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))
--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,IWEWelding & Metallurgical SpecialistOntario, Canada
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Naasief Navsa
Sent: Thursday, November 20, 2014 4:33 AM
To: materials-welding@googlegroups.com
Subject: RE: [MW:22307] Compare Argon with Nitrogen as Purging gas for Super duplex stainless steelsHi 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: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Ahmad el-sharkawy
Sent: 20 November 2014 09:21 AM
To: materials-welding@googlegroups.com
Subject: Re: [MW:22304] Compare Argon with Nitrogen as Purging gas for Super duplex stainless steels
On Wed, Nov 19, 2014 at 11:13 PM, Ahmad el-sharkawy <ahmad.sharkawy88@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.sharkawy88@gmail.com> wrote:dear Naasief Navsa use mix of argon and nitrogen and use low heat input.
--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.
--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.
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