Refractory recipes

jpfabricator

jpfabricator

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Im gathering the supplies to construct a small aluminum foundry. I have a company that sells 2800 degree refractory, but its expensive.
Does anyone have, or has mixed a suficient home brew refractory?
I have 120#s of fire clay powder.

Jake Parker
 
Watching your thread with interest, because I would like to build a small foundry too. :biggrin:

Eventually, I would like to be able to melt cast iron, and that may require the expensive 2800 degree refractory cement you mentioned.

GG
 
The company is called High Temp, in Longview TX. They have some 3500* also, but the price difference is almost tripled!

Jake Parker
 
You might want to consider using insulating refractory bricks, and putting a coat of refractory cement on the inside. The bricks insulate like crazy, keeping the heat inside. The refractory cement takes the heat in the furnace, and is much tougher than the bricks. You can safely hold your hand on the outside of my furnace, even when melting brass.
The refractory cement lining can be touched up as it spalls and erodes (which it will!), and the resulting furnace body is *much* lighter. I still recommend the base and lid be made of cast refractory cement, the kind with fibers in it. Don't forget to reinforce the lid and allow for a way to lift it.

Also don't forget a drain in the bottom of the furnace. If you miss the crucible, or it fails, you won't end up with a ruined furnace, just a big mess.
 
I made my own from a mix of refractory cement from a home improvement store perlite and kitty litter. I think I used around 1 part cement to 5parts perlite and 2 parts kitty litter. The kitty litter was used as it came from the bag I just soaked it in water for a few days first to try and soften it a little and so it wouldn't suck water from the mix and dry to fast. I added enough water to the cement to get it to mix better but tried to keep it as dry as I could and still work with it. I rammed it into my furnace a few inches at a time. Then I covered it with plastic for a few days to dry as slow as possible. I let it sit for a few weeks to dry before I tried it out and when I did I used very low temps for a few hours. It's held together for a few years now. I have melted little areas of it but no major damage. I don't think I have managed to harden the whole thing yet though. The furnace cement needs to reach 400 degrees I think to harden and the outside never gets anywhere near that hot. My lid got wet in a flood and turned to mush because it had never been hardened so I made a new one from a stainless skillet. Overall I'm happy with it and it has worked well but i have been thinking about making a larger furnace and would not make it the same way. I would either try a chimeny liner backed up by loose perlite or firebrick with a hot face of furnace cement.
 
I used a recipe from http://www.alloyavenue.com/vb/forum.php, it works fine but it does not have the strength nor insulating power of commercial refractory. IMO commercial refractory is actually cheaper in the long run. I needed about 150Lbs to make my furnace, 15" diameter 19" tall. I used furnace cement as a hot face but it blisters and the burner turns it to glass, it needs constant maintenance. I cast Aluminum and make rough billets for my projects, I need to improve my pattern making skills to get greater benefit from the furnace. I can buy scrap Aluminum for $1 per pound, the propane is about $1 per pound to melt, so creating rough stock is fairly cheap and I can have any size or shape quickly. There is a bit of upfront work, building the furnace, the burner, crucible, foundry and moulding tools, high pressure gas regulator and acquiring the knowledge to cast safely. On the flip side you expand your metal working capabilities greatly. Aluminum melts at 1400F, relatively easy to do, Brass or Bronze at 2000F significantly harder and more expensive, Cast Iron at 2700F is a real challenge.
 
Perhaps Google gingery lathe or gingery furnace or gingery smelting /smelter . I found it several years ago & from what I already knew about casting metals in a small foundry I realised it was the best around .

You have to slowly cook it dry to stop it cracking but like a lot of things in life , waiting a bit longer often gives you a better result .

Somewhere in there is a sensible recipe for a mix of vermiculite , green sand & fire proof cement powder as well as some brill ideas for making a real dandy propane gas fired long lasting smelter /furnace that you can even melt brass or cast iron in.

If that is no good to you , there are light weight silicon sand building/ construction blocks that are used for insulation jobs & internal light load walls .. These can also be disc cut to a wedge shape to give you a six inch thick wall to a round smelter , or if joined with plenty of fire proof cement mix can be simply slid in and mortared up like normal uncut bricks ..


Dave


P.S.
Remember to leave a drain hole at the bottom of the smelter over a half filled can of sand can just incase you have a crucible melt down or failure .... it's to help contain any molten metal that flows out the smelter.
 
You can kind of cheat on the way you build to cut down cost. Use the lower temp to do the outer part of the furnace then go with a layer of higher temp refractory after baking that use a thin coat of a ceramic coating which would give you a much higher temperature furnace than the 2000°.
Nelson Collar
 
Nelson has got it, a 2" inner lining of "good stuff" backed 4-6" of broken up firebricks with a home brew mix or the ceramic wools. Be careful with old firebrick, could have asbestos, need to take proper percautions. It's real important to cure your refractory slowly, not just the inner layer but all of it. I've been using Mizzou mix from ApGreen / Harbison. Sometimes you can get expired or leaky bags for cheap. I also make fire bricks for forges and wood stoves by making a metal form. These mm bricks are more durable than what are in most stoves and forges.
 
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