Small casting (alluminium) aty home.

Drawfiler said:

When melting aluminium beware of iron, if the scrap includes screws etc or if you use an unlined steel melting pot, the iron can leech into the metal causing it to go very sluggish an impossible to work with.
A good source of metal scrap is old car engine pistons they are pretty iron free and actually are a special alloy to resist heat in service.

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Yes I agree with this,

Although it seems strange that a hard, high melting point metal like Iron (or Steel) can actually dissolve in a softer, lower melting point metal like Aluminium, It can and does happen.

I'm sure the Metallurgists among us can explain the exact mechanism behind it. If so please chime in. I would be interested to know the reasons why this happens.

Best Regards Mark

I recently built a furnace for melting aluminum. It runs on 120vac. So far I have just tested it by melting scrap and pouring into a muffin pan. It gets up to 1400 deg F at a rate of 0.5 degree/second. I can provide more detail if anyone is interested.

That looks excellent. I am attracted by the idea of controllable, silent, non-smelly non-smokey heat - can you tell that my desire not to spend money means that my furnace runs on waste motor oil! I'd be interested in more detail, type of wire for elements, rough power consumption to melt a pint of aluminium alloy, etc.
cheers
Mark

froudeg490 said:

I recently built a furnace for melting aluminum. It runs on 120vac. So far I have just tested it by melting scrap and pouring into a muffin pan. It gets up to 1400 deg F at a rate of 0.5 degree/second. I can provide more detail if anyone is interested.

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Yes, I am interested. I have several vids I have down loaded from utub and other places, however, I am always MORE interested in something I know that someone has done, someone whom can give me advice if I needs it when I start on a foundry package. I thimpfk I will start with a gas foundry then move to an electric one.

I decided to build and electric furnace so that I can set different temperatures and have the capability of following a "Ramp Soak" profile for investment burnout. Attached is a video that provides an overview. Most of the information to build the furnace I gleaned from YouTube. The heating element is 16AWG Kanthal A1 wire formed around a 3/8" OD metal rod. The element is 10 ohms, which means that I should be getting about 1.4kW. The mains voltage is about 120VAC at the breaker panel, but the receptacle I'm using is at the other end of the house and there is a voltage drop of about 5VAC. At the moment the plan is to make small castings about the size of a 2.5cc model diesel crankcase. If I decide to make larger castings I think I'll need to make a propane version and just use the electric for investment burnout or possibly heat treatment (?).

I'll let you into a secret. Crucibles are much cheaper if you buy them directly from Morganite and buy say 3 at a time.

Morganite is a gemstone. Can you elaborate, a little more information.

rutzen said:

I'll let you into a secret. Crucibles are much cheaper if you buy them directly from Morganite and buy say 3 at a time.

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Chiptosser said:

Morganite is a gemstone. Can you elaborate, a little more information.

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This is what came up in a search for "morganite crucible": Homepage | Morgan Molten Metals Systems - is this the source you are referring to?

Yes it is, they are Salamander crucibles I used. They were great to deal with. They actually sent me the wrong size ones the first time I ordered, they just told me to keep them and they sent the right ones! I was very happy to do that.

Lucky chap, free crucibles, can't be bad !

And yes, you are right, they ARE cheaper if bought direct.

Best Regards Mark

Sounds like a hot deal ...

skyline1 said:

Although it seems strange that a hard, high melting point metal like Iron (or Steel) can actually dissolve in a softer, lower melting point metal like Aluminium, It can and does happen.

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From other forums in the past years I gleaned the notion that iron oxide does not interact so much with aluminum alloys, so my crucible has been a rusty 4" schedule 80 pipe section with a steel disk welded in for a bottom. It looks horrible and has to be scraped out between pours, but it has lasted for years and does not seem to cause any problems with the castings.

DKGrimm said:

From other forums in the past years I gleaned the notion that iron oxide does not interact so much with aluminum alloys, so my crucible has beenView attachment 125761 a rusty 4" schedule 80 pipe section with a steel disk welded in for a bottom. It looks horrible and has to be scraped out between pours, but it has lasted for years and does not seem to cause any problems with the castings.

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That's very intriguing. I wonder if bluing a steel crucible would have a similar effect? No doubt nothing is as good as a "real" crucible, but for those of us who are just doing an occasional casting with whatever is at hand ... maybe?

I guess this needs a chemist or materials expert to explain. If the steel has a ferrous oxide (black rust) surface coating then possibly this is acting as an electrical insulator to prevent the electro- potential between the iron and aluminium from causing the iron ions from permeating into the liquid aluminium?..?
E.g. on your car, the steel body has been dipped in a phosphate solution to cause the surface to gain a few molecules of ferrous phosphate. This is an insulator to prevent any electrolytic corrosion from the electro-potential differences between iron and other metals. Thus prolonging the lifetime of the car body.
In a similar way, the iron oxide in the steel crucible may be doing the same prevention of the dissolving of steel by liquid aluminium?
Anyone really know?
K2

I agree with steel crucibles they work just fine for our 'aluminium' needs, i find they last just as long if not longer than ceramic crucibles and are much safer to handle.
I use the bottom section of a CO2 tank.
Although steel does desolve in aluminium its realy no concern if you use decent aluminium and quick melt times.
I think you usually get crap gummy castings from over cooking the aluminium and burning off the silicon and other alloys and absorbing hydrogen well before the iron contamination becomes an isue.
There are ceramic paints available to coat steel tools but a small tin costs as much as a good crucible so ive never found a need for it myself.

