HIC & PWHT FOR S316/S316L MATERIALS

[meetnixhere]

one of our client asking to carry HIC testing as well as PWHT on weldment of 316 material. is it possible to carry the test or we can deviate the requirement by any technical reason.

 

[metengr]

http://www.nace.org/cstm/Store/Product.aspx?id=9aac572d-e659-df11-a321-005056ac759b

For PWHT, this is really unnecessary for 316 stainless steel, and will lower the corrosion resistance in certain environments. I would try to avoid exposure to PWHT.

 

[SJones]

If the HIC testing is NACE TM0284, you could advise your client that it applies only to carbon and low alloy steel. If they still wish to proceed, and they are paying for it, let them be parted with their money. If they are requiring PWHT under ISO 15156, then it will have to be as directed in Table A.2 therein.

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.

 

[EdStainless]

The only PWHT for a SS to SS weld is full solution anneal.
The gentlemen above have quoted you chapter and verse on why neither PWHT or HIC apply to an austenitic stainless.

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P.E. Metallurgy, Plymouth Tube

 

[nickypaliwal]

Do you mean that PWHT for SSt is never asked? As ASME does not exclude PWHT of SS316..

Also if it is applicable then which cases or scenario?

 

[EdStainless]

These are austenitic stainless steels, no brittle phases form during welding so there is no use for PWHT.
If it is a small fabrication you could solution anneal after weld to get better corrosion resistance in the welds, but that is the only choice.

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P.E. Metallurgy, Plymouth Tube

 

[Chumpes]

hello
PWHT is not recommanded for austenitic Stainless Ssteel SS material, unless the manufacturer can certify that the properties will be as initial material. solution annealing is probably the only accepted PWHT, also for brittle phase transformation.
as per ASME I think it is not applicable
PWHT (around 600-620°C) usually refers to TTH of Carbon Steel CS welds to relax internal stress for reducing risks of SSC and SOHIC of CS materials. welded austenitic SS materials usually already have low harness and low internal stress levels after welding.
SS material shall be used in accordance with NACE MR0175 part3
I never heard about HIC damage on austenitic SS material, maybe because low corrosion rates on SS induce low hydrogen generation and low HIC risks, and maybe also because the cfc austenitic matrix can accept more hydrogen before saturation than a cc ferritic or martensitic matrix. Level of inclusions is also probably lower in SS than in CS material.

 

[metengr]

There are indeed instances where PWHT (1650 deg F) or a solution anneal is used to prevent reheat cracking after welding in heavy section 347H stainless steel material and with certain Ni-base alloys, and to remove the affects of prior cold working from fabrication.

 

[EdStainless]

The HT that Metengr mentions is one that I have only seen applied to stabilized alloys (321, 347, 625) since these alloys are designed to resist sensitization.

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P.E. Metallurgy, Plymouth Tube

 

[Chumpes]

@EdStainless : I ve never seen stabilisation HT of 321/347 applied post on-site weldement but only on the raw material along manufacturing before delivery and welding operation