# crucibles for iron casting



## kd0afk (Dec 23, 2012)

I have read that Hessian clay crucibles are what you want to use for melting iron but when I try to find one for sale on line all I get are links for some stupid metal band. Where can I get one of these big enough to melt the iron it would take to cast, say a plate 1"x7"x5" or where can I buy the materials to make one. I did a search on this site for hessian clay crucible and got no hits. I would like to set up a small foundry and I would like to do iron, brass, bronze and maybe some aluminum but mainly the higher temp metals.
Or would a graphite crucible be ok? I'm very new at this but I really want to try it.

Thanks


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## kye (Dec 23, 2012)

hi kd

i cant really give you any info regarding locating a clay crucible on the internet, however i can in regards to the use of a graphite crucible and iron. any form of iron alloy cant be used in a graphite crucible as the iron at melting temps dissolves the free carbon out of the crucible subsequently destroying both the crucible and depending on the iron being melting the desired properties of that alloy as the carbon content increases, but mainly it destroys the expensive crucible. it may also help to give your relative location as that will help people to narrow down whether any viables sources are nearby .

regards mackye


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## kd0afk (Dec 23, 2012)

Im in Fort Bragg Ca. on the north coast. What about materials? What kind of mix should I use? How should it be fired?  
Thanks.


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## Wagon173 (Dec 23, 2012)

Sounds like you need a cupola furnace.  They're fired by coke.  I'm not too familiar with iron melting but a source for coke is http://www.phalenhorseshoeingsupply.com/Coke.html  If you do some digging I'm sure you can find one closer to home though.  Do your homework on the cupola though.  I'm in Crescent City, CA way up by oregon and our fire restrictions are pretty stiff up here so I imagine that these may be against some sort of fire code.  Your neighbors would need to be chill too since they're reasonably loud and even the small ones have a pretty sizable flame screaming out of the top.  If you're not planning on casting much iron though you can modify a propane furnace to melt brass and bronze and such.  And have a local licensed blacksmith cast the couple of parts you need in iron.  I did read about one guy that modified propane to melt iron, but it sounded like it was a very research intensive project and quite the money pit.  Good Luck!


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## aonemarine (Dec 23, 2012)

http://www.lmine.com/mm5/merchant.mvc?Screen=CTGY&Store_Code=LMS&Category_Code=crucibles

I use clay graphite for melting iron and have yet to see a problem with doing so, they do recommend using the silicon carbide though...


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## aonemarine (Dec 23, 2012)

Just wanted to add my furnace is propane powered, uses a hiar dryer for forced air to lean out the mix and get the temp up. A naturally asperated propane burner will not get the temp up high enough to melt iron, you need to use forced air. To see it in person fire up a crucible full of iron with just a naturally asperated burner. note the color of the crucible should look orange yellow type color, then force in some air. You should see the crucible go yellow white in color. Really a neat thing to see. Once you know how to get the temp up melting and pouring iron is easier then pouring aluminum, just alot hotter.


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## kd0afk (Dec 23, 2012)

aonemarine said:


> http://ww.lmine.com/mm5/merchant.mvc?Screen=CTGY&Store_Code=LMS&Category_Code=crucibles
> 
> I use clay graphite for melting iron and have yet to see a problem with doing so, they do recommend using the silicon carbide though...



They don't say how much the sic crucibles hold. Kind of like the Sherwin Williams web site not showing the colors of their paint. I would like to do 40 lbs per run. 
I also saw a guy make his own out of clay. I have nothing against making my own.  I'm pretty certain the constituent parts are cheaper than the whole thing premade. that's usually how these things go. I'll be making my furnace out of a 55 gallon drum with a double burner and probably forced air.


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## solarenergyadventures (Dec 23, 2012)

Hi Kd!​I don't know where you are located, but in the us, crucibles are usually sized by how many pounds of aluminum they will hold. So a #6 crucible will hold 6 pounds of aluminum. You can figure out how many pounds of any other metal it will hold like so: 
Oops! too many words! see Next Post!


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## solarenergyadventures (Dec 23, 2012)

Crucibles continued: First Divide the Crucible # (in this case 6) by the density of aluminum ( .097) to get the volume of the crucible in cubic inches. (6/.097=61.85 cubic inches) Next: Multiply that volume (61.85 cubic inches) times the Density (iron in this case at about .264 pounds per cubic inch) to get the amount in pounds the crucible will hold.
(61.85 cubic inches * .264=16.3 pounds of iron) Notice that 16 is pretty close to 18 which would be 3*6, so a common rule of thumb is that a will hold "about" 3 times its number ( say a # 6) in iron. But this little math excercise will let you calculate what any crucible filled with any metal will hold. If you want to do 40 pounds of iron, You will need a # 16 Crucible.

Regarding furnaces and such. You WILL need forced air. If you undersize your burner and air supply, You will just frusterate yourself....ask me how I know! My furnace runs on propane and a 10" diameter fan running at 3450 rpm. This is a little overkill, but it will melt about 30lbs of iron from cold in about 30 minutes.

