Welding really cruddy aluminum casting

[Tobias-B]

So, "Oil Me", the #3 Ettco tapping head, had a cracked boss that forms the cup that holds the 'don't spin' rod.

It's now cracked and slagged- there is SO MUCH contamination in the aluminum that I can't
get a decent puddle to form with the tig (Miller 180 transformer) for long before it opens up more inclusions.
At first, I thought it was oil in the cracks, so I cut the crack open. Nope- just keeps getting uglier,
no matter how much I try to flow, clean, reflow, clean again. Stainless brush, acetone, swearing, filing, brushing again...

I'm starting to see why my friends who actually CAN weld well don't like touching older castings.

Anything else to try before I cut the boss off, file it smooth, and make a holder that attaches to the case screws?

I've never run into aluminum that's so... poor before. I can't even 'goober it over-' the inclusions break up the puddle.

I actually went back and made a few test beads on some 'scrap' just
to prove it wasn't me, or the machine, or something in the air...

I'm tempted to preheat with the tig, then pour mig wire into it just to fill the holes.
But I'm not sure that'd even... stick.

thanks
t

[danlb]

My experience mirrors yours when repairing castings made of an unknown alloy. I have more often than not melted the part as I chased inclusions.

But... I've been able to clean up much of the mess with a file, leaving the inclusions in place. In most cases that actually worked (at least short term) simply because there was more material due to the bead.

Dan

[fjk]

How about something like low temp silver solder?
or, my favorite when faced with challenges like this, something like JB Weld? (JB Weld is a curse word among the welding elite ... but it has its uses!)

[Bob La Londe]

Is the arc an off color like... pink?

[nickel-city-fab]

I like to use soap-water with a green scrubbie on dirty alu jobs. The SS wire brush would work too. Castings are always problematic like that -- clean with the soap-water and scrub the weld area. Only weld a little dab at a time, the size of a normal tack. Let it cool, clean it off with the soap-water, put another dab of weld. Been there, done that. I think you'll be surprised how much easier the soap-water is, I usually just let the heat from the piece evaporate it and start the arc right back up again. The soap-water seems to act like a mild flux that helps the aluminum, "float" the impurities etc to the surface of the puddle. It also breaks up the surface oxides before the TIG finishes the job.

[BigMike782]

My experience is if you are getting area that vaporize it has a fair amount of zinc. The more zinc the tougher it is to weld. I generally will puddle an are, brush then add filler until I can get enough clean material to run a bead. Part of you issue is horsepower, 180 amps is not helping your cause. If you think it is oil soaked run the arc over the area to heat it until the oil smokes out, stop, brush then heat some more. Eventually you will get to a point where you will get a clean puddle and can run a bead.
It is possible that it is magnesium but I doubt that.

[markx]

Would it be possible to separate and heat the casting part in an oven to vaporize most contaminants that have collected in the pores? Below the melting point of the part obviously Perhaps it would make it easier to get a functional puddle going.

[Tobias-B]

Yeah, Bob, and Mike, it's funny you say that- I tried several different filler rods,
thought 'huh, the arc on the filler looks odd, maybe that's not the right 'generic' filler
and THEN noticed that the arc on the casting was 'off color'. NOT the rod, which at the time, looked blue- green.

To make matters even worse, I have a 'older' version of this welder that doesn't let me change the A/C waveform- I thought,
'wait, it's an SD, isn't there a way to vary the waveform (more electrode positive time) to get more cleaning?'
Yeah, no, that knob's not on mine. That feature showed up 2001, I guess. Mine appears to be a '99.

I'll try the soap and water next time I work on it- and yes, I have the old toaster oven!
So clean and easy- bake, like they say...
But I got enough of the hole closed up to use it, so I'll tap a bunch of holes with it,
and then take it apart (again) and try more cleaning, more filler, and more heat.
And when that fails, yep, 2- part epoxy is prolly strong enough for this job.
This has become more of a challenge than a requirement- there are other ways to
hold this thing if I melt the boss off entirely!

The old leather cone clutches are amazingly sensitive- it took me 3 or 4 test holes in the mill to
get the 'feel'. Very much smoother than a Tapmatic!

Thanks, all!

t