Cyclic crack growth rates of X-60 pipeline steel in a neutral dilute solution

Journal Article · Tue Jul 01 04:00:00 EDT 1997 · Corrosion

DOI:https://doi.org/10.5006/1.3290290· OSTI ID:514788

Ahmed, T M; Lambert, S B; Plumtree, A ^[1]; Sutherby, R ^[2]

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1. Univ. of Waterloo, Ontario (Canada). Dept. of Mechanical Engineering
2. Nova Gas Transmission Ltd., Calgary, Alberta (Canada)

An experimental investigation was carried out to measure transgranular stress corrosion crack growth rates (CGR) in precracked X-60 steel specimens exposed to neutral (pH 7) dilute simulated ground water (designated NS4) while being cyclically loaded in cantilever bending. Testing was carried out over short-term (generally < 40 days) and long-term periods ({approximately}1 y). Loading and environmental conditions in the long-term tests were similar to those for buried natural gas pipelines, with the R ratio (minimum/maximum load) varying from 0.82 to 0.98 and frequencies ranging from 1 to 400 cycles/day. Cyclic loading conditions for specimens in the short-term tests were more severe, with R ratios ranging from 0.5 to 0.9 and frequencies from 40 cycles/day to 5,000 cycles/day. Post-mortem metallographic examination by optical and scanning electron microscopy was used to evaluate crack growth. Average CGR from 4.50 {times} 10{sup {minus}8} mm/cycle to 1.25 {times} 10{sup {minus}4} mm/cycle (equivalent to 1.4 {times} 10{sup {minus}9} mm/s to 7 {times} 10{sup {minus}7} mm/s) were measured, depending upon applied load range. For the more severe loading conditions in the short-term tests, the observed growth was attributed to corrosion fatigue. Under the less severe loading conditions of a high R ratio and low frequency, growth was attributed to transgranular stress corrosion cracking.

• Sponsoring Organization: NOVA, Calgary, AB (Canada)
• OSTI ID: 514788
• Journal Information: Corrosion, Journal Name: Corrosion Journal Issue: 7 Vol. 53; ISSN 0010-9312; ISSN CORRAK
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
36 MATERIALS SCIENCE
CORROSION FATIGUE
CRACK PROPAGATION
GROUND WATER
LOW ALLOY STEELS
MECHANICAL TESTS
NATURAL GAS
PIPELINES
STRESS CORROSION