Welding techniques for 4130?

First let me correct something in my post (there I go, reading my own
posts again). For filler I meant to say "ER70S-6, -3, or -2..."

Let me make a comment on your experience with the EAA forum. I am sorry
to hear that there was conflicting info given out at the forum. Yes,
there should be consensus between those instructing as to what basic
information will be conveyed.

Cracking a valve for a split second before mounting a regulator is
standard practice taught at all welding technical colleges and trade
schools whose curriculum I have seen. It clears trash, dust and bugs out
of the valve nozzle preventing then from entering and damaging the
regulator.

Let me make a point about why mild steel filler works and why you are
not sacrificing any strength. WHen welding with mild steel filler on
4130 there is ever so slight add-mixture taking place as some of the
alloying ingredients migrate in the molten puddle from the 4130 to the
mild steel filler. So the filler is a bit stronger and there is virally
no decrease in the strength of the tube. But, this really makes no
difference. If there were no add-mixture taking place the strength of
the weld would STILL exceed that of the tube.

Think about the fact that the tube you are welding usually has a wall
thickness of .065" or less...much less for the most part as most
fuselage tubes are in the range of .035" to .045". Even with TIG it is
not likely that you are going to make a welded bead (fillet)that is
smaller than 1/8" across the face. That makes the welded leg aprox.
..35". So under destructive load you have .35" worth of weld pulling
against .035" worth of tube wall. The failure is going to occur in the
tube. The mild steel may be ONLY 60,000 psi strength material while the
4130 tube is 100,000 psi, but for the amount of weld present, the weld
is many times stronger than the tube.

"Matthew P. Cummings" wrote:

On Wed, 03 Sep 2003 06:10:26 +0000, Bruce A. Frank wrote:

This is really getting some odd information presented here. The filler
rod intended for use with 4130 tube used to build a fuselage is MILD
STEEL. The weld is stronger than the tube even though welded with MILD

I agree it's odd, and I won't be doing as the volunteer at the EAA welding
forum suggested because everything he said flies in the face of what the
rest of the world is doing. He was the guy who said to crack the valves.
I don't have an opinion one way or another on it, but the other guy said
to not crack it at all, and by that he meant a quick open and shutting of
the valve. He claimed that the Acetylene might blow up if you crack it
and the other problem was you released that gas in the shop you are going
to weld in. I can't disagree with that however.

Honestly, I was very disappointed in the quality of the welding forum and
thought that if the EAA puts their name on it, then they should have some
sort of standardization to go with it. To me, it was a joke and not worth
the time spent there. How is a new user supposed to reconcile the polar
opposite information presented in one forum? That's why I didn't enjoy
the forum, one guy says do this, another says don't. One says use this
rod, the others say don't every use it unless it's in a motor mount. One
says stress relive, the other says that will CAUSE more problems than it
solves. In the end, everything I was taught about welding was said to be
wrong by the volunteer giving the presentation, yet, what I was taught is
what is still currently being taught and held as acceptable. If the
volunteer had facts to back him up it would have been nice, but take this
bit of information he presented. He claimed that why would you weld 4130
tubing and use something like mild steel for the filler thus causing the
4130 to loose tensile strength. So he said you MUST use 4130 in order to
retain the tensile strength of the tubing, ignoring the fact that the act
of welding lowers the strength. Based on his mistakes I did not learn
much since how can I trust an instructor when they present as fact
falsehoods? He also gave out smith numbers for the tips to use for
welding, but the problem was Smith does not use a number system like he
said, so a newbie would not know what to ask for because they would have
to find a compatible source. I.e. a 0 in one brand might not be a 0 in
another. How would a new user know there is no standardization in tip
sizes, especially when he said Smith has this number and they don't use
those numbers for the body he described?

If the EAA can't put on a unified front then they should not be involved
in teaching something like welding. They should take a page from other
groups which have a manual for the instructors, the instructors then go by
it and do not add their own information to it thus presenting a unified
classroom setting without causing confusion.

My desire would be for Budd to add a hands on to his presentation, he did
a respectable job getting the information across and did not have the
problem of giving conflicting information.

So, here's my plan. I'm using a rod like RG 45 for welding my 4130
tubing with my Smith AW1a torch.

--
Bruce A. Frank, Editor "Ford 3.8/4.2L Engine and V-6 STOL
Homebuilt Aircraft Newsletter"
| Publishing interesting material|
| on all aspects of alternative |
| engines and homebuilt aircraft.|
*------------------------------**----*
\(-o-)/ AIRCRAFT PROJECTS CO.
\___/ Manufacturing parts & pieces
/ \ for homebuilt aircraft,
0 0 TIG welding

While trying to find the time to finish mine.