Dear experts,
-- Here I am preparing WPS for Duplex material using robotic welding machine. The details are as follows.
Material designation - SA 790 UNS S32205
Pipe dimension - 4", 6 mm thick
Welding process- TIG(Root), MAG(fillup & Cap)
After the PQT while doing the pitting corrosion test it got failed. The pitting corrosion test was done as per ASTM G 48.
For TIG welding earlier I had used 98% Ar + 2% H2 as shielding gas. Now I have changed it to 98%Ar + 2% N2.
For MAG welding pulse method is used. Shielding gas used is 98% Ar + 2% CO2. Purging gas used is 99.997 % Ar.
Heat i/p calculated is within the range 0.6 to 1.5. Also the interpass temperature was below 120 degree. What else can be the reason for Pitting corrosion? It came more in the capping. So I am worried about the shielding gas used for MAG. Which other shielding gas can I use for the MAG welding of duplex material??
Regards,
Aby K Jose
QA/QC Engineer
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