korean institute of surface engineering
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• v.47 no.5
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• pp.257-262
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• 2014

In this paper, the behavior of hydrogen embrittlement of 680MPa DP sheet steel according to hydrogen charging conditions in acid and alkali electrolytes atmosphere was investigated. At this time, 0.5 M $H_2SO_4$ and 0.5M NaOH was used for electrolytes atmosphere and the effect on embrittlemnet of 680MPa DP sheet steel according to current density and charging time was evaluated by the change of subsurface microhardness in DP specimens chared hydrogen. As a result of this experiment, the microhardness of the layer directly below the surface was increased more than the microhardness of the subsurface zone in both electrolytes cases, but the change of the subsurface microhardness in both electrolytes was more affected by the increase of charging time than the increase of current density. The microhardness of subsurface zone in 0.5 M $H_2SO_4$ acid electrolyte was increased more than the microhardness in 0.5M NaOH alkali electrolyte. It was supposed that acid atmosphere was more sensitive to hydrogen embrittlement than alkali atmosphere on electrolyte atmosphere of hydrogen charge.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.4
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• pp.309-317
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• 2022

There are 2,517 buses on 143 routes in Busan. One company is operating 36 hydrogen city buses (1.4%) and two hydrogen charging stations. By 2030, the number of hydrogen city buses will be increased to 500 and 40 hydrogen charging stations. In the survey of city bus companies, 61.5% of respondents answered 'not reviewing (at all)' and 23.0% of respondents '(actively) reviewing hydrogen buses'. And as for the level of help that hydrogen city buses give to bus companies, 23.5% answered 'helpful'. In order to promote the introduction of hydrogen city buses, first, it is necessary to stipulate support for hydrogen bus purchase cost and hydrogen charging station construction cost in related ordinances so that bus companies do not increase their burden of purchasing hydrogen buses in the future. Second, identify the number of new city buses introduced, convert about 50% to hydrogen city buses by the mid-term, and build 50% of the chargers in public garages with hydrogen chargers. Third, expand hydrogen refueling stations in city bus garages.

• Transactions of the Korean hydrogen and new energy society
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• v.5 no.1
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• pp.33-39
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• 1994

The changes of hydrogenation properties of $LaNi_5$ by hydrogen charging condition were investigated using the P-C-isotherm curves, DSC(Differential Scanning Calorimetry), GC(Gas Chromatograph), X-ray diffractometer. As a results of static hydrogen charging, the hydrogen storage capacity gradually decreased and the plateau region severly slopped. Most of the degraded properties could be restored by the annealing treatment. The degradation of hydrogen storage capacity was related with the formation of stable hydride, which was not dehydrided at room temperature.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.3
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• pp.163-171
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• 2021

Securing energy sources is a key element essential to economic and industrial development in modern society, and research on renewable energy and hydrogen energy is now actively carried out. This research was conducted through experiments and analytical methods on the hydrogen filling process in the hydrogen storage tank of the hydrogen charging station. When low-temperature, high-pressure hydrogen was injected into a high-pressure tanks where hydrogen is charged, the theoretical method was used to analyze the changes in temperature and pressure inside the high-pressure tanks, the amount of hydrogen charge, and the charging time. The analysis was conducted in the initial vacuum state, called the First Cycle, and when the residual pressure was present inside the tanks, called the Second Cycle. As a result of the analysis, the highest temperature inside the tanks in the First Cycle of the high-pressure tank increased to 442.11 K, the temperature measured through the experiment was 441.77 K, the Second Cycle increased to 397.12 K, and the temperature measured through the experiment was 398 K. The results obtained through experimentation and analysis differ within ±1%. The results of this study will be useful for future hydrogen energy research and hydrogen charging station.

• Corrosion Science and Technology
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• v.10 no.4
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• pp.131-135
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• 2011

The demands of high-strength steel have been steadily increased to reduce the weight of vehicles. Although the TRIP steel has been the promising candidate material for the purpose, high strength hinders the application due to the susceptibility to hydrogen delayed fracture in the corrosive environment. Moreover, the testing method was not specified in the ISO standards. In this work, the test method to evaluate the susceptibility of hydrogen delayed fracture was studied by slow strain rate testing technique. The four test experimental parameters were studied : strain rate, hydrogen charging time, holding time after hydrogen charging, and holding time after cadmium plating. The steel was fractured by hydrogen in case the strain rate was in the range of $1{\times}10^{-4}{\sim}5{\times}10^{-7}/sec$. It was confirmed that the slow strain rate test is effective method to evaluate the susceptibility to hydrogen delayed fracture. The holding time over 24 hrs after hydrogen charging, nullified the hydrogen effect, that is, the specimen was no more susceptible to hydrogen after 24 hrs even though the specimen was fully hydrogen-charged. Moreover, cadmium electroplating could not prevent from diffusing out the hydrogen from the steel in the experiment. The effective experimental procedures were discussed.