"Leon Fisk" wrote in message
...
On Sun, 01 Jan 2006 09:47:16 -0600, Wayne Cook
wrote:

On Sat, 31 Dec 2005 21:38:27 -0800, "Harold and Susan Vordos"
wrote:


"Wayne Cook" wrote in message
. ..
On Sat, 31 Dec 2005 17:22:35 -0800, "Harold and Susan Vordos"
wrote:


Don't get the wrong impression, Wayne. I'm not hot, nor was I upset by
your
response. Just adding more comments to what is a good conversation and
a
learning experience for everyone that isn't familiar. I figure you and
I
have exchanged views long enough that we understand one another.

Agreed.

To quote what you said earlier:

I'm afraid I'll have to disagree at least a little in this
statement. I actually believe that 4140 was developed to be a high
strength material that could be welded reliably.

The material in question here is actually 4130, not 4140 or the others
(4340 is chrome nickel moly). 4130 is low enough in carbon that it
won't
heat treat hard enough to create the problems the others do, and *can*
be
welded reliably.

4130 was developed specifically for aircraft applications in the 1920s. It
was designed for reliable welding, good ductility, toughness, and strength,
generally in thin sections, primarily as tubing. It can take heavy shock
loads very well.

Initially it was expected to be welded with O/A. Through the 1930s, many
tubular aircraft spaceframes, including those for military aircraft, were
welded with stick -- yes, stick.

It has a quirk. It has a slow quench-hardening rate, approaching that of
air-hardening steels. So welds can wind up hard, with a transition to a
soft, more-or-less annealed heat-affected zone (HAZ), and then with another
transition to the parent metal, which usually is normalized and a bit harder
than annealed. It depends on weld thickness and welding method.

So there is a long-standing controversy over whether to "stress-relieve" the
welds. Most aircraft weldors today say not to, in sections thinner than
1/8".

FWIW I ran some informal, non-scientific tests on TIG-welded 4130, 3/4"
tubing with 0.065" wall thickness (16 guage) a few years ago. I smashed them
with a hammer on an anvil until they were flatter than a road-killed
'possum. The welds were the qualification samples my welding instructor had
performed for an Air Force airframe-repair re-certification, and they were
really good welds. It was an experiment/demonstration for the class.

They did not crack until I had them smashed about dead flat, and then the
cracks started on the surface and did not penetrate. The parent tubing was
beginning to crack at the same stage of smashing. So much for all of the
controversy, as far as I'm concerned.

--
Ed Huntress