crucibles for iron casting

[kd0afk]

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

 

[kye]

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

 

[kd0afk]

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.

 

[Wagon173]

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!

 

[aonemarine]

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...

 

[aonemarine]

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.

 

[kd0afk]

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.

 

[solarenergyadventures]

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!

 

[solarenergyadventures]

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

 

[aonemarine]

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

 

[aonemarine]

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​

 

[aonemarine]

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.

 

[solarenergyadventures]

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

 

[kd0afk]

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.

 

[kd0afk]

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.

 

[aonemarine]

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.

 

[kd0afk]

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

 

[solarenergyadventures]

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

 

[aonemarine]

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.

 

[starnovice]

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