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Smelting Steel from iron ore

Nancy Reading

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I've been considering the possibilities of making steel from raw materials. Mostly because I think it would be amusing. Our rock here is basalt, the remnents of an ancient volcano that straddled the Irish sea. I believe I can collect black sand from our local beach as a starting material. Ihave no idea what sort of quality metal I may end up with, but there is a local knife maker who may be interested in making something if I come up with something useable.

This thread then is a project thread to collect together some resources and report on progress as and when any is made. I'm happy for people to chip in if they are also either succeeding in smelting, or wishing to have a go too.

I found this article on iron processing on britannica.com fairly useful as an overview. It seems that a katana furnace, which is used in Japan to make steel is pretty similar to a bloomery furnace. This 'blog post about Japanese swords going a little into the metallurgy of the swords. I went down a few youtube tunnels and found a few that are of interest:

A little delving into the metallurgy suggests that the simple bloomery furnace gives a metal that is easier to work with if you have an unknown ore, because more of the impurities (Phosphorus and Sulphur) are able to escape during the smelting process. When heated in a crucible (known as wootz steel) the post smelt process is more involved to get a fine quality steel.
I'm interested in seeing whether somehow the crucible process could be adapted to let the impurities out as obviously this will be easier to adapt to the rocket stove as per Uncle Mud's furnace. Otherwise there will be a lot of charcoal involved.

Questions:
Would the j tube (or batch) get hot enough to smelt steel without forced air? The video of the natural draft furnace implies this is the case, although their yield was rather low. How hot does it need to be for how long?
Could an open crucible let the impurities escape? I'm thinking load a crucible with ore, appropriate amounts of iron sand, charcoal and maybe some oyster shells to promote cleaning, and heat up in reducing atmosphere in the riser as per Uncle Mud's rocket forge from the low tech jamboree.
How do I tell what sort of quality steel I have (assuming I get any!)? Spark test shows carbon content, but what about the Phosphorus and Sulphur impurities?

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Joshua States

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Nancy,
You are embarking on a journey that will take you down many rabbit holes. I was about to direct you to https://permies.com/t/240809/tech/DIY-Steel-melting-foundry, but I see you have already been there.
The links and reference materials I posted there are excellent places to start. I am not familiar with any of the videos you posted and cannot comment on the reliability of any info they provide.
If I can be of any help along the journey, please reach out to me. I will be following this thread as well.

What I can recommend is using the iron sand in your area rather than the basalt. Extracting iron from ore is a rather tedious process with good quality limonite or bog ore. Extracting it from basalt is another thing entirely. Sifting and sorting the high iron sand out of the batch is an easy process and will help reduce the slag (impurities) in the smelt. Just get one of those big pickup magnets and pull out anything that sticks to it, discarding what doesn't.

A supercharged location of smelting information from modern-day people who are actively pursuing the craft requires you to join Facebook, if you haven't already done so. There is a FB group called "Iron Smelters of the World". and you should join. They keep an online library of historical documents that you can download, and people post frequently when they do smelts, discuss results, and are generally very enthusiastic about sharing information and helping others to learn. I also have some documents you might want to read, which I can send you via email.

Crucible steel and bloomery are very different products with very different processes. While you can put ore into a crucible and make steel, (this was how Pulat or Wootz was made) I would not recommend putting iron sand into a crucible. It boils out of the crucible and makes a gigantic mess in the furnace. Ask me how I know.

I can try and answer some of your questions:

1. Would the j tube (or batch) get hot enough to smelt steel without forced air?
Traditional methods used bellows to stoke the fire to achieve the temperatures required to melt iron. This is roughly 1540 degrees C. Failure to achieve and hold this temp results in an incomplete melt and inferior product because the impurities do not separate from the iron. The airflow doesn't have to be excessive. A hairdryer will work on a small smelter. A shop vac is better though. It must be able to fluctuate speed so you can reduce the flow when adding ore and fuel to the smelter without stopping airflow altogether.
2. How hot does it need to be for how long?
As stated above you are looking at 1540C for long enough to reduce the amount of ore to melt it down. That depends on how much ore you have in your run. In a crucible furnace like mine, I use a propane burner with a blower, and it takes about an hour to reach temperature and about 20-30 minutes of hold at temp per kg of material in the crucible.
3. Could an open crucible let the impurities escape?
Whether you use an open top crucible or a closed crucible, the impurities rise to the top of the melt and can be discarded. Most of the people I know (myself included), making crucible steel use a layer of crushed glass on the top of the charge inside the crucible. This serves a number of purposes. It melts pretty quickly compared to the iron/ore/charge materials and makes a sealed layer that prevents oxidation. It also collects the impurities out of the charge leaving the iron or steel at the bottom. The glass layer is then chipped out with a chisel to release the puck from the crucible.
4. I'm thinking load a crucible with ore, appropriate amounts of iron sand, charcoal and maybe some oyster shells to promote cleaning, and heat up in reducing atmosphere in the riser as per Uncle Mud's rocket forge from the low tech jamboree.
I have not watched said low-tech jamboree, but it sounds dicey to me. If I were to suggest a method for you, it would be to build a small smelter to reduce the sand into iron bloom. Refine the bloom through a subsequent melt and start forging it into bars. Stack, forge weld, repeat as needed to homogenize the material. If it proves to be low grade steel or pure iron, you could refine it in more melts or use it as stock in a crucible melt. The iron needs carbon to become steel. The only way to do that is to melt it in the right atmosphere with a carbon source and pray to the smelting gods that the iron absorbs enough carbon. If it absorbs too much carbon, you get cast iron, which is not a forgeable material. It can be used in a crucible with lower carbon content material to "even out" the carbon content and make it useable.
5. How do I tell what sort of quality steel I have (assuming I get any!)? Spark test shows carbon content, but what about the Phosphorus and Sulphur impurities?
The spark test will give you a rough idea of the carbon content. At least it tells you the carbon content of the area held against the grinder...... To tell what other elements have alloyed with your product requires sending it out to a lab for testing. Bloomery is not a homogenous material. Carbon and other alloying are not uniform across the entire bloom. It takes refinement to create a uniform material, or a contained and complete melt in a crucible.

