Welding Inconel UNS 6625 to Low temp Carbon Steel (A333 Gr6)

[Thuhuongengineer]

Hi Friends,
We qualified PQR inconel UNS 6625 weld to low temp Carbon Steel (A333 Gr 6). All mechanicate passed except Root bend test. The defect lack of fusion at boundary have appeared manny time. We try many time but still similar defect.

Would like give some information for your study:

Welding Consumable: Tech-Rod 112, ER NiCrMo-3 Techlloy
Heat input: 1.2-1.8 (Kj/mm)
Type bend: Root Bend
Jig Bend: 40 mm (4xt)

The picture for your refer

 

[jwhit]

You may be running into an issue with the filler metal melting before the base metal puddle is fully formed. Another possibility is poor cleaning of the base metal prior to pass deposition, oxide formation on the base metal interferes with fusion.

 

[metengr]

Given that Inconel filler metal is not the easiest to handle, I would bet the lack of fusion has more to do with welder technicque. Have the welder reduce the need for a wash pass along the edge of the weld cap.

 

[wegm]

I agree with metengr, I suggest you change WPS and perform buttering on the Carbon Steel as described at this link:

http://www.weldinguide.com/gdanastasiadis/viewtopic.php?f=5&t=58

 

[wegm]

In addition try to follow these instructions:

http://www.weldinguide.com/gdanastasiadis/viewtopic.php?f=2&t=9

 

[vanci]

How are you seeing lack of fusion in the cap when performing a root bend? Your description and picture are in conflict of each other. If the lack of fusion is in carbon steel side of the root as it appears in your picture (root bend or side bend), it appears there is missmatch at the lands. I would think you would fit the joint so the lands are even with each other. I agree with metengr, probably welder technique. What position is the weld in? Is this single V groove?

 

[Duwe6]

What metengr said: ". . .bet the lack of fusion has more to do with welder technique"

Inconel is notorious for being hard to weld or use as a filler. Hire the best welder you can find. It'll be much less expensive than all the rejects/repairs you have been having. A top-notch welder can make that weld. But not an average one.

Cheap welders can be incredibly expensive. Expensive, excellent welders can end up being cheaper than run-of-the mill welders.