Re: [MW:34434] Corrosion Test Fail For Duplex Steel

Gents,

In the past a had a project with Super-Duplex with the same problem.

To solve this we liked to use Ar-N2 as a backing gas, but this was not in stock.

We switched to 100% N2 as a backing gas, and this worked out well for the corrosion test (40 degrees centigrade for Super DSS) and the complete PQR

In all cases the use of cold pass technique (thicker root pass (HI 1.2 kJ/mm max, thin second pass) interpass max 150 centigrade, overall HI max 1 kJ/mm has to be maintained 

Regards

Ir. Jurgen Prinsen IWE

Metallurgical and Welding Engineer

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Van: "materials-welding" <materials-welding@googlegroups.com>
Aan: "materials-welding" <materials-welding@googlegroups.com>
Verzonden: Woensdag 19 juli 2023 15:36:34
Onderwerp: Re: [MW:34431] Corrosion Test Fail For Duplex Steel

Gentlemen excuse me if I have interrupted. This is a  Forum where everybody shares their  Technical knowledge and experience so that it is useful to the concerned. Sometimes we may be wrong also and take it sportively without being offended.

Argon + 2% N2 mixture is highly recommended for purging and shielding for the below purposes.

1.  Nitrogen is an Austenite stabilizer and promotes Austenite formation in the duplex matrix.

2. It improves Pitting corrosion resistance.

3. The maximum solubility of Nitrogen in DSS A32205 is 0.2% and anything more than that will come out of the solution.

4. Nitrogen delays the formation of Intermetallic phases.

 

5. Nitrogen may be more efficient in aiding ASTM G48 corrosion test.

But in ASTM A923, the weight loss is mainly due to Intermetallic Phases as higher PREN electrodes used such as Super duplex and Nickel base electrodes does not cause in weight loss due to pitting corrosion. I feel the main reason is higher alloy contents of Cr, Mo,W in the welding consumable which causes Intermetallic phases. Though N2 mixture has some effect but unless care is taken on correct welding consumable it is difficult to prevent and also equally dependent on WElding conditions like Heat Input, Preheat and Interpass temperature.

Some portions below on sigma phase.

Thanks & Regards

J.Gerald Jayakumar

On Wednesday, 19 July, 2023 at 09:08:39 am IST, Babur Khan <mbabur.bwp@gmail.com> wrote:

Greetings,

In pas we faces same issue and after that we get recommendations from test laboratories to use mixture gases for shielding and purging.

Argon + 2% Nitrogen mixer with ER2594 filler wire.a

 Babur Khan Lashari 

Sent from my iPhone

On 18 Jul 2023, at 2:16 PM, Ashish Chacko <iamashleo007@gmail.com> wrote:

Backimh and shieldimg gas was argon grade 4.7 b ( 99.997%)

On Tuesday, 18 July 2023 at 11:10:50 UTC+3 Vishwas Keskar wrote:

What was the backing and shielding gas ?

Sent from my iPhone

On 18-Jul-2023, at 10:56 AM, Ashish Chacko <iamash...@gmail.com> wrote:

I am currently working on developing a Procedure Qualification Record (PQR) for Duplex Steel. In the process, I conducted welding using the base material SA 790 (UNS:32205) and utilized two different filler wires: ER-2594 and ER-Nicr-Mo-14 for different coupons. Size of the coupon 6" Thick:10.97 mm.

However, I encountered a concern during the corrosion testing phase, as per ASTM A923-03 standards. Both test materials failed the corrosion test. I'm seeking guidance from the experts in this group to understand the possible reasons for the failure and to explore potential solutions or alternative approaches.

If anyone has experience with similar issues or insights into the matter, I would greatly appreciate your assistance.

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