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Welding with Low Alloy Steel Filler Metal of X65 Pipes Internally Clad with Alloy 625: Application in Pre-Salt Oil Extraction

O'Brien, Evan Daniel
http://orcid.org/0000-0002-5354-2116
http://rave.ohiolink.edu/etdc/view?acc_num=osu1469018389

Abstract Details

2016, Master of Science, Ohio State University, Welding Engineering.
In the oil & gas industry, extraction of oil reserves from pre-salt subsea oil fields requires pipelines and risers to be joined with welds that overmatch the X65 pipe yield strength by 100 MPa, have high toughness, and do not utilize a PWHT. In typical oil extraction, these internally clad pipes are welded with fill passes of Alloy 625 that match the internal clad, however, the strength requirement for reeling is not met with this alloy. To meet the strength requirement, low alloy steel consumables were studied as fill passes to join X65 pipes that are internally clad with Alloy 625 with root passes welded using 625 filler metal. The problem with this metallurgical combination is that solidification cracking can occur in the low alloy steel weld passes that have been diluted by Alloy 625. Computational modeling was performed to screen potential consumables and welding trails were completed for consumables that demonstrated compatibility. Upon establishing welding parameters, bead-on-plate design of experiments were performed with low alloy steel (ER100S-G) welded over two different nickel-based alloys (Alloy 625 and Alloy 686). Buffer layer solutions were also tested using two other Ni-based alloys, UTP A 80 Ni and Alloy 625 LNb, to isolate the root pass material from the fill pass material. Solidification cracking was eliminated in bead-on-plate welds of ER100S-G over Alloy 625 using small weave amplitudes, however, Alloy 686 was determined to have better compatibility with the low alloy steel filler metal to avoid solidification cracking. Welding experiments in a narrow groove were performed for the compatible combination, ER100S-G fill passes over a root pass of Alloy 686, and solidification cracking was eliminated from the fill pass welds. During this study, a defect previously thought to occur only in castings has been identified in welds of low alloy steel filler metals over Ni-based alloy substrates. Referred to in this study as “shrinkage porosity”, these defects were encountered in the compositional transition zone of these welds and were related to the large difference in solidification temperature ranges between the low alloy steel filler metal and the Ni-base alloy substrate.
Boian Alexandrov, Dr. (Advisor)
Avraham Benatar, Dr. (Committee Member)
184 p.
Engineering; Materials Science; Metallurgy
Low Alloy Steel; Solidification Cracking; Shrinkage Porosity; Cold Metal Transfer; Welding Metallurgy; Computational Modeling; Thermo-Calc; Oil and Gas;

Recommended Citations

Citations

  • O'Brien, E. D. (2016). Welding with Low Alloy Steel Filler Metal of X65 Pipes Internally Clad with Alloy 625: Application in Pre-Salt Oil Extraction [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469018389

    APA Style (7th edition)

  • O'Brien, Evan. Welding with Low Alloy Steel Filler Metal of X65 Pipes Internally Clad with Alloy 625: Application in Pre-Salt Oil Extraction. 2016. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1469018389.

    MLA Style (8th edition)

  • O'Brien, Evan. "Welding with Low Alloy Steel Filler Metal of X65 Pipes Internally Clad with Alloy 625: Application in Pre-Salt Oil Extraction." Master's thesis, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469018389

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.
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