Lower - % Ferrite in Super Duplex Stainless Steel

[Chintan]

Dear Expert, 

After Filling & Capping of  Weld Metal, During % Ferrite check via Feritoscope  values are showing less than requirement, How ever all other test i.e. Hardness, PMI etc. are well accepted. 

Kindly advice on  possible root cause as well as tips to achieve high Ferrite 

Please find below details for your quick ref. 

 Material Grade - SDSS -UNS s32760

Joint type -Pipe - Butt weld - 18 mm thick 

Welding Process - GTAW + SMAW 

Welding Consumable - ER 2594 + E 2594-15

% Ferrite - GTAW ( Root ) - 35%, SMAW ( Capping) - 25 -28 %, Base metal - 35to 40%, HAZ - 32 to 35% 

% Ferrite - Spec Req - 30  to 70%

Inerpass mentained - 100°C for GTAW, 120°C for SMAW

Heat input - GTAW - 0.8 to 1 KJ/mm

SMAW - 1.2 KJ/mm

[Ahmed Osman]

Dear Friend ,

try to replace E 2594 by E2595 .. it have W element which is promoting ferrite

Best Regards ,

ENG. Ahmed Osman

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[Shyamal Das]

Hi

Please check the  shielding Gas 

Argon + 2 % Nitrogen  purity levels 

purging gas  100 percent Argon . Better to control with less than 100 ppm

You should have purge monitor with least count .001 

Nitrogen also play important role is Austentic and ferrtic phase distribution .

Kr

Das 

[Alcindo Jardim]

Some results indicate that it is not just the shielding / purge gas that is interfering. The ferrite in the base metal is also off limits. I suggest investigating the factors further. it may be that the base metal is not within the standards, and the heat imput may also be high, changing the transformation kinetics. Run more tests before making the next weld.

Alcindo O. J. Jr.

21 96676-1511

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