"Spencer" wrote in message
ups.com...
I have been doing much reading about sand casting lately, and am
interested in playing with the zinc-aluminum alloys.

I would like to be able to make permanent molds for casting a part in
these alloys, and would like to know if anyone has done this. I
understand that steel molds are used in die casting where the melt is
injected under pressure, but this is obviously different. Lead bullets
are cast in steel (and aluminum!) molds all the time.

What kind of steel (or non-steel) is usable for the mold? Is 12L14 OK?

Is mold-release needed?

What questions am I not smart enough to ask?

Parts would generally be smaller than a hockey puck. I am planning on
using a steel crucible in a muffle furnace for the melt. ZA-27 is the
target alloy.

There's been some confusion over the years about permanent-mold casting
because the use of terminology has changed. Permanent molds have been used
for aluminum and zinc casting for many decades.

Originally, the molten metal was poured in through a tall sprue, made of
clay or ceramic, and it typically was 3 feet or more high. Early on, they
started calling this "low pressure die casting."

Then, sometime later, they started actually using some pressure, and the
term was switched to that method. The gravity method is now usually called
"gravity permanent mold casting." My basis for saying this is that I had to
research it once for an article, and I had access to an excellent old
engineering library at the time.

Many permanent molds actually were made of cast iron. Others were made of
steel, of various grades. One of the more dramatic examples of permanent
mold casting, using the tall sprue, was the B-O-P V8 engine block, made in
the very early '60s. They located the cast ribbed steel cylinder liners in
the mold and cast the block around them, in place. My vague recollection is
that the molds were made of cast steel.

I have read that they smoked new molds to keep them from sticking. You can
do that very quickly with an acetylene torch, with the oxygen turned off.

--
Ed Huntress