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Strange discontinuity near SS pipe surface
3

Strange discontinuity near SS pipe surface

Strange discontinuity near SS pipe surface

(OP)


Hello,

We have examined SS pipe surface condition. There are some stress corrosion cracks on OD surface. But this subsurface discontinuity (please see attached file) is very strange. What is your opinion? I see the shape of defects like this in the first time in my practice.

Thank you in advance for any idea.

RE: Strange discontinuity near SS pipe surface

Do you have any other pictures?
Does the part of the pattern follow forming flow lines?
I would suppose that it is SCC connecting with inclusions.
Can you take the piece that was adjacent to this and section it longitudinally?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Strange discontinuity near SS pipe surface

I see locally deformed material along the surface, and at this interface are indications. This could be SCC that was present and during forming smeared over to appear subsurface.

RE: Strange discontinuity near SS pipe surface

(OP)
This pipe was damaged during removal from service. There are strong deformation line near OD surface and mechanical damage (like notching)of surface so identification of discontinuity isn't clear.

I have attached other photo (with deformation lines, notching and cracks like SCC).

RE: Strange discontinuity near SS pipe surface

That is a lap (or fold) from the manufacturing process.
Corrosion started as crevice corrosion in the lap, and then progressed as SCC.
That would be my call.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Strange discontinuity near SS pipe surface

Agree with Ed.

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