On 11/20/2009 05:27 PM, Jack wrote:
> A friend does argon for Aluminum, and a argon/co2 mix for most other. Only
> because
> argon is a pretty inert gas. But it is significantly more costly than CO2
> or the mix.
>> <> ... Jack
I agree with the cost issue, my 80 CuFt argon bottles cost me around
$40.00 each to refill the last time I took them in, and they last me
between 8, and 12 hrs of use each.
I'm currently renting a 25/75-C02/AR mix bottle, which I rarely use,
but when it's empty, I will be buying a couple of CO2 bottles, and
machining a custom mixer valve, to interface with my argon bottles.
That way, I can precisely meter the percentage of mix being used, and,
my overhead will be lower, as I won't need to rent/buy different ratio
mix bottles.
The type of gas used is determined by the type of material, it's
thickness, the type of filler wire being used, and the welding process.
GTAW (TIG) uses argon only, heliarc uses helium, GMAW (MIG) uses
argon, AR/CO2, or CO2.
FCAW (flux-cored MIG), and SMAW (Stick) uses no external shielding
gas, because the flux creates it's own.
You don't use just any old gas available, strong welds are the
cornerstone of good welding practices. Your welding wire will state
which type of shielding gas is preferred, but the entire welding
practice needs to be looked at as a whole.
Helium is mainly used for heliarc welding, and gives very good welds
that stand proud of the surface, and gives good penetration. It is
rarely used these days, mainly because of the exorbitant costs.
Argon causes a weld bead to flow out, and can stand slightly proud of
the surface, lay flat, or even depressed slightly below the surface,
with very good penetration. It is the only shielding gas used for TIG,
but is frequently used for MIG.
CO2 causes a weld bead to stand proud, giving a good fill, and decent
penetration, but suffers from porosity problems. It is rarely used, but
works ok on mild steel over 3/8".
AR/CO2 mix is a good compromise, as it allows a good buildup of a
weld, gives good penetration, and reduces the amount of porosity in the
weld. It is the most common shielding gas for MIG on mild steel over 1/4".
Flux-cored MIG is the most popular type of welding these days, but
TIG is the most versatile. You can pretty much TIG weld any type of
metal, including copper, brass, titanium, etc... Even highly reactive
metals like magnesium can be TIG'd with proper shielding. TIG is very
much similar to oxy-welding, only with a arc, instead of a flame, and it
doesn't suffer from warpage any where near as bad as oxy-welding.
There are several other welding procedures, and I've probably taken
this too far OT, but I consider welding to be a essential part of
machining, because I generally machine sub-assemblies, and then weld
them into finished parts.
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