welding of SS321 and SS316Ti 2

[Baedor]

I'm designing Furnace transfer line to crude column

The design Temp. is 390 degrees C and The designed material of the line is SS316Ti. I found our pipe fitting vendor shipped one of the elbows with SS321.

Please give me a clue if it's okay to use in terms of both the design condition-wise and weld-ability.

Many thanks to you in advance.

 

[metengr]

Based on what you have provided in terms of background information, I would not use the TP 321 in lieu of TP 316Ti. I do not like mixing different grades of pipe matertials, second, they are different in terms of corrosion resistance and weldability. At only 390 deg C, the TP316 Ti will have better corrosion resistance in comparison to TP321. Beyond this, you would really need to evaluate the corrosion impact of process fluid against the TP 321.

 

[EdStainless]

Since they are both Ti stabilized grades you probably could weld them together.
But I wouldn't. If 321 was good enough from a corrosion point of view no one would have speced 316Ti (bastard that it is) for this service.
Get the correct part.

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P.E. Metallurgy, Plymouth Tube

 

[WKTaylor]

Questions.

CRES 316Ti alloy is a bit unfamiliar: what spec/spec-allowance is there for this variation? Is there suitable test/allowables data for the welding of this alloy?

Also,

Is 316Ti a low-carbon version [316L] that is more suitable for welding?

NOTE.
In aerospace, when welding is crucial, CRES 321 is the [AISI] alloy of choice... followed by 347. However, I am all-too-aware, that WHAT the CRES alloy is exposed-to, in-service, makes a huge difference in alloy selection, overall... as long as the fabrication methods are suitable for developing final properties.


Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true.
o For those who believe, no proof is required; for those who cannot believe, no proof is possible.
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion"]
o Learn the rules like a pro, so you can break them like an artist. [Picasso]

 

[metengr]

wktaylor

Seek and ye shall find;

thread330-87879

 

[WKTaylor]

metengr...

OK OK OK... Read the thread You referenced: however, it did NOT point to any discrete specifications [ASTM, ASME, AMS, SAE, etc] for 316Ti.

Ahhh... Google Search helped... 316Ti [UNS S31635] appears to be made per following non-aerospace specifications, thus...

ASTM A 240: Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications

ASTM A 276: Standard Specification for Stainless Steel Bars and Shapes

ASTM A 959: Standard Guide for Specifying Harmonized Standard Grade Compositions for Wrought Stainless Steels

Still struggling to understand properties of 316Ti in relationship to welding and high heat exposure/resistance to the specified fluid [crude...?]


Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true.
o For those who believe, no proof is required; for those who cannot believe, no proof is possible.
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion"]
o Learn the rules like a pro, so you can break them like an artist. [Picasso]

 

[EdStainless]

316 is often used for higher TAN applications.
The use of 316Ti over 316 is largely a local issue.
316Ti should have better weld corrosion resistance, and it comes in handy to resist sensitization in higher carbon versions (316H).

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P.E. Metallurgy, Plymouth Tube