Welding of cladded pipes

[onrush]

Dear members,

I am a very novice for cladded piping.

My questions are;

1. Are there any special requirements when welding between inconel 625 cladded carbon steel pipes to be used in sour service?

2. Should welding between inconel 625 cladded carbon steel pipes be done at manufacturers' shop? I wonder if this welding could be done at site under sound WPS&PQR and what the general practice is.

Thanks in advance.......

 

[stanweld]

Welding of such pipes is generally done using GTAW for the initial pass and second pass with matching ERNiCrMo-3 welding filler mtal or somewhat more corrosion resistant filler metals like ERNiCrMo-4 or ERNiCrMo-10. Inert gas back purging is required to protect the root from oxidation. Fill passes may be made by higher deposition rate processes like SAW (shop) or SMAW, GMAW, FCAW in field.

 

[SJones]

The first requirements will be governed by ISO 15156-2, -3. ISO TR 17671-5 will give some basic guidance on welding requirements for clad steel. ISO 9692-4 will indicate some joint preparations that may be considered. In most cases (in the oil & gas industry), the end user of the fabricated clad piping generally desires that as much spooling as possible takes place in the shop with only the barest minimum of field welding. Key points to watch will be: achieving the correct chemical composition in the root area; hardness of the fusion zone between 625 and carbon steel and any detrimental effects of PWHT if it has to be applied.

Steve Jones
Materials & Corrosion Engineer

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

 

[Metalmeister]

Never weld carbon steel onto the higher alloy clad. Weld the clad side last.

Contact a clad steel manufacturer for details.

In general, strip the clad side back, weld the carbon side, then finish the clad side with clad alloy. Or do the whole thing with clad alloy.

 

[MikeMet]

Metalmeister; You can not weld the ID of small diameter pipe last with a baton strip. For thick cladding you machine the weld detail so the clad produces the land of the weld bevel. Some make an autogenous root pass by melting the matching lands if the cladding is thick enough, say over 1/8". If it is thin cladding, the weld bevel details is the same for non-clad pipe and the root pass is made as described above with NiCrMo filler. I also make the first hot pass with the NiCrMo filler. Welding out the carbon steel back can be done using NiCrFe filler or the NiCrMo filler or combination thereof. See the attached taken from an AWS Article