mig welding 4130 fuse

[hvacrbert]

i have decided to build a legal eagle xl but before starting I looked around for an unfinished project well I found one however I am not too sure about it. the fuse has been mig welded I have been told that the heat from mig welding cause the 4130 to lose strength. there are other concerns about this opportunity I will state them here although maybe I need to start a different thread after I figure out if the fuse is usable for me. included is a Teledyne 042 engine and prop. I am pretty sure I will go with 1/2 vw as designed by mr milHolland, the last issue is it also comes with alum. delta honcho wings I would be more comfortable with a metal wing as It would fit my skillset better than wood however I saw a post on here that stated roll control was sluggish anyone here with experience with these wings on the le xl thank you

[martymayes]

If the welds pass a visual inspection, I wouldn't worry about it. If this is the right deal for you, don't let it get away.

[akroflyer]

Nothing wrong with mig welding 4130

[hvacrbert]

thank you gentlemen i should call him back then as the cost of the whole package is probably not much more than i would have paid for just the steel for the fuse

[Charlie Becker]

Just to add to the MIG answer, here was a Q&A I wrote up a number of years ago but the answer still stands:

• Q. In most of the articles I see in Sport Aviation, I see builders using gas to weld tube for aircraft fuselages. I recently bought a Lincoln 220V wire-feed MIG welder for a business venture with the thought that, at some point in the future, I would be able to use it to build other projects, one of which might be an airplane. It will accept a gas bottle for shielding although I have not used that option yet. Can this type of welder be used to weld tubing in an aircraft fuselage?
• ​Yes, a properly welded MIG (GMAW) joint will be more than acceptable for an aircraft fuselage. However, amateur builders need to think about more than just the strength of a properly welded joint. MIG welding's primary advantage over TIG (GTAW) or oxyacetylene "gas" (OFW) welding is speed. From a production standpoint, speed makes MIG the preferred welding process. Speed isn't as important to homebuilders compared to price and ease of attaining and maintaining proficiency.
  MIG is more expensive than gas welding but about half the price of TIG. From a cost standpoint, MIG sounds like a reasonable option, and it's probably the easiest method to learn for welding thick, flat material (just pull the trigger and go!). But for a fuselage, you need to weld thin wall tubing, and this is probably the most difficult use of the MIG process. Even experienced, professional MIG welders have difficulty the first time they attempt to MIG weld thin wall tubing.
  For builders learning to weld so they can build their fuselages, learning and maintaining TIG or gas welding proficiency is easier than MIG. This is one reason why most of the articles mention these welding methods. However, because you'll be using MIG regularly in your business, all it will take is practice to be able to transition to MIG welding thin wall tubing.
  In researching this answer, we spoke with Richard Finch, an aerospace engineer, Technical Counselor, Flight Advisor, and author of Performance Welding and Welder's Handbook (both available from EAA at 800/843-3612), and he agreed with the above. "The only thing that I would add is that most of the kit-plane manufacturers use MIG for speed and accuracy, but they practice, practice, practice before they turn a welder loose on a salable MIG weldment." For detailed information about the pros and cons of welding thin wall 4130 tubing with MIG, see Performance Welding.

[Mike Switzer]

Just to add my 2 cents - it is very easy to make a mig weld that looks good on the surface but does not have good penetration. If you are buying something done by someone else I would have it inspected by someone who is experienced in inspecting mig welds. (most fabricating shops have a weld inspector).

I have a mig, and I have gas welding equipment. I will be using gas on my fuselage. I find it is much easier to make a good weld with gas if you are not welding frequently enough to stay in practice.

[Bill Berson]

Just to add my 2 cents - it is very easy to make a mig weld that looks good on the surface but does not have good penetration. If you are buying something done by someone else I would have it inspected by someone who is experienced in inspecting mig welds. (most fabricating shops have a weld inspector).

I have a mig, and I have gas welding equipment. I will be using gas on my fuselage. I find it is much easier to make a good weld with gas if you are not welding frequently enough to stay in practice.

I think you may be thinking of TIG.
A TIG welder can lay down a beautiful looking weld that lacks penetration.
Not so with MIG, from my years of experience. To get a nice looking weld with proper flow out with MIG takes lots of heat and this results in full penetration, especially on thin tubes.
Actually, the main problem for beginners with MIG is a tendency to burn through.
Skilled MIG welders can control this excess heat with trigger pulsing. A quality machine is also needed in my opinion. Not big, just good quality like a Millermatic 135 for example.
It is best to avoid broad generalizations (like I did here) about welding, because it all depends on the particular welders skill, his equipment, the metal thickness and alloy, position.....

[Mike Switzer]

I have seen the same problems with a MIG. Someone scared of getting too hot gets it hot enough it looks good on the front side but it doesn't penetrate. At any rate I would have someone inspect it that knows what they are looking at.

[pacerpilot]

I'm with Mike on this subject. MIG is a production process and is used for speed not strength. It can be used, but you'd need to verify the process and do lots of samples for DT/NDT to be sure your settings are right. I've encountered many MIG welds that look beautiful only to have the joint separate leaving only son much as a heat mark on the parent material. TIG or gas is the only way to go. You are forced to establish a melted puddle with gas and TIG prior to adding filler thereby nearly ensuring penetration and proper deposition. I really like MIG (I've been welding with it for over 30 years) but I'll use gas or TIG on an airframe.

[Aaron Novak]

From a pure engineering standpoint, Mig is probably the last process you would want to use on 4130 in an uncontrolled situation as you have with a homebuilt. 4130 is VERY sensitive to cooling rate, with too rapid of a cooling causing a microstructure to form in the HAZ that has a very low fatigue limit. Mig welding by its nature can lead to some extremely fast cooling rates, and therefore low fatigue life. In production the weldments are controlled and consistent, with previous weldments OF EACH CLUSTER being tested. Just because a setting worked on one cluster, does not mean it will work on another. Weld appearance means nothing. Add to this cold starts, an cold laps.......and it does not paint a pretty picture for Mig. Unfortunately to the uneducated on the subject, it seems like a really good way to go, and indeed Mig has its place, however I (and many others knowledgeable on the subject) feel that 4130 welding (non production ), is not that place. Off the top of my head I cannont think of an OEM that uses Mig for critical weldments on 4130.