Weld overlay chemical analysys

[MirjafariSM]

Hi Dears
Please read the follow technical matter:
If we have cladded plate, we have to done weld overlay in junction.
for testing chemical composition of weld overlay ,in our specification, we have to take a sample from 3/4 weld overlay thickness. as you know generaly overlay THK. is greater than clad THK. and overlay THK. is not considered in design and calculation thereupon the thickness of base metal for equipment shall increase.
this subject have a huge cost for us!
-am I right?
-if the answer is not please tell me how i can abstain increasing of base metal thk?
thanks alot

 

[vesselfab]

I really lost you about 3/4 way down.

are you saying that 1/8" nominal overlay has hot to be tested at 3/4 way down?

if so you would drill down 3/32" and take samples leaving 1/32 for dilution

most people do a thicker overlay than 1/8" say 3/16 for conversation sake.

you would drill your pqr chemical sample plate down the same 3/32 from surface leaving 3/32 for dilution

all production welds will have the same number of passes

I am assuming that these drilled samples are just for qualification and the production welds will be inspected by PMI


could be wrong though

 

[SJones]

It probably refers to 3/4 of the way UP the overlay from the interface (a la ASME IX QW-462.5 a) to ensure that the material near the surface has the correct chemical composition. Why parent material mechanical properties are getting thrown into a chemical composition test I don't quite see. If we separate the two issues, is it not that a butt weld is being back welded with a cap of overlay for restoration purposes which shouldn't have any mechanical property issues?

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[weldtek]

Mirj,
Typically the chemistry has to be verified at a depth equal to the clad thickness. As you say normally the restoration at welds is thicker than the adjacent clad thickness. Using this criteria, if your clad is 1/8" thick you would test the restored area ( weld overlay ) at 1/8" below the surface.

 

[gr2vessels]

My two cents;-
My specification is asking for the same location of the sample for testing the ferrite content. The only different is that the required test to be done on a production test plate. Also, the same test was required in the WPS/PQR.
Honestly, I cannot imagine a Client to ask for damaging the completed welding and expecting rework with fully approved repair welding procedure...
Also, please read the ASME SA 264/265 and ASME VIII Div 1 for details of the inclusion of the cladding thickness in the pressure resisting thickness calculations.
Cheers,
gr2vessels

 

[EdStainless]

I have seen times when there were questions and a sample was milled from the actual weld for analysis and then the slot was weld repaired (though since it is all a weld anyway repair does not have the usually meaning).

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