Setting up a furnace, with a couple questions

[Michael Spaulding]

Hey folks!

I just finished 8 years in the US Army, and bought a house with a big back yard so I can finally build the forge and furnace that's been bouncing around my head for the last half decade.

I'm building a closed clay and brick crucible furnace. The plan is to fire iron and pig iron to make high carbon steel (along with some vanadium, Molybdenum, and some other elements) let it cool with the furnace, and then remove the solid ingots the next day.

I have no experience handling molten steel, or any other metal, and don't have any intention of starting now. I'm not particularly interested in casting, and if I wanted to cast anything, I wouldn't be starting with steel.

I do, however, have experience forging (though it's been a few years) but I'm very interested in the science behind the different types of high carbon blade steels we see in history, and I want to try my hand at recreating them.

 

So, on to the questions!
I plan to make my own crucibles of fire clay and grog, which is rated for temperatures upwards of 1700c (I don't plan to get any higher than 1260c) so it should handle the temperatures.
Are there any considerations for using a crucible like this for ferrous metals?
Is there any likelihood that a given crucible will survive having an ingot tapped out of it, or should I expect to have to smash each one?
Any materials you'd suggest adding to create a crucible with higher survivability, or for any other reason?

I'm also considering making a removable lid, to avoid having to rebuild the top half of my furnace every time I want to use it. I'm not too worried about heat loss, as I'm not trying to capture the entire 1400c capability of a charcoal furnace is capable of. I'm more worried about devising a removal system. I don't know what sort of strength fire clay has, but I imagine any removal and replacing of a clay lid will cause wear on something that large. I'm considering adding two holes across the top of the lid, to insert rebar and lift it off the furnace, but then I'm requiring a smaller amount of the fire clay to bear the weight of the majority. I could incorporate rebar within the clay lid to act as "handles" to run additional rebar through and lift, but then you have heated rebar within the structure of the lid, and I don't know what effect that will have on its longevity. Any ideas on a good method to ensure easy and repeatable removal of a lid of this sort? Is there another material I could consider that would do the job of a lid, but without the longevity concerns? I see what appear to be concrete lids on a lot of propane crucible furnaces, but the highest heat rated concrete I can find is FireRok, which is rated to intermittent temps of up to 1000c, and sustained of 300c, which do not meet my needs. What are these lids made of?

 

Okay. Lots of questions, I know. I still have more and I'd love to pick your brains, but this will put my on a good start towards putting the finishing touches on my design.

Thank you!

[ThomasPowers]

Will your crucibles really be larger than the vent needed for a furnace to work?  Will you need to be able to remove them hot instead of a slow cool to enhance the crystal size of the Wootz puck?  Messing around with home made crucibles full of molten steel seems to be putting Darwin on the speed dial.  If you are making your own crucibles I would expect them to be more of a one shot deal.  

BTW have you read Crucible Steel in Central Asia, Dr Feuerbach's thesis?  Lots of info on the crucibles they used ar Merv. How about Steelmaking before Bessemer vol 2 Crucible steel

As for lids: the larger the piece of refractory the more prone to cracking. try to design a sectional system.

 

Really you need to talk with Ric Furrer as an expert on this sort of thing.  Hopefully he will chime in!  (I was designated helper when he did his "3 ways of making steel" at quad-state one year and he mentioned the "Steelmaking before Bessemer"and as soon as I got home---still wearing my coat I was ordering a used copy (only one listed in the USA at that time)

[Michael Spaulding]

Thomas,

Thanks for the frank answers. I don't plan to remove the crucibles from the furnace before they're cool. I'll be testing a few different cooling times (between 30 minutes and several days) to test the effects of cooling time on the creation of the dendritic structures in watered steel, but I'll be doing that by batch (I plan to have a large enough furnace to run multiple sealed crucibles at a time, between 2 and 4, will require testing) so I wont need to remove any before the furnace, and the ingots, are cool.

I plan for the vent to be in the back (compared to the air intake) and not the top, so removal could prove difficult that way. Though, the idea for sectional pieces is perfect, and is probably what I'll shoot for. Instead of a cap on the entire thing, just one quart of the cap is removable. Reduce the size by a factor of 4, and still leave me enough room to get a tons in there and pull out a crucible.

