[MW:6881] RE: 6879] Re: Duplex and Super Duplex Stainless Steel

Dear Limesh,
The Avesta leaflet on how to weld duplex steel will ready help to find
answer of your question.
Please find attached copy of same.

With best regards

Naveen Kumar

-----Original Message-----
From: materials-welding@googlegroups.com
[mailto:materials-welding@googlegroups.com] On Behalf Of hpi001
Sent: Monday, September 06, 2010 3:35 AM
To: Materials & Welding
Subject: [MW:6879] Re: Duplex and Super Duplex Stainless Steel

Dear Limesh,

The difference between Duplex and Super Duplex is the so called PREN
values (Pitting Resistance Equivalent Number) which for Super Duplex
should be >40. So this material has better properties against pitting
corrosion compared to standard Duplex Stainless Steel. PREN is also
called PI (Pitting Index) in some specifications.
You can calculate this value by way of the following formula: PREN =
%Cr + (%Mo x 3.3) + (%N x 16) , so to get this value above 40
manufacturers will add some extra Cr, Mo and N compared to standard
Duplex.

The P.no. for most of the Duplex and Super Duplex materials is P.no.
10H, Group No. 1 but some materials (f.e. UNS 32205 (2205)) has no
P.no. but a S. no. (see QW 422 of ASME section IX).

The reason that your impact test fails often is related to the
presence of inter-metallic inclusions such as Sigma Phase in the micro-
structure, which is caused by not controlling the heat input during
welding. Inter-pass temperature should not exceed 175 °C in order to
prevent such unwanted inclusions. An other possible cause can be
cooling down slowly from 850 °C to 350 °C which can cause brittle
structure as well.

Hopes this helps you out.

Best Regards,

Herman Pieper

On 5 sep, 18:29, limesh M <limes...@gmail.com> wrote:
> Dear All,
>
> What is the difference between Duplex and super duplex stainless
> steel?
>
> What is the P. No for duplex and super duplex stainless steel?
>
> One of our duplex stainless steel PQR failed in impact test.What would
> be the reason?
>
> Thanks and Regards,
>
> Limesh

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