Recipe for making crucible steel?

[Bo T]

I was at a hammer-in last year where I talked to a gentleman about making crucible steel. He had a large quantity of magnetite of high purity. During the process of refining the magnetite, how much carbon is needed? Is the carbon oxidized to carbon monoxide, carbon dioxide or both? We were talking about a steel @ 1% C.

[Nobody Special]

There's a number of processes, most of which are insanely complex. If you're talking about coming all the way from ore, it only gets worse.

One of the cooler ways that it was done in the western world was the uber secret process developed by carburizing iron into blister steel, then cutting it up and remelting in a sealed crucible. It's crazy slow, inefficient, and needs to be carefully controlled, but it works great. If I remember correctly it was originally done to make consistent springs for clockwork, then stolen by competition in a very shady process. (the full dramatic story involves a weary traveler taken into the shop to rest, feigning sleep, and then making off with the secret in the middle of the night.)

Carbon amount depends on the process, and the method used to add it, (or take away from if you're talking about burning out carbon from pig iron to remove it, although is that really crucible steel? meh.) The carbon ideally should not be oxidized, but exists within the crystalline structure of the steel, the exact shape of which is determined by the heat treating process. Generally the point of melting it in a crucible is to get a homogenous product and to keep much oxygen from getting in during the process.

If you're thinking about homemade wootz, Ric Furer offers an occaisional class that walks you through the process.  Expensive for a hobbiest, but well worth it as a one of a kind workshop. There's some video of it on youtube, as well as some of his other steel making, creating blooms and tamahagane.

Generally speaking, making iron or steel is a lot of fun for the hobbiest, but fairly advanced and costs a LOT of time, effort, and/or money. I would strongly consider trying blooms and getting a strong casting background before playing with crucible steel.

[Bo T]

I am thinking about a batch process where the magnetite is reduced in the crucible. The carbon would be used as the reducing agent and as an alloying element. the result should be steel, but....it could end up as cast iron or half baked magnetite. I'll check the video to see if I can glean info from it. I did download a paper where the process was used on pig iron.

[ThomasPowers]

It's a totally different process when using pig iron as you are trying to oxidize the excess carbon in pig iron  and deoxidize the ore when using magnetite.  So this comes out somewhat like " I'm trying to make ice in a pot; I downloaded a paper on how to boil water for information on the process"

Huntsman was the englishman credited for the crucible steel innovation in england. Other cultures had it way before his work in the 1700's

May I commend to your attention "Steelmaking before Bessemer; Vol 1 Blister Steel, Vol 2 Crucible  Steel" K.C. Barraclouth and "Crucible Steel in Central Asia it's Production and Use" Dr A. Feuerbach.  Really helps to understand what's going on before trying to to it on an ad hoc basis.

[Bo T]

Ah, so your references will deal with the reduction of the ore in the crucible? I noted the pig iron process as that is similar to what I have been able to find. And, I am not really interested in it as it seems horribly inefficient but successful. There was some reference to a 'west hill process' from a millennia ago but few details. I'll check the Huntsman clue and your references. As for the current videos and information that I have found for hobbyists it appears to be - adding a little carbon to low carbon steel to make wootz. 

The one step reduction of iron ore to steel, which I am interested in, is conceptually very simple but as usual the devil is in the details.

[ThomasPowers]

Nope; historically I have not found much about reduction in a crucible just making crucible steel in a crucible.  Dr Feuerbach postulates that they used bloomery material in Merv and The crucible steel process in England used blister steel IIRC.

Reduction in a crucible is an expensive small scale process and so why go that way when you could be producing huge amounts of material other ways more cheaply?

BTW "Mastery and Uses of Fire in Antiquity", Rehder, has instructions on building a "foolproof" bloomery using modern techniques.

I'd talk with Ric Furrer if you want to melt steel at home...

[DanielC]

Many friends in my circles make crucible steel using various starting materials, including ore. I could connect you to them.

