The addition of nitrogen has a positive effect on strength, increases resistance to local corrosion, prevents ferritization in the weld area – previously a problem with ferritic-austenitic steels – and retards the precipitation of carbides and intermetallic phases in heat affected zone that means improves CVN results.
Duplex stainless steel possesses good weldability. The goal of welding is that the weld metal and heat-affected zone (HAZ) retain the corrosion resistance, strength, and toughness of the base metal.
The welding of DSS is not difficult, but it is necessary to design welding procedures that lead to a favorable phase-balance after welding and will avoid precipitation of detrimental intermetallic or nonmetallic phases.
For example 2205 has a microstructure of 40-45% of ferrite and 55-60% austenite, obtained after solution heat treatment at temperatures between 1000 and 1200 ºC, followed by water quenching.
2205 can be welded by: GTAW, GMAW, SMAW, SAW, FCW and PAW
However, during long periods of heating(or welding), when temperature is between 700 and 900 ºC, precipitation of a hard and brittle Cr-rich phase(Sigma phase) can occur, resulting in lead to Cr depletion at the metallic matrix surrounding sigma phase, resulting in brittleness and lower corrosion resistance.
To form an adequate ferritic-austenitic structure in the weld, filler materials containing higher amounts of nickel (approx. 8 % - 9 %) are usually used. Particularly suitable filler materials are 22%Cr-9%Ni. Nitrogen additions in filler metal and in shielding gas are preferred.
Welding is usually carried out without preheating and the interpass temperature should not exceed 150 °C. To achieve a good ferriteto-austenite ratio, heat input should be between 0.5 and 2.0 kJ/mm depending on thickness. The weld should not be subjected to accelerated cooling.
If there is a risk of long periods of heating or welding (between 700 and 900 ºC), solution heat treatment is required at temperatures between 1000 and 1200 ºC, followed by water quenching...
Ramin Kondori 
QC/Welding Engineer
IWE AT 0070
On Tue, Jul 26, 2011 at 6:43 PM, V B <vikas.bhandari349@gmail.com> wrote:
use of Argon+ 2% nitrogen as a shielding gas is a good option.On Tue, Jul 26, 2011 at 6:13 AM, Vanchinath S.A. <vanchinaths@gmail.com> wrote:
Try FSH( selectarc ) superduplex basic flux cored wire with Argon/co2 mix gas.vanchiOn Sat, Jul 16, 2011 at 8:31 AM, 박종민(PARK, JONG MIN) <carpediem@dsme.co.kr> wrote:
--Dear Experts
I wan to use FCAW process for welding of duplex stainless steel.
However, CVN value shall be min.50 Joule at -46 degree C.
Is there any flux cored wire which meets this requirement?
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