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I Forge Iron

Refractory Choices ...


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I am finally building my ribbon burner forge as Borax has consumed my brick pile forge to a dangerous level. The forge design is built to allow hard bricks to be used as a sacrificial floor though I fancy I will be using a disposable 1/4" wall metal pan when welding anyway as borax is just nasty on the insides of the forge. That being said, I have a quandry when it comes to insulation. The forge is designed to be modular with 2" of insulation on all sides and faced with ITC-100. So I have a couple insulation options.

Pleated Superwool. This is the "healythy" stuff and I could pleat it and hold it with 1/4" stainless rods coated with ITC 232. The disadvantage is that the wool has an rated temp of about 2300 but we can guess more accurately a healthy working temp of 2100. When welding I typically hit 2500 with my current venturi and I would be surprised if my new blown ribbon burner couldnt leave that in the dust. I dont think the ITC will be good enough to protect the superwool so I have to think of something else to coat it with.

Refractory mortar wont do because it doesnt insulate. I would need a 3000+ degree castable and then I would have to devise some manner to bond the castable to the superwool. I could try and cast it right on top with an inch of superwool and an inch of castable but I think that the bond wouldnt be good and the castable would just tear out the superwool. In fact I cant devise a means to do a coating that will really hot face the superwool, and hold with minimal cracking. I figure with most castables I need a 2" pour minumum to make a viable structure when it comes to thermal cycling.

So perhaps I should just cast the whole thing. Of course then you worry about if it will have enough insulation if you do that. Castables are loads denser than wool and correspondingly less insulating capacity. However the ITC coating would help out a great deal and there would be no question of durability. Cast-o-lite 30li has a good rating but then I worry about insulation amount. Sure the cast option would take longer to come up to temperature but that would be ok. The question is, is 2" of cast-o-lite going to be enough to have a viable forge that keeps the heat in?

One idea that I had was to use some kind of castable that is made of phosphate bonded materials to resist the borax. The problem is I cant find a supplier of that on the internet. If I could get a castable like that, it would be great.

So, any opinions? Any light to shed on the decision? Thanks in advance.

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I sure can't help you, but I did hear a guy by the name of Joe Miller in Brasstown talking about some castable he uses that contains micro-rebar or something like that. It's SS pieces of wire mixed through the stuff, and when the refractory cracks, as it all seems to want to do, this stuff will hold together because of the micro-rebar (my term).
Problem is, I don't have a clue what it's real name is, or the cost of the stuff.

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