Some other reputable online information sources:
Crucible steel making: https://www.wootzsmithforum.com/forum-2/
Bloomery and crucible steel making: https://www.bladesmithsforum.com/index.php?/forum/25-bloomers-and-buttons/

I belong to both of these forums and one of your local knifemakers is a frequent visitor on the second forum, but not in the Bloomers and Buttons section.

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Nancy Reading wrote:I've been considering the possibilities of making steel from raw materials. Mostly because I think it would be amusing. Our rock here is basalt, the remnents of an ancient volcano that straddled the Irish sea. I believe I can collect black sand from our local beach as a starting material. Ihave no idea what sort of quality metal I may end up with, but there is a local knife maker who may be interested in making something if I come up with something useable.

Nancy -

You've received a very helpful reply from Joshua, but I'll stick my oar in these waters, just a bit.

I have a coworker who is a custom knife maker. I've bought a couple of his Slojd blanks. He mostly makes knives by stock removal (milling and grinding) and uses a lot of fancy sintered powder metal tool steel alloy blanks. He makes both fixed blades (the Slojd knives or other wood carving specialty blades, or kitchen knives and butcher knives), and folding blades (high end liner lock pocket knives). He also makes sheathes for his knives from vegetable tanned leather. He also does some hand forging, and has built a hydraulic forging press.

One of his ongoing projects is to try to make Wootz steel, using magnetite sand collected from a local beach. We, too, have a lot of basalt around, but not exclusively; it's also interbedded with conglomerates, mud stones or shales (and even a bit of true metamorphic slate) and sand stones. I know of only one small outcrop of limestone (called Limestone Mountain, locally, but it's just a hill, really). As far as I am aware, our local basalt doesn't have a high iron content. There are iron mines (historical and currently operating) within a hundred miles or so of where I am located, but that was exploiting specular hematite (early) and iron oxides (current). My coworker used a magnet, as has been suggested by Joshua, to separate the magnetiite from other material. Where we are, most of the beach sand is actually a fairly "blonde" quartz sand, so the layers of black sand are very distinct, visually. He has collected several 5 gallon buckets (US gallons) of this sand. He is also patient and methodical. He designed and built a high powered inductive power supply to run the furnace. That's beyond what most people could do, but high speed switching power supply design is his "thing", so this is right in his wheelhouse. He's tested the power supply by heating steel bar forging stock. It will make the end of a bolt or bar hot enough to forge pronto - in a handful of seconds - using a properly sized coil. He also has a rolling mill mostly designed, so that he can more easily make bar stock from the eventual Wootz melts. He chose the induction furnace approach because he can more carefully control the melt feed stock and atmosphere (and, he knows a lot about making and building inductive power supplies).

I can ask him if he has any suggestions for you, beyond what Joshua has already provided.

I am interested in the forging aspect of J-tubes, myself. I had recently collected an old hand cranked forge blower in usable condition, and was intending to build a forge pot out of an old heavy truck brake drum from the salvage yard, at least for starts. But, a J-tube rocket (considering I have a collection of salvaged brick, and can get fire brick from a local brick yard) might be a straighter path to the goal, which is to heat ferrous alloys sufficiently that they can be hot worked rather than cold worked. A bit of heat treating, too. Among the projects I have in mind is a shingle froe, for which I have collected a piece of broken truck leaf spring from the side of the road. Though I am not much of a welder (but I am mean with a grinder!), I could try to arc weld the froe blade to a sleeve of pipe or tubing, but I'd still need to flatten the arch out of the spring. I could do that with a charcoal fire in a pit, but I think I'd prefer to have the handle socket integral with the blade, rather than relying on my as-yet dubious arc welding skills.

I'll see what my suggestions my buddy may have. If he has anything additional to Joshua's info, or at variance to it, I'll pass it along. I'm not very knowledgeable about steel smelting and forging.

Michael Cox

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Interesting project. It looks like fun.

One suggestion, if you plan on using black sand, is to separate it from the other minerals first. Black sands tend to be more dense as they contain more iron. The techniques that gold prospectors use for gravity separation can help you out. For small batches you could use hand panning, for larger batches you may want to try some kind of sluice.

While you beach sand looks "black" I would expect it to have lots of other mineral grains as well which can be separated out.

[youtube]https://youtube.com/shorts/mBVwSN-0VBY?si=wfI2lp9uSDNQCJZv[/youtube]

Can can also try using a magnet system like this:

[youtube]https://youtube.com/shorts/FsTKm1wcPww?si=dD_aFpULsbEG4CRG[/youtube]

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Kevin Olson

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Michael Cox wrote:The techniques that gold prospectors use for gravity separation can help you out. For small batches you could use hand panning, for larger batches you may want to try some kind of sluice.

The black magnetite sand we have around here also has a (very) small amount of fine gold in it - more nearly the same densities, I suppose, so laid down together, but that's just a guess. A few hobby prospectors are "washing" these black sand deposits using small portable sluice boxes - on the order of the size of a rain gutter - with silicone riffle mats laid in the bottom. The riffle mats have special (and proprietary) molded patterns, because the gold is such small particles ("flour gold"). The flow rate of the water, and the slope of the sluice box, must be carefully controlled to separate the gold. Even then, I'm pretty sure the gold collected would barely cover costs. But, they have fun doing it. I've thought about getting a small sluice setup for my wife, since she's actually the rocks and minerals enthusiast in our household. Come to think of it, Christmas is coming...

Joshua States

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Michael Cox wrote:I am interested in the forging aspect of J-tubes, myself. I had recently collected an old hand cranked forge blower in usable condition, and was intending to build a forge pot out of an old heavy truck brake drum from the salvage yard, at least for starts. But, a J-tube rocket (considering I have a collection of salvaged brick, and can get fire brick from a local brick yard) might be a straighter path to the goal, which is to heat ferrous alloys sufficiently that they can be hot worked rather than cold worked. A bit of heat treating, too./quote]

Building a simple forge from bricks is not that difficult. https://permies.com/t/179207/pep-metalworking/Basic-backyard-forge
I used to have a tire rim forge. I traded a small anvil for it some years ago. It had a real coal forge duck nest (fire pot) installed in it and an electric blower with variable speed. The outside of the fire pot was packed with some sort of white clay for insulation. You could build a similar forge using the hand crank blower you have. You might want to create a firepot out of some clay or castable refractory.

