Creep deformed AISI 316L, is it possible to undo the deformation?

[dandius]

Hello guys,
we use some Aisi 316L steel plates (50mm thk) as load on some components that have to be brazed.
After many cylces the plates suffer of creep deformation.
Is it possible to undo this deformation? Maybe with a solubilization applying some load on the deformed plates?
Thanks.

 

[metengr]

Creep deformation is irreversible permanent strain in the plate. You can attempt to move the permanent strain to a different location on the plate by using heat and or force, but you will not remove it.

 

[EdStainless]

Replacing them with new material is how you 'un-do' it.

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P.E. Metallurgy, Plymouth Tube

 

[dandius]

Ok, for the purpose is more than enough, afterall the plates are only used as dead-weight.
I'll try heating and applying some force.
About the specific performances, are there better alternative than a AISI316, considering that the working temp. is about 1050°C?
Thanks a lot.

 

[EdStainless]

I suspect that this is not creep, but differential thermal expansion effects.
Set them on a flat plate (maybe Mo or ceramic?) and stack them up and heat.
At least the bottom ones will be flat. Remember to coat them so that they don't stick together.
What is your atmosphere?
Something with lower thermal expansion would be better, a ferritic stainless perhaps.
Low carbon 430 or 446 might be options.

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P.E. Metallurgy, Plymouth Tube

 

If the part is just dead weight, how is creep happening?
Regardless, you cannot force this part back into anything approaching original condition without melting it down first.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[dandius]

Ok, let's say it's not creep.
You can see looking at the attached pictures the deformed plates.

So is it only thermal distortion, caused by the repetitive thermal cycle?
To properly get to the point i should give you the characteristics of the thermal cycle:
heating: from 20°C to 1100°C, 350°C/h
stasis: 3.5hrs @1100°C
1st step cooling: from 1100 °C to 900°C, 100°C/h
2nd step cooling: from 900°C to room temp, quenching.

Consider that this cycle is non-stop, 24/7.
Thanks a lot and forgive my inexperience.

 

Thanks for the pictures. I concur with EdS; the damage is caused by repeated thermal cycling (obviously), not helped by the high coefficient of thermal expansion and poor thermal conductivity of the austenitic SS.
Are you finding surface cracks?
Is 316L used for any particular reason? It seems to me you could switch to cheaper 304.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[weldstan]

You could also use more expensive nickel base alloys but there will be a tradeoff of extra life versus higher cost of alloy.

 

[dik]

Remember to coat them so that they don't stick together.

Nearly choked on my coffee... I could see me forgetting about that...

Dik

 

[EdStainless]

I still like the idea of using 430 or 446.
They will stay flatter, and cost less.

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P.E. Metallurgy, Plymouth Tube

 

[dandius]

Thank you guys for the support!

 

[Maui]

446 stainless is an excellent choice. Inconel HU (UNS J95405) would be an even better material to use in this application.

Maui

 

[EdStainless]

The cast version of 446 is called HC, this would be easier than making these from plate.
You could also use cast HD.
These alloys both have much lower thermal expansion and good high temp properties.

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P.E. Metallurgy, Plymouth Tube