Properties at cryogenic temperatures for CF8M material
Properties at cryogenic temperatures for CF8M material
(OP)
Hello,
i want to do an thermal FEA with Ansys. Material is CF8M (1.4408). The Analysis require thermal expansion coefficient, thermal conductivity, elastic modulus and poison ratio at -196°C (77k)
Can anybody tell me where I can get these values? I asked Google but i cant find anything. ASME only provides material properties for "room temperature".
Thank you!
i want to do an thermal FEA with Ansys. Material is CF8M (1.4408). The Analysis require thermal expansion coefficient, thermal conductivity, elastic modulus and poison ratio at -196°C (77k)
Can anybody tell me where I can get these values? I asked Google but i cant find anything. ASME only provides material properties for "room temperature".
Thank you!





RE: Properties at cryogenic temperatures for CF8M material
RE: Properties at cryogenic temperatures for CF8M material
Search cryogenic properties of 316 stainless steel
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P.E. Metallurgy, Plymouth Tube
RE: Properties at cryogenic temperatures for CF8M material
RE: Properties at cryogenic temperatures for CF8M material
Try this:
https://www.nickelinstitute.org/~/media/Files/Tech...
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P.E. Metallurgy, Plymouth Tube
RE: Properties at cryogenic temperatures for CF8M material
You have touched on the most significant issue here. ASTM casting standards permit a quite high maximum ferrite content, such that physical properties like CTE will be variable through the allowable range. Not to mention that ferrite significantly impairs cryogenic fracture toughness.
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: Properties at cryogenic temperatures for CF8M material
Then the castings should be gently temperature cycled, say from RT to -200F, back to RT then to 1000F (for stress relief). I would do this a couple of times.
As for the OP question, data for analysis, he needs to make some assumptions.
The data for wrought 316 will be the best case possible.
The worst case? It might be real ugly.
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P.E. Metallurgy, Plymouth Tube
RE: Properties at cryogenic temperatures for CF8M material
RE: Properties at cryogenic temperatures for CF8M material
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P.E. Metallurgy, Plymouth Tube
RE: Properties at cryogenic temperatures for CF8M material
Has anybody got an idea where to get 316 properties? A datasheet or something?
RE: Properties at cryogenic temperatures for CF8M material
https://www.nickelinstitute.org/en/TechnicalLibrar...
RE: Properties at cryogenic temperatures for CF8M material
If I buy a commodity, mass-market CF8M investment cast article such as a 3pc ball valve, should I expect that the caster has cared much about residual ferrite, or has done a post-casting anneal? I thought that residual ferrite in these cast materials was in there by design, as it is in some of the weld filler metals?
The other thing people sometimes forget about CF8M is its carbon content. To my knowledge, there is no CF8M/CF3M dual certified material available, unlike the F316/L material which is ubiquitous. Am I incorrect on that?
RE: Properties at cryogenic temperatures for CF8M material
RE: Properties at cryogenic temperatures for CF8M material
We used to buy CF3M casting to the CF8M mechanical properties, so I guess it could have dual certed, but never was reported that way. And to be honest what we got was CF3MN, they used nitrogen to increase strength and improve austenite stability.
Ferrite control is important for cryo service as well as for acid service. There are many weak acids that will dissolve the ferrite quickly (both castings and welds), fluids such as tomato sauces and orange juice come to mind.
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P.E. Metallurgy, Plymouth Tube
RE: Properties at cryogenic temperatures for CF8M material
See page 23
http://nvlpubs.nist.gov/nistpubs/Legacy/IR/nbsir81...
RE: Properties at cryogenic temperatures for CF8M material
As for residual ferrite, it is not necessarily a bad thing. Sometimes it may be intentional to 1. eliminate corner cracking, 2. prevent weld hot cracking, etc.
RE: Properties at cryogenic temperatures for CF8M material
RE: Properties at cryogenic temperatures for CF8M material
They will stay fully austenitic to LH2 temps. Our LH2 lines stay fully non-magnetic.
Castings have other issues as well, you need some ferrite on initial solidification to help prevent hot tearing but you also need additions to promote castability. You end up with a slightly different balance of elements, but when solution annealed you should be able to remove all ferrite, unless someone cheated on the Ni, Mn, N content. This gets harder with low C since C is an austenite stabilizer.
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P.E. Metallurgy, Plymouth Tube
RE: Properties at cryogenic temperatures for CF8M material
Link
I remember i read an article saying wrought 304 has a martensite transformation at low temp alone, while 316 does not, when no strain was present (unfortunately i couldnot find the site of the article). composition makes the difference, 304 does not have much Mo to stabilize austenite.
Lots of our Kovar alloy customers request to test martensitic transformation at -80C and -196C. we sometimes got 0-10% transformation at -196C, and I ever had a project to add a bit more carbon to prevent transformation without much effect on CTE. Invar 36 does not have this problem due to higher Ni content.
RE: Properties at cryogenic temperatures for CF8M material
The unstrained portions are still 100% austenite.
We have run ITER material, but the Ni content was much higher.
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P.E. Metallurgy, Plymouth Tube