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.

[Bill Berson]

Instead of just making comments "off the top of your head" perhaps some research is advised.
Plenty of OEM's use MIG, especially Kitplane companies. Any dedicated homebuilder with the proper quality equipment and training could duplicate the conditions and processes used in a typical Kitplane factory. It isn't a question of the process, only the skill and knowledge of the welder. And that applies to all welding methods.
As an inspector, I have been scanning for accident reports dealing with weld failure for 30 years. The only fatal weld failure incident I can recall was a crash that killed two EAA pilots in a Lycoming powered Wright Flyer replica a few years ago. In that case the NTSB provided detail photos of the failed TIG welds (lack of full penetration). I have not read or heard of any fatal MIG weld failures in any official NTSB report yet. Please report if you have anything.
It's sadly funny to read these comments. MIG can be ideal for many airframe parts. Maybe not all, but what is?
MIG is FAA approved, see AC 43.13

[Mike Switzer]

My comments were not "off the top of my head", they are based on my experience as a Professional Engineer, several years of which were in a fabrication shop where I was the primary engineer responsible for the design of welds. I never said you can't use a MIG, I said make sure it is inspected by a qualified individual, because inexperienced welders MAY make a weld that looks good on the surface but does not penetrate properly. We primarily used MIG and the guys did that every day & were very good, but some welds still did not pass inspection.

[akroflyer]

Perhaps you and the others "knowledgeable" in mig welding should tour the American champion aircraft factory and report back to us uneducated home builders. F.Y.I. I can't think of an OEM that doesn't use mig.

[Aaron Novak]

Perhaps you and the others "knowledgeable" in mig welding should tour the American champion aircraft factory and report back to us uneducated home builders. F.Y.I. I can't think of an OEM that doesn't use mig.

I have toured it. If you will notice I said "critical weldments". American Champion, Maule, Bellenca (back in the day) use a combination of Mig and Tig on their fuselages. Mig in non critical and Tig on critical. Heck there are fuselages that are arc welded that are just fine, however that was under factory controlled conditions. There are probably some small kit manufacturers that use all mig, and if their design analysis allows for it, that's fine.

Bill, you are incorrect. The skill of the welder has little to do with the resultant condition of the base metal with the mig process (providing a constant process schedule). It is all engineering control. Cold starts and laps can be somewhat controlled. That being said, a simple tee cluster welded in 2 passes might be ok, while the same welded in 3 or 4 might not be due to the difference in energy input vs. time.

There are actually numerous failures of both Tig and Mig, luckily most are caught before they cause a fatality and most end up as service bulletins or AD's. Again, not saying Mig cant work, just saying that for some pretty serious reasons, It has better applications than a homebuilt fuselage. The only reason people have ever given me to using it, has been speed, and cost of equipment. Pretty weak arguments considering the implications.

[akroflyer]

There are NO non critical weldments on an airframe, even if its just a bracket holding a data plate if it fails it could jam the controls. The skill of the welder has everything to do with good welds in homebuilding, and I have never heard of anyone making 2,3 or 4 passes on a T cluster. Every time I get in my plane (mig welded) I know my life depends on the welds, its worked for 25 years.

[Aaron Novak]

Sorry, should have said segments, not passes. What I am saying, is that with some materials and processes, the "skill" of the welder has less to do with structural integrity of the weld, than the process and method itself. 4130 and Mig are one of those combinations that can be real touchy. Now there are many designs out there that are heavily over engineered, and so the clusters can withstand some discontinuity and loss of ductility (good for homebuilding). Some can not. There is no dispute of the technical nature of welding, only as to a designs ability to cope with it. I.E. what works on a Whitman design may not on a Stolp due to different calcs used during design.

[eiclan]

Gday Chaps, As a fabricator of long standing , this discussion is very interesting. I am very experienced withe mig and oxy, tig not so much. As I intend to begin a build in the near future I will go with what I do best and that is the mig. The mig seems to be disparaged as unworkable with 4130 but while I have never welded it before I will do as I have always done and practice and set up the machine and get on with it.
I think the problem is , is that the mig is hard to do well. Unlike the tig or oxy, the mig wire speed is what it is while the weld is happening and the same with the amps. To do a competent weld on thin material requires skill and loose trousers, you need the ball room!
The tig and oxy by comparison are so much easier, the heat is easy to control, the input of filler wire much more controlled.
This is an argument that could go on forever and all I know is that I feel better with that mig handpiece in my hand than anything else, and yes as I cut and cope 4130 tube I will be practicing my skills and machine setup on the off cuts because I know my mig welds will always be better than my tig welds and the oxy is just too slow. Cheers Ross

[Aaron Novak]

Ross,
Very understandable that you want to do what you are comfortable with, and there is value in that. From a technical perspective the issue with mig is low total heat input, and so a rapid cooling rate through the transitional phase near the weld toes in the HAZ. Preheat temp can be a big influence here as it can help mitigate cold starts, and reduce the post weld cooling rate. Some caution should be used when building a design that was proven on O/A welding (or other), with another process. The mechanical properties can be quite different between processes. Designs with less fatigue margin typically fare better with a correctly used O/A or Tig process.

