Difficulties to qualify TTS weld for Inconel 625. Seek advise.

[mohd fahmi]

Hi, Good Day.
We are to qualify tube-to-tubesheet weld strength for material & pWPS details as per below. However, faced difficulties for the PQR as the macro examination criteria not able to be met (3 times) - lack of fusion (LOF); as well as lack of penetration (LOP).

Tubes material: Inconel 625
Tubesheet material: Inconel 625
Groove bevel: 45deg
Groove bevel depth & width: 2mm, 2mm
Tube protrusion: 3mm
Filler metal: Inconel 625; MIG wire 1.2mm (previously used 1.6mm diameter filler rod, found LOP)
Welding method: GTAW

Seek advise on how the weld fusion can be improved, whether specific parameters need to be set-up.
Feedback from the welder, he found that it's quite hard to control the melting metal (material factor) and to fill-up the corner bevel.

Really appreciate your view! Thanks!

 

[EdStainless]

How about a quick sketch for us.
How much of the tube protrusion are you trying to melt?
How deep is your penetration supposed to be?
Personally, that sounds like a very small bevel.

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P.E. Metallurgy, consulting work welcomed