Direct reduction in a crucible?

[ZebDeming]

While reading deker's recent thread about preping for a wootz smelt, I heard it mentioned that a direct reduction in a crucible from ore is possible. Rather than clutter up his thread I figured I'd start new. I did some searching around and found that a few people around here have done it. I've got some ore here that's waiting to get smelted soon as I get some more charcoal around and a stack built, hoping it'll be soon, but my time has been at a premium lately, with all the wife's projects around the house.

While I'm gathering up the materials to do the smelt I figured I'd expiriment a bit and see if I could reduce some of the ore into steel in a crucible. The crucible I'll use is IIRC an A2 and I'll have no problem getting it to temp as my furnace is an oil burner. What I'm wondering is what kind of ratio of charcoal to ore should I start with? I realize that it's going to be variable based on the ore and the desired carbon content, but I'd like to know a general idea of where to start expirementing, I'm not trying to get wootz, just some sort of crucible steel to play with, I don't mind at all even if I've got to carburize it afterwards, but I don't really want to make cast iron. Just looking for some insight before I fire up the furnace

 

Thanks

Zeb

[Christopher Price]

Tricky balance, depends on the surface area of the carbon you're using, the uptake of carbon from the crucible, and the atmosphere of your burner. I'd start at equal amounts, and adjust from there.

[kyle o'donnell]

Tricky balance, depends on the surface area of the carbon you're using, the uptake of carbon from the crucible, and the atmosphere of your burner. I'd start at equal amounts, and adjust from there.

(good luck)

[Mark Green]

Hi Gang,

To play with this a bit, I tried a crucible smelt with, cast iron (I had made while smelting) some iron bloom bits, some raw magnetite ore, and some charcoal/vegi matter.

I have lost the pics somewhere, I will add them if I find them.

I'm not sure if it got hot enough, or went long enough. After about a 2+ hr burn, I let it cool overnight. It was much like a sponge bloom. It sparked pretty high carbon.

I cut it in half, and have been able to forge it out. The smaller piece I have folded a few times, and it is working like a solid billet now. The larger piece, is still in the works.

I haven't etched any of it yet. I guess I should, just to see.

 

I assumed, that it melted most of the way, but was just a bit short of full liquid.

 

I will look again for the pics of the whole process, I thought I had posted a few here in B&B.

 

If I have time, I will maybe etch up the near finished billet to see what I have.

 

OK, I couldn't find the cooking pics, but here are a few of the results in progress.

This is the larger piece, just compacted down a bit, and started grinding for the first fold.

 

This little bar is folded a couple times. It is showing kinda normal bloom steel grain.

 

 

Mark

Edited March 19, 2012 by Mark Green

[Christopher Price]

Mark, your experience sounds like it could have just gotten a bit hotter, a bit longer, and settled into a liquid charge. I'll admit not having done this myself, but I've seen it done over a dozen times now, with results all over the map. Jeff Pringle's the most consistently successful person I've seen with my own eyes, but he does things a little different and for some specific reasons.

[blackanvil]

You might want to check out a copy of "The Mastery and Uses of Fire in Antiquity" by J. E. Rehder. In addition to describing the direct reduction, he goes into a bit of how carbothermic reactions in a crucible work out, and iirc even gives some sample recipes. My copy is packed away while the house undergoes renovations, but I'll see if I can figure out which box it's in and pull a relevant excerpt if you can't find a copy.

[ZebDeming]

Thanks for all the input guys! Tonight I tinkered around a bit. I ground up 60 grams of ore and mixed it with 60 grams of charcoal, loaded it all in my blender and mixed it all up into a powder (the blender didn't like that one bit). I loaded it into a crucible that I've been drying for quite some time, the crucible is just made from a mix of clay from the backyard and some mizzou refractory. I've used mizzou for a home casted crucible before, but this time I decided to add a bit of clay to the mix to make it a bit more sticky and easier to mold. I had intended to use this one for some bronze, but I decided to see if it would hold up. I loaded the powder into the crucible, put some broken glass on top and sealed the top almost shut with some kaowool.

Into my oil burner it went and stayed there for a bit longer than 2 hours. The furnace didn't make it, the poor thing was on it's last leg anyways so I kept on burning while the walls were melting The homemade crucible held up very well, but no iron still just powder under the melted glass. Alot of it stuck to a magnet and there were a couple very small bits of iron, weather it's steel, iron or cast, I'm not sure as they were just very small.

All in all I learned one thing, that my homemade crucible's are pretty dang tough. Other than that I'm thinking that maybe I'll try some solid chunks of ore instead of the powder next time, but I'm gonna have to rebuild my poor furnace. Maybe it's just too small of a charge as well? More tinkering to do.

