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MIG Welding AL

Subject: MIG Welding AL
Date: Thu, 28 Oct 1999 20:56:07 -0700
I haven't used an SP-170, but I do have significant experience with both MIG and
TIG welding aluminum, so might be able to provide some useful advice. First be
sure that your base metal alloy is weldable and that you have a reasonable
filler metal for the base alloy. Since you're feeding the wire through a gun
cable, I suspect that you're running 5356 wire, which will work OK with most
aluminum alloys, but will have problems with 1100 series (i.e. close to pure
AL). 4043 wire is (in my experience) a bit easier to weld with (though again not
on 1100 series), but won't feed as well through a MIG cable. 4043 is commonly
used in MIG spool guns, and for TIG welding.

If you're sure your filler metal is compatible with your weldable base alloy,
then be sure that your base metal is very clean. Start by wiping down the
surfaces with acetone. Follow that by brushing with a stainless steel wire brush
that has not been used for anything other than brushing clean aluminum. The
acetone should remove any oils from the surface, and the wire brush will remove
the layer of aluminum oxide from the surface. Clean your gun tip of any
"anti-spatter" dip or spray you might use when welding steel. I don't know of
any of those product suitable for use when welding AL. You want everything as
clean as is practical.

Someone questioned the welding polarity you were using. You should be set up for
DCEP ("DC reverse"), which is the same as running steel hard wire with shielding
gas. The only time MIG is run DCEN ("DC straight") is when running flux core
wire. Set the gas flow at about 25-30 cf/hr. Aluminum MIG welding is generally
done at significantly higher torch travel speeds than steel welding, with the
machine settings "hot" - i.e. high voltage and high wire feed speeds when
compared to steel. AL welding is mostly done in spray-arc mode as opposed to
short-arc that you're most likely used to from welding steel. Lincoln should be
able to provide you with starting point settings, but in general increase the
heat until you're melting through quickly and back it off a little. You don't
state what wire diameter you're running, but welding 1/8", .035" wire should be
run at around 350 inches/min. To measure this clip the wire flush with the tip,
point the gun away from any grounded surface, pull the trigger for 6 seconds and
multiply the resulting length of wire by 10. In increasing your machine settings
I recommend increasing the wire speed first, and then increasing the voltage. If
you crank the voltage too high for your wire speed you'll melt the wire back to
the tip and ruin the tip. I find that on aluminum I run a lot more "stick out"
than with steel - i.e. hold the gun further from the work. Remember that the
voltage sets the arc length, and with the voltage cranked up you'll have to hold
the gun further from the work or you'll once again burn the wire back to the
tip. Particularly on relatively thin AL (e.g. 1/8" and under) I always try to
back up the joint - clamp a piece of 1/4" or thicker AL to the back side of the
joint to  control burn through. On 1/8" I would not bevel the edge. 

Harry Phinney

> -----Original Message-----
> From: Dave Desilets - Sun BOS Hardware [SMTP:Dave.Desilets@East.Sun.COM]
> Sent: Thursday, October 28, 1999 11:48 AM
> To:;
> Cc:;; Dave.Desilets@East.Sun.COM
> Subject:      Re: [Fwd: [rr MIG - what to  get?
> As long as we're on the subject of welders.....
> I have a Lincoln SP-170, which is the 220 Amp version.
> I have had one very difficult time trying to weld Aluminum.
> I've got the Aluminum kit installed.
> Fresh tank of Argon Gas,
> Kept the torch lead straight as possible.
> Tried more feed/less feed
> Tried more gas/less gas
> Tried more amps/less amps.
> Trier more stick-out/less stick-out.
> Varied all of the above, and almost totally covered
> a 2'square piece of aluminum with weld, practicing.
> Nothing looked good or continuous.
> Tried butting up a couple of beveled 1/8" plates, and
> the welds basically looked like crap.
> Could not get the right technique/combination to produce
> a good weld.
> I can lay a good bead on mild steel, but Aluminum apparently,is
> an entirely different beast.
> Has anyone on the list tried running aluminum wire with
> success on a Lincoln???
> Any tips would be greatly appreciated.
> Dave

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