"Morgans" wrote in message
...
OK, so there has been a lot of talk around here, about casting aluminum
for VW heads. It was here that I first learned that you can not use iron
crucibles for melting aluminum.

So, what if you need to cast a little job for something that does not to
be a pure aluminum part, for a non-aircraft application, where strength is
not very important? Would it be good enough?

My part is a socket (retainer) to go on top of a tractor shift lever.
Think like a donut, with the inside of the hole shaped like would be
formed around the outside of a sphere, or half of it. It has a retainer
that screws down around the outside of the part, holding the shift lever
and ball around it, down onto the transmission.

I believe the metal part that needs to be replaced is/was made out of what
is usually called "pot metal." What the heck is that, anyway?

So, what do you all think? Contamination from a cast iron crucible OK for
this part?
--
Jim in NC


Iron pots or crucibles are often used for melting aluminum. Coat it with a
clay or graphite slurry before each use for best results. Steel will work,
but will not last as long as iron, and coating is a must. Molten aluminum is
very corrosive to clean steel. Rust or blasting will help a clay based wash
adhere to steel or iron, where cast iron is usually rough enough as cast. I
personally prefer to allow new steel ladles to rust outside, then coat
regularly with a graphic based wash. I have never personally used cast iron.
All my crucibles are silicone carbide.

Drying is not terribly important after a wash if you are starting with cold
metal. The time and heat required to melt aluminum will dry the pot or
crucible long before you see molten metal. But if you are coating a ladle to
dip molten aluminum, adequate drying it's an absolute must.

Pot metal is usually just slang for die cast aluminum with high zinc
content. It makes it very difficult, if not impossible to weld, but I'm told
it flows well in high production die casting.