TIG welding

[giro5]

On a recent thread we were putting our 2 cents in on various welding methods. I got a little curious and sent a email to the NHRA. The answer came back today.

Yes “ Top Fuel and Funny cars must be Tig Welded and the frames are heat treated.

This makes a lot of sense to me.

 

[danmcgee]

ARC welding is a very strong weld but reduces the temper of the item being welded alot. If you are welding a material that is heat treated or case hardened the TIG is the only way to get a deep penitration weld without greatly reduce the materials strength.

Dan

 

[scottessex]

Did you see the Nascar wreck the other weekend?
The driver (Carl Edwards I think) got out of the car and ran across the finish line after
the accident, the car was toast, but the welded cage held up, very impressive.

video

 

[giro5]

What I was trying to get across was after the frames are TIG welded in a jig, the whole assembly is put into an oven and re heat treated to bring weld areas up to the strength of the origional chrome moly and this also stress relieves the whole assembly. Keeping it in the jig keeps the frame from warping.


The pits special aircraft frames are also heat treated in their jig as a whole assembly after welding

The average home builder doesn't have the know how or oven to re heat treat a welded frame. But he can heat the joint up with a torch and let it air cool in still air. If one builds the frame in a jig and relieves the joints while the frame is still held by the jig then this offers some stress relief to the welded joint and prevents warping of the frame. But it does not make the material around the welded joint as strong as the origional heat treated chrome moly tubing. Regardless of which method is used for welding the welded joint is weaker than the origional and if not re heated as a whole there is a lot of stress in the joint. With TIG one would not get as much warping as with gas but I think the weld area would be under a lot of stress and be subject to failure.

I just think one is better off to do something to stress relief the welds than not to.

 

[JEFF TIPTON]

If I am not mistaken, most of the aircraft are welded up using 4130 that is not heat treated.

Leo Loudenslager would jig up an airframe and then cut the tach welds. He would then send the tubes to be heat treated. From there the tubes went to a machine shop where the tubes were ground down in a center less grinder, leaving I believe it was three inch's on each end untouched. The untouched ends allowed for the material loosing the heat treated strength while the fuselage was welded up.

I believe he saved around seven pounds of weight.

 

[Alan_Cheatham]

Most welded-tube aircraft fuselages are not heat treated and modern research has indicated post weld "stress relief" by the average homebuilder provides no benefit. The loss of strength from the welding process should be calculated and compensated for during the design process, even TIG welded aluminum can be used if the joint design compensates for the strength loss.
.

 

[docrob]

Whatever you do, don't try to stress relieve light tig welded structures (less than .120) with an gas torch. You'll set up stresses that you won't believe in the welds and the adjacent areas. My source on this is Miller and Lincoln, and all the professional welding and engineering schools. This idea of stress relieving came along about the time TIG came into common use, and we can't seem to kill it. It seems logical, but this is one of those times when logical and true are not the same thing. I'm sure I'll get flamed for this post by folk on the forum who still believe in it, but check with the professionals and see what they say.

Dr. Rob

 

[Edypaul]

Richard Finch ( the guy that updated AC4313 for the FAA. ) Does not recommend post stress relieving Tig welded 4130. He has written many books on performance welding . Its imposable to control the temperature with the torch.You will cause more damage then good. Correctly designed joints will make up for any strength lost in the weld area.

 

[Papa Smurf]

NASCAR frames and roll cages are MIG welded mild steel tubing.