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How Not to Hate Casting Aluminum

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vtsteam:
I did a little research online, and I believe that the extrusion which created the worst muffin ingots was called an 8020 1515 linear rail, and it seems these are typically 6063 -T6 alloy. Good to know in general.

My guess at the alloy from the bell housing that made the best looking, very low shrinkage muffins is either AlSi12, aka A413 (US)and D6 (GB), also used for pistons. Or AlSi18 aka A390, which has the lowest shrinkage I can find, of the aluminum casting alloys.

6063 has a thermal elongation coefficient of 23, A413 is 21, and A390 is 18. (I'm leaving out units here, but you get the idea.

This is all of interest to me presently because I'm considering trying a cast iron piston in an aluminum cylinder, and thermal behavior is what I think will make or break that combo.

vtsteam:
I did another set of consolidation melts today. I'm trying to get more room in my shed, so melting stuff down kills two birds with one stone. Plus it's fun. I thought you all might like to see the results from some other scrap types. Result, about 30 half pound ingots.

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Stock: I melted down a light aircraft wheel hub, a small Tecumseh engine, and a bunch of thin architectural extrusions, plus small odds and ends.

The Tecumseh engine was probably about 4 hp horizontal, which I removed most of the steel and iron from. Actually, see my Avatar up left? Well that's it! You're seeing an exhaust and intake port view of it. It's been hanging around in storage for many a year. It had thrown a rod, so not much use.

I don't know where I got the aircraft wheel hub from. It was conical shaped with internal ribs. I think that was its use.. not totally sure. 

The thin extrusions looked like window molding stuff.

Anyway here they are as muffins. The motor made beautiful shiny puffy versions with fine grain. The wheel, meh, not as nice, but usable, fairly coarse grain fair amount of shrinkage.

And the mixed scrap and extrusions turned out pretty good, considering. Maybe just a little better than the wheel aluminum, finer grain for sure.

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I've taken to marking muffins now for future reference when mixing, and matching for purpose.

Another way not to hate casting aluminum!

Endnote: BTW I test every major piece of casting material before melting, by taking a small sliver off of the piece, and subjecting it to my MAPP torch. We don't want to mistake magnesium for aluminum! Magnesium burns with an intense white flame. And as I found out a few years ago upon doing the same test, the nice big VW bug engine block I was given was made of magnesium. Darn!!!! that had a lot of material in it.

And this time I was glad I did, as well. An old carburetor found half buried in the ground from some ancient vehicle seemed suspiciously heavy. A little piece of it turned yellow in the torch flame -- zinc based pot metal. Not good to mix with aluminum. In fact I do wonder if the casting defects seen in Ironman's video were due to zinc contamination. Zinc has BIG shrinkage, and coarse crystalization, not unlike the appearance of those castings.

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