the_white

refractory cement

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After some extensive search I found some refractory cement sold in a bag of 25kg for 35$ a bag. I need to drive 1:30-2 hours to get it too. Here is the technical information on it. Company is vesuvius, product SURCAST

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I made a forge out of refractory cement. That price sounds about what I paid for it last year (2008).

Some things I would do different:

* My design was too deep a pot
* My air pipe was too small
* I expected the cement to hold the vertical air pipe with friction only. Not good.
* I got water on the hot firepot several times, it started to crack.
* the form was made of 2x4s. They were a pain to take off, so I left them on. They start to charcoal after about six hours of continuous forging.
* I would reinforce the concrete with wire and mesh

This being said, the refractory cement did not get clinker stuck to it (though the clay I used to raise the bottom did...) All in all, it was a good, but expensive choice for me. Good if you do not have the ability to make your own firepot in metal

-Doug

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Thanks for the price check information. Only thing is I'm doing a propane forge, I think you are speaking of a coal forge pot. Your information are still valuable to me, I will translate them on my project.

the_white :D

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I didn't do a price check but were I going to use a hard refractory this is the Vesuvious product I'd use.

Technical Specification Datasheet Level 3

It's a phosphate bonded high alumina refractory which means it'll be a LOT more resistant to welding fluxes. It also claims it has good low and high temp strength which says to me it doesn't suffer from thermal cycling like some hard refractories do.

The product you are asking about looks okay to me but without giving it a try it's a crap shoot.

The downside to building a gas forge with hard refractories is their generally poor insulating properties. However, products with high insulation values are generally fragile in direct proportion.

I got around this with one of my early forges by using a high phosphate air set rammable refractory to make a 3/4" thick inner liner and surrounded it with 1" 8 oz. Kaowool for insulation. I should've used 2" of Kaowool but as it was (is) it's held up very well. Every once in a while I take a scoop to the inside to remove the pool of molten borax flux that collects in the bottom.

It doesn't come to heat nearly as quickly as a straight Kaowool liner but it comes to heat a LOT faster than a straight hard refractory liner.

It's a hybrid with the better properties of both types of liner, just not in full measure. EXCEPT tough, the hard refractory I used (no longer available unfortunately) is concrete hard and caustic resistant at 4,000f. The stuff was developed to line furnaces operating at 4,000f with an AMMONIA atmosphere. Compared to that 3,000f borax is laughable.

Frosty

Edited by Frosty

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Great reply has always frosty. My only question is the product you linked Technical Specification Datasheet Level 3, is it a cement? I read plastic refractory...


I ill see if they have it in stock tomorrow. If they do I'm planning on going to buy the stock Monday. It's on the Quebec side near Montreal. I'm from Gatineau so if anyone near ottawa region need some stuff, now is the time to talk!

the_white:D

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Great reply has always frosty. My only question is the product you linked Technical Specification Datasheet Level 3, is it a cement? I read plastic refractory...


I ill see if they have it in stock tomorrow. If they do I'm planning on going to buy the stock Monday. It's on the Quebec side near Montreal. I'm from Gatineau so if anyone near ottawa region need some stuff, now is the time to talk!

the_white:D


You don't actually want cement. You would you plastic refactory as a liner.

Hard liners of ramable plastic refactory are very durable. The trend in the last twenty years has been away from dry mix to premixed (moist) refactories.
It has to do better chemistry and broader range application products.

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Plastic refractories are pre-mixed for optimum performance and cements are generally for sticking things together, think fire brick mortar.

To use a rammable (plastic) refractory you ram or hammer it into a general form with a mallet till the mallet bounces. This gives you the best density.

When I made the cylindrical forge liner I was talking about before I used two Sonotubes. (cardboard cylindrical concrete forms)

I wanted a forge with an ID of 6" so the OD of the inner sonotube was as close to 6" as I could find. This was the inner form.

The outer form had an ID of as close to 7 1/2" as I could find.