Home-Made crucible = one shot deal. That's what I figured, and expected, but was curious if there were anything I could add to mix to increase life span. If not, I'll plan to making multiple crucibles.

I've seen you recommend Steelmaking before Bessemer before, and I've looked into it, but $150 isn't an insignificant price. I'm hoping to find a deal on it at some point.

I will look into Dr Feuerbach's Thesis, though. I'm very interested. I hold two things closer to my heart than anything else, and that's Reading, and the Scientific method. So expect lots of documentation and even a dissertation on my findings when I get things up and running!

[ThomasPowers]

You should be able to ILL that book at your local public library.  I've been able to ILL much harder to find books at mine in NM.  ILL is the hobby researcher's friend.

You might enjoy "The Mastery and uses of Fire in Antiquity" Rehder   on biomass furnaces used for heat intensive processes in antiquity.

[Charles R. Stevens]

Please take my comments for what they are worth, as I am an interested bystander and in no way a participant in primitive/historic iron and steel making.

as I do have an interest in the material culture of iron and its availability I have fallowed some of doings in the world of experimental archeology in steel and iron making. 

might I ask why you don't use a more modern design for you furnace? As you seem interested in using a crucible that is hand made, assumeably control the effects of contaminants by duplicating period materials. I would think that the sealed crucibles would eliminate any contaminates from the furnace its self. Certainly the less variables the better the science, and a modern (less than 100 years) furnace would not only make access, durability but also temp. and time more controled. 

This not to say that the period furnace didn't effect the product, and the fernace itself, as well as its performance are not important. In fact you will have to study them so you can replicate there performance. But as of a hundred years ago small fernaces were built for meteralogical research (before the masspectromitrr and the electron microscope) and one would assume that that they are still built today to allow manufactures to brew up new steel alloys.

modern refractories are presumably more effecient, longer lasting and easer to work with for testing multiple saples of material, 

this ofcorse doesn't even address the sorce or sources of your beginning stock, as the impurities in the ores that the base Iron was made from effected its composition and performance. In an example " Swedish iron" is it your plan to replicate the material strictly from chemical composition? 

My opoligies for sticking my nose in where I obviusly have no business being.

[Michael Spaulding]

Thomas,
Man, I never even knew that was an option. I will be spending a lot of time on MNLink tonight tracking down books.
Any other suggestions while I'm at it?

Charles,
It's mostly my being stubborn that makes me want to recreate (as far as reasonable) the methods used. I do plan to seal the crucibles to reduce uncontrolled variables, but something about a charcoal fueled furnace sounds particularly romantic, if difficult. The biggest concern I have is temperature. After some discussion, and gem of a suggestions, I'll be using an industrial blower, and the AC Motor equivalent of a Dimmer Switch, which allow me to dial in a particular amount of air moved in a given amount of time. From there, the old rebar test to ensure the furnace is reaching the correct temperature, and to dial in that nice golden yellow (1260c), mark the position on the dimmer switch, and always add the same amount of fuel, and we should be looking at a more consistent temperature between my batches, than any two blacksmiths of that age could get between eachother. If I run a couple batches and we need to adjust the temp a bit to get everything to come out right, that's part of the scientific fun.

Does anyone have a suggestion for a way to determine the temperature of a furnace of this sort in the 1200c to 1300c range that's more accurate than sticking a long bit of rebar in there and seeing what color it turns?
 

[Charles R. Stevens]

There is an I phone app fur determining the temp of a glowing object as well as some high dollar thermocouples. Tho not so expensive ones buried in the refractory and some experimentation to determan the difference in temp should work, especially if you use more than one.

i appretiate the romance of doing things the hard way, lol. Not an in depth article but " metalworking" by Paul N. Hasluck discusses small experimental fernaces, including one built from a largish crucible. 

