you can use A 59 alloy a AWS 5.14 AWS ERNiCrMo-13 - (UNS N06059)

https://www.soges-spa.it/en/catalogue/mig-mag-wire...

Yes. The matching 625 filler metal can be used as well as oher Ni based filler metals.

When I was a rocket engineer, my welder would use Hastelloy W rod as filler for a mixed joint like that.

The filler suggestions are all valid.
No PWHT required as these are both austenitic alloys.
Getting a procedure and qualifying it and the welders will take some work.

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P.E. Metallurgy, consulting work welcomed

Thank you guys, seems it is no issue to pair 625 with 316.
Btw. It would be helpful if anyone could advice a reliable supplier for ally 625 welded or seamless pipes. We will build a new plant in the US too so currently delivery time is long up to 9 months.

It is taking mills over 6mo to get raw material.
An 9mo delivery sounds good to me.
What sizes are you after?
And how much?

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P.E. Metallurgy, consulting work welcomed

New design will be following ASME code so it not ready yet but we need from 1" up to 16". We just failed to get it from China. Procurement and engineering underestimated the delivery time and they were forced to order from China. There was still 10 days quarantine to enter so they used other sources to inspect..................... End of the stoy is that we received neither alloy800H nor 625 but 316L. Now we have to go to court with the supplier.
We have a Chinese office and sourced new alloy 625 which will be available from 30-60 days. Next week we will check the stock material and take it immediately after testing.

What are you building? Are these marine exhaust systems? Your application seems unusual do to very high temperature and corrosion resistance but no mention of pressure. 316SS might be fine inside the pipe but is going to experience corrosion under insulation.

Tugboat, it is a new hightech anode powder factory. We have pyrolsis exhaust gas with 700-850°C. low pressure non corrosive line (ducts) max 80mbar. But the high temp requires alloy625. They didnot find any other suitable materials

I know some materials are hard to obtain and find, and if you can get some in the right material, it maybe useless because the company is not on your customers approved supplier list? One option that ive done a lot of NAVY Propulsion Fabrication with is CAST/FABRICATION. Where the fittings, flanges, nipples or transition pieces were cast then machined for fabrication, I think this is a option that gets overlooked. You can get material that has been qualified on weld procedures, ht, ect, to ASME, ISO, AND MIL STANDARDS with NAVSEA 250-1500 welding requirements if you have the skilled welders? Sometimes this can solve alot of problems in the time of need.

Stefan, At 850C virtually any Ni alloy would work, and I would suppose that 310 is an option also.
310 would not be as strong or corrosion resistant as 625, but it costs a lot less and handles these temperatures well.

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P.E. Metallurgy, consulting work welcomed

Hello EdSteinless,

yes we use some 310 but their engineering was much too late and pipe stress analysis faced many problems. It will be considered for the next plant.

I was unable to find authoritative data on this odd mixed-metals welding... I625 and 316L are soooo different.

There is an old military saying 'Just because You can, doesn't mean you should'.

Recommendation. Whatever You do to join these metals, there will probably be limited authoritative data for strength, durability, corrosion resistance, etc... I suggest in-house testing of typical welds to develop allowables, processes/inspections and long-term durability in Your operating environment.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

How about this:
https://www.welderdestiny.com/images/Dissimilar-We...
The 686 would give higher corrosion resistance, but you don't need it.
The 82 is more versatile and can be used for a lot of dissimilar metal welds.
Using 625 filler is the most straightforward option.
The biggest issue will be the higher melting point of the 625.
There are other alloys that would work, but stick with things that have been used.
You have looked into the difference in thermal expansion between these two alloys haven't you?

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P.E. Metallurgy, consulting work welcomed

Dear All,

we are not going to use 625 and 316L as we finally found 625 plates and can get our DN400 pipes finished in 3 weeks. The line is operating at 850°C with exhaust gas from a kiln and we do not want to operate with unknown conditions in the welds. Thanks anyway for all your precious feedback.