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 iPhoneOn 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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