# Concentrating heat?

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I've been hit with a wave of revival for my fascination with blacksmithing, and, in particular, sword-smithing and armor-smithing. In order to have any hope in pursuing this interest, I need a furnace (of sorts) that is capable of heating iron, and eventually steel, to red-hot temperatures. I would prefer this to work in conventional means, and not involve the use of gas. In addition, it would be a definite plus if it was of minimal size, which leads me to my question:

Is there any way that I can concentrate the heat and increase the resulting temperature of the interior of a heating chamber? I know adding a permanent bellows (basically, a continual fan blowing up from underneath the heating chamber) is an option, but is there anything else?

If you have any questions, feel free to ask.

Hopefully that wasn't too vague. Thanks in advance,

Calbit

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Farriers using standard forges use a bank of fire bricks to focus the heat sufficiently to heat different grades of metal so that they can be beaten together (welding a laminate, as when making a sword). Instead of having an open bed of glowing coke, they rake the coke into a mound in the centre and bank up the sides with the fire bricks to keep the heat in and use a fan which results in enough heat to take iron and steel to white heat.

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Would clay tiles work the same way? Well, the more appropriate question is, would they be practical? I can't describe them, other than you can get 'em for a couple US at random home-improvement / building shops.

Where could I obtain coke? How much would it cost me?

Also, could regular coal be used instead? If yeah, would it be any cheaper?

[Edit: wouldn't a high-temperature-tolerant parabolic mirror be better? That way, the center is incredibly hot? Or a combination thereof? I don't know the temps where steel/iron gets white-hot or red-hot, but I do know that aluminum in particular has an incredibly high melting point.

Then again, looking at melting points in particular, that doesn't look like it's going to be feasible, or even possible.]

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I think anything that could insulate the core of your forge would work. I don't know whether or not coal would work. It'd probably be more smoky and I think it burns at alower temperature and produces more ash. Coke or charcoal would work. Charcoal was used for the same purpose in the iron age, they made pretty good laminate swords back then too. It burns at a very high temperature, particuarly with bellows and produces little ash and not much smoke and fumes. You should be able to get coke and/or charcoal at any proper ironmongers or DIY place. Neither costs that much in the volumes you want.

The temps charcoal burns at with bellows is high enough to melt copper and tin in a suitable crucible. They've been doing that since the bronze age.

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coal will give of acid vapors too, thats not so good for your metal purity.

Coke is made by heating coal in an enclosed space and then distilling off the gasses (coal tar is a product), the remainder left in the vessel is the coke.

you could use the industrial Blue Brick and fire clay to make your forge also, youll get fire clay from most places that sell indoor fireplaces.

Ive used the coke furnaces and the ceramic bead types with the forced air propane burner, the Coke is Much better IMO, I dont know if youre going 100% traditional and using Bellows, but if youre not, you can use a simple low power vacuum cleaner with a speed controler (just rem to put the pipe on the other end to BLOW).

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Will charcoal heat steel and iron to white or red-hot temperatures? I never knew it could be so hot. Just the run-of-the-mill kind, like you would use for a grill? Out of curiosity, what kind of temperatures can plaster of paris withstand?

YT, I'm not in any way worried about being ultra-traditional. Almost anything that makes it more practical or cheaper is fine by me.

What I'm thinking right now is that I'll use bricks or tiles of some sort (probably fire bricks... You say most stores that sell fireplaces will have them?) so that I can reconfigure the furnace for other things - for example, melting copper, bronze, etc in a crucible for detail work and castings, or if I feel like it, just a grand ol' bonfire with some good ol' wood.

Thanks for all the help, it'll definitely do worlds of good.

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plaster of paris isnt all that good to be honest, the heat Super dries it and itll crack and crumble back to a powder again eventualy.

as for the charcoal, when its just left to glow away as on a BBQ its not all that hot, when theres Air forced past it, it gets plenty hot enough! as it actualy Burns with a flame then, and yellow hot is easily attainable (white hot for iron is a bit much for just charcoal), youll be "feeding" it alot more and faster than you will with a BBQ, so youll need plenty by your side, dont use the BBQ Briquettes either, a high percentage of them is Clay, Lumpwood charcoal is best

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You can through a layer of those little grey stones as a bed under the heat source coz it reflects heat. It should help. hope it does. Maybe if you can explain how ur furnace looks like and can get ideas.

