Fuselage Welding

[astjp2]

Re: Fuselage Welding

The difference between a race car welder or industrial welder is his a$$ is not liable for the welds, as an a&p, mine is and that is why aircraft are pre and post heated in my shop.

If the part will be heat-treated after welding to achieve very high strength, a matching chemistry filler metal to the 4130 should be employed. Because of the relatively high carbon, a minimum of 200 degrees C, (400 degrees F) preheat and very slow cooling after welding should be used to avoid cracking. After welding, the part can be heated to 870 degrees C (1600 degrees F), quenched in oil or water then tempered back to say 370 degrees C (700 degrees F). A complex cycle, but this will result in a tensile strength of approximately 1380 MPa (200,000 psi). Since the weld is the same chemistry as the base material, it and the heat-affected zone will have the similar properties as the base material when heat-treated. All critical welds of this type should be inspected for internal soundness to assure they are free from cracks.

I have been an A&P for 23 years along with a full career in the aviation and racing industries; fabricating, machining, shaping, spinning, welding and heat treatment of structural metal components.

AWS certified in welding pressure vessels in the aircraft industry! Trained to Boeing, Douglas, Grumman and Lockheed (WPS) Welding Process Specification!

Welded chassis and pressure vessels for Toyota Racing Development to there engineering specs.

Please do not pre and post heat the aircraft structure no matter what process you use!!! No matter if it is mild steel 1020 & 1025, normalized 4130 or heat treated 4130!

All you are doing is inducing "shrinkage" into the structure!

As for A&P's, they should be smart enough to know when to rely on a welder in the industry, not some preconceived antiquated practice!

Attached is a picture of a few of the welding references I use in decision making about welding. None of these advise the practice of pre and post heat of thin wall tube aircraft structures!!!

[Guest]

Re: Fuselage Welding

Hi Tim,

We small old airplane folks don't normally deal with heat treated parts or heavy sections or high strength issues.

Most work is on non heat treated and is thin wall.

Splices, patches, assemblies and weldments that are light, small and Sut<95Ksi.

That changes the process requirement doesn't it?

Dave

[astjp2]

Re: Fuselage Welding

Nope, the requirement is the same, the prewar's did have a few pieces of 4130, so I will treat it all as 4130 to be safe, if you use the torch, you are 100% ok if the welds are sound, if you tig, pre and post heat to a dull red and air cool, even on .028 wall. Tig is so hot in such a small area that the weld wont crack, but it can in the transition area between the heat affected zone and the rest of the tube. I actually bought a victor j-40 and a J-28 and a guy on metal meet had adapters to use a meco midget tips on a victor. I really enjoy the 40 because I have carpal real bad and my hands cramp after a few hours. Tig is beautiful and approved for NHRA and NASCAR, but Torch is the approved method for aircraft, unless you have approved data that says otherwise.

Kit fox migged their fuselages and I have see 2 that have crashed/ground looped and both had major structural failures at or near cluster welds. Some will argue but I am going to limit my liability and stick with torch for most of my repairs. I have a tig but its 1970's technology with no foot or thumb control so I limit what I weld with it. Tim

[Guest]

Re: Fuselage Welding

Tim,

So why isn't this mentioned in 43.13-1B? (referring to TIG actually)

Dave

[rail]

Re: Fuselage Welding

Wow,

I would assume the gentleman that worked for Vultee during WW2 conveyed false information to me about welding!

I would assume the Boeing, Douglas, Grumman and Lockheed aircraft Welding Process Specifications are incorrect!

I would assume Miller and Lincoln has incorrect data!

I would assume the major manufacturers of 4130, chemistry's data is incorrect!

I guess all the drivers that walked away from a 190+ mph crash never happened!

I would assume the AWS Welding Metallurgy book is incorrect!

I would assume SFI specifications are incorrect! (Chassis Construction)

I would assume that one of the gentleman that consults for AWS taught me bogus practices!

I should not get up in the morning and go the the R&D shop and build jet aircraft the fly at 400+ knots!

