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I have been doing research for along time and would really like to do a run. I work in the auto service industry, so that allows me access to lots of cast iron shavings from turning brake rotors. Now i know that starting with low carbon is the best way start to go. However I have pounds of sand sized shaving. It looks as those most of the cast iron is around 4-5% carbon.

 

From what I have read a blast furnace is the only way to get the carbon content down to a level for making steel.

 

Just looking for some insight.

 

Thanks,

Jo

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I don't want to discourage you, but you have some reading to do.

 

Smelting is the conversion of iron ore into metal, not just remelting material into a solid piece.

 

A blast furnace is usually the term for the making of cast iron, or pig iron, in pre-industrial times. Reducing carbon from liquid cast was usually done in a puddling furnace, or other arrangement where the cast iron was heated to liquid then exposed to oxygen, burning carbon off until the desired chemistry was reached. All this was overtaken by the Bessemer process in the mid-19th century.

 

 

If I may ask, what's your desired end-product, and have you ever worked with someone smelting to assist and get an idea for what's involved?

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Oroshigane Jo,

 

I would give it a try and just see where it takes you..if you end up melting cast iron to cast iron, so what...you will have a direction given to you with your trial results. You may want to talk to Mark as to how he reduces the carbon content of the material..my guess is you want a very shallow fire and some formulated slag in the bowl where the metal will end up. I would buy some FeO (Black Iron Oxide) and some fine silica ..silica is just sand but it is hard to get it very fine at your local building yard. Both are available at a ceramic supply house.

 

I would build a very shallow furnace (12 " high at the most) with a slightly ( see Marks posts ) hollowed out sandy bottom and place a horizontal air supply right at the lip of the shallow bowl ( lets say the bowl is 1.5" deep) . Give yourself a long, slow preheat ( 20 minutes min.) and start meting some of your slag first then add ,some of your fines maybe using a sieve to sprinkle it onto the very well sorted charcoal fire. Keep the charcoal fines out, as the furnace has to breathe.

 

Let's say your bowl is about 6" to 8" in diameter , your charcoal has to be large enough to allow the fire to grow to the bowl size...fines will limit the fire size, bad.

 

Your slag formula is about 4/1 iron oxide to silica ( well mixed )..watch this stuff as it will want to fume out of your furnace..added over a hot slow fire...it will melt at about 1200 C. Meaning you can really rev up the furnace but slow it down during the addition of the slag mix. When these two are melted to together in the furnace they will form a liquid slag rich in FeO and looking for the carbon in your fines.....but it ( the slag ) has a fairly tight melting point range and once a given amount of FeO is consumed you will have a slag of very high viscosity ( not to useful).

 

If we can assume your carbon content starts at 4% C and you want to end up at just over 1% Carbon, you have to lose 3% carbon..some is removed by the slag and some by the blast of air.

 

Let's say you want to work with 1 kg of material per event...3% of 1 Kg is 30 Grams your slag will only work at a 25% efficiency at the most....or....you will have to add 4 times the amount of slag due to a viscosity change when the slag begins to become depleted of FeO .

 

To work with a weight of 1 kg of your fines ( at the assumed 4% Carbon ) you will have to add 800 Grams of formulated slag and these addition have to be divided up proportionately.

 

Good luck, lots of preheat and dust protection...it may take you a while but it is definitely doable.

 

By the way you can spread your fines in a large SS bowl and play a weed burner on them..get them really hot and hope they start changing color ( oxidizing and losing carbon ) I would definitely give that a try...about 20 minutes per shot. That will give you a bit of a jump on it all. ( stirring required)

Everything at the bottom of that furnace is going to get real gooey Try not to mess with the air supply too much. Start out with small batches and small additions like 200 fines and 160 slag until you get familiar.

 

I hope this gives you enough to get started with..I am anxious to see your results.

 

Jan

Edited by Jan Ysselstein
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Wait a minute.....what?

Are you saying it is actually possible to turn cast iron into usable steel in my backyard? Because I probably have a hundred pounds of cast iron in my backyard, well side yard. Anyway, this intrigues me. I'm going to have to reread Jan's post and try and grok this process.

