ERW and DSAW pipes
ERW and DSAW pipes
(OP)
Does anybody here know whether there are differences for corrosion resistance of welds of ERW and DSAW pipes? per API 5L for same grades.
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RE: ERW and DSAW pipes
RE: ERW and DSAW pipes
RE: ERW and DSAW pipes
In comparison, double submerged arc welded pipe requires a filler metal.
Anytime filler metal is added you have a local region that is somewhat different in chemical composition to that of the surrounding base metal because the weld metal is an as-cast structure (like a casting). Depending on conditions, I could see where you might have corrosion of the either the DSAW or adjacent base metal, along the fusion line. In comparison, the ERW is formed from the same material and is considered homogenous in chemical composition with the base metal.
For water wetted conditions, I would stick with ERW.
RE: ERW and DSAW pipes
Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/
RE: ERW and DSAW pipes
RE: ERW and DSAW pipes
RE: ERW and DSAW pipes
Was the ERW pipe subjected to a normalization heat treatment to remove the base metal HAZ? If this was done for ERW pipe, there should be NO corrosion. The normalization heat treatment may have been done for the double SAW pipe.
RE: ERW and DSAW pipes
I did some study and I found that both ERW and DSAW pipe have been involved in SCC-related failures. There is no obvious unique metallurgical characteristics associated with the failures.
For the time being, I won't consider their corrosion resistance difference anymore.
RE: ERW and DSAW pipes
Depending on the manufacturer of the ERW pipe, you may find increased leak sources in its weld seam due to increased number of flaws in the weld seam relative to that found in DSAW pipe. Flaws open to the surface provide a profile which may be susceptible to accelerated corrosion.
With regard to heat treated condition of EFW pipe, I performed testing whereby the weld seam was locally induction normalized, locally induction tempered, full body normalized and full body tempered. Only the full body normalized pipe had a homogenous microstructure. If there were no inclusions to verify the upset during welding, one could not locate the weld seam in the full body nornmalized ERW pipe.