Super duplex weld coupon cleaning -G48 Testing

[GSB89]

Hi all, new to the forum and any forum actually so please bear with me.

We have an offshore superduplex project relating to manufacture of desalination equipment.
The end user has their own set of specifications which are in addition to the requirements of our current ASME IX PQR’s.

Therefore we are having to re submit coupons in retropect to undergo additional G48 corrosion testing amongst other testing. All in all, across two PQRs I have 16 welder qualifications which need to retested.

We have never had an issue previously passing SDSS quals but previously have never had to undergo the additional tests.

I have two concerns, first being gas -our RWC has always used a 97,5%argon 2.5% Co2 shielding mix and pure argon backing.

It seems a lot of people say to optimise corrosion resistance there should be a 2% nitrogen addition?

This would mean our PQRs would need to be done from scratch, can I ask people’s thoughts on this ?

Although regarding cleaning the coupon welds after the procedures, would you wire brush (st/st) , acid pickle, or use an electropolishing set like the tig brush, which I believe pickles and passivates and may leave a cleaner surface less susceptible to pitting?

I believe just pickling using Antox (+neutraliser) and leaving to air passivate for 24hrs has been our previous approach.

I Would greatly appreciate input, I’m not a welder and SDSS only accounts for a small% of our companies production.

Naturally I want to learn as much as possible.

Thanks in advance.
Grant

 

[EdStainless]

For weld gas I have always specified Ar +2%N2 (1.5-3.0), never any CO2.
They can ass He if they want to for a more stable arc.
For corrosion testing coupons, they must be finished as it will be in production.
Though in most cases a coupon will be cut and some surfaces may be prepared depending on what is being tested.
I don't do G48s.
I require Austenite:Ferrite ratio, A923-C, and low temp impacts.
For the A923-C the surfaces must be freshly ground (180 grit I believe) and then tested with no treatment.
If I was doing G48-c I would require the exposed surfaces to be untouched and the sides where I cut the coupon would be polished so that they were less involved.
Special cleaning of the test surfaces is changing the rules.

 

[GSB89]

For weld gas I have always specified Ar +2%N2 (1.5-3.0), never any CO2.
They can ass He if they want to for a more stable arc.
For corrosion testing coupons, they must be finished as it will be in production.
Though in most cases a coupon will be cut and some surfaces may be prepared depending on what is being tested.
I don't do G48s.
I require Austenite:Ferrite ratio, A923-C, and low temp impacts.
For the A923-C the surfaces must be freshly ground (180 grit I believe) and then tested with no treatment.
If I was doing G48-c I would require the exposed surfaces to be untouched and the sides where I cut the coupon would be polished so that they were less involved.
Special cleaning of the test surfaces is changing the rules.

Thanks very much for the reply Ed.
I’ve read a lot of your responses regarding various queries and always find them helpful.
We actually have two jobs coming up and one stipulates G48 and the other only mentions A923-c
Appreciate your comments regarding the special cleaning. The production fabrication requires pickle and passivation to ASTM a380.
There several scavengers with 12 laterals, 6 per side flanged. They will have to be dipped to reach the full pen welds, then the sheet metal troughs which are 2mm tig welded stitch fillets we are planning on electropolishing with a cougartron fury200 which pickle and passivates simultaneously