Hydrogen embrittlement in vintage grade 290 pipeline steel and its welded region via ex-situ and in-situ testing
Bibliographic record
Abstract
The effect of hydrogen embrittlement on the base metal and seam welds of CSA Z245.1 Grade 290 pipeline steel was examined through slow strain rate tensile tests utilizing both gaseous ex-situ and in-situ testing methods, followed by fractographic analysis. Ex-situ testing was conducted after one month and two months of pre-charging in 100% hydrogen (99.999%) at room temperature under 2.07 MPa (300 psi) of pressure. In-situ testing was conducted in a custom autoclave setup which maintained 2.07 MPa of pressure throughout the test at room temperature. The tensile results from this study emphasize the significance of in-situ testing, revealing that the hydrogen embrittlement index for the base metal and weld samples tested in-situ were 30.5% and 19.8% higher compared to the next closest tested conditions. Specimens tested with in-situ hydrogen exposure displayed shallow dimples, cleavage, quasi-cleavage facets, and lamellar cleavage, in contrast to the clearer micro-void coalescence seen in ambient and ex-situ tests. In-situ tested specimens showed more prominent localized plasticity and micro-cracks compared to those tested under ambient, one-month, and two-month pre-charged ex-situ conditions. • In-situ hydrogen tests show higher embrittlement than ex-situ in vintage steel. • Fracture shifts from microvoid coalescence (ex-situ) to quasi-cleavage (in-situ). • HELP and HEDE mechanisms mainly drive hydrogen-assisted failure processes. • Gaseous ex-situ tests may misrepresent real-world hydrogen embrittlement.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".