All of this has just been a practice in vain, all of the training from the certified schools are invalid, my experience is plain out worthless!

I am a practical person with an ability to learn from every person that I come in contact with. All of this information has came from experience and practice not theory!


"Lets talk about thin wall "normalized 4130" tubing, not 4130 heat treatable tubing and plate!"

Charles

[rail]

Re: Fuselage Welding

Nope, the requirement is the same, the prewar's did have a few pieces of 4130, so I will treat it all as 4130 to be safe, if you use the torch, you are 100% ok if the welds are sound, if you tig, pre and post heat to a dull red and air cool, even on .028 wall. Tig is so hot in such a small area that the weld wont crack, but it can in the transition area between the heat affected zone and the rest of the tube. I actually bought a victor j-40 and a J-28 and a guy on metal meet had adapters to use a meco midget tips on a victor. I really enjoy the 40 because I have carpal real bad and my hands cramp after a few hours. Tig is beautiful and approved for NHRA and NASCAR, but Torch is the approved method for aircraft, unless you have approved data that says otherwise.

Kit fox migged their fuselages and I have see 2 that have crashed/ground looped and both had major structural failures at or near cluster welds. Some will argue but I am going to limit my liability and stick with torch for most of my repairs. I have a tig but its 1970's technology with no foot or thumb control so I limit what I weld with it. Tim

The base material and filler material melt at the same temps with Tig or gas.

I guess Boeing welds its components on a 57 million dollar aircraft with a gas torch?

Charles

[astjp2]

Re: Fuselage Welding

Boeing actually welded aluminum with a torch Oxy/Hydrogen until 1996 when the flux was considered toxic and not cost effective. Go look at the tin mans website, what he can do with a torch is amazing on Aluminum.

Dave, It used to be there, but with all things FAA, it might have fell by the wayside. I need to find my copy of cam 18 and see what it says. I have a friend that teaches high school and university aircraft welding and he told me to pre and post heat too. It seems that depending on what expert you talk to, will give you thier version....

[astjp2]

Re: Fuselage Welding

What is the size of the HAZ of tig compared to Torch?


The base material and filler material melt at the same temps with Tig or gas.

[rail]

Re: Fuselage Welding

Boeing actually welded aluminum with a torch Oxy/Hydrogen until 1996 when the flux was considered toxic and not cost effective. Go look at the tin mans website, what he can do with a torch is amazing on Aluminum.

Dave, It used to be there, but with all things FAA, it might have fell by the wayside. I need to find my copy of cam 18 and see what it says. I have a friend that teaches high school and university aircraft welding and he told me to pre and post heat too. It seems that depending on what expert you talk to, will give you thier version....

Aluminum pressure vessel fitting specimen before cleaning! Sectioned for penetration inspection. TIG process!

[rail]

Re: Fuselage Welding

Pre and post heat for tig, I would rather gas, less requirement for tight fitment of the joints. Tim

Please explain???

[FAT KID]

Re: Fuselage Welding

Holly cow this is getting good!

I think everyone is getting a little too defencive about the welding process they use.

If you like Oxy-Ace and prefer it great! Its an FAA acceptable method of welding.

If you like Tig welding and prefer it great! Its an FAA acceptable method of welding.

The point with both of these methods of aircraft welding should be knowing how to use either of them properly. One method is not better then the other. Both methods can be done incorrectly with disastrous results.

I would like to see a little more constructive discussion about this topic.

What method do you use? Why do you prefer it?
What filler rod are you using? Why do you prefer it?
If Oxy what pressures are you running? Why?
If Tig what kind of Machine are you using and how do you have it sent up?
What problems or mistakes have you made?
If heat treating how are you gauging temps?

I know i can Google and get the text book answers for all of these Questions but that is not what I'm after here. I have been welding for a while and I'm always interested in learning from other people. Lets help each other out here and not get into a pissing contest over who method is better.

[astjp2]

Re: Fuselage Welding

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Please explain???

The filler rod is typically larger and you can fill larger gaps easier from my experience. I have seen gaps of 3/16" filled on a piece of .035 tube and it looked ok and had good penetration.

