Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Hydrogen Effect on Linepipe Steel and Material Compatibility to High Pressure Hydrogen Pipeline
Nobuyuki Ishikawa*1, Junji Shimamura*2, Daichi Izumi*2, Hiroshi Okano*3and Yoshihiro Nishihara*3*1

Plate Business Planning Dept., JFE Steel Corporation, Tokyo, Japan
Steel Research Laboratory, JFE Steel Corporation, Fukuyama, Japan*3 Steel Research Laboratory, JFE Steel Corporation, Kawasaki, Japan.
*2(KIH) than recent high grade steels. But, further higher grade linepipe
such as X100 exhibits lower KIH value (Ronevich, 2021). Abnormal
fracture such as separations was seen in the fracture surface of thespecimen tested in hydrogen (Stalheim, 2010). Fracture toughness oflinepipe welds is also reduced in hydrogen (Ronevich, 2021). Most
significant effect by hydrogen is seen in fatigue crack growth behavior.
Fatigue crack growth rate (FCGR) is largely accelerated in gaseoushydrogen and there are many experimental investigations for linepipe
steels (Cialone, 1985; San Marchi, 2010; Slifka, 2013, 2018). Hydrogeneffect is modest under a low ∆K region, which is around the thresholdstress intensity factor for fatigue crack growth, but the ratio of FCGR inhydrogen to that in the air is increased with increasing ∆K. Linepipe
welds show fatigue crack growth behavior similar to base material(Slifka, 2015). This may insists that fatigue crack growth in hydrogen is
not largely affected by steel microstructure. However, it was reported
that the steel with finer microstructure by an optimized plate rolling
condition exhibits smaller FCGR (Stalheim, 2020). Effect of hydrogenmixture to the natural gas on fracture and fatigue properties were
investigated for the consideration of the hydrogen transportation withblending to an existing natural gas pipeline (Meng, 2017; Nguyen, 2020;Ronevich, 2021). It was demonstrated that even with small mixture ofhydrogen can reduce the fracture and fatigue properties of linepipe steels
significantly.

ABSTRACTIn this paper, basic material behavior and mechanical properties oflinepipe steel under high pressure hydrogen were investigated. Hydrogen
exposure test was first conducted to evaluate hydrogen absorption into
the steel from gaseous hydrogen up to 25MPa. It was found that around0.1ppm hydrogen was absorbed into the steel, which is the level ofhydrogen absorption under mildly sour environment. This result reminds
us a possibility of hydrogen stress cracking, accordingly proper material
should be recommended for the hydrogen use. Then, fracture toughness
and fatigue crack growth test were conducted using a recently produced
Grade X65 DSAW linepipe with fine grained bainitic microstructure,
revealing excellent performance of fracture and fatigue resistance under
21MPa high pressure hydrogen. Integrity assessment for hydrogenpipeline was finally conducted based on ASME B31.12.

KEY WORDS:High pressure gaseous hydrogen; linepipe steel;hydrogen embrittlement; fatigue crack growth; fracture toughness;hydrogen permeation.

INTRODUCTION
Infrastructures for hydrogen storage and transportation need to be safely
used for a carbon neutral society. One of the most important issues forthe integrity of hydrogen system is material degradation caused byhydrogen. It is well understood that solute hydrogen in steel causes
degradation of material properties, so called hydrogen embrittlement.
Hydrogen effect on the mechanical properties of linepipe steels havebeen extensively investigated in these decades. Slow strain rate tensile
test with smooth round bar specimen under gaseous hydrogen showedmodest loss of ductility while yield and tensile strength do not show large
affection by hydrogen (Hoover, 1981; Cialone, 1985; Stalheim, 2010).
On the other hand, hydrogen effect on ductility becomes significant in
the case of notched specimen and shows large drop in reduction of area
because the quasi cleavage fracture was seen in the surface. (Hoover,1981; Zhou, 2021). Fracture toughness is also reduced in high pressure
gaseous hydrogen (Hoover, 1981; Cialone, 1985; Gutierrez-Solana,1982; Stalheim, 2010). It seems that low grade linepipe steels such as
X42 or X52 tend to show lower fracture toughness value in hydrogen

Above mentioned degradation of mechanical properties of steels underhigh pressure gaseous hydrogen is considered to be caused by hydrogen
embrittlement. Once hydrogen atoms uptake into steel, hydrogen atoms
can easily diffuse in the steel lattice and accumulate at the region withmechanical discontinuity such as crack tips and defects driven by thehydrostatic stress gradient (Sofronis, 1989; Krom, 1999; Ishikawa, 2015).
Accumulated hydrogen activates the process of hydrogen embrittlement
mechanisms such as (i) the hydrogen enhanced decohesion mechanism,HEDE (Oriani, 1987; Yamaguchi, 2012), (ii) the hydrogen enhanced
localized plasticity, HELP (Birnbaum, 1994; Sofronis, 1996; Robertson,2001) and (iii) the hydrogen enhanced strain-induced vacancy model,HESIV. (Nagumo, 2001, 2004; Neeraj, 2012), and then enhances brittle
and/or ductile fracture leading to the reduction in fracture toughness andthe acceleration of fatigue crack growth. However, the behavior ofhydrogen absorption into a steel from high pressure gaseous hydrogen3019