Metal Casting Zone

I have put together a list of ingredients for my furnace.
(The percentages are approximate)
* 20% Fire Clay (max temp 2912ºF) properties- high temp binder

* 25% 200 mesh silica sand (3002ºF)- hardness, hardening agent, very low shrink-swell properties

* 40% Bentonite -filler

* 5% Borax (1369.4ºF) -glaze for refractory surface durability and will glassify to glaze and will remain hardened, helps prevent surface fissures and cracks, also prevents refractory expansion.

* 10% Alumina - (3761.6ºF) -extreme thermal resistance, enables Iron and Steel casting, ingredient in commercial grade refractory, refractory longevity, also hardening agent, very low shrink-swell properties

This mix is estimated to give up to 3300ºF of heat resistance before irreversible damage could occur. Sustained long period use of the furnace from 3150ºF-3300ºF can cause accelerated degradation of the refractory.


A list of metals that all can be melted in a furnace with my refractory recipe. Remember that the ideal pouring temp of steel and iron is about 200ºF higher than the melting point

Stainless Steel 2550
Steel-High Carbon 2500
Medium Carbon 2600
Low Carbon 2700
Cast Iron 2300
Iron 2786
Inconel 2540
Nickel 2646
Silver 1762
Aluminum 1218
Brass 1652-1724
Bronze 832-1562
Copper 1981
Gold 1946
Lead 621
Tin 450
Zinc 786

Welcome to the forum.

Keep us posted on how it holds up.

I also was thinking the other day, how do I measure all this out from a percentage base? Well I thought some other amateurs may have trouble with this stuff as well. So my solution: just take the bag of material that you have the most of (in my case Bentonite) all of it in fact, put it in or on something big like a large wheelbarrow or tarp. Then spread it out about a inch thick, then take the next largest amount of material and calculate (by poundage) or estimate the amount and add it, and so on and so forth. Remember never ever add anything with lime or calcium in it, this could result in premature failure or explosions (if you added to much water). It is convenient and cheap to buy Wyoming Bentonite from a drilling mud suppliers but this kind is enriched with calcium (no no) and it will also gel up while mixing with water, after all that is what is designed to do. But also remember only add enough water to be able to squeeze it by hand to cake and stick together. It would be only to convenient to just pour it like concrete, that would make our lives easier, but that's a no. 1 no no.

Hey I was looking at your recipe and I was going to add Borax to my mix also, but I was just reading on the www.lmine.com site under the flux section that borax is used as a flux for smelting gold and other precious metals...I mean I don't want my furnace to burn itself up.
I am quite new to all of this casting stuff and attempting to make my own furnace with my own refractory recipe and I am just a little confused. Please anyone with more knowledge than myself please fill me in here.
Here is a list of refractory materials I have collected so far:
100lbs very fine silica sand
100lbs of fire clay
50lbs of alumina, the most expensive thing so far at $55 for the bag.
anyways my furnace should only need approximately 1.2 cu ft of mix so I will have stuff left over to make some plinth blocks or a hot plate to set the crucible upon after I pull it out of furnace and switch tools lifting tongs to the pouring shank.
DT

i add "potash" to to my recipe..... i dissolve it into the mixing water.