 

Zeb

[Richard Furrer]

Thanks for all the input guys! Tonight I tinkered around a bit. I ground up 60 grams of ore and mixed it with 60 grams of charcoal, loaded it all in my blender and mixed it all up into a powder (the blender didn't like that one bit). I loaded it into a crucible that I've been drying for quite some time, the crucible is just made from a mix of clay from the backyard and some mizzou refractory. I've used mizzou for a home casted crucible before, but this time I decided to add a bit of clay to the mix to make it a bit more sticky and easier to mold. I had intended to use this one for some bronze, but I decided to see if it would hold up. I loaded the powder into the crucible, put some broken glass on top and sealed the top almost shut with some kaowool.

Into my oil burner it went and stayed there for a bit longer than 2 hours. The furnace didn't make it, the poor thing was on it's last leg anyways so I kept on burning while the walls were melting The homemade crucible held up very well, but no iron still just powder under the melted glass. Alot of it stuck to a magnet and there were a couple very small bits of iron, weather it's steel, iron or cast, I'm not sure as they were just very small.

All in all I learned one thing, that my homemade crucible's are pretty dang tough. Other than that I'm thinking that maybe I'll try some solid chunks of ore instead of the powder next time, but I'm gonna have to rebuild my poor furnace. Maybe it's just too small of a charge as well? More tinkering to do.

 

Zeb

 

Sounds like you lacked an effective reducing agent.

Did you get and frothy foaming of the ore at all? It is common with this technique to have the crucible vomit several times...it is the lighter friable dross escaping from the container.

 

Ric

[ZebDeming]

There was no foaming at all. The charcoal I used was just plain store bought hardwood lump charcoal. Reading a bit on this, it seems that alot of the crucible steel "recipies" call for some kind of green plant matter? Maybe it needs some of the volitle gases to get the reaction going?

[Kutvonen]

I had some attempt like this, I think, if i get point right.

I wrote to my blog this episode : http://www.pajauttelu.blogspot.com/2011/08/i-try-something.html

 

Good pics, worst text and language

 

Then I brake this ignot and smelt it again, adding litle materials, and results:

http://s951.photobucket.com/albums/ad360/KUTVIS/Puukot/Wootz/?start=160 Pics 229-235

BLACK glass on top then Slag? something soft, sparkles little when gring

and bottom, tight very high C, cast iron? take no forging at all,

cracking when you put it down to anvil

[ZebDeming]

Thanks for the link Kutvonen! It definatly looks like you're on the right path, it's exactly what I was looking for.

Another question, carbon monoxide is what reduces the ore to iron, correct? It isn't direct contact with just the carbon source, it's the gas that does the reducing at a certain temp? If the crucible is sealed up tight with melted glass, there's very little oxygen in there to burn up the charcoal to make carbon monoxide. I may be over thinking this. I'm gonna give it another run probably tomorrow night, I patched up my furnace tonight and I think it'll survive another run. I'm not going to powder everything up like I did last time and not use any glass as a cover. We'll see.

On a positive note I roasted about 30 pounds of ore tonight as well, the charcoal should be here next week for the smelt and I'm hoping to build the furnace this weekend, so either way, I'm hoping to have homemade steel soon Thanks everyone for your input!

 

Zeb

[Jokke]

yes, it is the C-Ox that reduces the Fe-O to Fe

I had tried it in a very small crucible, heating the oolithe ore up to >1550°C for nearly three hours

no visible effect besides very small Fe-beads in a baken cakelike mass

no foaming but I did not set a half/half option with carbon material though

 

that is why I decided to rather use a rennoven to reduce the ore to iron

 

I hope to be able to discuss Janne's experience with him in end of June

[Jeff Pringle]

Just to restate what Jokke said, the carbon takes the oxygen from the ore, that is how the ore turns into metal. With a crucible full of ore and carbon you should at least get sponge iron, you may need some flux ingredients to get a liquid charge which speeds things up and helps you get to liquid steel.

What kind of ore are you using?

[Mark Green]

Hi Jeff,

Would that be glass, or borax or either?

With the one I did from above,I had about 1/2 small crushed up bloom bits, with the raw ore. I figures that there was plenty of slag like material in it already, so I didn't add any glass. But I did have pomegranate rind in mine.

It was a wild spongy mass. I wish I hadn't lost the pics. You saw them I think, when I sent you the results last fall.

It seems to be compacting ok.

 

I think zeb just roasted his ore well.

 

 

Mark

[Niko Hynninen]

Hi.

 

Here is my first result from years back.

Crucible was A12 ( both) that I used.

