SA-182 F316L and F316

[stopsunset]

Can anyone explain why the allowable stresses for F316 are higher than F316L in SA-182? It appears that above 850'F, 316L is not suitable wheras 316 has allowable stress up to 1500'F.Other than the low carbon content in the L grade, I see no difference in the composition.

 

[EdStainless]

That is it, the carbon. It is an interstitial strengthener that gives higher strength across the temp range.
for comparison look at the numbers for 316H.

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Plymouth Tube

 

[EdStainless]

There is a detail that goes un-spoken these days also.
That is the dual certified 316/316L.
One reason that today's L grade will make straight grade mechanical properties is because of a little bit of N in the alloy.
While the nitrogen is a good strengthener at low temp it does not raise creep strength as much as C would.
This is why you are only allowed to use H grades (with min C) in creep limited applications.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[metengr]

Please read the notes at the end of the stress lines. This is why they are there and explain the differences.
Example -
G12 At temperatures above 1000°F, these stress values apply only when the carbon is 0.04% or higher on heat analysis.

 

[stopsunset]

Thanks for the insight.