Thread: Thermite Casting

Mmmmm. Can one buy thermite or does one have to make it?

First of all, thermite is used by railways to weld sections of rail together....so it must be available although I've never actually run across it.

You are talking about totally different things when you say lost wax and green sand.......

Lost wax is for very intricate items or those with very fine tolerances. For instance some rifle actions are lost wax casts...as is most jewelery.
Lost wax involves a wax replica of what you want, which is put in plaster then the wax is burned out and metal poured into the plaster mould.
Usually needs a vacuum or pressure source to ensure full mould filling. There is also the lost foam method where the original is styrofoam...no burning out you just pour in and the foam vapourises.

Green sand casting.......easier to do, doesn't hold the same level of detail, less equipment needed.
The box doesn't need to withstand metal temp....it is a wooden box upper and lower, with locating tapers or pins to make sure they come together exactly the same each time.
The boxes have no top or bottom.
The casting sand is loosely packed into one half and levelled off and lightly tamped.
The pattern (usually wood) is tamped in so the parting line is level with the sand surface.
Then the other half box is fitted, the pattern and sand is dusted for release then sand is rammed around the pattern.
The whole lot is turned over, the first box of lightly tamped sand is removed and shaken out then replaced.
More dusting and the box is rammed hard full of sand.
The top box is lifted off and the pattern removed then the mould is reassembled and metal poured in.

Naturally the more complex the casting the more there is to it, there are several good books on the subject and I would advise checking out Plough Book Sales who sell quite a few....

Yeronga TAFE used to have a course Introduction to Foundry Practice. Due to the continuing and eventually successful legal actions against the TAFE by a neighbour concerning noise, fumes, traffic and parking, the foundry, fabrication, blacksmiths and machine shop were closed. Foundry apprentices now go to Bremer TAFE at Bundamba. Why don't you 'phone there and ask if they still have the introduction course? Hobbyists were welcomed at Yeronga.

Originally Posted by 123rover50

Mmmmm. Can one buy thermite or does one have to make it?

I won't post the ratios here, but thermite is basically iron oxide (rust) and aluminium powder.

I've since come to the conclusion that using thermite may be too difficult to create a consistent end-product. I always thought that the aluminium oxide waste product was mainly jettisoned off in the sparks, but now I suspect it might make its way through to the casting, which would affect the quality of the final product. If anyone has any ideas as to how to prevent this though, let me know.