SAF 2507 GMAW spray transfer or pulse

By timczx6 Date 10-20-2009 00:38

We are about to do WPS qualifications on this material. We have welded 2205 before using spray transfer and Argon + 2% CO2 with good results and I would like to use the same process and gas with the 2507 as we don't have many pulse machines. We are welding full strength groove welds in 10mm, 20mm and 40mm plate welded from both sides and 8mm fillet welds. We have a heat input limit of 1.0 kj/mm which I think will mean the fillets welds will need 3 passes. Most publications I have found so far suggest using pulse mode and argon + helium + CO2 mix. I would like to know what process and gas is best for this material keeping in mind that using pulse will mean buying a few more machines.

By Steve.E (**)

Date 10-20-2009 09:18

If all your welds are downhand (flat) stay with spray.

By Lawrence (*****)

Date 10-20-2009 12:02

Don't have much knowledge of super-duplex alloys. So can't speak to the gas issue.

But in the most general performance terms. Your 10mm plate will join very productively with traditional spray transfer.

GMAWP can be an exceptional value in stainless steels that are less than 1/8 inch (3mm) in thickness.. Great fusion at fillet roots compared with short circuit with no burn thru that you might see with spray.

GMAWP can also be a big advantage in out of position joining, providing spray transfer quality and good control out of position. But as Steve said.. If your work can be positioned in the flat and horizontal fillet positions... I'm hard pressed to see a production advantage to GMAWP

By js55

Date 10-20-2009 19:49

I just don't think pulse is necessary. And in my opinion 1.0 kj/mm seems a bit low as a max. Remember, even with supers you have to pay attention to phase balance. Duplexes are NOT austenitics. They do not have the hot crack concerns, and therfore the max heat input concerns of austenitics.
Though with supers of course you have much greater time at temp intermetallic sensitivity to be considered.
Do you have any testing regimes imposed?
I would certainly do some ferrite testing to evaluate the phase balance.
Also, when you say you have a heat inut limit of 1.0 kj/mm, what was the criteria for that number? How was it established?
I'm guessin that if your runnin 1.0 with GMAW your ferrite is gonna be high.

By timczx6 Date 10-20-2009 21:25

The testing required is dye penetrant on all welds and UT on all butt welds. There is no ferrite testing required. When we did some work with 2205 for the same customer which also had a heat input limit of 1.0 kj/mm, they said is was to limit distortion???

By js55

Date 10-21-2009 12:46

I am surprised there is no corrosion or phase balance verification with the weldment.
As for distortion, this is interesting also in that duplexes will not distort as readily as austenitics(even 2205).
Given that a specific application could have a requirement for fine distortion control I would still wish to verify the ferrite content with such low heat input(given that it appears this is your first foray into supers I'd start aquiring some phase balance data). The biggest problem with high ferrite will probably manifest in the HAZ. Base metals are not chemically balanced for such fast cooling rates.
I can't help but think the customers specifications are more consistent with austenitics than duplexes, which is not uncommon even with people who should know better.