Welding thin wall tube flush

[BillE.Dee]

Could you be more specific? What do you mean?

I've got no idea what your budget is or how much work you have to do. Look up ultrasonic welding and you might find what your looking for. We've used ultra sonic systems to install parts that have interference fits. But there is ultrasonic welders too.

[shovelon]

This seems like an interesting option. You mention residual graphite -- is this just on the surface of the weld (not mixed in the weld itself)? This is an aerospace application, so I'm going to get a lot of questions in engineering review.

Surface carbon is dissolved by passivation. Don't know if any dissolved into the weld.

[smithdoor]

At point more detail on part is need and how many are need too

Dave

I've got no idea what your budget is or how much work you have to do. Look up ultrasonic welding and you might find what your looking for. We've used ultra sonic systems to install parts that have interference fits. But there is ultrasonic welders too.

[bulrich]

Are you looking for a perfect seal. I would be interested to know how you weld inside a 1.5" inch tube? Seems like it would be difficult to see?

Yes, it needs to be liquid tight up to some pressure -- I'd have to look up how high. And yes, it is quite difficult to see. Our poor welders put up with a lot.

[bulrich]

So you're welding the .070" tube to the OD of the 1.5" tube? Why is that "fiddly" to access?

The ID of both tubes has to be purged with argon then it shouldn't close up unless excessive heat is used,
then I would expect you'd blow a hole in the thin tube anyway.

Can you post a photo of your setup?

Alas, I can't post a picture -- corporate intellectual property, etc. It's "fiddly" to access because we only have access to the ID of the large tube, and the welders have to reach in about an inch with the torch to get access.

Our argon purge isn't high enough pressure to keep from closing up the end of the tube.

FWIW, we have no access to the OD of the large tube, and can't see any of the small tube at all except for where it comes flush with the ID wall of the larger tube.

[bulrich]

Attachment 1732727

Not quite. There is no access to the outside of the large tube, and the small tube only protrudes slightly into the large tube.

[bulrich]

So it turns out when we tried silver soldering in the past, it was very difficult to get a good seal all the way around the small tube, since it's basically impossible to see what you're doing while you're torching it, and difficult to inspect except with a pressure test.

We're going to try silver solder / torch brazing again (as tapwelder suggested very early on), and toy with how we're applying the alloy to see if we can get good wetting all the way around.

Thanks everyone for your input! I've certainly learned a lot, and even if it doesn't apply to this part, it may very well help with some other part in the future.

[Kevin Morin]

bulrich, is this an application where a very small induction heating element might be configured into an L or J and reach into the area around the joint inside the larger tube? If some very fine wire/solder were rolled into a circle, then dipped in flux- and laid into the two tube edges- end of the smaller tube and inside edge of opening in larger dia- then the small induction tip held over that area- it's likely the joints would seal very repeatedly without needing to get a torch inside?

I looked on utube and there seem to be many vendors of all sorts of induction elements- including some that are at the end of a fairly fine tip? So, if you could bend the heating element into a shape that allowed access of near access to the intersecting edges of the two elements- it seems this method of soldering is very widely used - judging by the number and variety of videos?

Since the induction heat controls could be 'tuned' to a pulse of power- it seems like you could tune/adjust the heat (net BTU) and duration (het on time) and end up with a workable solution with no or very few rework pieces?

Just another thought on how you might solder this joint?

Cheers,
Kevin Morin
Kenai, AK

[bulrich]

bulrich, is this an application where a very small induction heating element might be configured into an L or J and reach into the area around the joint inside the larger tube? If some very fine wire/solder were rolled into a circle, then dipped in flux- and laid into the two tube edges- end of the smaller tube and inside edge of opening in larger dia- then the small induction tip held over that area- it's likely the joints would seal very repeatedly without needing to get a torch inside?

I looked on utube and there seem to be many vendors of all sorts of induction elements- including some that are at the end of a fairly fine tip? So, if you could bend the heating element into a shape that allowed access of near access to the intersecting edges of the two elements- it seems this method of soldering is very widely used - judging by the number and variety of videos?

Since the induction heat controls could be 'tuned' to a pulse of power- it seems like you could tune/adjust the heat (net BTU) and duration (het on time) and end up with a workable solution with no or very few rework pieces?

Just another thought on how you might solder this joint?

Cheers,
Kevin Morin
Kenai, AK

Ironically, we were just discussing if this would be possible, without realizing that it was already a pretty common process. Thanks for pointing me in this direction!

[danielplace]

Furnace brazing without the furnace. Bring the heat right to the joint. Cool stuff.