 

Way too much charcoal....but at end it was directreducted steel

 

http://www.bladesmithsforum.com/index.php?showtopic=10000&view=&hl=&fromsearch=1

 

BR

Niko

[Mark Green]

That's very cool Niko

That is just what mine looked like. I need to finish working those bars.

[ZebDeming]

 

I think zeb just roasted his ore well.

 

 

Mark

 

I honestly think that's what happened. Not sure why, but I'm gonna give it another try tomorrow. 114 grams of ore has been crushed into a little bigger than pea sized chunks and about 10% by weight of charcoal chunks have been added. Not sure whether or not I'm gonna run a glass cover. The oil furnace runs a pretty reducing atmosphere as is, and without a cover I can add charcoal to the crucible as it burns off. I'll take pics along the way and report back tomorrow.

Jeff, thanks for the info. What kind of flux would work well?

Niko, Thanks for the link, I've read it a few times now, It's always nice to see that other folks have had success, It let's me know that the flaws that happen with my process are my own and to try something new next time

Jokke, Thank you very much for the input!

 

 

Zeb

[Jeff Pringle]

Usually, the problem is not enough heat, so perhaps it was an extra ore roast

To get truely fluxed up , you have to know what kind of rock your ore is surrounded with, so pour some vinegar on your rox - does it fizz? then you have carbonate or limey gangue, and need to add silica. No bubbles at all? Grab some marble or limestone, powder it up and mix it in. Were there areas that bubbled and areas that didn't? you may have a self-fluxing ore, though based on your first results that is not likely. You can, of course, get a lot more precise than this, but I bet you can get where you need to go with the above rough outline. Remember, bloomery smelting = two days of hard work, crucible smelting = two beers and you've got metal to play with

[Kutvonen]

Little ot,

Is this Nature article worth of 32$,in this case or other, has anyone read this or access to read.

http://www.nature.com/nature/journal/v379/n6560/pdf/379060a0.pdf

( http://users.ox.ac.uk/~salter/arch-metals/met-review.htm#1367 )

I have a Paypal, but they need a creditcard.

 

And, WAYMAN, M. & JULEFF, G.,1999, Crucible steelmaking in Sri Lanka. Historical Metallurgy, intresting too

 

I want to know did Juleff only bloom or did her play with crusibles too.

I must go these sites, when next time visiting Sri Lanka

[ZebDeming]

Thank you Jeff! The vinegar didn't bubble at all so I crushed up a bit of limestone and added it. I've got 140 grams of ore in the crucible along with about 10% by weight of charcoal. No glass cover and I fired the furnace about 1/2 an hour ago, now I'm just kicking back and attending to the fire, and its starting to drizzle, oh well the little bit of rain never hurt anyone

 

I'll report back in a few hours

 

 

Zeb

[Mark Green]

Lee Sauder, and his gang, did a wind-powered iron smelting furnace. The link may be here somewhere in B&B. I will look.

It was pretty cool looking. I got to see it on a visit. It was in a bit of a protected space, so I think it was all about drafts, rather the blown winds. It was very spiff. It looked like a lot of work.

 

I couldn't find the link. maybe it's on his website.

[ZebDeming]

Wind powered would be pretty cool! The whine of a vacuum cleaner gets old pretty quick

 

Well it wasn't a total failure today. Once things settled down in the crucible, I would add a bit more ore and charcoal. I finally charged a little over 300 grams of ore and then let it cook. At about 2 hours and 15 minutes in the crucible broke so I shut it down and extracted what I had. It wasn't liquid so I didn't loose what was in the crucible. After some sorting and chipping I had almost 90 grams of bits and pieces of iron

 

It seems like cast iron, very crumbly under the hammer. I'm gonna fire up the forge tomorrow and see if I can stick it all together, we'll see. Even if it is cast, I've still made iron from rocks and I'm pretty happy about that. My furnace is now officially done for, and needs rebuilt, but I've got a burner from an oil burning boiler and a 2 gph nozzle for it that's gonna come in handy for the next furnace. My burner on this one is a siphon burner and it requires an air compressor to run, its quite the contraption

 

Zeb

[Mark Green]

Spark it. If it is just sponge iron. Make you an Aristotle, and turn it into steel.

If it is cast, save it to make some more crucible steel.

Edited March 24, 2012 by Mark Green

[ZebDeming]

I don't know why it didn't occur to me to spark test it, duhhh. It sparks, but very dull and not alot of sparks at all. I'll see if I can take a short video.

[ZebDeming]

Here's a short video of the sparking on my 1x30.

 

http://www.youtube.com/watch?v=fCokMPyCxKw&feature=youtu.be

 

Let me know what you think, I'm still kinda new at this stuff.

 

Zeb