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[MW:36018] SS304/304L Tubes to CS Tubesheet Mock Weld -Cracks found

By Materials & Welding
Dear Sirs,

We have made 2 MockUp PQRs as per ASME Sec IX QW-193.

The Tube sizes are 19.05OD x2.11T and 15.88OD x2.11T, the
tubesheet plate is SA-516-70, 50T.

Amps used Max 145, Volts Max 13, welded with GTAW AWS Class ER309 with 1.6mm Filler , 2 passes.

We found minor cracks on the weld root and some on the surface too, but not for all the 10 tubes welded, but randomly found these cracks

When we did PT after welding on the surface, no cracks were found. But found after Macro etching at the test lab.

Can I switch the filler to ER309LMo for this MockUp weld ?

Are these cracks called Hot cracks ?

Please give me some advice.

With best regards,
Saravanan Sornam,
Ansan city,
S.Korea.


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