Component test to simulate critical conditions of hydrogen assisted cracking in submerged arc welded offshore steel
- Offshore Wind Turbines (OWT) are a key factor in tomorrow's sustainable energy generation. The ever� increasing installation depth and weight of OWTs require suitable foundation concepts such as monopiles or tripods. Typically, mild steels such as S420ML are used with plate thicknesses of up to several hundred mm, resulting in high restraints in the welded joints. The large plate thickness requires high-efficiency welding processes such as submerged arc welding (SAW) with multiple wires. Due to the very high stiffness and plate thickness of the large-scale offshore structure, a susceptibility to time� delayed hydrogen assisted cracking (HAC) may occur. For this reason, a minimum waiting time (MWT) of up to 48 h must be considered before NDT is conducted. The evaluation of the crack susceptibility is complex due to the component size and stiffness of real offshore structures. For this purpose, a near-component test geometry has been developed to transfer the real stiffness conditions toOffshore Wind Turbines (OWT) are a key factor in tomorrow's sustainable energy generation. The ever� increasing installation depth and weight of OWTs require suitable foundation concepts such as monopiles or tripods. Typically, mild steels such as S420ML are used with plate thicknesses of up to several hundred mm, resulting in high restraints in the welded joints. The large plate thickness requires high-efficiency welding processes such as submerged arc welding (SAW) with multiple wires. Due to the very high stiffness and plate thickness of the large-scale offshore structure, a susceptibility to time� delayed hydrogen assisted cracking (HAC) may occur. For this reason, a minimum waiting time (MWT) of up to 48 h must be considered before NDT is conducted. The evaluation of the crack susceptibility is complex due to the component size and stiffness of real offshore structures. For this purpose, a near-component test geometry has been developed to transfer the real stiffness conditions to laboratory (i.e. workshop) scale. The 350 kg mock-up consisted of heavy plates (thickness 50 mm, seam length 1,000 m) joined by a 22-pass submerged-arc weld. Additional stiffeners simulated the effect of high restraint or shrinkage restraint of the weld. Extreme scenarios of hydrogen absorption during welding were simulated by using flux in dry (HD < 5 ml/100g Fe) and wet (HD > 15 ml/100g Fe) conditions. Weld residual stresses were determined using a robotic X-ray diffractometer. Areas of critical tensile residual stress (at the yield strength level) were found in the weld metal and in the heat affected zone, suggesting that these weld subzones are the most critical in the case of hydrogen ingress. To identify possible delayed cracking, the welds were inspected by phased array ultrasonic testing (PAUT) after welding, 6 h, 12 h, 24 h, and a maximum of 48 h. Summarized, no significant occurrence of HAC was detected, indicating the high crack resistance of the welded joint, i.e., a suitable combination of base material, welding consumable and parameters.…


| Autor*innen: | Kjell ErxlebenORCiD |
|---|---|
| Koautor*innen: | Michael RhodeORCiD, Arne KrommORCiD, Tobias Mente, Daniel Brackrock, Denis Czeskleba, Thomas KannengießerORCiD |
| Dokumenttyp: | Vortrag |
| Veröffentlichungsform: | Präsentation |
| Sprache: | Englisch |
| Jahr der Erstveröffentlichung: | 2025 |
| Organisationseinheit der BAM: | 8 Zerstörungsfreie Prüfung |
| 8 Zerstörungsfreie Prüfung / 8.4 Akustische und elektromagnetische Verfahren | |
| 9 Komponentensicherheit | |
| 9 Komponentensicherheit / 9.4 Integrität von Schweißverbindungen | |
| DDC-Klassifikation: | Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten |
| Freie Schlagwörter: | Cold cracking; Component test; Hydrogen; Minimum waiting time; Offshore steel grade |
| Themenfelder/Aktivitätsfelder der BAM: | Energie |
| Energie / Wasserstoff | |
| Energie / Windenergie | |
| Material | |
| Material / Degradationsmechanismen | |
| Veranstaltung: | Materials Week/Steel Innovation |
| Veranstaltungsort: | Frankfurt am Main, Germany |
| Beginndatum der Veranstaltung: | 02.04.2025 |
| Enddatum der Veranstaltung: | 04.04.2025 |
| Verfügbarkeit des Dokuments: | Datei im Netzwerk der BAM verfügbar ("Closed Access") |
| Datum der Freischaltung: | 07.04.2025 |
| Referierte Publikation: | Nein |
| Eingeladener Vortrag (wissenschaftliche Konferenzen): | Nein |

