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TitleEvaluation of current tank car TC128B steel weld performance
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LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorXu, SORCID logo; Chen, J; McKinley, J; Liang, J; Yang, L; Laver, A
SourceCanmetMATERIALS, Report no. CMAT-2020-WF 49867504, 2022, 31 pages Open Access logo Open Access
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Year2022
Alt SeriesTransport Canada Publication (TP) TP 15470E
PublisherCanmetMATERIALS
Editionupdated
Documentserial
Lang.English
Mediaon-line; digital
File formatpdf
SubjectsScience and Technology; Transport; welding; Materials technology; Steel; Rail transport
Illustrationsphotographs; tables; schematic diagrams; profiles; photomicrographs; plots
ProgramCanmetMATERIALS Joining and Structural Performance
Released2021 02 01; 2022 05 13
Abstract(Summary)
This report summarizes the results of the evaluation of current TC128B tank car welds. The sample coupons were received from a DOT-117J tank car. The experimental work in this report included the determination, from a longitudinal weld, of (i) chemical composition, microstructure and micro-hardness (ii) tensile strength and failure locations in the temperature range of 23°C to -60°C, and (iii) Charpy transition curves. Typical fracture features of low Charpy weld metal samples and volume fractions of acicular ferrite (AF) were characterized and discussed. The results of the longitudinal weld were compared to those from a circumferential weld characterized previously from the same tank car including updated Charpy testing at -34°C, and the main conclusions are provided in this report.
The TC128B welds were created using a double pass procedure. The first-pass (or root pass) weld was made from the inside of the tank and the Weld Metal (WM) height was about 1/3 of the weld thickness while the second-pass (or cap pass) weld completed the joints. For the two welds, the combined weld and Heat Affected Zone (HAZ) widths were approximately 14.8-19.8 mm close to the mid-thickness (the smallest). The HAZ width ranged approximately 1.3-5.7 mm. WM and HAZ showed typical microstructures although AF volume was low. The hardness values in the weld and HAZ were considerably higher than those of Base Metal (BM), i.e., demonstrating desired weld strength over-matching. The hardness values of the two welds were comparable. The average values of micro-hardness of BM, HAZ and WM of the two welds were 164, 191 and 201, respectively. All-WM specimens tested at 23°C showed that the welds were manufactured to the required strength specification and the welds were stronger than the steel. The Ultimate Tensile Strength (UTS) of the cross-weld specimens decreased with increasing temperature from -60°C to 850°C. All cross-weld specimens tested failed at BM except for two cross-weld tensile specimens at 800°C failed at WM indicating that the weld overmatched (stronger than) the BM. Charpy V Notch (CVN) values of WM were significantly lower than those of BM and HAZs specimens. Interpolated CVN values for circumferential WM specimens at -34°C (average 18 J) indicated that the weld toughness values may be lower than the benchmark of AAR specification requirements for pressure tank (i.e., average 20.3 J). Additional Charpy tests (3) and a retest (of 3) at -34°C showed that the toughness of the circumferential weld were lower than the bench requirements (i.e., average of 20.3 J and minimum of 13.6 J). The results indicate that Charpy testing is important for tank cars in low-temperature climate applications. The Scanning Electron Microscopy (SEM) fractography examinations indicate that low TC128B WM toughness was associated with weld microstructural constituents and/or inclusions. The volume fractions of AF in the circumferential and longitudinal welds were estimated to be 25% and 40%, respectively.
Summary(Plain Language Summary, not published)
This report summarizes the results of the evaluation of current TC128B steel tank car welds. The sample coupons were received from a DOT-117J tank car. The experimental work in this report included the determination, from a longitudinal weld, of (i) chemical composition, microstructure and micro-hardness (ii) tensile strength and failure locations in the temperature range of 23°C to -60°C, and (iii) Charpy transition curves. Typical fracture features of low Charpy strength weld metal samples and volume fractions of acicular ferrite (AF) were characterized and discussed. The results of the longitudinal weld were compared to those from a circumferential weld characterized previously from the same tank car, including updated Charpy testing at -34°C, and the main conclusions are provided.
GEOSCAN ID328117

 
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