With the inner form spaced in the outer form there was a gap (annulus) of 3/4" all around. The tubes were attached to a piece of plywood with sheetrock screws so they couldn't shift around. They were also cut to length, about 16" as I recall.

Then I used a piece of 3/4" sq. bar as a rammer and a hammer to ram the refractory into the space between the sonotubes. Do this in 2" lifts (a little, 2" at a time) or you will NOT get it compacted well enough. Go round and round till the form is full to the top being sure to ram it good and hard at the top. I just piled it a bit above the forms and used a mallet to hammer it till it bounced.

BEFORE you peel the inner form use an OLD cheapolla hole saw to drill your burner ports. If you do this after it sets and before it dries you will minimize the chance of cracking the liner making the hole(s).

If you wait till it dries you will have to buy a carbide masonry hole saw and those are EXPENSIVE. A LOT more expensive than an el-cheapo bargain store hole saw that works just dandy when it's still wet. It will kill the hole saw but it's a cheapy. yes? Also you can get a cheap hole saw in any number of sizes where the masonry hole saws come in limited sizes. Like one size ONLY around here.

I let it set for a day then peel the sonotube from the inside to allow it to dry. You don't have to get it all, if a little paper sticks to the refractory that's okay, you're more likely to damage it trying to get every little bit than a little wet paper is to damage it. Peel the inside form because the refractory will shrink as it dries and if there's something strong inside it will check (crack). The outside form will support it while it dries without a chance of damaging it. The shrinking will in fact pull it away from the form slightly making it easier to peel. I just cut the outside tube with a utility knife once the liner was dry it's pretty tough.

If you live in a humid climate place a light bulb inside to aid in drying.

Once it's dried and installed in the forge shell it's time to cure it. Follow the directions on the product if any. If there aren't directions start out with a SMALL fire, I like sticks and paper for the first firing. This just gets it hot enough to drive off residual moisture. Once it's reasonably cool light your burners for a few minutes and let it cool down again. Cover the openings so it cools slowly.

Next firing I like to get it to red heat for a while, keep the burners turned down. If you don't see any large heat checks (cracks) or spalling (pieces popping off the inside of the liner) it should be ready to go to work for you.

Frosty

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Plastic refactory is more like stiff modeling clay. You put in two or three inches pack it down to get out all the air. Put in two or three more, pack and so forth. I cann't find Frosty's description at the moment, but that is the way. Home builder supply places have cardboard tubes pupose made for molding round objects. You can actually make it any shape you want so long as it is well packed and more or less constant thickness with no voids.


Any thing that would be pourable like cement would not stand the heat. I fool with pottery clay some and know that the more refactory the clay is the stiffer it is.
Plastic refactory is about like the clay used to make Ceramic sculpture.

Edited by Charlotte

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This will teach me for writing long drawn out posts. ;)

This is pretty much what you want it to look like though most folk introduce their burners at the top. I don't know that it's the best though, I can think of some advantages to placing them as you've drawn.

There are problems though, mostly is the unburned oxy directly in the flame though I put my steel directly in the flame so I don't think it's a huge down mark.

Anyway.

A castable is more liquid than a rammable and you can use forms just like I described to form it up. Castables are less dense than rammables though AND have a cement component to make them set so they aren't generally as strong nor as high temp.

The dark zone, (inner liner) is way thicker than neccessary and the light zone (kaowool) should be 2". My 3/4" thick inner liner is about 17 years old and still in okay condition.

Frosty

Ok good to know. But is it pourable like a cement so I can make the inside of my round forge layer? foundry_tv.jpg Thanks for your time!

the_white :D

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I'll have to read it again but I think I understand your concept (hehe main language is french :P). I was thinking of doing my forge inside an air tank or something. So if i do it in between 2 sonotubes, after I remove the cardboard, will I be able to make it tight enough to the k-wool that it won't move all the time. For the image burner position, you have to remember i took this image on a foundry based plan which heat at the bottom when the foundry is at the vertically, which I'm not gonna do so I am probably going to but in sideway like most people do.

the_white :D

P.S you guys reply so fast I had to refresh before posting just after reading at longer frosty post hehe.

