Joined carbon steel clad with UNS 6625

[marci81]

Hello Guys, i have a question regarding the weld beatween a pipe carbon steel cladded with uns 6625 wall thk 28mm. The consumable required is UNS 6625 . My client required pwht according to B. 31.3 but i would not to do pwht because the uns 6625 not required this procedure. The weld literature do not recomanded the pwht for joint welded with UNS 6625. I have proposed to increase the preheat permitted by ASME VIII but i'am not sure that to will be approved. Do you have some suggestion? Do you know if there are Asme interpretation?

Thanks Marcello

 

[EdStainless]

Normally this weld would be made with both 625 filler and steel filler.
If you doing it with all 625 then you may need to put a butter pass on the parts, then PWHT, then weld the joint in 625.

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P.E. Metallurgy, Plymouth Tube

 

[metengr]

PWHT would be required if the base material thickness requires it by Code. In this case, you apply a butter layer using Inco 82 or 182 electrode, perform PWHT and complete the weld joint using 625.

 

[pradipgoswami]

You may try to apply the clauses of Table 331.1.3: Exemptions to Mandatory Postweld Heat Treatment, after discussion with your client, provided PWHT is not deemed mandatory as per project specifications. Note-4 of this table explains mandatory PWHT requirements.
The immediate concern after PWHT could be the failure of bend test due to Carbide precipitation & reduced ductility. You may refer this document for overall guidance.
E-ER-NiCrMo3 is usually the consumable of choice, however stringency over and above ASME Sec II, Pt-C may be required.

Thanks.

http://www.nipera.org/~/Media/Files/TechnicalLiterature/10064_EngineeringWithCladSteel2ndEd.pdf

Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299

 

[SJones]

If you are working with B31.3 don't pull in ASME VIII and complicate matters. If your client is not also specifying a corrosion test to qualify the welding procedure, an increased preheat/interpass temperature may be tolerable, but try to ascertain why a PWHT is being mandated. Since the material is clad, PWHT for internal service exposure shouldn't be a consideration; is this a subsea external hydrogen embrittlement issue? If the client remains adamant, keep the temperature below 590 deg C and use the shortest soak time possible.

Steve Jones
Corrosion Management Consultant

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

All answers are personal opinions only and are in no way connected with any employer.

 

[weldstan]

Per B31.3 PWHT is not required on P No.1 material provided a 200 F min preheat is performed/maintained for T > or = to 1". It is quite possible that your client's specs are out of date in this matter.

 

[marci81]

Hi Sjones,
i am agree with you and @pradipgoswami.I must be in compliance with ASME Code + B31.3 e for this kind of wall thk (28mm) the pwht is mandatory( except for Table 331.1.3), the pwht is not required for the type of process. Anyway my client ask me to do PWHT AT 621°C minimun for 2h and qualify a PQR whith ASTM G48 Pr.A, PMI, Ferrite Test. I have already proposed your opinion but my client writes me that delete the pwht only if i show that Carbon Steel joined with UNS6625 without pwht is permitted in ASME or B31.3 or other official code. I have tried to demostrate it with old pqrs qualified without pwht with good result but is not enought. I think will be very difficult to obtain something. Anyway thank you for your opinion.