Pointers for Copper Nickel to 304L stainless fillet welds

Date 07-20-2009 16:40

Viscosity is going to demonstrate some variance. As a guess I'd say reduce volts (arc length) reduce torch angle to almost perpindicular, and reduce wire size while perhaps feeding a little more aggresively.

By Kix

Date 07-20-2009 17:48

Tried all of that and it runs like your not supposed to use that filler. lol The only thing we've found that helps is to butter the CuNi around the toe area with the ERNi-1 rod and then run it. It just takes to dam long to do it that way though. This process is whippin my a$$ and that doesn't happen to often.

By ssbn727 (*****)

Date 07-21-2009 02:34 Edited 07-21-2009 23:08

Hi Kix!

Are you using a Special Metals "Monel 67" filler rod for the ER Cu-Ni to weld Cu-Ni to an Austenitic Stainless such as 304L and getting good results as far as not experiencing undercut on the Monel side?
Here's the product sheet for the above mentioned rod:

http://www.specialmetalswelding.com/products/datash/fm67.pdf

Here's a .pdf on the (Nickel FM 61) Er Ni-1 rod that you mentioned, and are having problems with on the Cu-Ni toe of the fillet weld (Please correct me if I misinterpreted you)?

http://www.specialmetalswelding.com/products/datash/fm61.pdf

The first thing I notice in the different chemical compositions is the huge variation in the amount of Cu between the ER Cu-Ni filler, and the Er Ni-1 filler which would obviously explain why there's no undercut with the ER Cu-Ni filler as opposed to the ER NI-1 filler... Are you depositing a "barrier" (Buttering) layer on the 304L with ER Ni-1 or on the Cu-Ni member? Almost as important, are you making darn sure that both members are very clean prior to welding?

By any chance, do you visit this site?

http://www.specialmetalswelding.com/

Here's a good .pdf for reference:

http://www.specialmetalswelding.com/publica/joining.pdf

Here's another good one if you also work with Inconel 600 or 690:

http://www.specialmetalswelding.com/publica/Special%20Metals.pdf

Here's a good one on fabricating:

http://www.specialmetalswelding.com/publica/fab.pdf

I would suggest you check out the info in at least the first three .pdf's in order to arrive at an appropriate explanation as to why you're experiencing the difficulties you mentioned... I would then go to the following link to the selector guide, (One must register first) and when they approve your registration, you can log in and the link will match you with the appropriate filler metal specifically for your application for which I only have some info regarding the application itself so, your own query will most likely be more complete than my own since certain variable may need to be included in the selector guide that I may not have at my disposal currently. Here's the link to the selector:

http://www.specialmetalswelding.com/wpcselector/login.aspx?ReturnUrl=%2fwpcselector%2fdefault.aspx

Anywho, good luck with your hunt!

Respectfully,
Henry

By Kix

Date 07-21-2009 14:53

Hey man, thanks for the killer info! The CuNi piece is the piece with the bad undercutting problems so we butter that piece. The stainless does not undercut and transitions into the base material nicely. We're not supposed to use the CuNi filler for the CuNi to stainless weld seam, but we were just screwing around on some scrap and it welds slick with the CuNi rod.

By ssbn727 (*****)

Date 07-21-2009 23:30

I agree with you if that's what the WPS is calling for but, what about the suggestion from Lawrence and, making darn sure that your arc length be as tight as possible, and adjusting the work & travel angles just a tad to see if the undercut is eliminated on the Cu Ni side of the toe of the weld? I say this because if the procedure has already been proven to be acceptable without the amount of undercut you're experiencing currently then, it's gotta be just a matter of making some minor adjustments, and/or a matter of either cleaning the base metals better and the filler as Lawrence suggested earlier.

Btw, what is the measurement of undercut you're experiencing currently? Remember that your arc length needs to be as close to the work as possible, and make darn sure you're using the best possible work & travel angles. Are you depositing stringer beads, or are you weaving slightly?

Respectfully,
Henry

By Steve.E (**)

Date 07-21-2009 06:26

Hi Kix If you can , try a Argon Helium mix . I have always found it wets in and gives a better weld profile than straight argon on sluggish metals like monel.
Add plenty of that Ni you don't want the stainless mixing with the Cu Ni.

By Kix

Date 07-21-2009 14:55 Edited 08-13-2010 19:21

Our procedures are with straight argon, so we can't deviate. All of the procedures were qualified before my time.

By Lawrence (*****)

Date 07-21-2009 16:17 Edited 07-21-2009 16:26

Ray

I have two tiny little bits that may help make a difference.

Scotch brite or some other mild abrasive to the filler wire to take any oxide from the filler right before the weld.. It gets like a sausage skin with that stuff. (than wipe with solvent and lent free cloth) The less current it takes to melt the filler the better chance to avoid undercutting.. (smallest diameter filler will also help)

Secondly a more radical pointed tungsten tip as opposed to a long slim taper.

A common misconception is that the slimer and more pointy a tungsten is, the more control and penetration is achieved in fillets. The exact opposit is actually true.

So using the smallest diameter electrode that is practical, put a radical taper on the tip and if you have a diamond wheel even a very small blunt.. This will make your plasma cone a bit more conical (less bell shaped) and put more heat at the root or leading edge of the puddle rather than on the toes. (to help avoid undercut)

The exact tip shape on a tungsten is not often going to make a huge difference in normal production when manually doing GTAW, but yours is not a normal situation and every little bit of improved technique may make a difference.

By js55

Date 07-21-2009 16:41

Lawrence,
"Secondly a more radical pointed tungsten tip as opposed to a long slim taper."

This is true. I had forgotten this. It reduces the area for the actual cathode spot.

By Kix

Date 07-21-2009 16:43

I totally agree with you about the tungsten point and I teach that myself. I tell them that for walking the cup and putting in a pipe roots, it's ok to have that long taper, but for more penn and precision, you need to make it a steeper point. I'm smellin what your cooking and I have to tell ya that I did try that and still nothing. I will also tell you that I can compare the puddle reaction to having to much shielding gas blowing on the puddle and washing the toe of the CuNi piece uncontrolably. So, I reduced my shielding gas flow as much as I could to no avail. I'm going to try it on a different machine to rule out the posibility of air being sucked into the line somewhere inbetween the bottle and the torch cup. It's either that, or this process is a #$%! ;-)

By Steve.E (**)

Date 07-22-2009 06:36

Kix , often when welding Cu Ni alloys to dissimilar metals arc blow can be a real problem . From your description of the arc this could be your problem.
Suggestion ..... Put down a quick small fillet , it will still look crap but (sometimes) somehow it will seal of the problem . Then a second pass is usually a lot easier.
Don't you hate it when WPS,s are crap. Good luck.

By Kix

Date 07-22-2009 12:18

Thanks for the info Steve, but I've tried that as well. I'm at a loss in this whole deal. lol