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Ok, you get the idea. You can make the the refactory fit. I've never had any problems wraping things with insulating wool.

You will find that the refactory is HEAVY when cured so handle carefully. It won't move much once in place.

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Were I to make another cylinder forge I'd use Stainless steel stove pipe for the shell. It's light, tough, reflects heat, is easy to work with and commonly available. You can make custom diameters by snapping different diameter sections together. For instance if you need a 14" diameter shell you can snap a 6" and a 8" section together. (Along their seams)

When I made my pipe forge I discovered the double liner didn't want to slid into the pipe shell so I wrapped it in newspaper to compress the Kaowool and used a little tape to hold it. It then slipped in easily and the paper is probably still there if it hasn't rotted away.

I forgot to describe how to make flat sections of rammable refractory. Use a piece of plywood larger than the slab you want to make and screw wood the same thickness as you want the finished refractory to be. for instance 3/4" thick boards for a 3/4" refractory wall. Now you simply hammer the refractory into the form but when you get it near the finish thickness use a thick board like a 2x4 on edge that bridges across the frame and a heavy hammer. You will end up with a nice dense, uniform piece.

This can then be removed from the form and it's still flexible to a point till it starts to set.

Joining pieces is a little harder, place them in contact and cut them together with a butter knife and using something to back it gently hammer the parts together with a mallet or small hammer.

If you want a largish flat roof you'll need to support it till it sets.

Frosty

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Ok thanks for all the information. It's a chance I work in building supplies store ;), I will try and see if we have any damage insulated pipe to get it cheap.

the_white :D

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If that is a view from the side I would move the burner entrance up so if something ever melts and "runs" it won't be able to go down the burner tube...Also scale and crud don't build up in the tube.

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Here is a link of what I'm talking about.Catalogue - SuperVent 2100 (JM) (JM002-E)
If you look under technical pipe data it explain it's a pipe 300 series stainless steel 0.016'' thickness has inner layer. Then there is 2'' of insulation and another layer of type 430 stainless steel 0.015'' thickness. I don't know if the pipe is similar to what you were speaking of. I was thinking buying that, cut it and remove the insulation and put both my plastic refractory and K-wool insulation. The only concern i have is it's only 2'' in between the inner layer and outside layer, and you advise me to put 2-3/4'' total materials thickness. Since it's stainless steel I was wondering if i could let the inner layer inside has a permanent layer.....just thinking about it while I wrote those lines I guess it would melt..... :mad::(:rolleyes: .... Maybe you could link me a picture of the product you are speaking of, I think i got it wrong.

Another one for you Frosty you said I should take the Technical Specification Datasheet Level 3
I called in today and it's not a regular stock for them. The guy suggested to take this one instead, saying it's regular stock and better. Here is the technical sheet Technical Specification Datasheet Level 3
Here is the MSDS http://www.vesuvius.com/lwwcm/techspec.nsf/22EE9E9F8C03F3CB85256B0A0052C63E/$FILE/LES10072-5.pdf?OpenElement
Here is the instalation procedure http://www.vesuvius.com/lwwcm/techspec.nsf/50394B7A8D0C1EDF85256CE2005B44F4/$FILE/LES1301.pdf?OpenElement
Here is the drying and firing http://www.vesuvius.com/lwwcm/techspec.nsf/DBF338AF0301A95085256CE50068D5D3/$FILE/LES1801.pdf?OpenElement

It is worth BLU-Ram HS @ $ 40. 61 / per box of 25kg. (Canadian price)

Do you think this stuff would be good? --------->>>>> thanks again

the_white :D

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Okay, I wouldn't spend money on the insulated pipe. Are you familiar with single wall SS stove pipe? The stuff you use to get the smoke from a wood stove out of the house. Yes?

