PSI - Issue 68

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2025) 000–000

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 68 (2025) 1091–1097

European Conference on Fracture 2024 The mechanical properties of X70 steel pre-charged in blend of hydrogen and methan

Jan Kec*, Lukáš Jeníček, Jakub Jindra, Miloslav Poupa SVÚM a.s., Strength Laboratory, Tovární 2053, 250 88 Čelákovice, Czech Republic

Abstract This paper deals with the mechanical properties of X70 steel pre-charged in blend of hydrogen and methane. Specifically, the fracture toughness (FT) test, Charpy V-notch (CVN) impact test and tensile test (TT) were evaluated. The pre-charging was carried out at room temperature, 100 bar pressure and for 3000 and 6000 hours. The specimens for FT and TT were pre-loaded to the corresponding operational conditions and, on the other hand, the specimens for CVN remained in the unloaded state during pre-charging in the blend. The TT specimens were pre-loaded to 67% of the specified minimum yield strength (SMYS), corresponding to the operating pressure of 100 bar. The CT specimens for FT were initially fatigue-cracked and then bolt-loaded to a stress intensity factor K Iapp = 84,5 MPa.m 0,5 , which corresponds to internal semi-elliptical crack with a depth of a = 10 mm (0,46.t) and surface length of 2c = 60 mm (2,79.t) loaded at 100 bar. The decrease in fracture parameters was noticeable, whether it was the CVN results or the FT test results. The decrease in average CVN energy values was 30 J for circumferential specimens and 20 J for longitudinal specimens. The decrease in the size-independent fracture mechanical parameters J ic and J 0.2 was 50% and 40%, respectively. A decrease of 22% was observed for the size-dependent parameter J u(20) . © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers Keywords: Hydrogen embrittlement; X70 pipeline steel; Fracture toughness; Tensile test; Charpy V-notch test © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers

* Corresponding author. Tel.: +420 326 509 044 . E-mail address: kec@svum.cz

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers 10.1016/j.prostr.2025.06.174