Welding of ASTM A516 Gr 60 Plates, clad with TP304L

[0707]

We are going to replace a column in A516Gr 60 to be clad with TP 304L on top, between tray 2 and 3 and from tray 11 to the bottom. The previous column was not clad and was PWHT because it works in AMINE service.
The purpose of cladding this amine vessel is to prevent wet H2S cracking.
During the stress relief of c.s A516Gr60 plate’s clad with TP304L, is there the possibility of carbide precipitation between the carbon steel and the stainless steel? Would it be prudent to PWHT only the A 516Gr60 plates not clad or shall we PWHT the vessel as a whole, clad and unclad C.S. plates?

An answer would be appreciated

Luis Marques

 

[Metalguy]

Weld deposits are not affected by sens. to the same degree as SS plate would be. I'd go ahead and PWHT-just keep the time down to the minimum. It also helps to clad with 2 layers.

 

[0707]

The vessel is an Amine regenerator. The code requires to PWHT non-clad carbon steel plates between tray 3 and tray 11, because of HIC/SOHIC damage. The question is does the heat treatment on the boundary of clad and non-clad plates affect the TP 304L cladding?

Tank you

Best regards

Luis Marques

 

[Metalguy]

The PWHT will "affect" the cladding, but it should not be a problem. I assume that you're cladding the entire plate surface on some of the plates and then welding them together from the non-clad side. Depending on the actual C amount and the PWHT time and temp, you may have some carbide precip. but it probably won't matter.

The reason why the actual C level on the wet surfaces is of interest (in general) is because of the very steep precip. curve (time at temp. vs. C). For example, if your C is ~.035%, the time required for sensitization is much shorter than if the C is .02%. I don't have any curves handy, but there may be some good info right here in the archives. You probably wouldn't sens. .02% C even after a few hours right at the temp. that is sens. fastest--which will be a little different than the temp. for .035%C. But I don't think sens. will mean much for cladding--at least it doesn't for hot water service. I don't know much about amine service for SS.

 

[0707]

Dear Sir

The carbon steel plates are 13mm Thick with a 3mm thick clad of TP304L applied by explosion welding. We are going to link these plates to other carbon steel plate’s 13mm Thick without cladding.
For that reason I am afraid that the temperature developed by PWHT on the seam welding between clad and non clad plates could unbound the TP 304L clad.
I suppose we will decide to clad the entire column. The savings on heat treatment will permit that option

Thank you for the empathy

Receive my best regards

Luis Marques

 

[stanweld]

This type of welding with PWHT has been done many times in the petrochemical industry without disbondment of the cladding. It is assumed that you have purchased the clad plate with ultrasonic inspection to confirm bond integrity.

 

[unclesyd]

If the explosion clad was done properly there is noway that
PWHT can debond it. The bond is a Metallurgical bond the same as welding. Just watch you transition for the C/S to the Clad C/S plate. You want to make sure that you are welding C/S to C/S.