Welding of duplex steel 9

[christenhusz]

I'd like to ask what type of filler material to be used when welding Duplex stainless steel (31803). Can SS316 filler material be used or does Duplex stainless steel requires a special filler material?

 

[SJones]

http://www.nickelinstitute.org/mult...iterature_pdfs/other/39309_IMOA_Duplex_ii.pdf

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[metengr]

I would not recommend 316SS filler metal for welding duplex ss because of corrosion concerns and weldability issues.

Your best bet is to match or slightly overmatch the base metal with weld filler metal like 2205 or E2209. Also, make sure you watch your interpass temperatures (300 deg F max) during welding, and do not perform any PWHT.

I would suggest you visit the Ni Development web site;

http://www.nidi.org/index.cfm/ci_id/80.htm

or the Ootokumpu web site for further information on welding of duplex ss;

http://www.outokumpu.com/applications/documents/start.asp

 

[bruv]

Metrode have some good technical profiles and data sheets on their website

http://www.metrode.com

and follow the product information links

Bruv

 

[rorschach]

Depends on the duplex, I've used 25-10-4L from Sandvik on 25% Cr duplexes with good results (in fact it is the only filler metal Foroni will recommend for use with thier alloy 918). The extra nickel helps to offset the nitrogen loss.

 

[sayee1]

E/ER 2209

Thanks and regards
Sayee Prasad R CEng MWeldI MIOMMM


If it moves, train it...if it doesn't move, calibrate it...if it isn't written down, it never happened!

 

[sayee1]

In addition to Metengr's recommendations
1. HI should have both min and max restrictions as these influence the % ferrite/austenite
2. Most single sided butt/groove welding procedures for DSS for corrosion resistance will need high purity Ar backing with oxygen level monitoring using purge monitor
3. Cleranliness of joint and area where welding performed is critical for most applications w2ith Duplex.
4. Do not mix tools used for cs with duplex....tools like grinder, chisel etc. Special tools would be called for by clients with low impurities level so that the weld is not contaminated.
5. Filler wire traceability and control, gas traceability and control will be required for critical piping systems with DSS MOC.

Thanks and regards
Sayee Prasad R CEng MWeldI MIOMMM


If it moves, train it...if it doesn't move, calibrate it...if it isn't written down, it never happened!

 

[schrijen]

I agree with metengr. Use a standard duplex fillermetal because, looking to the ferrite-austenite ratio after welding, the duplex fillers are overmatched in nickel content mostly 3 or 4 % more than the basemetal.
Important for the ratio in the HAZ is the nitrogen content in the basematerial. When this is higher than 0.15 you always will have a network of austenite in the HAZ of more than 30 % austenite. The advantage of the higher nitrogen content is the basematerial is the fact that there is no longer a stringent relation with heat imput anymore and that the distributionfactor of the alloying elements in the ferrite and austenite fraction is lowered.
Normally the heatimput is between 8 - 15 KJ/cm but keeping a low interpass temperature is the most important parameter for the long term corrosion resistance.
Welding with 316 means that the ratio in the weldmetal goes out of the range because a minimum of 30% ferrite is nescessary for creating the ferrite network in the weld because the corrosion restistance of duplex is related to the ferrite (Cr+3.3Mo+16N), the corrosion weakest part is the austenite.
Using argon or nitrogen backing depends on your media. In our company we always use nitrogen as a backing gas.
Interaction of nitrogen backing with the weld practically do not occur because the dissiation temperature of nitrogen is about 7000 K.