Delamination on A106 GR B

[106coral]

I have been recently asked to find out why delamination on outside surface of 18" sch 80 A106 GR B pipe after post-weld heat treatment at field shop as per NACE MR 0175 was made.
I saw the photos of pipe taken, of which lamination depth are ranged from 0.08" to 0.12".
I looked into MTR supplied by steel maker and heat treatment report but I didn't find any error and/problems on these documents
so finally I have checked minimum required wall thickness to see if this pipe remains sufficient thickness to meet design conditions even though cutting delaminated area.
Foutunately, it seems this pipe is available.
Have you guys experieced this kind of problem before?
I would apprecate if someone give me your story and the reason why you got to know.

 

[metengr]

Sounds like lamellar tearing in the pipe base metal. Yes, I have seen this before.

The orientation of inclusions were aligned such that during welding, residual stresses coupled with any hydrogen introduced during welding process created a preferred fracture path after PWHT. Check the sulfur content of the steel, and elevate the preheat during repair.

 

[106coral]

Hello metenger,

The delamination occurred in pipe is not weld metal but the surface of outside.

I can figure it out if this was happend in weld metal.

I am not sure but this problem could be related to heat treatment because the laminated area was covered when post-weld heat treatment on welding area.

What about your idea?

Thanks

 

[Carburize]

Can you post an example of the pictures of the laminations so we can look at it? Use

http://flypicture.com/

or similar link

 

[metengr]

106coral;
How far away was the weld that required PWHT from the damaged area? If you have a picture, can you post it on the web site below?

One other possibility - check to see if a local weld repair was performed by the mill in this exact location by removing a sample capturing the damaged area of the pipe and performing a metallographic examination.

http://flypicture.com/

 

[106coral]

How can I do to upload some pictures on this forum?

 

[Carburize]

106coral to upload pictures use a web site like

http://www.flypicture.com

When you go to that web site it will walk you through the process.