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PRCI PR-202-9327
- Effect of Defect Size and YS/TS Ratio on the Plastic Deformation Capacity of X70 and X80 Pipe Steels
- Report / Survey by Pipeline Research Council International, 02/12/1996
- Publisher: PRCI
$198.00$395.00
L51739e
University of Gent-Belgian Welding Institute
(e-book version)Need: Modem micro-alloyed low carbon linepipe steels offer an advantageous combination of high toughness levels and a low carbon equivalent (CE or Pcm ) for good weldability. The continuing improvements in pipeline steel manufacturing practices (steelmaking and rolling techniques) have also led to pipeline steels with higher yield-to-tensile (Y/T) ratios and a corresponding reduction in strain hardening capacity. At present, API 5L allows yield-to-tensile (Y/T) ratios up to 0,93 for all linepipe steel grades. The effects of high Y/T ratios on plastic straining capacity and defect tolerance levels are, however, not well documented. The experimental data generated in a previous PRCI sponsored project (Contract no. PR 202-010) have shown that, for 254 mm (1,00 in) thick linepipe steels, flaw tolerance levels reduce with increasing Y/T ratios. This reduced defect tolerance was attributed to a reduction in strain hardening capacity.
Benefit: The objective of this research project, which is a logical extension of the work performed under Contract PR 202-010, was to generate additional experimental data to quantify the effect of plate thickness on the relationship between Y/T ratio and tolerable defect dimensions. To that end, an experimental program was undertaken on thin walled X70 and X80 linepipe steels in plate form.
Result:This research project generated additional experimental data on the effect of plate thickness on the relationship between yield-to-tensile (Y/T) ratios and tolerable defect dimensions. Several experimental tests were conducted on API 5L X65, X70, and X80 steels, including conventional tensile tests on round-bar, full-thickness prismatic specimens, unnotched wide-plate specimens, and notched wide-plate specimens. The effects of defect geometry and plastic prestraining (cold deformation) were also studied. The experimental data suggest that the Y/T ratio of thin-walled steels should be limited to 0.90. It was found that high Y/T ratio steels have only a minor resistance to ductile tearing. Using pipeline steels above 0.90 can lead to unsafe conditions, especially when gross plastic deformations may occur.
University of Gent-Belgian Welding Institute
(e-book version)Need: Modem micro-alloyed low carbon linepipe steels offer an advantageous combination of high toughness levels and a low carbon equivalent (CE or Pcm ) for good weldability. The continuing improvements in pipeline steel manufacturing practices (steelmaking and rolling techniques) have also led to pipeline steels with higher yield-to-tensile (Y/T) ratios and a corresponding reduction in strain hardening capacity. At present, API 5L allows yield-to-tensile (Y/T) ratios up to 0,93 for all linepipe steel grades. The effects of high Y/T ratios on plastic straining capacity and defect tolerance levels are, however, not well documented. The experimental data generated in a previous PRCI sponsored project (Contract no. PR 202-010) have shown that, for 254 mm (1,00 in) thick linepipe steels, flaw tolerance levels reduce with increasing Y/T ratios. This reduced defect tolerance was attributed to a reduction in strain hardening capacity.
Benefit: The objective of this research project, which is a logical extension of the work performed under Contract PR 202-010, was to generate additional experimental data to quantify the effect of plate thickness on the relationship between Y/T ratio and tolerable defect dimensions. To that end, an experimental program was undertaken on thin walled X70 and X80 linepipe steels in plate form.
Result:This research project generated additional experimental data on the effect of plate thickness on the relationship between yield-to-tensile (Y/T) ratios and tolerable defect dimensions. Several experimental tests were conducted on API 5L X65, X70, and X80 steels, including conventional tensile tests on round-bar, full-thickness prismatic specimens, unnotched wide-plate specimens, and notched wide-plate specimens. The effects of defect geometry and plastic prestraining (cold deformation) were also studied. The experimental data suggest that the Y/T ratio of thin-walled steels should be limited to 0.90. It was found that high Y/T ratio steels have only a minor resistance to ductile tearing. Using pipeline steels above 0.90 can lead to unsafe conditions, especially when gross plastic deformations may occur.
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