Ross,
My personal view is that it is not needed 99% of the time. The inside will "scale" and prevent much material loss.
Ross,
My personal view is that it is not needed 99% of the time. The inside will "scale" and prevent much material loss.
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.Originally Posted by 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.
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.
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.
Last edited by Tom Downey; 02-07-2014 at 12:59 AM.
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.
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