[MW:20076] Black spots on DSS Weld Joints.

Dear Experts,

We observe Dark spots on Welding of Duplex Stainless Welds.  

Material is : UNS S31803 ,  Filler Wire for root - ER2594, rest ER2209.

Sample pictures are attached for reference.

Oxygen level in shielding / Purging maintained well below 0.2%.

Interpass <150 Deg.C

Pl. share your valuable information.

Thank you.

P.Rao