Re: Tacking Al ***

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

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