I pulled the fire pot out and bult a solid fuel forge around it.

Joshua States

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I thought about another method of reducing black sand to extract the iron that I have done and can share. I will let @Nancy Reading decide if I should post that process in pictures here, or create a separate thread for it.
It involves direct reduction of black sand into small (2-3oz) cast iron buttons. These are then folded into a strip of wrought iron. The process is repeated until the heating effect of carbon migration provides for a usable and hardenable steel that you can forge into a knife or other tool.

Nancy Reading

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Thank you all for your comments!
I'm happy for you to post your button making method here Joshua. Or you can make a new one. It's handy for me to have all the information in one place, but a new thread (link it here please!) is also fine.
We have had a go at crushing the basalt. Some of it (called 'rotten rock' locally) really looks like it is nodules of iron, you break it and it has a shiny purple metallic look. However it is the harder building grade rock that seems to be more magnetic. This is one of my crap videos, but I think you can see the way the compass needle moves towards the rock face. It does something similar around our house. (edit: You might want to mute the soud out - it was a bit windy!)

Since nature seems to have done most of the work in separating out the magnetite out in the sands that using that does seem to be the easiest way forwards for me. I thought I had some pictures of our trials - but I seem to remember about half the beach sand would cling to a strong magnet. Here's a picture of some 'rotten rock' from when we were making the driveway - it looks a lot more iron rich than I think it actually is.

driveway_rotten_rock.jpg

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Joshua States

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Nancy Reading wrote:Thank you all for your comments!
I'm happy for you to post your button making method here Joshua. Or you can make a new one. It's handy for me to have all the information in one place, but a new thread (link it here please!) is also fine.
.

Done. Here is the link: https://permies.com/t/270554/permaculture/steel-making-process

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Joshua States wrote:Building a simple forge from bricks is not that difficult. https://permies.com/t/179207/pep-metalworking/Basic-backyard-forge
I used to have a tire rim forge. I traded a small anvil for it some years ago. It had a real coal forge duck nest (fire pot) installed in it and an electric blower with variable speed. The outside of the fire pot was packed with some sort of white clay for insulation. You could build a similar forge using the hand crank blower you have. You might want to create a firepot out of some clay or castable refractory.

I pulled the fire pot out and bult a solid fuel forge around it.

Joshua -

Thanks for the photos of your old setup. Yes, that's more or less what I was thinking, but I'll need to make the duck nest from fire brick or something, I imagine. I was intending to use a brake drum, because I know that cast is more heat resistant than high carbon steel.

Another acquaintance built what he styled a "Viking forge", which was basically a wooden box, with a thick lining of wood ashes. He claimed that this was typical for iron age Norse forges. I don't know much about the history, so I was happy to take his word for it, at least provisionally. His master's degree was in industrial archaeology, and he was "into" experimental archaeology (attempt to replicate past historical technological achievements, I think - that's based on my observation of his activities). In any case, he made this setup work for a number of years, though he eventually switched over to a propane forge when his life got busy with a wife and children. Unlike coal or charcoal, propane heats up pretty quickly, and is cools off quickly, too. So, I know simple can work, if the operator is skilled (or maybe just determined), but given my lack of skill, I am hoping a slightly more auspicious setup will sooner yield acceptable results!

My end goal is to be able to do minor tool building and repairs, and make use of a lot of metal which gets sent out for scrap. A lot of springs, broken axles and the like just get hauled off to the big scrap recyclers. That's fine, but I figure it's better to try to use some of that stuff one or two more times before is gets turned into some commodity melt, somewhere.

Joshua States

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Kevin Olson wrote:

Joshua -

Thanks for the photos of your old setup. Yes, that's more or less what I was thinking, but I'll need to make the duck nest from fire brick or something, I imagine. I was intending to use a brake drum, because I know that cast is more heat resistant than high carbon steel.

Another acquaintance built what he styled a "Viking forge", which was basically a wooden box, with a thick lining of wood ashes. He claimed that this was typical for iron age Norse forges. I don't know much about the history, so I was happy to take his word for it, at least provisionally. His master's degree was in industrial archaeology, and he was "into" experimental archaeology (attempt to replicate past historical technological achievements, I think - that's based on my observation of his activities). In any case, he made this setup work for a number of years, though he eventually switched over to a propane forge when his life got busy with a wife and children. Unlike coal or charcoal, propane heats up pretty quickly, and is cools off quickly, too. So, I know simple can work, if the operator is skilled (or maybe just determined), but given my lack of skill, I am hoping a slightly more auspicious setup will sooner yield acceptable results!

My end goal is to be able to do minor tool building and repairs, and make use of a lot of metal which gets sent out for scrap. A lot of springs, broken axles and the like just get hauled off to the big scrap recyclers. That's fine, but I figure it's better to try to use some of that stuff one or two more times before is gets turned into some commodity melt, somewhere.

My understanding of a typical Viking age forge is little more than two semicircles of fired clay stood on the flat sides parallel to each other with a bellows pump that blew air into the charcoal fire burning between the two semicircles. You can see this setup toward the end of the video linked in this thread: https://permies.com/t/55079/Community-production-iron#2837396.

Based on what you described as the work you are interested in doing, you should probably look at what is called a Rivet forge and try to model your setup after that. A typical rivet forge is small, portable, and can be used with either coal, coke, or charcoal.
https://www.centaurforge.com/Centaur-Forge-Rivet-Forges/products/385/

Nancy Reading

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Lots of good thoughts!
I have no idea if there is likely to be gold in our sand. I suspect not, but you never know. I'm now more interested in iron than gold anyhow at the moment.

