Post-forming heat treatment(PFHT) for material grade 10H (Duplex & Supper Duplex) 6

Can you please advise where H2S falls into category "Lethal Service" ?
Thank you.

In my experience at least two petrochemical companies required lethal service for particular vessels in H2S environments.

Annex D, D.1.2

Steve Jones
Corrosion Management Consultant


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

It doesn't matter if the Code does not require it if your customer does.
These would need to be supported to prevent distortion.
They would need to be quenched into agitated water.
The descaled, usually blasted and pickled.
If it were me, I would require A923 testing after annealing.

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P.E. Metallurgy, consulting work welcomed

Dear Sirs
Thanks alots for your valuable response.

I still concern about Duplex Forming and Annealing: as I mentioned that the fiber elongation is less than 5% for shell/head, which can complicate forming operations. Annealing after forming is usually meant to restore the ductility and correct the phase balance, but improper handling during annealing could exacerbate issues instead of solving them.

The challenges in annealing SDSS are particularly critical given its complex microstructure and sensitivity to heat treatment.
As I have been informed from Manfacturer, they have just did a demonstration test coupon and found decrease in ferrite content, result is (10-20%) but criteria (35-65%). Too little ferrite can compromise the material’s strength, toughness, and corrosion resistance.

From the perspective of metallurgical engineering and pressure vessel design, should we consider waiving the solution annealing process and leaving the rolled shell and formed heads in their as-formed condition, as mentioned in my previous post?

I greatly preciated for your response!

Issue a technical query to the client indicating the potential negative impact of having to perform the heat treatment, and request their reasoning as to why it is necessary. If this requirement has suddenly sprung up post contract award, you might like to cost out a claim to attach.

Steve Jones
Corrosion Management Consultant


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

I have the following, similar issue. Im curious to hear others opinion.
[ul]
[li]Construction code: B31.3 2022[/li]
[li]Piping MoC: DSS 2205[/li]
[li]Fluid service involves chlorides[/li]
[li]Client has no specs or specific requirements for this piping scope[/li]
[li]Piping requires bends with a larger radius than default B16.9 LR elbows.[/li]
[/ul]

For sake of simplicity, let's assume we require cold formed piping bends (instead of elbows) with a forming strain > 10% (calculated per ASME VIII-1 table UG-79-1), made from A790-S32205. Now,
[ul]
[li]B31.3 leaves me without any requirements for PFHT of these bends.[/li]
[li]ASME VIII-1 has no such requirement either (see my previous reply in [/li]
[li]Only API TR 938-C provides guidance in 7.8, indicating PFHT is required.[/li]
[/ul]
I'd say a PFHT is required, but looking further into 7.8 I found

Testing has shown that the properties of the U-bends without heat treatment are acceptable for refinery services
where chloride stress corrosion cracking is a concern, as long as the bend radius is at least 1.5 times the tube
diameter for 25 % Cr super DSSs grades and at least 3.3 times the tube diameter for S32205. Hence, various
users have adopted the practice of not requiring the heat treatment of U-bends, as long as there is a 3.3D
minimum radius for 2205 DSS; however, this may require the redesign of the inner row section of the exchanger
in a way that allows for the installation of fewer tubes with the U-bend positioned diagonally to accommodate this
larger minimum radius. [sup][38][/sup]

Click to expand...

Even though we don't have U-bends (our bends are a half U), Id say the above provides a waiver to skip PFHT.

Any thoughts?




Huub
- You never get what you expect, you only get what you inspect.

The F:A ratio in these alloys is dependent on the anneal temperature.
I would restrict the alloy to 40-60% ferrite.
The max austenite will be the equilibrium amount, usually about 55-60%.
However, the ferrite can go much higher since this is the primary solidification phase.
This is why the anneal temperature is so important. You have to be in the middle of the range.

I wouldn't have you re-anneal this if were mine and it passed A923 and G48 tests after the original anneal.
I would be far more focused on the welding procedure, testing, and qualification.

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P.E. Metallurgy, consulting work welcomed

@Huub - there are fabrication recommendations from the likes of IMOA that recommend heat treatment for cold forming strains of the value that you quote. I suspect that the client in the opening post is possibly a little nervous about sour service. Recommendations by the material manufacturer may be of more importance than the absence of definitive requirements in codes and standards.

Steve Jones
Corrosion Management Consultant


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

Table UHA-44 was a good place to determine if PFHT was required. Unfortunately, it does not list UNS S32750.
3.5% strain looks to be on the lower side to go for PFHT from mechanical perspective.
From Service point of view (H2S service), i will look into NACE MR0103, which requires a hardness of HRC 28 max.
If you are a part supplier of the Head only, i wouldn't bother about the solution-annealing.
It will be the fabricator who will do the head and shell welding to do an solution-annealing of the weld joint. It's a standard practice for welding high alloy steels like SS and DSS to do a solution-annealing to free up Cr from carbides formed during welding.

GDD
Canada

I would hope that there is no PWHT on this.
The weld procedures for these alloys are very rigorous.
I have helped write some and we could get properties that would be acceptable in mill annealed plate.

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P.E. Metallurgy, consulting work welcomed

Thanks guys for the valuable feedback.

Huub
- You never get what you expect, you only get what you inspect.