Welding of Internally Clad X65 and X70 Pipes for Pre-Salt Subsea Oil Applications Phase II

•Offshore Standard DNV-OS-F101 specifies that for pipe-reeling applications, the deposited girth weld metal shall overmatch the yield strength of the base material by 100 MPa.
•Girth welds of internally clad API 5L Grade X65 pipes produced using Alloy 625 have been shown to be:
ii.Unable to meet overmatching strength requirements
iii.Susceptible to environmentally induced hydrogen assisted cracking
•Manufacturing girth welds of internally clad pipes using low alloy steel filler metals can prove to be:
ii.Capable of meeting overmatching strength requirements
iii.Less susceptible to hydrogen assisted cracking
•Poor weldability is encountered due to TL (LAS) >> TL (625)
•Difference in melting temperature between the LAS fill passes and Ni-base alloy root pass results with:
o high dilution of alloy 625 → increases hardness → increases cracking susceptibility
•Metallurgical characterization and phase transformation analysis is required to identify cracking susceptible microstructures

For more information, see Phase I of Welding of Internally Clad X65 and X70 Pipes for Pre-Salt Subsea Oil Applications.


Industry Sponsors: Voestalpine Böhler, Vallourec Brazil, Serimax, TechnipFMC, Schulmberger

Faculty: Boian Alexandrov (OSU)

Graduate Student: Alejandro Alvarez

Industry Contacts: Martin Schmitz-Niederau, Hermann Josef-Weber, Ana Carolina Vilas Boas, Sebastian Leconte, Elliott Turbeville, Michael Buehner, Dean Hannam, Nash Ubale