Stabilization heat treatment for SS321

[Arty_pin]

Hi,
I am going to order a batch of SS321 piping (NPS14 sch.160 ; thk 35.71 mm) to use in estimated temperature of 500 C which is in sensitization susceptible range. Could anyone please suggest if I do require stabilization heat treatment after solution anneal ? If it is required (or recommended), please also help to suggest heat treatment conditions.

All comments are appreciated. Thank you.

 

[XL83NL]

Why are you using 321 over 316? Is there any change of condensate in the line that could lead to IGC?

 

[Arty_pin]

It was designed to be SS321 since its first day. However, it failed after about 10 years of service, so we need to buy new material for replacement.

 

[XL83NL]

Sorry for going off-topic here. Is there any change to reconsider the original MoC? Why did it the original 321 line fail?

 

[metengr]

If you are going to use the 321 ss, I would recommend a stabilization heat treatment to get you the best possible corrosion resistance in service.

 

[EdStainless]

Your temp is on the low end of the stab range, so having it done to the material makes sense.
I am with XL here though, why not use a low C 316L, it won't sensitize. Look up the curves for material with 0.015% C.

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P.E. Metallurgy, Plymouth Tube

 

[Arty_pin]

Microstructure of original line showed carbide precipitation at grain boundary while cracks are intergranular, so we believe that it was caused by sensitization and pressure it held.

thank you both XL83NL and metengr. Could you please also recommend heat treatment profile, is it 900 C for 4 hours ?

 

[EdStainless]

I would bump the temp up a little, maybe 950C.
Sensitized material is much more sensitive to SCC, there are many papers on this subject.

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P.E. Metallurgy, Plymouth Tube