[Bill Berson]

Aaron, you have repeatedly stated that MIG is incompatible with 4130 for some reason. Can you please provide a document link to this?
Apparently, FAA, EAA and all the factories have not seen this document.
It sounds like you may not have ever actually welded a fuselage with MIG. Some can, some can't, just like some can't land a taildragger. Landing a taildragger takes specialized knowledge and skill and it's fun. Same with MIG, it's fun.
I don't have time to participate in every nonsensical MIG discussion on all these web forums.
But this is EAA. People at EAA get the facts and build airplanes with the same skills, materials, processes and tools as the factories.

[Aaron Novak]

Bill,
Go back and re-read my posts please. Notice my point of concern is limited to homebuilts, not factory. This is simply due to mig being the most difficult process to use effectively for this application and material, for the average homebuilder.

[Bill Berson]

Aaron, there is nothing about 4130 that makes it difficult to weld more than any other mild steel.
It's easier for some people (to weld) with a MIG gun because the right hand can hold the MIG gun and the left hand can steady the right hand. Much easier than TIG where both hands are suspended in open space and any slight jitter gets the tungsten contaminated. The warnings are in AC 43.13 about TIG and tungsten contamination. No warnings about MIG in AC 43.13
Like I said, I don't think you have attained the skills and used a MIG on aircraft structure enough to give an opinion. And I am getting bored.

[Aaron Novak]

Bill,
Yes there is, not that the person doing the welding would ever notice. I am talking material science here, not how "easy" it is to physically weld. Boy you get bored easy.....no wonder you like Mig :P

[Tom Downey]

There isn't any thing written in the 43.13 about MIG simply because it wasn't available to the general public when the 43.13 was written.
The TIG is the easiest to do by far, it is nothing but an electric torch and the motions are the same as oxy/ace torch. If you can weld with one you can weld with the other. It's just a case of practice.

[Tom Downey]

Bill,
I am talking material science here, not how "easy" it is to physically weld. :P That's he problem, over thinking the issue. JMHO.

[akroflyer]

I agree with Tom, way over thinking the issue, this discussion has gotten way off track. The original question was "is mig welding a 4130 airframe acceptable" the answer is yes! You don't have to have an engineering degree or posess any voo doo black magic skills to do it. No matter what welding system you use you can have good welds or bad welds it it all depends on the skills of the welder and an airplane project is not the place to learn how to weld.

[Bill Berson]

There isn't any thing written in the 43.13 about MIG simply because it wasn't available to the general public when the 43.13 was written.
The TIG is the easiest to do by far, it is nothing but an electric torch and the motions are the same as oxy/ace torch. If you can weld with one you can weld with the other. It's just a case of practice.
Try a more recent copy of AC 43.13
MIG is mentioned in both the 1988 and 1998 version (AC 43.13-1B)

[Aaron Novak]

I agree with Tom, way over thinking the issue, this discussion has gotten way off track. The original question was "is mig welding a 4130 airframe acceptable" the answer is yes! You don't have to have an engineering degree or posess any voo doo black magic skills to do it. No matter what welding system you use you can have good welds or bad welds it it all depends on the skills of the welder and an airplane project is not the place to learn how to weld.

True I can be accused of over thinking . But in life it has served me better than under thinking. Study welds and you will wish you hadnt. Ignorance can be bliss sometimes.

After thinking on this a bit, I think that this was perfectly on topic. The OP asked if he should trust a Mig welded homebuilt. The final verdict was.....nothing. Some would, some would not. If I did the welding and testing, I would trust it. If it was someone else, not a chance for the reasons mentioned.

[eiclan]

Now now chaps play nice, In repy to Aaron, I understand your concern reguarding the size of the haz but while the oxy haz large , the tig haz is small as well and usually requires warming up with the oxy to stress relieve the joint. I would say that the same prcedure for the mig would solve any stress issues.
I am a practical man and have been a metal tradesman here in Australia for 35 years and am able to see problems on that practical level but am open to all opinions. I welded thin SS fertilizer bins for a long time so have experience with thin materials. Cheers Ross

[Aaron Novak]

Now now chaps play nice, In repy to Aaron, I understand your concern reguarding the size of the haz but while the oxy haz large , the tig haz is small as well and usually requires warming up with the oxy to stress relieve the joint. I would say that the same prcedure for the mig would solve any stress issues.
I am a practical man and have been a metal tradesman here in Australia for 35 years and am able to see problems on that practical level but am open to all opinions. I welded thin SS fertilizer bins for a long time so have experience with thin materials. Cheers Ross

Hi Ross,
Sounds like you have a good idea what needs to be done. I would also suggest a preheat to help minimize cold starts, something in the 400-500F range might be a good start. This also helps to "feather" out the toe of the weld and reduce the stress concentration at that point.
Good Luck!!

