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Evaluation of HIC Resistance in Two X70 Pipeline Steels Using Ultrasonic Testing
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- Author / Creator
- Gawor, Steffen
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An evaluation of the resistance of two different X70 pipeline steels to hydrogen-induced cracking in severe (pH 2.7 and 1 atm H2S) and intermediate (pH 5.5 and 1 atm H2S) sour service conditions was undertaken. The two steels used in this work, X70-X and X70-B, were selected based on their different calcium to sulfur ratios. X70-X and X70-B possess calcium to sulfur ratios of 2.5 and about 0.5, respectively.
Using the NACE standard TM0284-2016 and solution C, samples were tested at pH levels of 2.7 and 5.5 for test periods of 1 to 64 days. Cracking was then evaluated using ultrasonic techniques. At a pH of 2.7, both steels showed cracking after one day in test solution and reached a crack equilibrium after 4 to 8 days. Samples tested at a pH of 5.5 showed cracking after 32 days for steel X70-B and after 64 days for X70-X. For X70-B, a crack equilibrium seemed to be reached after 32 days. In direct comparison with the low calcium to sulfur ratio in X70-B, X70-X showed an increased resistance to hydrogen-induced cracking.
In this work, an ultrasonic procedure, using the crack to backwall signal ratio (CBR), was developed and is used to quantify the extent of cracking in X70-X and X70-B. CBR maps and histograms give information about the location, extent and distribution of cracks. To compare different steels and conditions, a global crack to backwall ratio (GCBR) is obtained by the numerical calculation of the normalized integral of the local CBR values. The GCBR for X70-X after 16 days in a pH 2.7 solution is about 0.3. For X70-B, under identical solutions, a worse GCBR of about 0.55 was recorded. X70-X generally shows a better resistance to hydrogen-induced cracking than X70-B in test solutions of pH 2.7 and 5.5 and for 1 atmospheric pressure of hydrogen sulfide. -
- Subjects / Keywords
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- Graduation date
- Fall 2019
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.