[Guest]

Re: Fuselage Welding

Holly cow this is getting good!

I think everyone is getting a little too defencive about the welding process they use.

If you like Oxy-Ace and prefer it great! Its an FAA acceptable method of welding.

If you like Tig welding and prefer it great! Its an FAA acceptable method of welding.

The point with both of these methods of aircraft welding should be knowing how to use either of them properly. One method is not better then the other. Both methods can be done incorrectly with disastrous results.

I would like to see a little more constructive discussion about this topic.

What method do you use? Why do you prefer it?
What filler rod are you using? Why do you prefer it?
If Oxy what pressures are you running? Why?
If Tig what kind of Machine are you using and how do you have it sent up?
What problems or mistakes have you made?
If heat treating how are you gauging temps?

I know i can Google and get the text book answers for all of these Questions but that is not what I'm after here. I have been welding for a while and I'm always interested in learning from other people. Lets help each other out here and not get into a pissing contest over who method is better.

Hi FK,

The "pissing contest" ensued because of the post from Forrest that equated the use of electric welding with the death of the aircraft occupants. That was bad and untrue and will unfortunately influence many.

I and many others use electric welding for aircraft work.

I have used one of those small Lincoln 125 amp/110v MIG machines for doing the straight weld on two sides of a sleeve repair. Also for flat plates when I repaired wing strut attach fittings. Actually I think that both wing struts on my tcraft and part of the upper cabin section may be help on partiallty by mig welds. I had no success using it for curved joints like scarfs or fish mouths. Some folks can do it but I can't. The wire squirts out faster than I can move around the compound curves.

I now have a 255 amp mig machine but I find it difficult to use for even the straight welds I mentioned above. The 255 amp supply will pump out a lot of current and I don't like that on thin material, it can burn through. I wish that I had kept my 125 amp machine (both are/were Lincolns, red).

I don't use my gas set up much in the last 10 years. What I didn't like about gas was the hot gas/air blow back when welding in "corners" and the lack of control of heat. I have a Smith airline set up.

My favorite is my Miller Dynasty 200 dx (blue). I has every bell & whistle I can think of, I only use a few, a waste of money I suppose.

For all the a/c tube work I set the max amp at about 90-100 but I have thumb wheel on the torch so the actual amperage is adjusted as needed. Most often I use the ER70s-2 (same as AWS A5.18 in ac43.13-1b table 4-15)wire or rod .035 dia. Basically the same for TIG and MIG but one is on a roll. On some field approval repairs I did I had to use ER80d-d2 (same as AWS A5.28 in ac43.13-1b table 4-15) to make the bead meet some spec that I forgot now.

Usually 1/16 tungsten works well, I found that .040 is hard to use and maintain, it gets too hot and deforms (could be me). Usually I use thoriated or ceriated which ever I pick up first.

With all the TIG bells and whistles I end up only occasionally using the dc pulser and the ac freq control.

I like the pulser for heat control and it makes pretty beads, more or less it helps prevent me from making welds too hot and enforces a cool off period. Or it just may make me feel better. When I was repairing some wing struts about 10-15 years ago a welding engineer whom I consulted told me I should use TIG with a pulser on them. I got a TIG at that time but could not afford the pulser. The struts came out fine. A few years after that I was able to afford this machine but I find that one can do as well without the pulser as with it, but it just takes more effort. That's what I think.

I have found that the AC freq control, ie. setting say to 200 hz forces a narrow arc and bead on aluminum.

Dave.

[flyguy]

Re: Fuselage Welding

This is way out of my area of knowledge, but Finch states that 1600 Aerostar tubular 4130 engine mounts were TIG welded without post or preheat and there is no recorded instance of failure or cracking.

It would be interesting to read any reports of extensive metallurgical and strength testing of TIG welds on 4130 with and without thermal stress relief after welding.

Darryl

[Ray36048]

Re: Fuselage Welding

Man, after reading all of this, I am going to stick with JB weld.....(;f