S32750 super duplex weld overlay

[Arafi]

Hi
I have super duplex weld overlay PQR on carbon steel pipe need to have ferrite 35 to 60% and ASTM A 923 PART C to be passed.

Base material thickness-7mm (carbon steel pipe)
GTAW-pulsed hot wire machine welding
First layer-ER309LMO (1.2 mm wire)
2nd layer-ER2594 (1.2mm wire)
3rd layer-ER2594
Shielding gas used for 1st and 3rd layer-Argon 99.997%
Shielding gas used for 2nd layer-98Ar+2%N.
Heat input for first layer-.5Kj/mm
Second layer-.5Kj/mm
3rd layer-.375kj/mm
Max interpass-100c
Forced cooling applied outside of pipe during welding for fast cooling.

Problem is that after three layer ferrite is less than 30% and need to pass ASTM A 923 Method c corrosion as well.

Can anyone suggest is the ferrite and heat input range acceptable?

 

[EdStainless]

So you have WPS, have you seen the actual PQR data?
This worked for someone, right?
How are you measuring the ferrite?
Are you sure that you are calibrated for THIS GRADE of duplex?
Are you sure that you are measuring vol %F and not FN?
Have you checked to intermetallics? You may have other issues here.
Let's see, if F% is too low that means that you have over stabilized the austenite.
Perhaps your N is higher than you intend?
Is your weld filler over rich in N?
Or it could be a temp issue.
100C interpass is higher than I would allow. I use that temp for 2205.
Your heat inputs look low to me. I am accustomed to values 2-3x these.
The slower the cooling the more austenite I would expect.
If you low heat input is resulting slow weld speeds then the cooling times may be too long.

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P.E. Metallurgy, consulting work welcomed

 

[Arafi]

Thanks for tour prompt reply.
First attempt of PQR failed in corrosion (923 Method C)with 300mdd (acceptable 10mdd), further tests haven’t done due to this.Pure argon was used as shielding gas.



2nd attempt of PQR,2%Nitrogen mixed argon is used for ER2594 first layer and pure argon for 2nd layer (cold pass). Ferrite is less than 30%, corrosion not yet done.

Nitrogen in the filler wire is 0.257 (MTC is uploaded).

To increase cooling rate i have decreased base current and increased base pulse time .welding was stopped at every 180degree of rotation. but still ferrite too low. Poor Melting also found in cold pass layer. Forced air cooling has been provided from outside of the pipe during welding. Welding position is 2G pipe rotate.

%Ferrite was measured using ferrite scope.

 

[SJones]

A clear demonstration of why weld overlay deposition of DSS/SDSS is avoided at (almost) all cost.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[EdStainless]

Yes SJ, weld overlay of SDSS is extremely difficult.
It would be easier and faster to use a 'C' type weld overlay.

You have checked your Ferrite Scope against a solid piece of 2507 which has a lab report of actual image analysis for ferrite/austenite content? If not I don't believe your numbers.

Have you checked the WOL ferrite after the second pass?

Have you considered using 2507 filler (instead of the high Ni high N version) for the last pass?

And have you checked for intermetallics? If you have any you have zero chance of passing.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Arafi]

Thanks for your reply.
I haven't verified ferrite scope against solid material. I will do that.
Ferrite after 2nd layer is quite low as i am using nitrogen mix gas to pass corrosion.
Wire selected as per client specifications.
Intermetallics not checked yet.