multi melt casting

[ramsies11]

okay gents. this is one of those, if it ever happens will it work? moments. if i was casting somthing larger (i probably never will but lets just say) an aluminum 50lb anvil. my crucible wouldnt be able to hold enough old soda cans to melt that lol. so would it work if i melted a pot fulla aluminum, poured it in the mould, melted a second pot full and poured it on the cooled aluminum already in the mold to finish the mould?

second question would be if i could do what was mentioned above^ could i layer metals ontop of eachother? like say a layer of aluminum, then copper, then aluminum (i dont know how close the points are specifically but it doesnt just have to be that. just wondering.)

[ThomasPowers]

No generally you can't get one layer to bind to another. You can cast ingots and then re-melt them to get more metal in the crucible than a pile of cans. You can have multiple furnaces and do a multi simultaneous pour too

Note that cans generally are not a good casting alloy, better off to sell your cans and then go by scrap pistons from a mechanic...

Note also you get more money for cans selling them as cans than as ingots, and less hassle and fuel wasted to make them ingots.

[Steve Sells]

Also most places will not buy home made ingots, as they have no clue to the alloy or what is inside that ingot, where as a simple can is a known alloy.

[pkrankow]

If you have several furnaces and crucibles to prepare the entire melt at once, then pour in sequence...maybe.

There are better casting alloys than soda and beer can. Think large castings like transmission shells, insides of laundry appliances, etc. Thicker pieces will produce much less dross, and much less annoyance while melting.

Phil

[ramsies11]

the soda cans wernt really what i ment. ill scrap soda cans. but i mean aluminum..... if that makes sense.

[48willys]

As haveing little cast practice I have done this before and it did work. But let me explain, I did this on a aluminum cut plat for my anvil. The mold was almost filled and then I ran out when filling the hardy shank, so instead of starting over I just melted a little more and finished. On to the problem, though it worked on this, a cut plate only uses the shank to keep it from moveing and really has little force on the shank itself,.You can see a line of what looks like dross between the first and 2nd pour in the casting and I'm sure it would snap right off with any hard use.
You are always better off melting more than you need and haveing a few ingot molds ready to pour the extra in. Besides the the bad castings you will get from doing two pours I'm not really sure what kind of safety problems you run into doing it.

[Syd Partridge]

If you intend trying your hypothetical question: When you have poured your first cast allow it to cool slightly, then push steel rods into the aluminum with half of the rod showing proud and allow to cool (you may have to support the rods to stop them falling over). The rods should be nicked so that the aluminum has some purchase and warmed before use to ensure they are perfectly dry (remember that rust holds moisture so ideally use bright steel). Before making the second pour, warm your first casting to just below its melting point. This will ensure both the mold and casting are absolutely dry and will reduce the draw of heat from the next pour. The second pour can now be made.
If the second melt of aluminum is hot enough it, will slightly melt the base, allowing the two pours to melt into each other. This will only happen at the interface.
However, I don't advise using this technique for anything you are going to hammer on, as the adhesion between the faces will not be good.
We used to make aluminum 'off the wall' paperweights by pouring a small amount of aluminum onto a flat plate, allowing to cool a little, then pouring a small amount on top of this and then repeating numerous times until it looked like something that could be displayed in the Tate Modern.
With regard to pouring copper onto aluminum, it is unlikely that you will get any bonding between the two materials as the aluminium will draw the heat from the copper causing it to cool before any intermetalic bonding can take place.
As a note; full safety protection should be used when working with molten aluminum. In fact I prefer a full face visor in preference to safety glasses.
Aluminium and moisture can be an explosive mixture and is extremely painful when it burns.