J.Kahn wrote:
Blueskies wrote:
I am a rookie at this welding stuff, and plan to get plenty of
practice before building real airplane parts. That said, what do you
all think about heat treating after welding? I will be gas welding. Do
I really need 4130 rod, or can I use another high carbon steel rod?
How about 'S2' rod (only if not heat treating?)?

I have seen all sorts of discussion about this, but none of it is
really clear. I know some of you folks are indeed experts so I am
seeking your advise.

Thanks All!

Dan D.
Kalamazoo, MI


Do not use 4130 rod, which would require oven heat treatment of the
welds. RG45 mild steel rod is best for gas welding. Also don't use ER
rod, which is also mild steel but which is formulated for arc and works
poorly with gas.

Mild steel rod provides perfectly adequate joints because the weld
fillet is several times thicker than the parent metal, while at the same
time being softer material it provides better fatigue resistance.

When doing finish welding of clusters, as the last weld of a cluster is
complete and while the cluster area is still hot, go back over the
cluster to bring the entire cluster up to dull red (not orange) then let
it air cool with no drafts. This brings the zone reasonably close to
the original normalized state of the parent metal and is all that is
necessary.

The secret to not burning through on thin tube at the start is to get
the parent metal just under the melting point and drop a molten bead of
rod on the joint, then heat the bead until the adjacent metal melts and
the bead blends into the parent metal. Then start adding more rod and
moving the torch.

The rod plays a role in heat control. When an edge starts to burn away
back off just slightly and put the rod in the way of the flame which
limits the heat to the burnout and deposits rod there to fill it in at
the same time, then keep going. This is the way to deal with burnaways
without getting all flustered and stopping.

Be generous with rod feed to the puddle to keep it "full" as you advance
to avoid undercut edges. If you get the puddle nice and full looking
and feathered into the parent material all round the edge, then just
move the torch along while keeping the puddle full with rod, you will
get a beautiful textbook bead that looks almost like a TIG bead with
full penetration.

Gas is great because it is very forgiving of imperfect technique and you
can go back over mistakes if necessary.


John

Everything he said, with one addition. Practice on strips of thin sheet
stood on edge. You should be able to move down the edge, making a
rounded off fat bead that sort of sits as a bubble on tops. You should
pratice moving the torch in and out, getting the metal to melt but not
flow, and holding it there. Once you can do that, the thin walled tube
will be much easier.