Re: Tacking Al ***

In article <1125359435.217339.94730@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
"Vernon" <vtuck@xxxxxxxxxxxxx> wrote:

> cl,
>
> DC TIG welding in steel is normally done electrode negative. This puts
> about 70% of the heat into the steel.
>
> The problem with DC TIG welding aluminum is this. Because alunimum
> dissipates heat so fast you need all the heat you can get into the
> plate.
>
> However, the problem is, that molten aluminum forms a surface oxide
> that melts at a much higher temperature than the aluminum.
>
> When welding with negative polarity the arc is actually jumping from
> the electrode into the puddle. This pulls the oxide down widdit.
>
> You CAN DC TIG aluminum. But unfortunately, this has to be done
> electrode POSITIVE. As the arc jumps into the ELECTRODE it "parts the
> water" on the oxide.
>
> However, because 70% of the heat is going into the ELECTRODE you're not
> getting enough heat into the aluminum unless you crank the amperage way
> up there.
>
> And if you do THIS you will tend to fry your tungstens unless you use a
> really big one.
>
> Therefore, I believe the pros in here will confirm that while you can
> DC weld aluminum this has to be at high amperage with large electrodes.
> Therefore, you're limited to welding pretty darned thin material with
> a large electrode at high amperage.
>
> Correct me if I'm wrong folks. Otherwise, that's my story and I'm
> stickin' to it.
>
> V

You can also weld aluminum with DCEN, but it is only used on really
heavy plate.
You have to use a high helium mix or pure helium, and feed in massive
amounts of filler.
It has insane penetration, and the weld will look terrible on the
surface.

It is used for *** welding 1" aluminum plate using an automated TIG
machine, and a cold wire TIG feeder.
After the weld the bead is milled off.

I have done it on 1/2" plate and it is UGLY, but does work.

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