brass

machine#construction: casting#materials: brass

Brass Casting

ripped from hobbicast:
I buy zinc ingots from a galvanizer. You can also get zinc "anodes"
from metal suppliers or construction suppliers. The anodes are used
in steel construction to prevent galvanic or cathodic corrosion. Just
make sure they are zinc and don't have anything else in them.
You can also buy magnesium anodes so make sure what you ask for. You just
need to add a little piece. About the size of a sugar cube in a #10
crucible. Theya re used in construction as sacrificial anodes as they
have a lower electriolitic potential and will corrode first before
the steel or aluminum does. The magnesium ones are used in the marine
industry attached to boats so the engines don't corrode. Don't get
them, get the zinc ones. They are placed in a bag and buried with a
wire attached to the steel bridge, guardrail or whatever. they look
like metal billiard balls but weigh like lead.

You need to skim the glass off first - same with any cover flux.
Phospher copper welding rods are exactly that, get them from a
welding supplier. And don't use too much. Only about an inch of rod.
They degass the melt and make the melt flow alot better. but don't
use too much. To keep things simple, I'd start out with no flux at all. it is not necessary for silicon bronze or mag bronze.

If you don't use a cover flux (glass) you need to replace the zinc in
the manganese bronze. At least the second time when you remelt your
ingots or sprues. You never need to add anything (flux, cover flux,
zinc and certainly not borax)to silicon bronze.

Leave the borax out. Borax is not a cure-all. The less crap you have
in your melt - the simpler and less things go wrong. Why did you put
borax in? Probably because some jewelery person uses it for silver.

Brass plumbing parts does not tell you that it's brass. Good chance
there's silicon bronze valve seats, leaded brass bodies, and possibly
manganese bronze bodies as well. I've seen all those alloys in
plumbing parts. If you can get ahold of large brass threaded rods
inside large valve bodies and fire hydrants, most likely that is mag.
bronze which is easy and fun to work with but with high shrinkage.
And most marine grade "yellow brass" is actually mag. bronze.
You should also wire wheel and clean the scrap first.

I hope you have not contaminated your crucible with a bunch of
unknowns. NEVER MIX SILICON AND LEAD. You will ruin your crucible,
your melt, etc. I have learned the hard way. It forms a non-metallic crystailine substance that will ruin your castings and line the inside
of your crucible. And it won't come off. Test your scrap first to make
sure what you are melting. Judging by color will not work.

I have mixed mag bronze with silicon bronze with no problem. But you
need to make sure the mag. bronze has no lead. Some mag bronzes have
a little (<1%) lead. Usually the ingot supplier can get a a chemical
certification.

LL lyle_landstrom
www.landstromsfoundry.com