Welding thin wall tube flush

admin

In our shop, we have a part where a very thin wall Inconel tube needs to be TIG welded flush into a hole in the side of a much larger, thicker tube. (The small tube is about 0.015" wall thickness and 0.070" OD, while the large tube is about 1.5" OD with a 0.090" wall thickness.) The hole for the small tube is about 1.5" down the length of the larger tube, so it's pretty fiddly to access.We currently stick the tube in just barely flush, weld it in place, and then spend some very tedious time EDMing the hole back open, which frequently fails and requires us to rework the part again.Any ideas of how we can keep the end of the tube from closing up during welding? We were going to try sticking a ceramic rod (https://www.mcmaster.com/87065K41/) through the hole, but we tried it under the TIG torch and it just explodes.
Reply:Can you use a different process for connection? Silver solder would probably provide more strength with flush fit, maintain tube dimensions, and require minimum finish on interior. Dremel work.If welding is required a Sacrificial brass bar could be inserted then ground away from inside the tube.
Reply:

Originally Posted by bulrich

In our shop, we have a part where a very thin wall Inconel tube needs to be TIG welded flush into a hole in the side of a much larger, thicker tube. (The small tube is about 0.015" wall thickness and 0.070" OD, while the large tube is about 1.5" OD with a 0.090" wall thickness.) The hole for the small tube is about 1.5" down the length of the larger tube, so it's pretty fiddly to access.We were going to try sticking a ceramic rod (https://www.mcmaster.com/87065K41/) through the hole, but we tried it under the TIG torch and it just explodes.
Reply:I have been told to gas (CO2 or Argon) in tube as you weld or solder. This would keep the tubing open.Never had job to try this one. Dave

Originally Posted by bulrich

In our shop, we have a part where a very thin wall Inconel tube needs to be TIG welded flush into a hole in the side of a much larger, thicker tube. (The small tube is about 0.015" wall thickness and 0.070" OD, while the large tube is about 1.5" OD with a 0.090" wall thickness.) The hole for the small tube is about 1.5" down the length of the larger tube, so it's pretty fiddly to access.We currently stick the tube in just barely flush, weld it in place, and then spend some very tedious time EDMing the hole back open, which frequently fails and requires us to rework the part again.Any ideas of how we can keep the end of the tube from closing up during welding? We were going to try sticking a ceramic rod (https://www.mcmaster.com/87065K41/) through the hole, but we tried it under the TIG torch and it just explodes.
Reply:When I do stainless sanitary tubing I use aluminum backer tubes, or rounds that are a few thousanths smaller than the stainless tube ID. You could also use copper, or graphite welding blocks, or rods. Aluminum is cheaper, and easy to machine. Maybe you could use some of the EDM carbons ?

Airco 250 ac/dc Heliwelder Square waveMiller Synchrowave 180 sdMiller Econo Twin HFLincoln 210 MPDayton 225 ac/dcVictor torchesSnap-On YA-212Lotos Cut60D
Reply:I think they are welding small tube from inside the 1.5 inch tube?
Reply:

Originally Posted by bulrich

Any ideas of how we can keep the end of the tube from closing up during welding? We were going to try sticking a ceramic rod (https://www.mcmaster.com/87065K41/) through the hole, but we tried it under the TIG torch and it just explodes.