welding after PWHT
welding after PWHT
(OP)
Greetings all,
A vessel is being designed to ASME VIII-1 with a shell made of SA-387 Gr.11 Class 2 (P-4) and clad with SA-240-321 ( P-8). PWHT is required. Would it be permitted to weld a circumferential ring to the clad after PWHT?
After reviewing the requirements of UW-40, Table UCS-56 for P-4 materials, UCS-56, UCS-68, UCS-85, and UCL-84, I was not able to find any specific prohibitions although UCL-84 does indicate that the clad shall be subject to PWHT if required for the base metal.
All comments and thoughts welcome
Regards,
RLS
A vessel is being designed to ASME VIII-1 with a shell made of SA-387 Gr.11 Class 2 (P-4) and clad with SA-240-321 ( P-8). PWHT is required. Would it be permitted to weld a circumferential ring to the clad after PWHT?
After reviewing the requirements of UW-40, Table UCS-56 for P-4 materials, UCS-56, UCS-68, UCS-85, and UCL-84, I was not able to find any specific prohibitions although UCL-84 does indicate that the clad shall be subject to PWHT if required for the base metal.
All comments and thoughts welcome
Regards,
RLS





RE: welding after PWHT
RE: welding after PWHT
Thanks for the reply. I should have mentioned that the clad thickness is 3/16". Do you still think consumption of the cladding and fusion to the base material is an issue? The ring, in all probability, will be GMAW double welded, full pen.
Thanks again,
RLS
RE: welding after PWHT
RE: welding after PWHT
Perhaps the thickness of the ring is such that there may be a concern that a great deal of weld is necessary to complete the full pen joint, still, I'm not so sure that you would heat the base to the critical temperature range. We've qualified procedures for dissimilar joints between pwht'd and non pwht'd components with a butter layer 3/16" thick on the pwht'd side. I think the suitability of a given technique depends on several factors one of which would be heat input. You didn't mention the transfer mode for the GMAW process, but if it's shortarc I would think you may be ok. There may be a possibility that the heat from the weld could cause disbonding of the clad, and this should be considered.
RE: welding after PWHT
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RE: welding after PWHT
Good point about buttering. However, I would expect that with a full penetration attachment weld, the cladding would be consumed in making the weld deposit and fusion would occur with the base metal. I agree, that further evaluation would need to be performed OR a temper bead method could be utilized for this method of attachment.
If this were a simple fillet weld, I would have no problem. Since this is a full penetration weld, my expectation is that this is a structural attachment and, as such, would require fusion with the vessel base metal.
RE: welding after PWHT
RE: welding after PWHT
I see no problem with that.
GB
RE: welding after PWHT
Just some thoughts: PWHT is usually meant to eliminate HAZ and to insure a proper structure of the material. If cladding is made due to contained fluid's characteristics, I thing welding should be avoided after PWHT, simply because pwht links carbures in a solid solution and that gives a greater corrosion resistance. Refer to your client's specifications
RE: welding after PWHT
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