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.

Thanks,

Spencer

Look into investment casting. It's probably the ideal solution for you if
you are into limited production. You make a plug from which you make
urethane or plastisol molds into which you pour wax, remove from mold, put
waxies on a tree, dip in ceramic slurry, cure, melt wax from mold, fill with
molten metals as hot as required for steel if you want. Break away the
ceramic and you have perfect, seamless reproductions.

Wayne
www.pueblaprotocol.com

"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.

Thanks,

Spencer

Graphite?

Harry C.

"Spencer" wrote in news:1116622401.700055.37570
@g44g2000cwa.googlegroups.com:

GOOD grade of H13 is what is used in many gravity aluminum molds.





--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

http://www.machines-cnc.net:81/

"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

Ed Huntress wrote:

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

For lead casting, bullets and model soldiers, we used to use a candle to
put a smoke carbon release layer on the mold surface, it worked well.
For "Spencer's" situation a candle should work too since he mentions
the part will only be the size of a hocky puck. Also a note on molds,
besides steel and cast Iron, brass or copper should work too.

----------------------------------------------------
Plain old hot rolled steel will work fine for short run permanent molds.
Some preheating of the mold is helpful to get started so that the castings
won't freeze short. Once the die temp has reached equilibrium no extra heat
is required. Die casting spray release will help too. Don't forget to leave
2 to 3 deg.of draft. It might be easier to buy 100 lbs of petro-bond and
sand
cast. It gives great detail.

Donald Warner

Don't let the facts interfere with your prejudices
-------------------------------------------------------------------------

Donald wrote:

Die casting spray release will help too.

I didn't try it, but anti spatter spray might*) work too (and be less
expensive and easy to obtain).

*) The one used for MIG/MAG welding

Nick
--
WDR Fernsehen:
"Ein Computer arbeitet so lange Befehle ab,
bis keine mehr vorhanden sind."
Muss ich die dann irgendwie nachfüllen?