[MW:4986] RE: 4958] Super Duplex Welding

 

Mr Pinho,

 

GMAW is one of the popular welding process for welding of Duplex and Super duplex. S.S. Often there could be more than one variable which could generate weld porosities in SDSS. Looking at your issues, predominantly it looks to be issues concerning the shielding gas and operating parameters.

 

GMAW  irrespective of thicknesses  is better controlled in Pulsed Mode, where three is synchronous transfer of limited amount of metal, under well controlled arc without much turbulence. 

Shielding gas/es that has proved most successful is for welding DSS/SDSS  Argon-30-35% helium-2% CO₂ though  are could be  number  of  different proprietary gases on the market with compositions similar to this.

 

Looking back at your problem I would think the following would help you:- 

 

·         Use of pulsed power, typical welding parameters 0.45" dia filler, 160-180A,26-28V

·         Proper cleaning of the groove, wire brushing and acetone cleaning , at least 2 inches on each side of groove. Ensure that acetone is properly dried before welding.

·         Use shielding gas  typically Argon-30-35% helium-2% CO₂ .More helium in  shielding gas increases penetration and weld puddle fluidity.

·         The gas tried in the first place Ar+20%He+2%CO₂  may also be good provided the best welding parameters are optimized for this combination.

 

In GMAW the causes for spatters are arc intensity and the ionisation behaviour of the shielding gas. As explained below "He" has more ionisation potential than "Ar", thus will dissociate at lesser speed than "Ar". But due to lighter weight, "He" blended gases will need more  gas  flow   rate  at the same welding parameters.

 

As regarding control of interpass temperature, it's mandatory for good  " Super Duplex S.S" welding,  the heat input and  interpass temperature  is very well controlled.

These two welding variables  is going to decide Ferrite: Austenite ratio  and the resultant properties, e.g. Impact Properties, Corrosion properties (Pitting or SCC) and other requirements as per the design code/specifications.

 

I have attached some illustrations for your reference.

 

 

Thanks

 

 

Pradip Goswami,P.Eng.

Welding & Metallurgical Engineer/Specialist

Email-pgoswami@sympatico.ca,

pgoswami@quickclic.net

 

 

 

 

 

 

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From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Rui.Pinho@pt.linde-gas.com
Sent: Monday, April 26, 2010 5:16 PM
To: materials-welding@googlegroups.com
Subject: [MW:4958] Super Duplex Welding

 

Dear All


We have problems for welding Super Duplex Nº 1.4410 (see attach of Base Material Certificate) with8 mm thickness.
The process is GMAW - MAG welding an use wire electrode AWS A5.9-06 : ER2594 (see attach of Wire electrode Certificate) and the shielding gas is Ar+20%He+2%CO₂

The bead of first pass is OK, but the next pass (interpass) have lots of porosity, no penetration and Spatter.

Will bo control the temperature of interpass?
Will be change the wire electrode?


Thanks for help

Best Regards


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

Linde Sogás, 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.pinho@pt.linde-gas.com, www.linde.pt

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