Duplex and Super Duplex Stainless Steel

[limesh M]

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

[hpi001]

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

[Naveen Kumar]

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

Dear Limesh,

Best Regards,

Herman Pieper

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[John Henning]

Herman,

Just a quick note. S-numbers have been deleted and where appropriate converted to P-numbers.

See 2010 Section IX, Introduction, Welding and Brazing Data - page xxviii, 2nd column, 3rd paragraph: "In the 2009 Addenda, S-Numberbase materials listed in the QW/QB-422 table were reassigned as P-Numbers and S-Number listings and references were deleted."

It is my understanding that the original intent was to permit extended welding qualification for materials approved for use by B31 committees but not included in Section II (and therefore not permitted by Sc I or Sc VIII). Section IX determined that this had nothing to do with weldability and the user should be aware of what/where the material was permitted to be used.

John

-----Original Message-----
From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of hpi001
Sent: Sunday, September 05, 2010 5:05 PM
To: Materials & Welding
Subject: [MW:6879] Re: Duplex and Super Duplex Stainless Steel

Dear Limesh,

Best Regards,

Herman Pieper

--

[limesh M]

Dear All,

 

Thank you for the valuable inputs.

 

Construction codes: ASME B31.3 and welding code ASME SEC IX

 

I want to weld ASTM A 790(UNS 32750) to ASTM A 790(UNS32750), ASTM A 928(UNS32750) to ASTM 928 (ASTM32750).Then ASTM ASTM A 790(UNS 32750) to ASTM A 928(UNS32750).What electrode and filler wire I have to select? Normally at what direction impact test doing on weld metal, ie, transverse or longitudinal or both direction? From where I can get the minimum charpy value required on impact test? I have reviewed ASTM standards, found minimum tensile and yield strength values, but couldn't find any minimum required impact value.

 

Regards,

 

Limesh

[vanchi]

Dear Limesh,
SFA 5.4 E2594 electrode for Smaw and SFA 5.9 ER 2594 filler wire for
GTAW is used for welding UNS 32750.
Impact values are not specified by the code. It depends on the
consultants requirement. Upto minus 30degC you could use rutile base
electrode -16 or -17. incase you want to go lower down to minus 50degC
one should use basic -15 electrodes. For GTAW there is no issue. It
will pass minus 50degC. impact to be taken on the weld , notch
perpendicular to direction of welding.
incase u require further information mail it van...@vsnl.com

> > w.r.t. applicable code/standard/contract documents.- Hide quoted text -
>
> - Show quoted text -

[limesh M]

Dear All,

Proposal came from client side as ER 2594 and E 2595-15.

What is the reason for using E2595-15 instead of E 2594 on this material for SMAW?at the same time they suggested ER 2594 for GTAW !!!  I have no idea.

Expecting some valuable comments in this regard.

Regards,

Limesh

[Vanchinath S.A.]

Dear Limesh,

E2595 has 0.7 Cu and 0.7 W which is absent in E2594 and PREN is greater than 40. It has better pitting resistance compared to E2594.

regards

vanchi

[limesh M]

Dear All,

 

I reviewed SFA 5.4 2007 edition and found that the minimum tensile value of E2954-15 and E2595-15 are 760 Mpa and which is less compared to ASTM 928(UNS 32750) minimum tensile value of 795 Mpa.Is there any problem for selecting E2594-15/E2595-15 for welding ASTM A 928 (UNS 32750) material?

 

I heard that the tensile value of consumable shall be equal or morethan the minimum tensile strength of the pipe /plate material.

 

 

 

Regards

 

 

Limesh