Homemade refractory recipe

[easilyconfused]

I've been reading about used oil burners for casting and trying to come up with a recipe for some homemade refractory for the burner. I have portland cement and perlite kicking around the farm and some hard firebrick. I was wondering if, while it will be a fair bit of work, crushing up the firebrick would work for the refractory or will I still need new fireclay or benntonite clay?

[johnny99]

I'm pretty sure that won't work. You could use crushed firebrick instead of the perlite, but you stiil need the clay, (I think)?
The cheepest unsented kitty litter you can find will be bentonite clay. you can either crush it w/a mortar and pestal, or contrive some kind of grist mill setup. Or you can be lazy like me , and just dump it in a bucket of water and let it set for about a week, stirring well a couple of times a day to turn it into slip.
But the question on my mind is If you have firebricks already, why not just use them for the insulation?

[metalmaster1766]

whatever you do, DONT use portland, best thing to use is fireclay, most building supply places have it,
i have crushed up firebricks and used it as grog for refractory, what i used was grog(crushed firebricks) fireclay and silica sand, i cant remember the amounts of each, but mostly grog
bentonite works but from what i have been told it wont take the temps that real fireclay will, and over time will fall apart

Ron

[Marc]

I tried a DIY refractory made of perlite, fireclay, and portland cement once. Both the perlite and cement melt at high forging temperatures and I ended up with a real nifty-looking glassy substance. But it was real soft in the forge at temp.

[easilyconfused]

Originally Posted by metalmaster1766

whatever you do, DONT use portland, best thing to use is fireclay

Could you elaborate why you shouldn't use portland? Everyone seems to use it but is there a safety issue? Or just that it doesn't work well?


I was planning on using the fire brick as insulation for the forge but for the burner, they would be too big and awkward to fit into a small space.

[johnny99]

Oh, ok. I was misunderstanding what you wanted to use it for. I belive you it is recomended that you don't use cement, as it can spall violently from thermal expansion. Basically the same as not using river rocks to build a fire ring.
If all you need is enough for a burner, Ace hardware sells quart sized buckets of furnace cement for under ten bucks that will work for what you want, I think.
BTW. I have to agree that the bentonite will degrade and crumble fairly quickly.

[metalmaster1766]

portland will degrade too, it fluxes when it gets up that hot and will crumble, i have never used portland in any of my foundry furnaces or forges, but i have seen a few that have and they never lasted
the portland has nothing to do with spalling, concrete on the other hand will, but it cant take the temps that an oil burner will get up to without crumbling
there is a lot of info on this very subject at the BYMC forum, a lot about perlite as well

Ron

[easilyconfused]

I've done some more thinking and am leaning to a square urtuze, or however you spell it, style burner so that I could use the whole hard fire bricks. I was just wondering if they would protect a layer of the recipe on melting metal in a home foundry, backyard metalcasting, metal casting if I used it as a thick layer of mortar behind the bricks, for support and insulation? I'd like to use the stuff up since it's been sitting in the shed taking up room for a long while but don't want it burning out after the first couple runs. Cheap is definately good since I'm a student and, since I'm learning, don't feel the need to spend money on high-end refractory during my learning curve. That being said, I also don't want to waste my time with really poor stuff that won't last a burn or too.


Another question that I haven't found the answer in the search button yet, is the approximate fluxing/melting temp of benotite.

[jim frank]

Hmm- my propane forge has a liner made of portland cement, clay dirt from the yard, silica sand, and perlite. The proportions were about 1:1:1:5, if I recall correctly. I use a layer of half inch kaowool inside a two inch layer of the above refractory, and have never had problems in many hours of operation. I've used portland cement in every homemade refractory I've ever made, and if you keep it under about 10% be volume, it seems to have few problems.

[JAFO]

I recently read and have since made and used a 50/50 mix of river clay and sand with a handful of hardwood ash thrown in for a binder. It is similar to adobe and should be put on in layers as one thick layer will crack as it dries.
I live in northern Florida and have access to a white clay that is found in most of the natural springs around here.