Compare Argon with Nitrogen as Purging gas for Super duplex stainless steels

[Murugesan Jeyaraman]

Dear All 

Which gas is better for purging gas of super duplex stainless steel welds. 

Please compare both technically, also suggest which is best to use in Duplex SS purging?  Is there any difference at all or both just gives equal result?

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Thanks and Regards

 

Murugesan 

[Ahmad el-sharkawy]

use mix of nitrogen and argon
 (Ar + 1 -2%N2 as a shielding gas)



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WITH MY BEST WISHES

AHMED ELSHARKAWY
QA/QC ENGINEER
DIPLOMA DEGREE IN WELDING ENGINEERING.
CERTIFIED WELDING INSPECTOR " CWI " 14072901.
ASNT LEVEL II " RT&VT&UT&PT&MT"
IRECA CERTIFIED LEAD EDITOR ISO 9001/2008.

PREPARING MASTER DEGREE IN WELDING ENGINEERING.

[Naasief Navsa]

Hi Ahmad,

 

Does using this combination of shielding gas (Argon and Nitrogen) have any influence on the weld strength (i.e. integrity of the weld), when welding super duplex stainless steels.

 

Regards,

 

Naasief

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[Sergio Antonio Muñoz Pinzón]

Nitrogen influence the balance of phases (ferrite and austenite), and microstructure influence mechanical properties, Nitrogen is also a key alloy element in corrosion pitting resistance. In duplex is added to shielding gas because it escapes easily from the molten pool.

Sergio Antonio Muñoz

IWE-IIW

http://Weld-ING.blogspot.com

[Noe Mota]

The best approach for gas purging when welding super duplex is argon 100%.

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[Naasief Navsa]

Hi All,

 

We use 100% Argon as a shielding gas when welding our super duplex stainless steel, we use Tig welding on our tube mills. We then hydro form these tubes, but find that weld failures are more prevalent with the super duplex stainless steels than with the other stainless steels we weld (i.e. 316, 312, etc).

 

Does anyone have any suggestions. Is there anything different we need to do when welding the super duplex stainless steel?

 

Regards,

 

Naasief

 

From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of Noe Mota

Sent: 18 November 2014 07:44 PM
To: material...@googlegroups.com

[Diganta Sarma]

100% pure Argon is the right choice, please ensure Oxygen content does not exceed the recommended limit in ppm. This has a wide variation depending on end usage, for eg 0.5% when with the residual oxygen it is still possible to pickle the weld if post weld cleaning is allowed in special circumstances. Many codes and manufacturers do not allow any colours which would mean a restriction of 50ppm will apply

Thanks,

Sent from my iPad

[Ahmad el-sharkawy]

On Wed, Nov 19, 2014 at 11:13 PM, Ahmad el-sharkawy <ahmad.sh...@gmail.com> wrote:

dear Noe Mota mixture of argon and nitrogen is the best gas purging for welding duplex and super duplex stainless steel


 

On Wed, Nov 19, 2014 at 10:34 PM, Ahmad el-sharkawy <ahmad.sh...@gmail.com> wrote:

dear Naasief Navsa use mix of argon and nitrogen and use low heat input.

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WITH MY BEST WISHES

AHMED ELSHARKAWY
QA/QC ENGINEER
DIPLOMA DEGREE IN WELDING ENGINEERING.
CERTIFIED WELDING INSPECTOR " CWI " 14072901.
ASNT LEVEL II " RT&VT&UT&PT&MT"
IRECA CERTIFIED LEAD EDITOR ISO 9001/2008.

PREPARING MASTER DEGREE IN WELDING ENGINEERING.

[Naasief Navsa]

Hi Ahmed,

 

Thank you (Shukran) for the valuable information. One more question, this mix of argon and nitrogen, what ratio’s would be optimum.

 

We are Tig welding material that is 0.15mm thick. We typically weld with about 18A, and a linear speed of 50mm/sec. At this point in time we are purging with 100% Argon.

 

Regards,

 

Naasief

 

From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of Ahmad el-sharkawy

Sent: 20 November 2014 09:21 AM
To: material...@googlegroups.com

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[Rajagopal Kannan]

Dear Naasief,

he has already given, 98% ARGON, 2% NITROGEN.

Thanks and Best Regards,

K.Rajagopal

[Rui....@pt.linde-gas.com]

When subjected to high temperatures and atmospheric oxygen, many metals tend to intense oxidation. The oxides generally appear as temper color, for example, with stainless steel or titanium materials. Temper  colors will greatly impair the corrosion resistance of such metals. Furthermore, severe oxidation will impair the formation of weld roots. Thus, in many cases, the root side has to be protected against oxygen in order to ensure optimum corrosion resistance.

For duplex and superduplex steels, using root-shielding gases that contain nitrogen or pure nitrogen improves corrosion resistance.






Rui Fernandes Pinho
Divisão de Gases Industriais
Desenvolvimento de Aplicação de Gases

Linde Portugal, Lda.
Travessa Joaquim Dias Salgueiro, Nº 44
4470-416 Vila Nova da Telha, Portugal
Phone + 351 22 999 8380, Fax: + 351 22 996 4039
Mobile + 351 91 473 9197
rui....@pt.linde-gas.com, www.linde.pt

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[pgoswami]

Hi Nassef,

 

Please see the attachment for additional guidance.A change of backing gas is an essential variable for procedure qualification on DSS/SDSSs(QW-408).

 

Both Ar,or Ar+ N2 or N2+H2(formier gas) are well proven as  backing gas while welding these steels. Presence of Nitrogen containing backing gases are advisable to protect the root from unfavorable austenite/ferrite ratio.This is critical if there's a requirement of ASTM G-48A pitting corrosion test (typically 25 Deg C  for DSS and  35 DegC and above  for SDSS).

 

In absence of the above pitting corrosion tests  pure (100%) Argon may also be used for backing.

 

Thanks.

 

Pradip Goswami, P.Eng,IWE

Welding & Metallurgical Specialist

Ontario, Canada

pgos...@quickclic.net

pradip....@gmail.com

http://ca.linkedin.com/pub/pradip-goswami/5/985/299

 

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From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of Naasief Navsa
Sent: Thursday, November 20, 2014 4:33 AM
To: material...@googlegroups.com
Subject: RE: [MW:22307] Compare Argon with Nitrogen as Purging gas for Super duplex stainless steels

[Ahmad el-sharkawy]

Nitrogen  have multi purpose  at welding  DSS and SDSS 

1- austenitic stabilizer element.
2- delay segma phase which destroy corrosion resistance of material.
3- increase pitting corrosion resistance.

***** you must know that formation of duplex is thermo mechanical process; at welding there are only thermo process so nitrogen is very important element to form austenite and remain the percentage of two phases (( ferrite  and austinite))