Joshua States wrote:I would not recommend putting iron sand into a crucible. It boils out of the crucible and makes a gigantic mess in the furnace. Ask me how I know.

Now I have to ask! I'm suspecting it went horribly wrong for you? - but if you tell me what you did, I may see another way around it :)

Separating the sand with a magnet is a pretty easy first step. At this point I'm more interested in achieving a metal, than what to do with it afterwards. Maybe it will be a knife blade (that would be pretty cool) but to be honest, I'd be pretty happy with a paperweight at this point. It depends on what I can achieve.

I'd really like a low tech approach and the bloomery process is pretty basic. I think the temperatures typically achieved do not go high enough to melt the iron, and I suspect that the 1100 C of a rocket stove will be enough heat to get a lumpy mass like a bloom or tamahagane.

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Nancy Reading wrote:

Now I have to ask! I'm suspecting it went horribly wrong for you? - but if you tell me what you did, I may see another way around it :)

Separating the sand with a magnet is a pretty easy first step. At this point I'm more interested in achieving a metal, than what to do with it afterwards. Maybe it will be a knife blade (that would be pretty cool) but to be honest, I'd be pretty happy with a paperweight at this point. It depends on what I can achieve.

I'd really like a low tech approach and the bloomery process is pretty basic. I think the temperatures typically achieved do not go high enough to melt the iron, and I suspect that the 1100 C of a rocket stove will be enough heat to get a lumpy mass like a bloom or tamahagane.

tamahagane

After my successful reduction of black sand in small quantities and subsequent folding those little buttons into an iron bar (https://permies.com/t/270554/permaculture/steel-making-process) I got the not-so-bright idea of putting a kg of sand and some charcoal into a crucible to see what happened.
What happened is called a "carbon boil" where the sand starts to melt rapidly and all the various stuff that isn't iron starts turning to gasses and liquids. It came out of the crucible (open top) and I shut down the furnace. You may have better luck at lower temps.
Anyway, I removed what was left in the crucible with a chisel and now I have a few hundred grams of chunky partially reduced magnetite.

They will stick to a magnet, so they are ferrous.

I intend to take these, and possibly make more at a lower heat, combine them all into a short stack furnace to refine the iron out of it.

I just haven't had the time. We moved recently and the shop has been packed away for 7 months. Now that I am set up again, I will try and get back to making steel, but it probably won't be until springtime.

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Joshua states wrote: I got the not-so-bright idea of putting a kg of sand and some charcoal into a crucible to see what happened.
What happened is called a "carbon boil" where the sand starts to melt rapidly and all the various stuff that isn't iron starts turning to gasses and liquids. It came out of the crucible (open top) and I shut down the furnace. You may have better luck at lower temps.

The reaction for the reduction of ore into steel produces carbon dioxide gas, so I can imagine that it it reacts too quickly you will get it boiling. The hotter the temperature the quicker the reaction. If you were 1400C that is way hotter than I think I will achieve in a simple rocket j tube. I do need to get a feel for what may be workable parameters still.

To make the process as 'sustainable' and Skye based as possible, I'd love to be able to produce the heat from my coppice wood. Making lots of charcoal, just to burn it off to produce the heat, is the known bloomery method, and I may fall back to that, but it will mean a lot of charcoal making (buying it is a fall back possibility).

I think what I will start with is making a rocket forge - similar to the one made by Uncle Mud at the low tech jamboree (here's another video from the kickstarter):

I'll get a moderate sized crucible. I guess I'm not aiming to make more than 200g (6-8Oz) of metal at a time. Charcoal is pretty bulky, the ore is only 30% yeild at best, so (thinks) maybe a 3 pint crucible may be big enough? I'll then experiment to see what temperatures I see in the crucible, maybe melting different compounds - sand, lower melting point metals. I'm not sure how high a temperature our FLIR camera goes, but that might tell me the temperatures I am reaching. If I can't get to 1100C ish then I wonder whether burning Charcoal in the rocket may be an option to increase the temperature? Otherwise it is stepping down from my aspirations and, yes a propane, or electric furnace might have to be considered. I'm short of clay here, so I don't really want to purchase tonnes of clay to make a chimney for a traditional bloomery furnace and buying more refractory sruff is maybe an extravagance I can't afford since I'm spending all my pocket money on a new polytunnel frame.

There is a quite a bit of 'playing' to scope out the possibilities yet!

I did look on the bladesmith forum (my registration still worked) but it doesn't look like anyone has tried a j tube rocket forge for smelting as yet. I'm staying away from Facebook as I dislike it and it is very difficult to use it as a reference. Duck duck doesn't throw up anything, although I did find this old permies thread, looking at smelting and forging other materials such as glass, although there is no follow up on it as yet.

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Question: How are you planning to measure the temperature in the furnace/crucible?

Nancy Reading

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I suspect there is a band of temperatures that will be suitable for smelting - slower at lower temperatures and quicker (as you maybe found) at higher temperatures. It looks like our FLIR camera doesn't go up that high so my plan at the moment is to build the rocket forge and play with it for a while - put different things in the crucible and see what happens.

Some melting points(degrees Celsius) from engineering toolbox:

Lead 327.5
Zinc 419.5
Aluminum 660
Glass 700
Copper 1084
Iron, Gray Cast 1127 - 1204
Iron, Ductile 1149
Silicon 1411
Steel, Carbon 1425 - 1540
Iron, Wrought 1482 - 1593
Steel, Stainless 1510
Sand 1550

So if I can get copper to melt I know I'm getting about the required temperatures. It looks like there is not much in between various cast irons and silicon (asbestos at 1300 C).
I'm interested to see that stainless steel has a pretty high melting point. That suggests that I could make a stainless bar support for the crucible rather than a brick one, which might then provide less obstruction to the hot gas flow and more heat transfer into the vessel.

I'm suspecting that with experience one will be able to tell by the glow and the chimney flume, how hot the forge chamber is getting.

I'm hoping I'm right that 1100-1200 C will be hot enough. this reference suggests that 1300 C was a temperature for a Roman bloomery, so maybe the temperatures in a normal rocket won't be high enough?

