Clad Steel Welding 1

[jsschweitzer]

I have a vessel constructed of A516 gr 70 clad with 316L Stainless Steel in accordance with ASME section VIII and my question is related to the welding of clad material. I do not have very much experience with this type of material and need to find out if the carbon steel side or the stainless steel (clad) side should be welded first? Also, if any problems may be caused by the wrong side being welded first? Are there any documents from AWS, ASME, or other organizations that discuss which side of the plate should be welded first?

 

[deanc]

I would weld the base material first. This would give a good base for work with the cladding.

 

[jsschweitzer]

Dean please elaborate on why you would weld the carbon side first, I am finding many resources that agree with you, however I am trying to understand why this is, instead of just blindly following what my research shows.

 

[deanc]

Well I think it is much easier. But get out your SecVIII and look at UG-99(g)(3). Then take a look at Part UCL[page 235]read the whole thing,I do not know how you are doing this job.
Also see SecIX for your procedure requirments.

 

[jsschweitzer]

I have looked at the specifications you have recomended and observe the following:
UG-99(g)(3)"all welded seams which will be hidden by assembly be given a visual examination for workmanship prior to assembly" - I do not understand the point you were trying to make with this reference?

UCL-31 - Joints in Integral or Weld Metal Overlay Cladding and Applied Linings it states as follows:
"(b) When a shell, head, or other pressure part is welded to form a corner joint, as in Fig. UW-13.2, the weld shall be made between the base materials either by removing the clad material prior to welding the joint or by using weld procedures that will assure the base materials are fused. The corrosion resistance of the joint may be provided by using corrosion resistant and compatible weld filler material or may be restored by any other appropriate means." - This appears to cover corner joints to me, does this cover butt joints as well?

This discussion is continuing on this thread thread330-61136

 

[deanc]

UG-99,if you cover the base material[SA-516] with cladding it will likely have weld joints in it,,yes? Therefore they need to be inspected prior to this.

UCL-31(a)this could also cover butt joints. See UCL-32,40,42,46.

 

[esf]

The procedure for welding clad plates (as I understand it) it to strip back the cladding from the joint by some mechanical means and completely clean the joint so there will be no cross contamination in the base metal weld. Then you weld up the base material, and finally do a weld overlay to repair the cladding (use a suitable material such as 309 Stainless for the first layer).

If you tried to weld the stainless first, you would not be able to weld the base metal without distorting the stainless overlay from the heat of the welding.

 

[ab1234]

The one important aspect is ferrite content in SS. There will be some limit fixed by the client for this.
To contol this it will be advisable that the base metal welding shall be carried out first and then clad restoration.
Some margin in base metal thickness also need to be kept say 0.5mm to 0.6mm while doing thickness calculation. This will be used while removing clad for base metal welding.

 

[zekibk]

I made some presuure vessels from cladded steel. Base metal was 20-30 mm P355GH and clad was 3 mm 316L. The bevelling is to be V shape. The welding must begin from clad steel with 316L filling material. But at the welding of the transition zone ( CS and SS ), the filling material must be high nicel like 309. Then base material (CS)is welded with filling materials per WPS. Finally, after grinding from SS side, one or two passes will be done with 316L filling material. Please take actions against high welding shrinkages due to the V shape bevelling.

 

[jsschweitzer]

The information contained in articles published by the organizations below support the two primary methods of welding clad steel as follows:

1. Remove cladding during joint preparation, then weld the backing steel (base metal) with the appropriate carbon or low-alloy steel consumable, and finally, the region where the clad was removed during joint preparation will be overlaid with the appropriate high alloy consumable

2. Weld the entire thickness of the clad plate with the appropriate full alloy consumable

Published Information Sources:

International Steel Group (formerly Bethlehem Steel) - page 7 (9 in pdf)

http://www.bethsteel.com/customers/pdfs/clad.pdf

Nickel Development Institute (NiDI), the American Iron and Steel Institute (AISI), the American Society of Metals International (ASM Int’l), and the Committee of Stainless Steel Producers - page 33…36

http://www.nidi.org/multimedia/tech...terature_pdfs/9000_aisi_publications/9002.PDF

Special Metals (formerly Inco Internetational) - page 23

http://www.specialmetals.com/publication/tech_bulletin_welding.pdf

 

[inspect]

I am also having a vessel built from the exact same material of construction that you listed above SA 516 Gr 70 backer with 316L Stainless Steel.

I am also in process of having numerous other alloy vessels fabricated and the same process applies. (2-1/4 Chrome with 347 Stainless steel clad with Inconel 625 weld overlay and clad restoration.)

The process is;

1. Shell plates will be rolled... before the shell plates are tacked up, the cladding will be stripped back away from the groove to allow room to make the full penetration weld on the backer/base material.

2. The backer/base material (carbon steel) will be completely welded.

3. After the base material is welded out, the clad restoration welds will be made with the same metallurgy as the clad material (316L Stainless). This normally takes 2 passes to achieve the same undiluted chemistry composition of the clad material (316L).

Regardless what the backer or clad material that is used, the backer has to be welded out first before any clad restoration welds can be made. The minimum requirement for the clad thickness is typically 7/64" or 0.109".

 

[carljpme]

Welding carbon steel to stainless steel will cause cracks.

Strip the stainless material back at least 1/2 inch from the edge of the weld bevel and weld the carbon steel. 309SS Stainless steel should be applied first pass and then the apply the final passes of 316SS.

 

[unclesyd]

Watch out for the possible dilution by welding that would effectively reduce the cladding tickness in the weld area Any dilution that would affect the weld chemistry, like 316 where molybdenum is the key to corrosion resistance can be detrimental. The transition weld configuration has to be well defined. Get your transition weld material closest to clad material as metallurgically possible.

 

[husni]

In case of PWHT is required (due to code requirement or process requirement), welding procedure and selection of consumable will become more specific. Schaeffler diagram normally be used to predict phases of the welded metal and its effect to PWHT.
Crack due to embrittlement always the main problem.
In case of ferrite control is specified by client, then proper selection of consumable is necessary.