Near-Neutral pH SCC of Two Line Pipe Steels Under Quasi-Static Stressing Conditions
Bibliographic record
Abstract
Most published SCC results for the near-neutral pH condition were produced under cyclic loading. However, the presence of stress corrosion cracks in pipeline systems involving very small pressure fluctuations suggests the cracking should initiate and grow without large dynamic loads. This study was designed to investigate this issue. A Grade 448 (X-65) line pipe steel and a prototype Grade 550 (X-80) steel were evaluated in near-neutral pH solutions. The maximum stress applied was at 95% of the respective yield strengths and the R values applied were between 0.98 and 1.0. Two solutions were used for each steel: NS4 and NS4/clay mixture. The solutions were purged with a gas mixture of 95%N2 and 5%CO2. Recognizing that the crack propagation rate can be very slow under such near-static conditions, relatively long-term tests were carried out. The durations of the three tests using the prototype Grade 550 (X-80) steel were 110 days, 54 days and 26 days, and the duration for the X-65 steel was 110 days. After 110 days, the majority of the cracks in the Grade 550 (X-80) steel were in the range of 5 to 30 micrometers (μm) deep, giving an average crack propagation rate of 2*10−9 mm/s. Tests at short durations revealed that only a few cracks were detectable after 26 days and that several more cracks were produced after 54 days. So majority of the cracks in the 110-day were likely produced after 54 days of testing. The NS4/clay mixture was found to be less aggressive than the NS4 solution for both steels studied. The cracks in the prototype Grade 550 (X-80) steel were deeper and more numerous in comparison with the X-65 steel. Possible reasons for this observation are also explored in terms of the presence of martensite-austenite (MA) phase in the Grade 550 (X-80) steel.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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 teacher head, 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".