Aluminum Casting Question

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MikeH
Posts: 53
Joined: Sun Jan 05, 2003 6:38 pm
Location: Greenville, SC

Aluminum Casting Question

Post by MikeH »

I read awhile back that the aluminum alloy used in small engine blocks (ie. lawn mower engines) will grow too large of a crystal if allowed to cool naturally in a sand mold after casting, causing problems with the finished item. Is this true? If so, how does one prevent this? I want to start casting some projects (I'm new to foundery work) and have access to a good supply of descarded lawn mower engines for the metal.

Thanks
Mike
ChrisPer

Re: Aluminum Casting Question

Post by ChrisPer »

Well, I cannot say for sure as I have never used one of those engine blocks.

I can say this: If you are casting in sand, there are so many nucleation sites that it is pretty unlikely that you will get really big grains in the metal. You can probably increase the number by dusting the mold cavity with aluminium filings, but I doubt it would be necessary.

Of course, if you are casting some very massive piece it may well be that you get huge grains. Probably true for most alloys though.

Have you read Casting Aluminum by CW Ammen? I haven't ;-0 but I bet he would have something to say if its true. I am requesting it from the library so I hope to read it soon!

Simplest way to be sure: cast a test piece, cut, polish and etch to show grains. Not very hard.
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