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]

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.

[Dan W]

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.

[Bentiron1946]

I have done bronze cast for several years with home made furnaces of varying size made from fire brick and fire clay or from fire clay, silica sand and Portland cement. The ones that have lasted the longest have been the ones out of fire brick. I usually pour my bronze when the pyrometer reads 2,450f so the furnace has to be some hotter then that. The problem with clay, sand and cement furnaces seems to be cracks that developed from heating and cooling over time. These have to be continually patched. The furnaces of both types have to dried out very slowly or expansion of moisture in the refractory will cause explosions. The Portland cement helps the castable refractory flow and mix better then the straight clay in my experience. Very little is required to help mix the sand and clay together with a minimum of water. It should not be so much pourable as packable.

[FritzDaKat]

Unfortunatly all I've got in any quantity right now is a rather abundant supply of a natural reddish-tan clay which closely resembles basic potters clay after a good washing, as in flower pot type. So using this, other than frequent patching are there any other concerns I should have? (pretty handy with a trowel )

Would adding drill turnings help any or hurt? (I've seen it suggested but this was for adding to fireclay) And considering I'm washing the clay, would it be best to add the wood ash and whatnot while the clay was still in a slip form or would I do better to blend it in after washing / drying was done? And any thoughts on adding crushed flint to the mix? I know it does wonders for thermal limits in glass but mabey I'm just being too wishful?

Yea' I know I should just go buy some fireclay, but money is in very short supply for me a.t.m. :(

[Charl. Crossforge]

Fritz. Do yourself a favour. There is stuff on the market called mouldable ceramic fibre. Basically it is chopped ceramic fibre mixed into a sticky mois clay base (White). After finishing your furnace, coat it with this. It will need to air dry for about 2 days (when packed 1 1/2 cm thick. It becomes hard and insulates very well. this causes the furnace to heat and cool at a slower rate largely reducing cracking caused by temperature fluctuations.

[leviath]

try this place
HIGHT-TEMP INC.

[Ice Czar]

portland will degrade too, it fluxes

calcium silicates (3CaO.SiO 2 & 2CaO.SiO 2 ) found in Portland Cement are pretty closely related to Limestone (Calcium Carbonate) + assorted typical silica contaminations. And when you consider that throughout history limestone was the primary flux employed in blast furnaces.....


following those two links will show the various temperature dependent polymorphic states both Alite and Belite go through

closing this little conceptual loop, steel making slags are often employed as components for concrete
Belite flux - Google Search
Advanced Concrete Technology ... - Google Book Search

[thingmaker3]

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.

Perlite melts at 1850C, or about 3300F. Is it possible your bag was mislabeled?

[pamike]

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

what is the fireclay called at the building supply stores? I have a broter-in-law that works at lowes and he hasn't been able to find fireclay. But then again most lowes employees are idiots.

[longhunter]

Dont think you will find fireclay at Lowes . You will need to go to a building supply not a home type hardware store The pace I picked some up speclized in blocks , bricks , stone

[pamike]

we have a hardware store locally that has a stone center that makes thier own concrete blocks and firebrick, they also sell alot of furnaces so I might be able to find something there.

[Frosty]

we have a hardware store locally that has a stone center that makes thier own concrete blocks and firebrick, they also sell alot of furnaces so I might be able to find something there.

You'll have much better luck there. Failing that try looking for an outfit that rebuilds furnaces and ask them. Sometimes it can be really difficult finding out what the Yellow pages calls a thing. Seems simple alphabetical order has gone out the window here.

Frosty

[Radagast97]

A pottery supply store will have fireclay or kaolin, usually at reasonable prices, depending on how much you want. I think I bought a 50lb bag for about $25. They will also sell grog (crushed, fired clay), but that will be a bit more expensive.

Dont think you will find fireclay at Lowes . You will need to go to a building supply not a home type hardware store The pace I picked some up speclized in blocks , bricks , stone

[blackpete]

Perlite on its own is not useful for temperature above 900 C. Perlite is usally used in refractories in conjuction with other materials to increase insulation. For example in refractory castable sometimes called refractory concrete

[Chrispy]

I am currently struggling to create a refractory for my Gas Forge. I have a friend who is an industrial chemist who is trialing a few options. He is using coarse fly ash and aluminium oxide and some other (unknown to me) household chemicals that generate heat when mixed and create tiny little air bubbles (Looks like Aero Chocolate but its gray). The sloppy mixture increases like expanding foam to fill the required space but gets too airy and won't support itself and collapses just prior to setting. We are still playing around with quantities, hoping that may solve the problem. When we tested the dried tile from the bottom of a plactic container mould it has fantastic insulation qualities, and dosn't break down with direct heat from my oxy acetylene torch. 10 - 15 minutes of intense heat directed onto 1 spot leaves the tiniest glazed mark. The sample is 1 inch thick and no heat is evident on the back surface. The glaze spot dries hard when the heat is removed and dosn't seem to be weakened or fatigued in any way although while the flame is in contact with the refractory the glaze is sticky but self supporting. If he works it out and is willing to let me know the recipe I will pass on the details in a new thread. Sorry I cant be much help at the moment.:)

[dagr8tim]

Not to drag up an old topic, but I figured it was better than starting another topic with the same basic question.

I'm trying to come up with a refractory recipe that will work for a charcoal/coal fire initially and eventually I want to get to propane.  The working plan is 10 pounds of bentonite as a binding agent and 50 pounds of fireclay.  I'm wondering if I need any sand in the mixture.  I know everybody has a prefered DIY refractory formula, and most DIY solutions are not as great as commercial ones.

 

This is a small forge that's made out of an old Balloon Time Helium tank (slightly smaller than a 20 # propane tank).  I'm hoping to avoid using sand, but if I have to use sand, using it as a filler material.

[Charles R. Stevens]

http://ezinearticles.com/?Depression-Refractory-Mix-For-The-Backyard-Foundry.&id=85797
Try this link. The problem with cement (yes I know a lot of Peaple use it and recommend it) is that it's made by decomposing limestone and clay in hight temp furnaces, the resulting material is ground to a powder. When ond adds water it undergoes a chemical reaction making concrete. One one heats it up to high temp, it begins to decompose turning back to cement.