[ThomasPowers]

Well you will go through a LOT of charcoal melting steel.  design it to make it easy to add and clean out the ash

Books?  I'm not so much a bibliophile as a biblio****; what are you interested in?   "The Knight and the Blast Furnace" Alan Williams goes into detail on the metallurgy of renaissance armour---900+ pages; "The Celtic Sword" Pleiner has a lot of info on Celtic ferrous swords, The Cementation of Iron and Steel, Giolitti has a bunch of interesting experiments on carbon diffusions---diamonds?  They work. No CO but carbon present? it works, etc.   Sources for the History of the Science of Steel 1532-1786, C.S.Smith; translations of works on steel in the Western Europe ending with a frenchman slapping his forehead and saying It's *carbon* that makes iron into steel!  (The list or renaissance quenchants is worth the read---wormwater and radish juice?  All guaranteed to make your steel stronger and whiter...Then of course Moxon's Mechanicks Exercises, the full version with the section on blacksmithing published in 1703, Astragal press puts out a facsimile copy with the f's for s etc.  The Metallography of Early Ferrous Edge Tools and Edged Weapons, Tylecote and Gilmour, Solid Phase Welding of Metals; Tylecote

 

Books run up real fast; so ILL can let you preview a book *before* deciding to sell a kidney to buy it...  Basically C.S.Smith, Tylecote, Pleiner, Williams anything their name is on is worth a look  

 

see IM  or not IM not working and the contact us on the error page doesn't work for the same error

so Are you on the Archeological Metallurgy mailing list yet?

Edited February 24, 2015 by ThomasPowers
IM failed

[Michael Spaulding]

Charles, that's really interesting. I might give an app a try, but I imagine lighting would be troublesome. Presumably they've given that more thought than I have in the last 2 minutes, so hopefully they've got more solutions for it than I do.

 

Thomas, I'm noticing these books do tend to run high. ILL will definitely help a lot, but I've got about 12 floor to ceiling built in bookshelves (three entire walls) in my beautiful, finished basement that need filling. Unfortunately, I've got a lifetime of books waiting for me to purchase them. Luckily my wife and I are both book nerds, so we've got... a third of the shelves filled already (That's a lot of books!)

I just have to save a shelf for historical mettalurgy

 

So that second to last line of yours, Thomas, is nonsense to me. I'm not sure what you're trying to say.

And no, I am not on the Archeological Metallurgy mailing list. Is there such a thing? I am interested.

[ThomasPowers]

When we moved from OH to NM we didn't move a couch, bed or tv, we did move 439 boxes of books.  Been at it a long time...

Our master bedroom has only 1 "clear span wall"  designed for the bed to sit against. We put the bed in the center of the room and did wall to wall bookcases; nice to go to sleep and wake up with a wall of books to gaze upon.

I was trying to send you an IM AKA PM, on how to join the mailing list and kept getting an error message; so I thought it didn't go through.

Then when I check my messages I see a half dozen of them.  I hope at least one made it to you.

[Michael Spaulding]

I did send two back your way, receiving the same error message both times.

Let me know if you did not get them.

[ThomasPowers]

I received the replies; still an open question

 

[Charles R. Stevens]

My understanding is that digital cameras actually are very sensitive to IR, thus the mirror finish, and the app works on some "black object radiation"voodoo or some such other hoodoo.

[Michael Spaulding]

Interesting. As I said, I'm less familiar with the process than the people making money off of it, so presumably they've got it figured out.

 

On another note, an old friend of mine just brought up a good point. Do I need a building permit for a foundry? I mean, as far as I'm concerned, it's an enclosed firepit. A glorified bbq grill. Where would they even draw the line between an in-ground BBQ and a Forge or Foundry?

And do any of you experience issues with noise complains when you spend all day at the anvil? I've only ever done it at a local workshop, with ear protection, indoors. So I have no sense of how loud it would actually be in the open air. I only have one neighbor I'm really concerned about with proximity, and they're agreeable folk so I'm sure we can work it out, but if it's not an issue in the open air, then I may not even bring it up.

[Nobody Special]

Thomas, I would also love to get info on that mailing list too, if you could sir. Are they any relation to the Historical Metallurgy Society?

Oh yeah, and Mike? Go Army. Beat Navy.

Edited February 25, 2015 by Nobody Special

[Michael Spaulding]

Hooah

[Michael Spaulding]

Well, I've reached out to my local city code officials, and was put in touch with the assistant chief fire marshal for my city.

So now when the cops show up because I'm blacksmithing and my neighbors freak out, I have a email traffic with the assistant chief fire marshal showing that my furnace is considered, officially, by the city a "Recreational Fire" which I can easily obtain a yearly permit for.

That was comforting.

[ThomasPowers]

Frame it!

[Michael Spaulding]

That's the plan!

