[mech engineer hat=on]

Normalization is a proper term for heat stress relieving.

It is not a stretch to say that all of the experimental tube airframes are mig welded. (ie: Kitfox, Avid, Just, etc, etc.) Low carbon wire is usually used. This could be the reason it's not used in certified planes.

I don't know why mig welding would cause magnetic problems and tig would not. Both use an electric arc to induce heat.

[hat off]

Av8r3400 wrote:I don't know why mig welding would cause magnetic problems and tig would not. Both use an electric arc to induce heat.

I think the distinction is between electric welding methods(MIG, TIG, stick) vs "Gas" welding, which is oxy/acetylene torch and filler rod.

"MIG" or GMAW has several different transfer modes that can be used for welding.. use the wrong one and you have a very good chance for cold lap, or lack of fusion. If you know what your doing, you can make perfectly acceptable and mechanicaly sound welds.

"TIG" or GTAW beautiful welds in the hands of a properly qualified welder. The heat affected zone can be VERY small and it can like to crack. If you pre and post heat the weld AREA you wont have any issues. It takes alot of practice to feed the wire and get your heat input right to make that visually perfect weld.

Oxy/ Acetelene welding or "gas" welding. The oldest tried and true (and cheapest set up) for aircraft welding. You can teach a monkey to do it in 30 minutes. The heat affected zone is much larger than tig, but it still takes a hand to learn to feed the wire right.

When you say "ARC" welding, most people think using a stick rod. Not a great way to weld up very thin tubes.

I am with Larry thinking that MIG welding should not introduce anymore magnetism than TIG would. Alot more magnetism is introduced by grinding and wire wheeling than by the actual welding.

Neat video. I was just flying with a guy a few days ago that said "I hate *%$*# Maules". I said I love 'em. They are an American rag and tube/aluminum taildragger still being built in Georgia by dedicated people powered with Lycoming engines, what's not to like? I feel like all the current American aircraft mfgr's put out a good product. As far as welding, I have been welding aircraft structures 33 years. It's a polite discussion here but there are many experts and welding wars on other forums. Kitfox,Rans and Maule etc have the MIG welding of 4130 airframes down pretty good. If you sandblast off that nice powdercoating they don't look all that nice but they are safe.

Here's Argon welding

That is GTAW or Gas Tungsten Arc Welding comonly called TIG (Tungsten Inert Gas) The argon is just the sheilding gas used.

The videos are pretty cool, but you have to remember the narator does not know crap about what they are talking about, just reading a script..

akavid is right.

4130 can weld beautifully with any technique. I either use gas or TIG on thin wall after a preheat with a torch and then stress relieve it after. MIG is really fast, but it can be messier. There are some differences when welding smaller,alignment critical stuff where intense heat control favors TIG, or metal phase characteristics are affected too much from sustained heat input from gas.

Many tube and fabric planes didn't bother with the sacred 4130 stuff...the truss designs were often not strength limited, but stiffness limited, and 4130 does not buy you anything for stiffness over mild steel. My old Piper's fuselage was largely made out of mild steel.