Chemistry Considerations of P1 Base Materials to Mitigate Hydrogen Embrittlement Exposure
Bibliographic record
Abstract
Abstract The coarse grain heat affected zone of welded structures made of P1 Group 1 and 2 carbon manganese (C-Mn) steels of which ASTM A516 is a common plate specification is subject to formation of high hardness microstructures. This hardenability is a function primarily of the chemistry of the base metal and the t8/5 (800 to 500°C (1472 to 932°F)) cooling rates. This hard zone is subject to hydrogen embrittlement either during fabrication or during service exposure to corrosive environments. This paper reviews the various chemistry prediction tools for heat affected zone (HAZ) hardenability to determine if a rationale could be put forward to define a specific chemistry limit that could be defined by users such as a carbon equivalent (CE) to achieve an HVmax of 248 required by industry standards when exposed to service hydrogen embrittlement. A literature review of the evolution of weldability and hardenability models from 1940 to the present day reveals that there probably is too much spread in the models to readily identify a practical chemistry limit specification alone. The models though do help in understanding the combination of chemistry, post weld heat treatment and weld procedure control implications. Chemistry limits alone would not appear to be sufficient to ensure maximum hardness HAZ’s and supplemental post weld heat treatment and/or rigorous welding procedure controls should be specified. It is suggested that NACE RP0472 consider the concept of t8/5 cooling rate found in BS EN1011-2. Implications of chemistry on the postweld heat treatment (PWHT) and weld procedure controls are identified and suggestions made to consider for these HAZ hardness control options.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".