Evaluation of Fracture Toughness of Welded Line Pipe Steels for Hydrogen Gas Transportation Based on ASME B31.12 and Alternative Test Method Development
Bibliographic record
Abstract
Abstract A high-strength line pipe steel grade, namely API X65, has been developed and qualified for its use under pressurized hydrogen gas following the ASME B31.12 code. The bolt-load compact specimens taken from the base metal, heat-affected zone, and weld seam of the electric resistance welded (ERW) pipes were tested using a constant displacement method in 100% hydrogen at pressure up to 13.8 MPa (2000 psi) for 1000 hours. All fracture toughness testing was conducted at RINA Consulting – Centro Sviluppo Materiali SpA and EWI Hydrogen Environment Testing Lab, using approximately 50 specimens from different heats produced at Evraz North America (ENA). At the fracture surface of the tested specimens, no significant crack extension was observed; the crack extension beyond the fatigue pre-crack was smaller than 0.25 mm after preloading and hydrogen exposure. Scanning electron microscopy (SEM) fractographs revealed a dimpled fracture surface in front of the fatigue pre-crack, i.e. no hydrogen-associated brittle fracture feature was noted. Based on these results, the minimum value of the threshold stress intensity factor, KIH, was calculated to be 70–80 MPa√m for all the specimens, i.e., fulfilling the qualification criteria (KIH > 55 MPa√m) described in the code ASME B31.12 Option B. The lessons learned during the qualification testing, ongoing efforts to develop alternative testing methods, including elastic-plastic fracture testing (i.e., ASTM E1820) and implications for the future will be discussed.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".