Model Forum / Radio Controlled / Air Models / May 2004

Thanks for the informative posts Martin.
I remember the argon-arc process from a shipyard back in the early
1960's.  There was a welding set (similar to ordinary arc-welder) with
the addition of a large argon bottle. The argon was fed by a pipe to the
welding tool... this resembled a gun type nozzle. The arc would be
started and the gas would surround the area to be welded. Hand held
aluninium rods (like in oxy-acetylene welding) were used to feed extra
metal into the weld..... it was a long time ago but I remember the setup
produced very nice welds and was reputed to be a very bad system to
suffer a "flash" from. One guy ended up in hospital his eyes were so badly
affected.

I would have thought a small aluminium welding job could be done fairly
cheap by most small engineering firms and would be better than messing
about with alternatives.

Reg

"Heliarc" seems to be a registered trade name for TIG welding:

Advantage Fabricated Metals performs a number of welding processes.
The two most common welding processes we use include TIG, an acronym
for Tungsten Inert Gas welding and MIG, an acronym for Metal Inert Gas
welding. TIG is also referred to as GTAW (Gas Tungsten Arc Welding)
and Heliarc®. MIG also is referred to as GMAW (Gas Metal Arc Welding).
We also provide oxy-acetylene welding.

TIG welding is also called GTAW (Gas Tungsten Arc Welding) and
Heliarc® welding. Heliarc® was the trade name given to the process by
Linde's when it was introduced decades ago. The arc is started with a
tungsten electrode shielded by inert gas and filler rod is fed into
the weld puddle separately. The gas shielding that is required to
protect the molten metal from contamination and amperage are supplied
during the TIG welding operation.

TIG welding is a slower process than MIG, but it produces a more
precise weld and can be used at lower amperages for thinner metal and
can even be used on exotic metals. TIG welding is a commonly used high
quality welding process. TIG welding has become a popular choice of
welding processes when high quality, precision welding is required.
The TIG welding process requires more time to learn than MIG. It is
similar in technique to gas welding.

<http://www.advantagefabricatedmetals.com/tig-welding.html>

Gas tungsten arc welding (GTAW) had its beginnings from an idea by
C.L. Coffin to weld in a nonoxidizing gas atmosphere, which he
patented in 1890. The concept was further refined in the late 1920s by
H.M.Hobart, who used helium for shielding, and P.K. Devers, who used
argon. This process was ideal for welding magnesium and also for
welding stainless and aluminum. It was perfected in 1941, patented by
Meredith, and named Heliarc® welding. It was later licensed to Linde
Air Products, where the water-cooled torch was developed. The gas
tungsten arc welding process has become one of the most important.

The gas shielded metal arc welding (GMAW) process was successfully
developed at Battelle Memorial Institute in 1948 under the sponsorship
of the Air Reduction Company. This development utilized the gas
shielded arc similar to the gas tungsten arc, but replaced the
tungsten electrode with a continuously fed electrode wire. One of the
basic changes that made the process more usable was the small-diameter
electrode wires and the constant-voltage poser source. This principle
had been patented earlier by H.E. Kennedy. The initial introduction of
GMAW was for welding nonferrous metals. The high deposition rate led
users to try the process on steel. The cost of inert gas was
relatively high and the cost savings were not immediately available.

<http://www.welding.com/history_of_welding2.shtml>

Welding aluminum is done using two preferred methods, both of which
employ inert gases, pure argon, or a mix of argon with helium. Any
contamination of these gases causes oxidation of the weld, as Uebele
inadvertently demonstrated trying to repair a mag-wheel.

“Mag-wheels are not magnesium, you know. They’re aluminum,” Uebele
said. “I knew that, of course, but the weld kept turning black on me.
Finally, I checked the gas supply and discovered I was using an
argon-carbon dioxide mix. We use carbon dioxide for welding carbon
steel. To weld aluminum you’ve got to use pure argon. We don’t use
helium here. It’s too expensive. But they do mix argon and helium to
increase welding temperatures for thicker sections.” Argon is about
ten times the cost of carbon dioxide, commonly used to weld carbon
steel. Helium costs another $12 per cubic feet than argon.

...

During WW II, TIG welding was developed. Old timers also called this
process heliarc welding. The word heliarc was a trademark of Linde Air
Products. Like many known trade marks the name became generic for TIG
weld­ing. The Linde Air name was sold to the German subsidiary for $60
million, and Linde became known as Praxair in the U.S.  

Today, TIG and MIG welding are the two recommended options for welding
aluminum. TIG means tungsten-inert-gas, a shorter acronym for
gas-tungsten-­arc-welding (GTAW). The process uses a hand torch with a
non-consumable tungsten or tungsten alloy electrode to strike an arc.
Pure argon and/or helium, both non-flammable inert gases, provide the
shield around the weld to prevent weld contamination from oxides and
hydrogen absorption. A filler rod of aluminum is fed into the molten
weld, wherever filler is necessary.

<http://www.nomma.org/support/Welding%20Aluminum/Welding%20Aluminum.html>