Foundry Info For The Hobby Metal Caster.
To cast things in metal, you need ingot stock to melt in a crucible, but there is no need to go out and buy ingot stock, it is easy to make ingots in your hobby foundry, in fact this is the best way to begin exploring how to melt metal to cast.
In our ebooks we explain how to make an excellent ingot mould (Mold in USA speak), making ingots also provides a great learning experience for the complete novice about pouring molten metal out of a crucible and into the ingot mould, the skills are basic, but essential for perfecting the pouring technique, it is bad practice to pour too fast, as it is equally bad to pour too slow, pouring ingots is a great way to get the feel of pouring molten metal because it wont matter if you make a mess of it.
The Scrap Metal Source.
Your first thoughts may be of collecting empty Al drink cans when looking for scrap AL.
Al cans may appeal to the newbie metal caster as a cheap, easy to collect source of scrap, many have tried to melt Al cans, only to be disappointed with the results.
The BIG metal recyclers do melt Al cans by the furnace full, but thousands of cans are first compacted into large solid cubes and then dumped into the melting furnace which is already half full of molten metal from other sources.
If the hobby caster tries to melt cans in a crucible, the thin gauge alloy will burn into oxide, and doesn’t yield good metal to pour into an ingot.
It’s simply a waste of valuable gas or whatever energy source you may use for melting.
The Best Source Of Solid AL Scrap Can Be Found with The Following.
- Discarded automotive inlet manifolds.
- Gearbox casings (Must be clean and free of oil).
- Cylinder heads. (Excellent quality scrap)
- Cast alloy brackets etc.
- Old cast alloy Vee belt pulleys
- Junked cast Aluminium lawn mower chassis.
- Aluminium drink cans??? (A lot of work for very little gain in metal)
- Automotive cylinder heads need to be cut up into smaller chunks so that theycan be melted down and poured into ingots.
- Any other item that can be easily broken up with a large persuader, (sledgehammer) but be very careful.
Aluminium Cylinder heads offer large amounts of metal for remelting, the trick is to find someone who can cut the cylinder head into smaller chunks, a metal band saw is ideal.
The method used to remelt the alloy into ingots is to place the small chunks into a rectangular shaped steel melting pot.
The melting pot is placed on a good charcoal forge, the forge is run with a pretty hard air blast to get a good heat build up, the melt happens reasonably quick, other jobs can be attended in the workshop while the Alloy is melting. Just check on it every now and again.
Once the metal has melted it is poured into the ingot mould. Recharge the charcoal in the forge; place another chunk of metal in the pot, and start the process all over again.
The valve guides, seats & plugs etc, will sink to the bottom of the pot, just scoop these out between each melt. When the ingots have cooled down, mark them with a texta marker to indicate what kind of metal it is. Eg piston alloy, cylinder head, etc.
There is no real need at this stage to de-gas the melt at this stage, carry out the degassing when you are remelting, and ready to pour a mould.
Old automotive pistons are also OK, but have a high silicon content of around 10 to 13 %, the piston alloy casts OK, but does not machine very nice, if you mixed in some scrap alloy like Al extrusions, would change the composition into a softer alloy and could be used for non-load bearing objects, general hobby castings and or art castings.
The idea is to experiment with what you have on hand, you’ll soon get to understand the process.