Richard Hed said:

Yes, I am interested. I have several vids I have down loaded from utub and other places, however, I am always MORE interested in something I know that someone has done, someone whom can give me advice if I needs it when I start on a foundry package. I thimpfk I will start with a gas foundry then move to an electric one.

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I use a propane gas furnace. Using a meter type of pyometer immersed in the melt has shown that the best AL pours occur right at 1200 F

I pour at 1425 °F

Dave

Aerostar55 said:

I use a propane gas furnace. Using a meter type of pyometer immersed in the melt has shown that the best AL pours occur right at 1200 F

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skyline1 said:

Yes I agree with this,

Although it seems strange that a hard, high melting point metal like Iron (or Steel) can actually dissolve in a softer, lower melting point metal like Aluminium, It can and does happen.

I'm sure the Metallurgists among us can explain the exact mechanism behind it. If so please chime in. I would be interested to know the reasons why this happens.

Best Regards Mark

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Hello Mark,

it is not at all a particular rare phenomenon. I repeat myself. Sugar has a melting point approx. 190° C table salt of about 800° C, both dissolve fine in water. Tungsten has a melting point of Three thousand odd °C if dipped into molten steel, it dissolves. A mix of 30% Tungsten and 70% Iron melts at 1529°C. ( I just googled that ) Carbon is another of the weird cases it can be at crazy high temperatures still solid, but is soluble in Iron just fine.
Antimony dissolves in Tin. ( SnSb solder )

The list goes on and on.

Drawfiler said:

When melting aluminium beware of iron, if the scrap includes screws etc or if you use an unlined steel melting pot, the iron can leech into the metal causing it to go very sluggish an impossible to work with.
A good source of metal scrap is old car engine pistons they are pretty iron free and actually are a special alloy to resist heat in service.

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I would take this advise from Drawfiler serious, Fe in the liquid Al is not a nice thing for reliable results. I would want to add that a steel melting pot can eventually fail. When this happens in the wrong moment and the liquid runs over someones safety flip-flops onto his wifes new carpet, that someone might be in trouble. I personally feel better with my cheap clay graphite crucible ( my opinion ).

Liquid Aluminium is as far as I remember an aggressive solvent to a lot of other Metals and some Ceramics as well.

Cheers Timo

awake said:

That's very intriguing. I wonder if bluing a steel crucible would have a similar effect? No doubt nothing is as good as a "real" crucible, but for those of us who are just doing an occasional casting with whatever is at hand ... maybe?

Click to expand...

I have spoken with several people that have used a piece of 4" steel pipe with a bottom welded on for a crucible with no ill effects. Also for material I have had good luck with automobile pistons and old transmission cases donated from a local repair shop. The cleaner and larger chunks make less dross and less gas in the melt. All the parts were sand cast in my little furnace for the engine on the right
including the aluminum base the iron flywheel and the brass intake tube.

It turns out that ALL metals and a few non-metals will dissolve in all other metals. But to say this, has great caveats. They don't dissolve necessarily 100%. Some do, like that which makes up solders, brasses and bronzes and some aluminum alloys. That's what they are called, alloys, as you all already know. The amount that will dissolve is also temperature dependent. Try alloying something like iron with lead. ONe has a very high temp but the other is likely to BOIL at that temperature, even so, some lead is alloyed with steel. In all cases, an alloy with two metals that have melting temp "A" and "B", if you alloy them at exactly 50% each, the melting temp of the alloy will be (A+B)/2. If one is 3/4 and the other 1/4, then whatever the 3/4 temp is it will be (3/4A +1/4B), etc. for all possible quantities. This can be useful, as no matter what your alloy is, it will melt at a lower temperature than the highest melting metal.

I understood that the Egyptians used an alloy called electrum. THis alloy was supposedly an unknown composition but suspected of having gold and silver alloyed. (Probably it is an element NOT on the periodic table. Har har) Well, that is silly in now-a-daze ability to distinquish chemicals. The point being that if electrum were ONLY Gold and Silver, one could determine the quantities by the melting temperature, if you were willing to test a bit. Problem is, it might have some copper or some other metal as well, then it would get complicated. But the same law of melting still holds with more than two metals, that is, the melting temp calculated with the proportion of that metal . . . etc. etc. etc. If you have non-metals, I does not know the law. (I'm also a speeder and likes to break the laws.)

Aerostar: Could you show a pic of you foundry set up?