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I suspect that a rocket forge may struggle with smelting. The temperature will be fine, but the smelting from ore is as much about ensuring that the atmosphere is reducing (high carbon, low oxygen) as it is about temperature. In a traditional bloomery, powered charcoal or coal is added in layers with powdered ore. The close physical mixing in the hottest part of the bloomery ensures that the reaction completes for convert your iron oxides/iron sulphides etc... to metallic iron.

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I'm sort of hoping that by mixing charcoal and ore sand in the crucible I will get the mixing and the atmosphere. According to engineering toolbox again the spontaneous ignition temperature of charcoal is 349 C . Hmm, maybe that means it will all have burned away before the iron compound is hot enough to react with the Carbon Monoxide? Alternatively, the CO might be heavy enough to stay in the crucible. Maybe I'll need a lid, maybe it won't work. As I wrote above, I couldn't find references to anyone who has tried smelting in a rocket. When people use crucibles they usually get hot enough to melt the iron, so closer to 1400C than 1100C, so it might be I'll end up with nothing more than hot sand

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Nancy Reading wrote:I'm sort of hoping that by mixing charcoal and ore sand in the crucible I will get the mixing and the atmosphere. According to engineering toolbox again the spontaneous ignition temperature of charcoal is 349 C . Hmm, maybe that means it will all have burned away before the iron compound is hot enough to react with the Carbon Monoxide? Alternatively, the CO might be heavy enough to stay in the crucible. Maybe I'll need a lid, maybe it won't work. As I wrote above, I couldn't find references to anyone who has tried smelting in a rocket. When people use crucibles they usually get hot enough to melt the iron, so closer to 1400C than 1100C, so it might be I'll end up with nothing more than hot sand

If you are going to use an air-draft rocket stove with a crucible, you should seal that crucible to create an oxygen-free atmosphere inside the crucible. That will keep the charcoal from burning out before the ore starts to react.
When smelting in a crucible with a propane furnace, we can adjust the atmosphere inside the furnace by changing the propane to air ratio. That leaves the inside of the furnace with no oxygen left over to burn the charcoal.
You can seal the crucible with some refractory cement or clay. I don't know what is available where you are, but you could ask those knifemaker guys where they get the stuff they line the insides of their forges with.
Here, I can get five pounds of Satanite refractory for 16 USD. I can make dozens of crucible lids from that much refractory. They are only about 1/2-inch thick.

I think what you will get will be more than hot sand, if you set it up right. You may not get enough heat to melt the iron out of the sand, but you just might get enough to melt all the other stuff off.
Some crushed glass over the top of the sand & Charcoal would also help to isolate the slag from the iron.
The glass melts pretty quickly and is lighter than the sand so it floats on top. There are a couple of videos of an open-top crucible in my furnace at this link: https://drive.google.com/drive/folders/1O7d9C1EAGKvgq4UqjYcd7wgDcOfEshis?usp=sharing
You can see the molten glass is bubbling as the gasses from the melting charge escape through the glass.

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Joshua States wrote: There are a couple of videos of an open-top crucible in my furnace at this link: https://drive.google.com/drive/folders/1O7d9C1EAGKvgq4UqjYcd7wgDcOfEshis?usp=sharing
You can see the molten glass is bubbling as the gasses from the melting charge escape through the glass.

That is so cool (hot!) thank you!

I've been doing more reading round the subject and sometimes I'm full of confidence, and at other times I think it will never work. I feel that I need a really good book, so that is probably going to be my birthday present to myself...

According to Erica and Ernie's The Rocket Mass Heater Builder's Guide 1 6in j tube in a moderate climate can get to 1100-1300 oC an 8in in a super cold climate to 1350 oC plus. The temperature needs to be above about 1100 oC to get a 'bloomery' style reduction going on - a bit hotter probably better for yield. For true steel making (as opposed to a mixture of different carbon concentrations) it seems you need to get hot enough to melt iron - approaching 1500 oC.

image source

From the Iron-Carbon phase diagram you can see that as the carbon content increases the melting point decreases, which is why it is easier to make cast iron than steel.

Some other interesting references:

Apparently the Haya people may have been smelting steel in a bloomery near West Lake Tanzania 2000 years ago: ref: Complex Iron Smelting and Prehistoric Culture in Tanzania, Author(s): Peter Schmidt and Donald H. Avery The main aspects that made it possible seem to be long tuyeres (the blower nozzles) that went right into the furnace so preheating the combustion air, a fine charcoal strata made from reeds which gave a good carbon surface and (my thought) possibly flux, roasting the ore for the next batch inside the furnace providing extra Carbon as it cools in a Carbon dioxide rich atmosphere.

I found a nice little article on a simple way of assessing ore for commercial exploitation, which might be a starting point - A crucible melt at 1250 oC for one hour with the powdered ore laid in between layers of Charcoal.

Assessing the Quality of Iron Ores for Bloomery Smelting, Ivan Stepanov et al.

Here is a thread from bladesmithforum on a crucible smelt.

If I get pure iron then the Georgian method seems a possibility for converting it to a good steel in a crucible in a second melt process:
Half the iron is placed in the crucible bottom, then a layer of glass or sand, then carbon and the rest of the iron in layers, finally a lid with hole. At 1200 oC the sand/glass melts and provides a barrier between the iron at bottom and the carbon layers. The upper iron absorbs Carbon and starts to melt at 1500 oC it falls through the molten sand and mixes with the iron layer which also starts to melt. After 1.5 hrs at 1500 oC it ends up as a steel nugget under a glass layer (sound simple (!) )

It seems that impurities of Sulphur and Phosphorus are the main problematical ones from a functional metal point of view. I found a breakdown of the raw basalt from this area (Eocene basalt of Isle of Skye (average of 14 analyses, Tompson et al., 1972)

:
SiO2 47.24
TiO2 1.84
A12O3 15.73
Fe2O3 1.86
FeO 10.63
MnO 0.2
MgO 9.17
CaO 9.7
Na2O 2.94
K2O 0.48
P2O5 0.22
Which shows no sulphur and little Phosphorus in the raw rock - what it is in the magnetite rich portion (that 1.86% Fe2 O3) that I can easily get out of the sand, is another matter of course! I hadn't appreciated how much FeO there seems to be - I guess that is what is giving the rotten rock it's rusty appearance.