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I was assuming the brake rotors were made of ductile iron which is pretty clean stuff, but has over 2% silicon in it..the silicon also loves oxygen ( more so than carbon ). The slag amounts above may be a bit overkill for the amount of carbon in ductile iron but I would try it and see. I have done something like this with Sorel Metal which is very low in silicon.

 

Jan

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JJ,

I reduced some white cast iron under the topic of Salem steel starting at post 64 in the Pit Charcoal Thread. That furnace is only 6" in diameter and the two air inlet configurations which worked best are ...horizontal at the lip of the bowl or at a 45 Deg angle targeting the center of the bowl...the air inlet does not reach into the furnace in either case. As soon as your cast iron starts to accumulate in the bowl the process starts, I may have pulled it too early as I was attempting to judge the sparks without much experience

 

The Sorel Metal was converted to steel in a small dish placed on my crucible furnace..intended to be an open hearth...that steel looks really good I should be able to find it . Unless one wants to experience a shaft furnace for the Romance of it I find the open hearth the most promising method. If you have any questions beyond this send me a PM as I am trying not to bump Jo off this post.

Jan

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I have been doing a lot of reading over the years. I know materials very very well. I have been a mechanical engineer for a long time. However the I have no experience with smelting. Heat treating and understanding known blades steels is something I specialize in but making my own steel is something I have wanted to do for a very long time. As an engineer I tend to research a subject to death before I ever light a fire to make it happen.

 

I bought 40 lbs of Fe2O3 a few years ago and at this point the only thing I have used it for is polishing blades with hamons.

 

Thank you so much for the input. I am going to try it this winter once I get all the materials together. I am currently working on building two charcoal kilns to make good pine charcoal. I live about 1.5 hours from some of the largest pine lumber mills in the country, so pine is cheap to get. I have been forging for a long while, but most of my customers want blades made from stainless and even more exotics steels that cant be forged. I enjoy forging more than stock removal but hey you have to pay the bills.

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Okay, now that we've established the parameters, it sounds like you need to do the following:

 

1. Smelt that Fe2O3 with your pine charcoal (lucky! :lol: ) and keep the slag. You're going to need a lot of iron-rich slag.

 

2. See what you can find on the Finery/chafery/indirect wrought iron process. This is a tough one, there is simply not much hands-on technical info out there beyond what Lee Sauder, Skip Williams, Mark Green, and Jan Ysselstein have done or cited here on the forum.

 

The idea is, as has been said, to melt the cast iron in a bath of molten slag with just enough air blowing across the top to remove the carbon you don't want. This was done a LOT in the early days of ironmaking in this country and elsewhere, but the trick is knowing when to stop before you end up with low carbon wrought iron instead of the steel you're after. I suspect you'll have more control over this in a shallow bowl hearth as Jan suggests, but you're still going to end up with some slag in the mix, essentially creating a steely bloom like in an Aristotle furnace, or something approaching tamahagane if you're lucky. As I said, they used to do this a lot in Catalan-type forges back in the 17th-18th-early 19th centuries using cast iron pig from a blast furnace, but they were going for wrought iron, not steel. They then almost always used the cementation process on the refined wrought to get shear steel out of the iron. Mark's research on the Evenstad process might be worth a shot as well.

 

Darn it, now you've got me thinking about a backyard puddling furnace again... :lol:

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Jo , you are welcome.

The decarburized cast iron samples have been absorbed by the broken dreams basket or they are in the for the future pile...but the Open Hearth piece is in my hand and I will take a photo of it and forge later today as I will take up welding some of the steel scheduled to get welded up. If I lived an an area without wood or charcoal or ore this would be my direction. This will be the post bloomery period here when I run out of blooms. There is a tremendous amount of literature on the Open Hearth Process and it works very well, very adaptable to small scale iron making. This should work with your ductile iron as well but you will get a silica slag whereas with Sorel you will get very little.

DSCN4983.jpg rough steel sample from an improvised Open Hearth melt? smelt? or Boil..boil sounds better.

DSCN4984.jpg

Jan

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