Chemical Analysis of Clad Plate Welds

[Angsi]

Code : ASME Section VIII Div 1
Plate: A516 Gr 70 + SS 316L
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Welds that are exposed to the corrosive service fluid need to maintain the corrosion resitance properties as much as possible and it is prefered that the chemical composition of the back cladding welds meet as closely as possible the clad material composition.

But how "closely" should it be? Will the ferrite count of 3-8% be adequate?

Please advise.

 

[metengr]

What is the specified ferrite content of the corrosion resistant cladding (316L) on your pressure vessel substrate (away from the butt or seam welds)? Or this is a roll formed clad of wrought 316L over carbon steel?

You need to have this information to make a proper comparison for the ferrite content of back clad welds.

 

[Angsi]

Hi metengr,

It is in reference to a roll cladded A516 Gr 70 material with 316L clad material. So far I have not made any clear ferrite content specification for the the 316L cald material. I am assuming that it will be within the range specified by ASTM for this grade.

What should the ferrite count then be metengr?

 

[metengr]

Some additional information is requested;

1. Are the vessel butt welds joining the 316/CS clad plate to clad plate being done with a carbon steel filler metal and after this operation is completed, you intend to back clad over the butt welds or are you intending to do something else?

 

[Angsi]

Yes, the intention is to back clad the cs parent metal weld. Welder position will be inside the vessel.

 

[metengr]

Angsi;
Ok. You will need to use a minimum two layer weld sequence, where the first layer deposited against the CS weld metal will be E309MoL followed by E316L.

The ferrite number for the back clad weld of E316L would probably be a minimum of 5 FN to avoid solidification cracking.

However, your main concern needs to be driven by chemical composition to assure comparative corrosion resistance, which using E309MoL/E316L will suffice.

 

[Angsi]

Thanks metengr.