[eiclan]

Hi Ross,
Sounds like you have a good idea what needs to be done. I would also suggest a preheat to help minimize cold starts, something in the 400-500F range might be a good start. This also helps to "feather" out the toe of the weld and reduce the stress concentration at that point.
Good Luck!!
Gday Aaron, Thanks for that suggestion about the preheat, l have a habit of touching off the wire just ahead of the start point and swifly moving back to give the pool time to heat up and then moving over the initial start point to get a consistent heat in the run. Quick question, what is you view on flooding argon through the tube to negate oxidisation on the inside. This was something I used to do when brazing refrig tubing though we used nitrogen. Cheers Ross

[Aaron Novak]

Ross,
My personal view is that it is not needed 99% of the time. The inside will "scale" and prevent much material loss.

[Tom Downey]

True I can be accused of over thinking . But in life it has served me better than under thinking. Study welds and you will wish you hadnt. Ignorance can be bliss sometimes.

After thinking on this a bit, I think that this was perfectly on topic. The OP asked if he should trust a Mig welded homebuilt. The final verdict was.....nothing. Some would, some would not. If I did the welding and testing, I would trust it. If it was someone else, not a chance for the reasons mentioned.
How can anyone judge the welds on the subject project without inspection ? every response here is an opinion of a method, any of which could be a viable method of welding the project when done properly. I've seen some very ugly welds that were safe as any done by professionals, I've seen some very pretty welds that weren't.

[Aaron Novak]

Tom,
Unfortunately there are conditions that cannot be inspected, and so we must rely upon the process and parameters used to determine weldment quality. In this particular instance there can be poor performance welds that would inspect just fine, and that is the single biggest drawback to this situation. There is no non-destructive test for microstructure, yet that is one of the biggest root causes of weld failure in 4130. Some welding technologies are more forgiving of process and technique, and so can be considered more of a "sure bet", if such a thing existed.

[Tom Downey]

Funny thing MIG, the auto and motorcycle industry uses it successfully every day.

Any weld can be inspected, it just a matter of how you want to do it, methods vary from full blown laboratory Xray to eddy current and dye. I have even gone as far as cutting the area open just to see how well the operator did. I'd have no problem using MIG to weld 4130 tube as long as the operator had the proper set up, which with MIG is vary apparent as the weld will not be right if it looks ugly spotty or rough in appearance.

OBTW I have a ATA in welding technology and a ATA in Marine technology and a A&P with IA privileges.

[Aaron Novak]

Funny thing MIG, the auto and motorcycle industry uses it successfully every day.

Any weld can be inspected, it just a matter of how you want to do it, methods vary from full blown laboratory Xray to eddy current and dye. I have even gone as far as cutting the area open just to see how well the operator did. I'd have no problem using MIG to weld 4130 tube as long as the operator had the proper set up, which with MIG is vary apparent as the weld will not be right if it looks ugly spotty or rough in appearance.

OBTW I have a ATA in welding technology and a ATA in Marine technology and a A&P with IA privileges.

Tom,
Xray, ultrasonic, DP, MP, etc do not tell you base metal condition. I do those frequently. You can have 2 identical testing welds on 4130, with one having 10x the fatigue life of the other. If you are ever near Oshkosh I invite you to see where we do weld failure analysis and other metallurgical testing, I bet you would get a lot out of it.

[Tom Downey]

The next time you are near here I'll show you how to lay down a weldment 2" wide and 1.5" deep connecting two top deck plates and the frame member below in one pass with a 650 amp flux core wire feeder in one pass and have the weld smooth enough for the flux to be swept away with a broom. Robot welders are a wonderful thing, so are MIG welders, when they are set up and used by competent users they can do any thing most other methods can. we use the MIG type welders for aluminum (CobraMatic) on boats, and the flux core on steel deck plates, and they do the job in 1/10 the time producing X-ray quality joints required by DOT and the coast guard.

I'm outta here before some one blames me for over thinking this.

[pacerpilot]

Aaron, you are correct sir. Gas and Tig form a nice big HAZ which allows stress relief and also allows the material to normalize (gas is better). You also don't get the embrittlement that occurs with MIG. I've welded with most processes for 40 years. MIG just isn't a process that can be trusted in your garage on an airframe without significant controls. My question is this: why would someone want to use a questionable process when the proven process is cheaper and more accessible? I've got a $1500 MIG rig in my garage, but I use my $200 gas rig on my airplane.