[Michael Spaulding]

So, for a blower, I've been looking around at my options, and I think the most economical would be a whirlpool/spa pressure Blower like the one here:

http://www.pool-spa-supplies.com/index.php/air-supply-of-the-future-blower-max-air-1-8hp-110v-9-0a-2518120.html?gclid=CjwKEAiAyMCnBRDa0Pyex-qswB0SJADKNMKAu8qGid9p_SxeCUgy-cHGQvwTbsA089Uh1dNtbmNtxhoCayjw_wcB

I cant get any info on how Much air it actually moves, or under what pressure, but I don't actually know how much air or pressure I need to achieve the temperature desired (1260c) and that would be dependant on the design of my furnace, which I do plan to be pretty large, fitting four crucubles and enough charcoal to achieve the desired temp. It may require some trial and error, which could get expensive if I start with an inadequate blower.

[ThomasPowers]

1.8 HP seems pretty high, I'd think a good blower with a 1/2 hp motor would do fine.  Charcoal takes a soft blast and remember they used to do this with hand powered bellows.

[arftist]

It isn't a crucible if you let the metal harden in it. Then it is a mold. 

In a crucible metal must never be allowed to harden else the crucible will be destroyed. There is nothing you can add to a crucible to change the laws of physics. 

Might I suggest you save a fortune and buy some steel? 

[Michael Spaulding]

afrtist, I plan to create my own crucibles using fire clay and grog (with some other stuff, maybe. Charred rice husks? Sounds like fun to try) so my investment in crucibles will be minimal (compared to buy clay-graphite crucibles for one time use)

I expect the crucubles to be destroyed when the metal ingot is removed. In fact, I'm sealing each crucible before firing, so destruction will a vital part of the ingot removal process.

And I'm not sure my intention is coming across, here. I want steel to work, sure. But working steel isn't my only intent here. I'm in this for the scientific and archealogical process. I want to recreate a historical type of steel, and test variables to determine their effect on the outcome. I'm as much in this for the scientific results as the resulting steel. I'm in this as much for the failures as the successes, because I want to see which variables I can change, and how far I can change them, before Wootz steel either becomes unworkable, or no longer Wootz steel (or, more accurately, modern Watered steel, and nobody seems to know exactly what wootz steel was, even historical documentation varies greatly on what they identified as wootz, so calling anything wootz steel in this day and age is inherently flawed, as we're only guessing.)

If I just wanted to hammer out steel and make some stuff, you're right. I could avoid making a furnace at all, but that's not why I'm here. Having a cool metal to work onto knives and eventually swords, is certainly part of it, but I'm here for the science, and I'm willing to spend "a fortune" to get it.

Though, I am starting a kickstarter campaign for my scientific endeavor. To see if enough other people are interested in the science, and furthering it, to support my idea. We'll see, I suppose.

[ThomasPowers]

Crucibles are what the experts call them in making wootz and other crucible steels, exp " The base of the crucible was either rounded or pointed, an important point to note as the resulting crucible steel ingot would reflect the crucibles interior shape. " Dr Feuerbach in "Crucible Steel Production and Identification"  Indicating that the crucible was used to hold the melt as it cooled.  

And yes they were 1 shot deals and the crucibles were then crushed and used as grog in making more crucibles.  Crucible steel was an expensive process in the early days!  Teeming would help to hold the cost down nowadays but for wootz you need the slow cooling so you would be in fact pouring from one crucible into another heated one and setting that one back in the fire.  Hmm might be a good idea if you wanted to make a number of pucks of the same melt and experiment with the thermo cycling 

 

If you want to play around with doing your own and making modifications to the alloying elements then this is probably the cheapest way.  Ask steel companies how much for a 5 pound melt with very specific alloy specs and very specific heating and cooling requirements and how much for a dozen different runs!

 

Over at Sword Forum International there was a fellow experimenting with using thermite to alloy steel and was getting some interesting results---until he posted that he was going blind. I guess his safety equipment was not as good as he thought it was.

[Michael Spaulding]

I'd be afraid to use Thermite, personally. I'll keep my eyesight in tact, if possible.

I don't plan to get too experimental with the stuff, just test the limits of the variable materials noted in historic wootz steel, and things like cooling time and forging style. I'll leave adding new materials to the experts. I'm certainly not that yet.