My thought at the moment is to try something very basic along the lines of Ivan Stepanov's process and see if I can get any metal, and then tweak the process from there. Don't expect it to happen anytime soon though! Since I will be working outside I need a period of dry weather; but maybe in April we might get a chance. There are a few essentials on my shopping list too. I'm OK for safety gear, due to my husband's welding hobby, but a crucible, tongs, clay and more firebricks are almost certainly required.
Methods will depend on what sort of temperature I can achieve. Even if I can't get the full conversion to steel, I'd be pretty happy with a metal nugget that could be worked and converted to something useful elsewhere.

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Oh no! Nancy is staring down a rabbit hole and is about to jump in!

About getting a book on the subject, most of the books about this type of smelting are long since out of print. However, there are a decent number of academic papers on the subject that you can download for free at https://www.academia.edu/. (if you can tolerate reading a PDF document rather than a real book).
Lee Sauder is an American blacksmith and possibly the foremost expert on the subject of bloomery iron and steel smelting still alive today. (https://independent.academia.edu/LeeSauder)
You can also find his videos on YT and there was one he did in Africa in a village once renowned for their steel production from ore. Search YT for Lee Sauder smelting in Africa
Other names from history on the subject of crucible steel are Al Pendray and John D. Verhoeven. They were mostly concerned with recreating the fabled Wootz, or Pulat steel from antiquity. They started with ore in a crucible furnace.

Sometime in April sounds like the same time I will probably start making crucible steel again. This winter has been pretty dry and unusually warm though. I could start up sooner!
Excited for you to give it a go.

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Definitely been exploring the rabbit hole! I've done a fair amount of reading round now, and am firming up my plans. I couldn't find the facebook group Joshua mentioned, but the bladesmith forum has some useful discussions. I've now ordered myself a copy of 'mastery and uses of fire in antiquity' which was mentioned in several places as a useful book. Unfortunately it's coming from the US, so I'll have a bit of a wait before I can read it.

One question I had was whether I needed to add lime for flux or not. At least one of the crucible smelts I read up on had a poor yield because the ore was already rich in calcium. Another used calcium carbonate as a flux and reducing agent rather than charcoal.

To test whether my sand is rich in calcium (although I was pretty sure it wasn't, since my soil is so acidic) I added a little vinegar to the sand. There was no reaction, so I'm pretty sure now that Calcium carbonate will be a good flux to add.

I've collected a good bucket of sand from the beach, which will probably be enough for my initial smelt trials. Whilst I was there I also collected some shells - just random limpets, winkles and cockles - these would be neat to use as the Calcium carbonate. I also collected a little sea glass. Crushed glass can be used as a surface layer to seal in the ore, and might also make the slag more liquid (which is a good thing) although with my acid rocks, maybe not so neccessary.

I had a go at sorting the sand with a magnet. The simple trick is to put the magnet in a plastic bag, then the sand simply falls away when the bag is removed from the magnet, rather than sticking to the magnet itself. It does take a while to do this way though (a case for productive downtime perhaps!) My husband does have a magnetic sweeper to get puncture seeds off the garage floor, so I may have a play with that and see if it might be useful for sand sorting....maybe even take it to the beach and sort dry sand there.

Below are some pictures I took of the sand before and after sorting. By eye there is a more dramatic difference - the magnetically sorted sand is finer in texture and darker in colour. The grains are less than a mm in size.

unsorted_sand.JPG

magnetite_rich2.JPG

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Your plan is to use charcoal for the smelt, right? If I remember correctly, a charcoal smelt is (at least partially) self-fluxing, since the ash component in the char contains calcium. I think that's for a bloomery, though, where you use (I'd guess) more char per ore, since it's both the fuel and the source of carbon monoxide. I don't know if it'd be the same in a crucible, maybe there won't be enough ash? Don't know.

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Eino Kenttä wrote:Your plan is to use charcoal for the smelt, right? If I remember correctly, a charcoal smelt is (at least partially) self-fluxing, since the ash component in the char contains calcium. I think that's for a bloomery, though, where you use (I'd guess) more char per ore, since it's both the fuel and the source of carbon monoxide. I don't know if it'd be the same in a crucible, maybe there won't be enough ash? Don't know.

Yes probably charcoal, although apparently you can smelt using just Calcium carbonate as I mentioned above. I don't know either! Logically as you say, the more charcoal you use the more calcium is available, so I think I will do well to start off with at least some addtional calcium source. Without getting my sand analysed I won't know exactly what proportions of the different elements I start with so at the moment it seems a bit more like a magical operation than a precise science

I'm prepared for it needing a bit of experimentation.

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Here's a few more pictures of the sand sorting and a little video of me playing with the magnetic sand. It was easy to remove over half the sand with the magnet, although it is quite a slow process.

sand_on_magnet.jpg

sorted_sands.jpg

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Borax is the traditional blacksmith/smelting flux. You can usually find it in the laundry soap aisle of the grocery store.

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Joshua States wrote:Borax is the traditional blacksmith/smelting flux. You can usually find it in the laundry soap aisle of the grocery store.

Not in Europe though :) It is considered too toxic for general use here. I think it is a more modern development for smelting. Although does seem to have been used for joining metals, it was in short supply in industrialised countries until the 19th century (ref I'll see how I get on. I can order some online once I've had a trial run or two, if it looks like things aren't working well.

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Nancy Reading wrote:

Joshua States wrote:Borax is the traditional blacksmith/smelting flux. You can usually find it in the laundry soap aisle of the grocery store.

Not in Europe though :) It is considered too toxic for general use here. I think it is a more modern development for smelting. Although does seem to have been used for joining metals, it was in short supply in industrialised countries until the 19th century (ref I'll see how I get on. I can order some online once I've had a trial run or two, if it looks like things aren't working well.