It comes with the seam down the side unconnected so they can stack lots more for shipping. To use it you simply snap the seam closed. how it works will be obvious when you look at a section. It typically comes in 3' lengths and a wide range of diameters from 3" to 12". (here anyway)

SS stove pipe is MY preference for making pipe forge shells though it's certainly not your only option. It is more than strong enough to support most any work you're likely to want to heat. It can be worked with aviation tin snips, hand drill and pop rivets so you don't need special tools at all. It is a POOR conductor of heat and will help keep heat inside the forge where it belongs.

There are more arguments for SS stove pipe but those are the main ones.

That's an even better refractory.

How I judge these things from a data sheet is this:

#1 Is it a high phosphate or phosphate bonded? A no means I'm not interested.

#2 Working temp @ 3,000f+. This is not the max temp, it's the max WORKING temp. for the refractory. A well tuned propane burner can reach 3,200f. It has to be a VERY well made and tuned burner like a Porter type 5 or better.

#3 I prefer rammables over castables but it's not a deal killer.

#4 The less SiO2 and the more Al2O3 the better. Aluminum oxide is more resistant to thermal cycling and hot caustics.

Thermal cycling is heating and cooling, every time you light your forge you bring it to very high heat in a short amount of time and when you shut it down it cools back to room temp pretty quickly. This is BAD for hard refractories so the more resistant it is to thermal cycling the longer it'll last.

Forge welding fluxes are usually borax based and borax at welding temperatures is very caustic. Silicon Oxide is susceptible to caustics, they disolve it. Aluminum Oxide on the other hand is pretty immune to caustics.

So, more Aluminum Oxide is better, less Silicon Oxide is better.

So this is how I read this refractory.

Phos bond. Good.

Workig temp 3,100f Good.

It's a plastic / Rammable. Good.

SiO2 is 20% and Al2O3 is 72% (yes, I round things off) Good.

I like it.

Frosty

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In the same line of idea's I sent a message to the salesman of Vesuvius with the spec sheet of kaowool blanket to know if they have a similar product.
( http://www.thermalceramics.com/pdfs-uploaded/datasheets/americas/514-205.pdf)
He sent me this http://www.fabricationspecialties.com/pdf/cerwool.pdf
(I had to find a link on the internet so it's not exactly the one he sent me but I think Vesuvius blankets were bought by ThermalCeramics so this link should be appropriate. I didn't see a lot of changes in it).
I just want to make sure I can use that product has outside layer. I

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Any of those should be just fine for the outer liner. I'd go for the middle one myself.

Frosty

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For the forge itself I was thinking doing like you said, 6 inches diameter inside. 34"-1" blue ram and 2" of kaowool like insulation. My question now is what length of forge should I build? I know it depends what you want to forge. I was thinking doing it 24" to 36" long. Considering the stuff is pretty expensive i want to buy the minimum I need. I was thinking to put 2 burners with a valve i can chose to close to run on only one burner. Any advise on that?

thanks

the_white :D

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I am building a 2 burner forge that is 11 inches long. The ceramic wool comes 24 inches long. I have found many many MANY websites of smiths using forges about a foot long. Calculate your volume and figure 200-350 cu inch per 3/4 inch burner. Choosing which burners are lit is nice, running more than needed is a waste of fuel. Frosty and I were discussing which single burner is best to run, but never came to a conclusion other than one more valve is cheap.

Before you decide on the length think about what you plan to make, and think about the longest item you expect to build. You can always build a larger forge in a few years once you have skills to take on larger projects.

Phil

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When I made that forge it was for someone else who wanted to forge knives. Unfortunately his cancer got bad enough he couldn't do much of anything before I found him everything he wanted. I ended up using the stuff and sold the anvil some years later.

Anyway, I found a 6" dia pipe forge very restrictive, I couldn't even heat a hay hook in it. Then again I don't make knives so it may have been perfect and I didn't know it. ;)

Like Phil says, figure the volume and use one 3/4" burner per every 300-350 cu/in for general forging and one for every 250-300 cu/in if you're going to do a lot of critical welding.

One thing you can do in a long forge is make a movable baffle (back wall) so you're not trying to heat the whole forge when you only need the front few inches.

Frosty

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