mig welding 4130 fuse

[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

[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.

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