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yeah, youll need a grill or mesh at the bottom to allow the air to pass through and then ceramic chips or those stones on the top, then yer charcoal or coke.

Nice idea acidhash

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Took me a second to get what you meant, acidhash, but yeah, that's a great idea - it makes perfect sense. Which stones are you talking about? Just little pebbles? Or are they something in particular? I'll do some materials scouting this weekend and let you guys know what it's gonna look like when I scrounge up some cash, and I'll be sure to keep you updated on my progress - and any suggestions you might have would be cool then, too. I suppose I should ask where a good place to get either coke or charcoal would be, then?

Again, thanks much for all the help.

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If I understand your question, to concentrate HEAT, you must have a larger MASS holding the heat

If you want to raise/concentrate TEMPERATURE, a focusing array of mirrors could do it.

If the heating element in the chamber is an electric resistor, a parabolic/eliptic mirror behind it will concentrate the temperature to a focal point.

Miguel

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If I recall correctly, the recrystallization temperature of steel is 727 C. That is how hot it needs to be in order for the molecules to have enough energy to re-align the micro-structure, creating different forms of steel.

that's HOT

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Yep. Not as hot as that forge is going to be, though.

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An idea just hit me - would using hydrogen as a fuel be practical? It's relatively easy to obtain and burns at very, very high temps... Or would that be too dangerous?

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dangerous and overkill (and probably expensive).

youde be much better off with Propane or even House gas (methane).

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I'd rather just use coke or charcoal, which brings me back to my previous question - got any suggestions of where to acquire some? Coke in particular, if you don't mind.

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Coke is easy to get. You should be able to find it at a large DIY store or just google for suppliers. Anywhere that deals with the (re)installation of period fireplaces and such should also be able to source it for you.

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Sounds like a trip to Home Depot would do loads of good.

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I had another idea about this for you, it Should be quiet easy to convert one of these Gas BBQs to make you a little forge, youll have to modify the burner and youll still need to have a way to force air under it (a little 12 volt dust buster vacuum). and some extra ceramic briquettes, but it would work excellently for small scale experiments.

Just an Idea

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Not a bad idea, but it might actually be cheaper to go with the fire bricks. I was considering hooking up a propane tank, but I think I'd rather just go with the coke. I should be finding some materials this weekend, I'll update you guys then.

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Get a furnace and a large ceramic cover and containter. Melt down metal, preferably aluminum and get it hot. It should remain molten red hot for some time. A quick dip of the sword would get it red hot. Although each dip would cause the metal in the container to stick to the sword but maybe a ceramic casing around the blade would do the trick. Or even dont worry about it and let the by product metal fling off while working the material.????

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That's quite inefficient, arkain - physics dictates that a lot of energy will be lost in between melting one metal and using it to heat another. Plus, it's simpler to just heat the desired metal in the first place - not to mention more efficient. But thanks for the suggestion.

My update is as follows: I've decided that I'm going to get an anvil before I worry about the forge itself. I'm not exactly sure where I'll get my materials, but we shall see. And as far as the anvil goes, I think I'll end up making my own - a bit of a task, but it'll save money, and the experience (as well as bragging rights) will be good.

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I think that is best if you use electric heater ,it will be not so expensive + if you put around him bricks you will have good oven.

If you like you can put electric energy direct on the object you like to heat and if you can control the current (A) you can precisely reach temperature

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That's not going to be practical for blacksmithing purposes. Additionally, that will NOT turn iron into steel, which I may end up doing, and it would be a massive power drain, especially to reach something like 500-2000 degrees celcius (depending on what I'm doing). Again, thanks for the suggestions, but I think I know exactly what I'm going to do.

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• 3 weeks later...

727C doesn't sound like much, anything under 1000C is easy with a solar Fresnel lens 1m in diameter. These are available for \$200-300 and can melt a penny to liquid in a couple of seconds. just google it to see the stuff people melt with them. I forget the exact calculation but a 1m lens will focus about 1KW of heat/light.

The other great thing is that there is almost no heat limit unlike coal or electrical elements, all you need to do is insulate and wait for the heat to rise.

Oh yeah and it's clean and free to use too

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