MIG welding thin wall 4130

By rotor Date 04-29-2003 23:01

I have been TIG welding 4130 aircraft structures, mostly of .035 wall tubing for several years. The welds have to be neat, uniform and beyond doubt. I would like to do most of this work with MIG but I HAVE NO EXPERIECE WITH MIG. I would like someone who has done this before me to say it is possible to do high quality mig welding on 4130 thin wall tubing. Any recommendations as to gas mix, wire and so on would be most appreciated. Thanks

By airweld (**)

Date 04-30-2003 17:22

I have a shop specializing in airframe repairs and modifications and have some experience with the issue you bring up. I TIG weld most of the time because as you say, the task requires the highest quality possible. However I am not doing what would be considered "production" work. All the OEM airframes are MIG welded because in a "production" setting it has some serious economic advantages. MIG welding .035" wall 4130 consistently and reliably is much more of a challenge than TIG. It can be done, but I submit that in any situation other than "production", it is a second choice. I use MIG for non-structural things such as tabs and brackets where the speed and one-handed advantages are nice, also in places where access is limited and you can sneak a wire in easier than a TIG torch. Also where the material is thicker, say .058", and the results are more certain. The nicest MIG welded airframes I've seen are from the Kitfox people. They have developed a procedure that works.

My recommendation is a 75/25 gas with ER70S-6 wire. Some use a ER80S-D2 wire. And lots and lots of serious practice with critical destructive analysis to verify the process. Good luck, Scott.

By rotor Date 04-30-2003 19:28

Thank you Scott. I phoned the Miller factory today and the tech rep I talked to basically said MIG would not produce guaranteed good welds in 20 and 18 guage materials. He also stated (and gave the reasons why) the welds might look perfect but have poor penetration. He talked me out of buyng a MillerMatic 210. His advice: when I am too out of position to TIG then go O/A. I love TIG welding at the bench but it is no fun when out of position. Jerry

By airweld (**)

Date 05-01-2003 15:18

I use a CK Amptrol slider on the torch for all my TIG work. You can't use a foot pedal in airframe welding very well. The CK clips on to your existing torch and after trying them all, it is my favorite. Scott.