Even for forge welding, there are alternative/older techniques. I think my brother, who attended a blacksmithing course, said they used silica sand instead of borax, somehow. I'll have to ask him for details, but as I understood it, you'd add silica sand between the pieces you want to join (like you would add borax) but rather than evaporating it will melt, somehow facilitate the joining of the metal pieces, and then get pushed out as you hammer. I understood that it's a bit trickier than borax, but doable.

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Eino Kenttä wrote:

Nancy Reading wrote:

Joshua States wrote:Borax is the traditional blacksmith/smelting flux. You can usually find it in the laundry soap aisle of the grocery store.

Not in Europe though :) It is considered too toxic for general use here. I think it is a more modern development for smelting. Although does seem to have been used for joining metals, it was in short supply in industrialised countries until the 19th century (ref I'll see how I get on. I can order some online once I've had a trial run or two, if it looks like things aren't working well.

Even for forge welding, there are alternative/older techniques. I think my brother, who attended a blacksmithing course, said they used silica sand instead of borax, somehow. I'll have to ask him for details, but as I understood it, you'd add silica sand between the pieces you want to join (like you would add borax) but rather than evaporating it will melt, somehow facilitate the joining of the metal pieces, and then get pushed out as you hammer. I understood that it's a bit trickier than borax, but doable.

In a crucible steel melt, the crushed glass becomes a flux of sorts, and the glass does contain silica. Silica in high quantities can produce an effect called "hot shortness" which causes the steel to crack and crumble during forging. So, it's best used in small amounts in any smelting/refining melt processes. This is why real wrought iron can be difficult to forge out without crumbling, but also why it forge welds to itself and other steels easily. It contains high levels of Si and is self-fluxing. There is a lot of strange chemistry happening during a smelt and the iron's ability to bond with other elements like carbon, silicon, and whatever else might be present in the ore used is largely dependent upon heat and oxygen. In a crucible melt, we can limit or eliminate the oxygen present, but in a smelting furnace, we deliberately add lots of oxygen to achieve the desired temperature needed to melt the metals. Oxygen will bond to carbon, iron, and other elements quite easily. In a crucible melt, the lack of oxygen promotes chemical bonding with the iron,

I used borax and borax derivatives as a flux for many years to make pattern-welded steel (Damascus). I switched to petroleum based fluxing agents (diesel fuel) for a while and now do most of my forge welding dry. This is all with known processed steels though, not in my crucible or smelting furnaces. I don't know any smelters out there who are adding any sort of flux into a smelting furnace with their ores. It's just ore and charcoal. Any fluxing agent is in elemental form as part of the ore.

In a furnace type smelt with raw ore, there is no need for a flux additive. In a crucible melt, its main purpose is to provide an oxidation barrier, but only if the crucible is not sealed. In a sealed crucible, a little charcoal over the top of the charge directly under the lid will burn up most of the oxygen leaving the iron to attract the carbon and any alloying elements added to the charge.

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Thanks for the comments Joshua - and the link to the Facebook group. I've applied to join, but haven't been back to see if I've been accepted yet. I really think the best thing I can do is have a go and see what happens. Without a chemical analysis of the separated sand I won't know really what I'm starting with. I think I had an inkling that impurities were more of a concern in crucible smelts, and you explain why - that in a bloomery furnace they are more liable to combine with the extra oxygen present for combustion, whereas in the crucible there is an oxygen poor atmosphere, so it all ends up combining with the steel. I did see one video where they did a smelt and had left cardboard inside the furnace to prove the lack of oxygen. I think it was one of the ones trying to produce Damascus steel from Damascus ore...

In a sealed crucible, a little charcoal over the top of the charge directly under the lid will burn up most of the oxygen leaving the iron to attract the carbon and any alloying elements added to the charge.

I'm sorry Joshua, can you repeat this in a different way? I don't think I'm reading it correctly.

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In a sealed crucible, a little charcoal over the top of the charge directly under the lid will burn up most of the oxygen leaving the iron to attract the carbon and any alloying elements added to the charge.

I'm sorry Joshua, can you repeat this in a different way? I don't think I'm reading it correctly.

In a crucible melt, you have a container (crucible) and a charge (all the stuff you put in the crucible), which provides the iron, any alloying elements, and a carbon source. You can have an open-top crucible or a sealed crucible. I have been doing open-top while I learned and tested my crucible forge. It allowed me to poke into the crucible with a metal rod to "feel" the melt and judge liquid/solid state of the charge and see whether my internal temp was enough to melt the steel rod. In an open-top crucible there may still be unspent free oxygen in the furnace that may infiltrate the crucible and your melt. This is the primary reason for the layer of crushed glass on top of the charge. It melts and forms a protective barrier against oxidation. It isn't perfect by any means, but it is better than nothing.

In a sealed crucible, you put a lid over the top of the crucible and use clay or castable refractory to seal the lid in place. There is invariably a small (or large) void inside the crucible and air in the spaces between the charge materials. A little charcoal over the top of the charge and below the lid should burn up any excess oxygen inside the sealed crucible rather quickly and prevent any oxidation.

Nancy Reading wrote: I think it was one of the ones trying to produce Damascus steel from Damascus ore...

I have no idea what "Damascus ore" could possibly be. Could you please clarify before I go full-on rant about what "Damascus" really is and how the name has evolved into something completely different from what it originally was?

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I have no idea what "Damascus ore" could possibly be. Could you please clarify before I go full-on rant about what "Damascus" really is and how the name has evolved into something completely different from what it originally was?

It was ore from a mine in Syria, supposedly with similar alloy compositions to historic sword steels. I can try and find the video reference if you like? It was US forgers that were smelting it.

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Nancy Reading wrote:
It was ore from a mine in Syria, supposedly with similar alloy compositions to historic sword steels. I can try and find the video reference if you like? It was US forgers that were smelting it.

If you have the video link handy, that would be great.
Warning: rant is brewing

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Joshua States wrote:

Nancy Reading wrote:
It was ore from a mine in Syria, supposedly with similar alloy compositions to historic sword steels. I can try and find the video reference if you like? It was US forgers that were smelting it.

