TEMPERATURE LIMIT FOR DUPLEX SS 3

[gengi]

Dear all,

I would be grateful if someone lets me know which is the suggestable temperature limit for the apllication of DUPLEX material ( 22% Cr - UNS N031803 - SAF 2205 )-

I learnt that, for ASME Code Div. 1 - Part II , the temperature limit is 315°C ( 600°F) ; over this temperature NO allowable stresses are available.

In addition to the tempearature limit could you please also explain the reasons of such limitation and the effect on the Duplex SS material if exposed at such high temperature ?

thanks in advance

GENGI

 

[metengr]

gengi;
The reason for the upper temperature limit imposed by ASME Section II subcommittee on Materials is that the duplex stainless steels develop harmful phases or precipitates at prolonged elevated temperature exposure that results in reduced strength and significantly reduced ductility.

 

[SJones]

Take a look at API Technical Report 938-C if you can.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[metengr]

If you need more technical information, go to the web site below and you can download a report on Fabrication of Duplex SS from IMOA for free

http://www.imoa.info/moly_uses/moly_grade_stainless_steels/duplex_stainless_steel.html

 

[EdStainless]

The problem with higher temps is complicated. The formation of intermetallics causes significant reduction in room temperature toughness. The material will still be ductile at operating temp, but when cooled any mechanical or thermal shock may cause severe failures. There is also an associated loss of corrosion resistance.
These alloys will work for many years at 600F. I have seen tests where a couple of weeks at 630F caused serious damage.
If the highest inlet temp of your unit can ever exceed 600F (not mean metal temp) then a duplex or ferritic stainless is not a safe option.

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