So far I've had no problems melting iron in Salamander clay graphite crucibles. Just go easy on the flux because (I believe, but could be wrong!) it eats the CLAY part of the clay graphite crucible. 

I hope this all helps!
Cheers! Chris


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## aonemarine (Dec 23, 2012)

Crucibles are rated in KG of copper they hold, your probaly looking at a #25 crucible in the budget line crucibles. Hope you have a friend handy who is interested in casting with you as a #25 crucible is very awkard to handle by ones self. Here is a #25 compared to a #6.
 To get an understanding of how heavy it is try lifting a car battery with a 4 foot pole and pour it


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## aonemarine (Dec 23, 2012)

Metal
Wt. per Cu. In.
Cast Iron..........................
.260
Wrought Iron......................
.281
Steel..............................
.282
Copper............................
.317
Brass and Bronze...................
.307
Lead..............................
.409
Tin...............................
.263
Aluminum.........................
.096


Read more: http://chestofbooks.com/crafts/meta...t-Of-Metals-Per-Cubic-Inch.html#ixzz2Fu4YsTmt​


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## aonemarine (Dec 23, 2012)

*Crucible Shapes:* 
*"Bilge" Shape:* Our Clay Graphite Bilge and Silicon Carbide Bilge crucibles are of high the highest quality and are used commercially. 
A bilge shaped crucible is shaped like a barrel. A rule of thumb states that the # of a "bilge" crucible gives its approximate working capacity in pounds of aluminum. For brass or bronze use 3 times the crucible #. For example a #10 crucible would hold approximately 10 pounds of aluminum and 30 pounds of brass. This is only applicable for "bilge" shapes. 
The "Bilge"shape silicon carbide crucibles are a carbon bonded silicon carbide having the longest service life. 


*"A" Shape:* Our "A" shape crucibles are typically used by hobbiests and casual casters. This shape is easier to make than the bilge shape and therefore is lower cost. Also note that "A" shape sizes and capacities don't correspond to bilge shape sizes and capacities. "A" Shape crucibles are rated in Kg of brass. Therefore a #10A will hold about 10 Kg / 22 Lbs of brass.​Check the tables below to find the right size for your job. *These crucibles run smaller than the equivalent bilge style. Get the next size up when in doubt.* 
I've got to admit that the "A Shape" crucibles are a bit "rough" around the edges. The surface finish is somewhat coarse and there are dents and dings in the rims and body. They don't have as finished an appearance as the bilge types, but in view of the price difference I would be inclined to overlook this issue. This roughness doesn't detract from their performance in any way. 
These "A" shape crucibles are formed from what appears to be clay, fire clay grog and a smattering of silicon carbide particles.


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## solarenergyadventures (Dec 23, 2012)

Aww shucks, You beat me to it! ;D 
Cheers! Chris


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## kd0afk (Dec 23, 2012)

so the plan thus far is to make a furnace of a 55 gallon drum lined with fire brick using 3 quarter inch forced air propane burners and a number 25 crucible made with hessian clay. if I can find it if not use clay graphite.
Fire and personal safety equipment of course. The  lifter will have a t handle and I will always use a friend to help me pour.


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## kd0afk (Dec 23, 2012)

And the entire thing will be portable so i can relocate it to where i will do the thing.
It would be sweet to be able tip the whole furnace and pour. I'm thinking it might be safer.


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## aonemarine (Dec 23, 2012)

solarenergyadventures said:


> Aww shucks, You beat me to it! ;D
> Cheers! Chris



Lol, yea I forgot bulge shape crucibles are rated differently, I have yet to buy one due to thief cost especially when you consider that they are a consumable item in the foundry.
 I haven't tried making my own crucibles yet but I have been saving my old ones to use for grog when I do. At this time it is just cheaper for me to buy them.


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## kd0afk (Dec 23, 2012)

One more thing will that cream color brick work okay for a furnace or will I have to use that styrofoam looking white brick?


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## solarenergyadventures (Dec 23, 2012)

Hi KD,
Have you ever done any metal casting? My humble recomendation if you haven't is to start small, start with Aluminum, and find someone who has some experiance doing it to help you before you plan on a 40 pound iron pour. A full pot of Iron at white hot temperature is no joke. Just my 2 cents. 
Cheers,
Chris


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## aonemarine (Dec 23, 2012)

kd0afk said:


> One more thing will that cream color brick work okay for a furnace or will I have to use that styrofoam looking white brick?


Depends on the temperature rating, color and density don't tell you much. There are soft white bricks rated to 3200'F  and some only rated to 2400'F.
 I agree with Chris, a small furnace casting aluminum is a good starting point to learn from.  An old propane tank is a good size for a #6 A shape crucible with about a 2.75" thick refractory wall.


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## starnovice (Dec 24, 2012)

Ditto.  You can build an a furnace for Al out of firebrick in your backyard.  Make yourself a Rhiel burner (google it) and you can be pouring in a weekend.  Look for a cast iron skillet or pot for a crucible.  Do this a couple of times then think about moving up.