[Bo T]

ThomasPowers, The cost argument is a good one as one can get several pounds of exceptional steel for the cost of making a single crucible. However, the direct conversion of ore in the crucible controls some of the variables that occur when smelting ore > steel in the furnace. For example; better control of the reduction process resulting in a  more uniform composition of the product. Also, I am not sure that the cost would be that much more than building and running a backyard smelter. It seems, to me, the main difference is the cost of the crucible. Dr. Feuerbach has an amazing thesis. I have had the opportunity to read a portion of it. I have also reviewed Ric Furrer's video. I am aware of some people around here who have smaller furnaces capable of melting cast iron for a pour. Such a furnace should be capable of heating a crucible to make steel. At this point the discussion is still academic but very interesting.

58 minutes ago, DanielC said:

Many friends in my circles make crucible steel using various starting materials, including ore. I could connect you to them.

DanielC,

Yes, and thank you.

[ThomasPowers]

Dr Feuerbach kindly sent me a copy of her thesis when it was published.  I agree that a crucible can be managed to control various factors; by people with the background to do so.  We run into a lot of people here who seem to expect that they can mimic the results of people with decades of experience their first trial and so tend to be a bit of a wet blanket.  Which hopefully will not interfere with the people willing to do the research and experimentation.

It's funny though that the bloomery smelting group I used to be a bellows thrall and cob worker for did a dozen runs where the net cost was for the charcoal used.  The early trials produced very small amounts of iron but by by the end we were producing 15 pound blooms on a regular basis---not bad with a no electricity all human powered effort!  (I will say that our ironmistress did other smelts in between our yearly ones at our campsite at Pennsic)

Working with people with the experience is probably the fastest way up the learning curve; if nothing else just to answer questions.  (Why I volunteered as helper for both Ric Furrer and Al Pendray when they demo'd at Quad-State...Ric is the one who told me about "Steelmaking before Bessemer"  and I ordered my copy from ABEbooks.com before I had my jacket off when I got home from Quad-State.) They can also help with the required safety precautions.  Sword Forum International had a very interesting thread of a fellow using thermite to produce odd steel alloys---up until he reported that he was going blind...

[DanielC]

If you come to Fire and Brimstone, there is always a smelt, and a lot of crucible steel made and forged with all kinds of fun machinery.

 

My recommendation is to talk to Jeff Pringle. He is really good with crucible steel. There are a lot of people out there to talk to, though some expect payment in return for some of the more subtle information. Jeff isn't that type.

Edit: Ric is also a fountain of knowledge.

[Bo T]

Thanks DanielC, I sent an e-mail to Jeff.

Unfortunately, Fire and Brimstone is on the other side of the country and I am (at this point) lacking in time and disposable income.

[alex L]

theory is simple. fact is its more like art. going from iron ore to steel in one shot. lot of math. if you have iron oxide all you would need to know is the weight of oxygen that is in it. then add that much carbon to make pure iron, and lots of heat. by product co2 and iron. any extra carbon makes steel. under 2% but just the theory. i my self am struggling to get the mix right. get wrought iron or cast iron. no usable steel yet. so at part where trying to turn the cast into steel. last run dident dilute the cast iron enuff still really brittle. 

[Tim Mitchell]

You can reduce the ore directly into a steel ingot and some have done it that way.  The Georgian process could be used to process ore as well as bloomery iron, you can read about it here Georgian Method There is a summary of the method on Bladesmithsforum.com. 

The main issue with the direct reduction method is that it makes poorer quality steel. The bloomery processing of ore removes lots of unwanted things and leaves a cleaner product.  The bloomery iron still has some phosphorous and possibly sulfur as well as silica and other impurities in it which were historically reduced through adding ingredients in the crucible processes.  The Charcoal does clean up the charge significantly but to get a really high quality crucible steel you need to either add a bunch of stuff to the crucible such as manganese, calcium, tannic acid containing plant matter etc. or you need to start with a well forged bloomery iron and cast iron mix (or oxidize cast iron).  In my opinion you will always get a better product in the end if you use the highest quality ingredients.

There were many different methods of making crucible steel (Bulat, Pulad, Wootz) but only a very few created a good pattern and a high quality sword material. Many of the swords made of crucible steel in the early to mid 1800s were of inferior quality according to Abbott.  He had one sword which was of the legendary quality.

Anyway I hope you explore crucible steel however you do it.  It does take time but it isn't as hard as many make out, it takes time and educating yourself and a willingness to explore new processes.