On Oct 20, 12:25 pm, Ecnerwal
wrote:
In article ,
Stealth Pilot wrote:

what aluminium alloys do you use for casting?
which alloys do you avoid like the plague?

More from reading than from doing thus far, but obviously if starting
with scrap, start with _nice_ _cast_ aluminum scrap - a good source of
which is old computer hard drive casings.

I'll be interested in the responses to your questions from those doing
more.

--
Cats, coffee, chocolate...vices to live by


Here is a qualitative description of what I know about this topic:

Metal molds, aka die-casting dies, are made from MOLD STEELS.

A variety of steels is available for different temperature ranges,
life expectancy, and of course, costs.

The molten aluminium is injected into the mold under PRESSURE to
ensure strength and absence of voids and leaks.

Aluminium can be sand cast; cylinder heads, older model transmission
cases and differential housings spring to mind. Surface finish and
dimensional accuracy are quite a bit coarser than die castings or
INVESTMENT CASTINGS.

Investment casting is an alternative for the model maker. A wax
pattern is produced (for mass production these may be molded in a
die!) and "invested" in a ceramic slurry. The wax is removed by
melting it out, and the ceramic shell heated and the molten metal
poured in (very abbreviated description).

The pressure required to fully fill the mold depends on a number of
variables such as alloy, mold complexity, size of the mold cavity,
etc. For simple dies I would think that 12" of head would suffice.

Simple steel molds have been made by modellers using common hot rolled
or cold rolled steel. For a dozen or so castings this metal is just
fine. A simple plunger injector can be arranged to force the metal
into the mold.

If you wish to carry out this process in your home workshop try to
read some reference works on this topic dated from the 1930's or so.
Early die casting used simple equipment and was used for producing
automotive radiator grilles.

As for the alloy to use....I would start with modern transmission
cases or cylinder blocks. I know for a fact that the TOYOTA small 4
cylinder block is a die casting.

Wolfgang