Pat


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## kd0afk (Dec 24, 2012)

Well there is a couple things I can make out of Al.I have a couple questions. As long as it's temporary, can I use charcoal brickettes in an old weber? Also, the two things I want to make are my adapter plate and crank handle for my milling attachment. The plate will be 1" thick. Would recycled can metal be OK for this? I have nothing against aluminum but I was looking at the long run.


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## MuellerNick (Dec 24, 2012)

> Would recycled can metal be OK for this?



Use scrap aluminium castings and just change the shape. 


Nick


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## aonemarine (Dec 24, 2012)

Cans are horrible to cast with. Try finding  some good cast aluminum stuff, you'll have much better results. A charcoal furnace works just fine with forced draft but to me they are messy and a pita. Build yourself a reil burner, you can build one in 20 minutes and be running on nice clean propane. Plus its good for when you want to go for iron as well, just add air.


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## kd0afk (Dec 28, 2012)

Through two contacts on CL I scored a BBQ grill sized propane tank. And two that are really tall and one a bit shorter. The two huge ones have triangular knobs. All for free.
Question about aluminum. Is can metal just bad structurally or can it be used to make ornamental stuff or is it bad to work with period?


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## kd0afk (Dec 28, 2012)

Forgot photos.


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## solarenergyadventures (Dec 28, 2012)

Hi kd!
Regarding using aluminum cans for casting. The problem is that aluminum cans are very close to being pure aluminum, and the properties of pure aluminum are pretty poor, such as low stength, and poor machinability ( kinda like trying to machine bubble gum). When casting pure aluminum, you have a huge amount of shrinkage so you need large risers, the aluminum tends to "hot tear" as it goes from liquid to solid, and it is not very fluid. Adding silicon to aluminum drastically reduces all of the afore mentioned problems. Other alloying agents such as copper, zinc, magnesium, and iron are all added to aluminum to tweak its properties in some way.
Aonemarine's advice is spot on. Go find yourself something that was sand cast in aluminum, and melt it down. Chances are the alloy is pretty close to Alloy A-356 which is 7% silicon, .2% iron, and .3% magnesium, and has waaaaaaay better properties than pure Al. My personal fav is aluminum intake manifolds off of 4 or 6 cyl inline engines (v-6 or v-8 manifolds are pretty tough to break up unless you heat them first). They are readily available, easy to smash up with a sledge or slice into pieces with a band saw, and in my experiance give fantastic results.  Nice score on the propane tanks by the way!
Cheers!
Chris


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## aonemarine (Dec 28, 2012)

If all you have is cans then you might as well make use of them, I would advoid trying a thick casting with them as shrinkage is extreme. The other thing you will run into is alot of dross when you melt them, melt a crucible full of cans, skim dross, crucible now half full....and thats no exaggeration.  Use what you have for now, but keep your eyes open for the "good stuff".
  Nice score on the propane tanks! they come in handy for all kinds of things... oh yea, now you have some brass to melt from the valves in them.


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## kd0afk (Jan 1, 2013)

aonemarine said:


> If all you have is cans then you might as well make use of them, I would advoid trying a thick casting with them as shrinkage is extreme. The other thing you will run into is alot of dross when you melt them, melt a crucible full of cans, skim dross, crucible now half full....and thats no exaggeration.  Use what you have for now, but keep your eyes open for the "good stuff".
> Nice score on the propane tanks! they come in handy for all kinds of things... oh yea, now you have some brass to melt from the valves in them.



After i melt them down into ingots to remove dross, what would i add in to make it a stronger alloy?


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## aonemarine (Jan 1, 2013)

That's a difficult question to answer without knowing the exact alloy you have to begin with, I would really have to look into it a bit before making a recommendation.  Copper and silicon are the first things that come to mind though.


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## terrywerm (Jan 1, 2013)

Waaaayyyyyy back in the day when I was in high school, I did quite a bit of aluminum casting. I only needed to do a couple of pieces, but I really liked it, so helped out some of the other guys that were having trouble. As a result, I rammed up quite a few molds (or instructed others) and oversaw the melting and pouring of quite a bit of AL.  Here is what we would do:
Start out with some pop cans, typically a #6 bulge crucible about half full of crushed cans, then add some extruded aluminum from old storm doors, etc. While this is starting to melt, we'd have a couple pieces of broken cast aluminum heating up on the top of the furnace lid. Once the metal in the crucible started to melt, we would add some preheated cast aluminum, and we would add it very slowly. Once it melted, we would skim off the dross, add more cast AL if necessary to fill the crucible. Once the full pot was ready to go, skim once more, then pour into ingot molds.

Ingots would get tested for 'gumminess' by drilling a test hole in the ingot. If it was deemed as material that would machine reasonably well, a sharpie was used to place a mark on the ingot. Ingots with marks were then saved for casting projects that would require machining later, such as pulleys for belt sanders. Unmarked ingots were used for casting simpler items like ash trays, hood ornaments, etc. that required little if any machining. It was a simple and rather inaccurate system, but it gave students the chance to pour a number of times by making ingots, and also gave some idea of the differences in alloys. As someone mentioned earlier, using more good cast aluminum in a pour usually resulted in the best ingots.


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