Investigation of sulfide-stress cracking at pipe seam welds
- Battelle, Columbus, OH (USA)
A metallurgical investigation was undertaken to identify the factors that are responsible for sensitivity to sulfide-stress cracking (SSC) in the heat-affected zone (HAZ) of microalloyed high-strength line-pipe steels, when the HAZ does not contain regions of high hardness. Sustained-load tests were conducted in the NACE laboratory sour-gas environment to determine the regions in which SSC initiated, and thereby to identify which regions were most sensitive to SSC. In almost every steel studied in this task, SSC initiated in a specific region of the HAZ, usually in the region that was heated into the intercritical temperature range during welding. One steel exhibited SSC sensitivity in the region adjacent to the weld metal, which was heated above the upper critical temperature during welding, and another steel exhibited SSC sensitivity in the base metal following a laboratory normalizing heat treatment. In all of the steels that were studied, the region that exhibited sensitivity to SSC contained columbium carbonitride precipitates, 100 to 200 Angstroms in diameter, which were coarser than those that were present in the pipe body (<50 Angstroms in diameter) which was immune to SSC as fabricated except at very high stresses. Steels that did not contain columbium exhibited no sensitivity to SSC at applied stresses well above the specified minimum yield strength.
- Research Organization:
- American Gas Association, Inc., Arlington, VA (USA); Battelle, Columbus, OH (USA)
- Sponsoring Organization:
- AGA
- OSTI ID:
- 6893411
- Report Number(s):
- NG-18-184; ON: DE90012841
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
032000* -- Natural Gas-- Transport
Handling
& Storage
36 MATERIALS SCIENCE
360101 -- Metals & Alloys-- Preparation & Fabrication
360103 -- Metals & Alloys-- Mechanical Properties
ALLOYS
CHALCOGENIDES
COHERENT SCATTERING
CRACKS
CRYSTAL STRUCTURE
DIFFRACTION
ELECTRON MICROSCOPY
HARDNESS
HEAT AFFECTED ZONE
IRON ALLOYS
IRON BASE ALLOYS
JOINTS
MECHANICAL PROPERTIES
MICROSCOPY
MICROSTRUCTURE
PIPES
RESIDUAL STRESSES
SCATTERING
STEELS
STRESSES
SULFIDES
SULFUR COMPOUNDS
TRANSMISSION ELECTRON MICROSCOPY
WELDED JOINTS
X-RAY DIFFRACTION
ZONES