"David Billington" wrote in message news
On 01/09/17 20:36, Bob La Londe wrote:
"Terry Coombs" wrote in message news
On 9/1/2017 2:54 AM, Ed Huntress wrote:
On Thu, 31 Aug 2017 20:59:45 -0500, Terry Coombs
wrote:

On 8/31/2017 8:37 PM, Ed Huntress wrote:
On Thu, 31 Aug 2017 16:04:36 -0700, "Bob La Londe"
wrote:

I 've been saving all my 6061-T6 scraps for ages. I was planning to
do some
casting with it, but now that I am getting close I find that 6061 - T6
is
reported to be not very good for casting. I wasn't planning to make
structural parts out of it or anything, but is there anything I can do
with
the stuff other than sell it to the recycler for pennies on the pound?

Seems like it has to be formed at pressure and temperature to be of
much
use.
I've never tried it, but it's supposed to be a fairly good casting
material. Why don't you just give it a try?

BTW, the T6 temper has nothing to do with it. Long before you reach
melting temperature, the temper is gone and it's indistinguishable
from annealed 6061.

For a pure 6061 casting to be reasonably machinable it needs to be
chilled as soon as it comes out of the mold and then aged for a while or
it's gummy and smears . Aluminum that was cast originally will machine
easier right out of the mold but also is harder on (HSS) tooling .

--

Snag
Right, but Bob mentioned T6 a couple of times, and I wanted to be sure
that he knew that had nothing to do with 6061's castability.

The chill and aging both contribute to the hardness of the ingot .
Can't get it back to T6 without special treatment , but maybe T4 or T5 ...
*********
Seems going from liquid to solid quickly results in smaller grain size.
Might have to do some experiments then with cooling speed using water,
super quench, and circulated refrigerated super quench. I have very
little HSS tooling other than drill bits and a few hand ground lathe bits.
Just about all of my mills are carbide, and I tend to reach for carbide
insert tools on the lathe except for nasty cuts where the slightly better
flex of HSS might survive better.

Have to make molds from low carbon steel or they might shatter. That could
get interesting. LOL.




A mate works in engine design and development and he has mentioned
before that things like cylinder heads are carefully cast so IIRC the
main cooling is at the cylinder head face which results in the most
beneficial dendrite formation resulting in the highest material
properties and as it is critical they also use virgin alloys for those
products to ensure the proper metallurgy. Maybe not an issue in your case.

That's interesting to know. It might also be so the face holds shape and
continues to draw metal from the rear as it shrinks and cools.
Hemispherical heads are cool, but I suspect not such much for a piston.
LOL. Yeah, not super important for what I currently plan to do, but who
knows what I might try in the future. I never thought I'd be working in
machining when my wife gave me that little toy 7x10 lathe for Christmas 2005
either. Figured I'd die as a communication contractor up in somebody's
attic with the wire I was pulling clamped in my teeth in a knock down drag
out fight trying to fend off giant mutant rats with a pair of pliers and a
razor knife. LOL.