If you have the video link handy, that would be great.
Warning: rant is brewing

Doh, my memory is getting worse! However, excusing this, I think this is the video I was (half) remembering....

If you'd like to educate us that's fine

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I have seen this video before. Al Pendray was one of the pioneers trying to recreate what is commonly called "wootz" steel.
I will watch it again and see if I can shed any additional light on the subjects discussed.

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So, I think we should define some terminology because the words "Damascus", "Wootz", and "Damascus Steel" often mean different things when used in contemporary conversation.
We also need to talk about the differences between "crucible Steel" and "bloomery" steel and iron.
Bloomery steel is made in smelter, much like the first furnace Al uses in the video to process the raw ore into iron. This is a tricky process, because a smelter of this type can produce iron, steel, or cast iron depending on the carbon uptake during the smelt.
Crucible steel is made in a closed container and will produce steel or cast iron, depending on the carbon uptake. It is worth noting that the smith can control the carbon uptake much more easily with the crucible method than the smelter method because the carbon donor quantity is controlled by what is put into the crucible, whereas the carbon uptake in a smelter is controlled through a variety of factors that small differences make large changes.

Crucible steel is ancient. The video may give you the impression that it was invented in Jordan/Syria during the reign of Saladin, but that is not accurate. Saladin reigned during the latter part of the 12th Century C.E. and crucible steel predates that by several centuries. "Wootz" as it is called today is a form of crucible steel dating back to the 3rd or 4th Century C.E. from what is now called India. Side note: Wootz is probably a mangling of the word Ukku, which is the word for steel in some dialects in India. Anyway, some tribes in India were making crucible steel long before Saladin and the Persians, who occupied the subcontinent, controlled the trade of these steel cakes or bars and brought them back to the Middle East for processing into swords. Wootz was also called by other names, Bulat, Pulad, Indian Steel, and others. It was largely traded in Damascus Syria and came to be known in Europe as "Damascus Steel".
Not all crucible steel is Wootz, but Wootz is a crucible steel. In order to get the patterning present in Wootz, there are a few criteria.: High carbon content in the 1.3%-1.8% range and some sort of carbide forming alloying element. There are also heat control, and forging techniques that aid in creating the pattern.

It is important to note at this point that the work of Veerhoven and Pendray to rediscover the secrets of this steel were foundational to leaning the secrets that had been lost in the mists of time. That video was released 7 years ago, but the work shown was done much earlier than that. There are many smiths around the world Who are currently making Wootz steel. Niko Hynninen from Finland was making Wootz as early as 2010.

Other smiths making Wootz today are Daniel Cauble and Spencer Sandison, although Wootz production has soared worldwide and there are many others too numerous to name here.

Now for the word "Damascus". Most modern knife afficionados use this term to refer to what should (IMNSHO) actually be called "Pattern welded steel". This is an ancient process as well and involves layering two or more different steels or iron and steel into a stack (called a billet) and forge welding the stack together. This stack is then manipulated through forging processes to create a pattern in the steel. This process likely originated during the Viking Age in Europe (700 CE-1100 CE) as smiths were processing iron ore in bloomery furnaces with varied results. It is a matter of conjecture that that mixing of low-hardenability iron/steel with high-hardenability steel produced a hardenable edge with a more flexible core in the blade that would neither bend nor break during combat.
An example of this technique from around 900 C.E. found in Helsinki.

A few examples of modern "Damascus" or pattern welded steel of my own work.

I am among a group of smiths who would prefer to abandon the term "Damascus" altogether as it causes too much confusion. I prefer the term "Wootz" to refer to the classic watered pattern produced in a single-steel blade through appropriate carbon and alloy content, while using the term "Pattern Welded Steel" to refer to the effect produced by layering and manipulating two or more iron/steel components to create the pattern.

I apologize for the hijack of this thread as this is moving away from the original intent, which was to discuss the reduction of ore/sand into steel.
The only thing it may add is the differentiation between the smelting process and the crucible steel process. When starting with ore (sand is an ore), you generally need to process it down to iron or steel before you can use it in a crucible.

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I'm very happy to have the detour into historic steel terminology, thank you Joshua. It is all so beautiful, and intriguing that you can get superficially similar effects from very different processes. Those blades (all of them) are truly works of art - stunning!....I have to admit at this stage I would be fairly happy with a paperweight; if I can make a lump of metal at all that will be great!

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Nancy Reading wrote:I'm very happy to have the detour into historic steel terminology, thank you Joshua. It is all so beautiful, and intriguing that you can get superficially similar effects from very different processes. Those blades (all of them) are truly works of art - stunning!....I have to admit at this stage I would be fairly happy with a paperweight; if I can make a lump of metal at all that will be great!

I'm sure you can achieve a lump of metal. If your learning curve is anything like mine has been, you will probably make a few of them!
I'll put up a thread showing a refinement process experiment I did about 4 years ago and provide a link here. I think a similar basic smelter set up will work for you either with or without a crucible.

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That post is now live: https://permies.com/t/274766/pep-metalworking/Refining-carbon-steel

I suggest you build something similar to do your initial smelt of sand into metal. You may want to build it taller, maybe 20 inches of bricks tall. The sand will need time at temp to melt and the only way to achieve that in a smelter such as this is to increase the distance from the top to the bottom.
Once you have the initial bloom, or small blooms of semi-smelted sand, you can decide to further refine it one of several ways:
1. Put it through the same furnace again. This may require multiple remelts to consolidate and remove impurities.
2. Load what you get into a crucible and bury the crucible in the same furnace and try to make crucible steel.
3. Do both 1 & 2 depending on what you get the first time.

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Joshua States wrote:That post is now live: https://permies.com/t/274766/pep-metalworking/Refining-carbon-steel

I suggest you build something similar to do your initial smelt of sand into metal.

Do you think that a rocket forge just won't get hot enough Joshua? Or that I won't be able to get the right mix in my crucible? I'd really like to try the 'low tech' approach and not use a blower and charcoal if I can help it. I know that doing something different is sometimes a bad idea, but I can't see an obvious problem at the moment, other than the unknown.

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