small shop steel production

I was just Wiki-walking instead of working, and while reading the Wikipedia page on steel, came across the statement:
"Though steel had been produced by various inefficient methods long
before the Renaissance, its use became more common after more-efficient production methods were devised in the 17th century. "
And it made me wonder -- do any of these _efficient_ methods apply to the small-scale workshop (i.e., one or two people, or at most a dozen), or if one were inclined to do a spot of home steel-making would one be reduced to using methods from the 1600s?
Not that I'm going to go digging for iron ore on my property or anything; I'm just curious.
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http://en.wikipedia.org/wiki/Crucible_steel
I've seen a reference somewhere on making carbon steel from wrought iron in a horizontal-draft forge. As it absorbs carbon the melting point decreases, so the smith continually removes the molten droplets.
http://www.corrosionist.com/iron%20carbon%20phase%20diagram.jpg
jsw
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Tim Wescott wrote:

Just guessing but I'd say no because of the square- cube law and the heat needed.
OTOH, you're the man that made that tiny engine run...
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On Mon, 12 Mar 2012 10:57:03 -0700, Jim Stewart wrote:

That was hardly tiny as such engines go, just kinda small.
The smallest production model airplane engine that I know of was the Albon Diesel, at 0.009 cubic inches; Cox successfully made an 0.01 cubic inch glow motor for years. Individual machinists have made engines as small as half that size, and made them run.
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wrote:

No. They involve working with large amounts of molten steel and forcing air, oxygen-rich iron ore, or pure oxygen into them to burn out the excess carbon, while fluxing the whole mess to remove unwanted elements.

Yes. There are small-scale ways to burn out excess carbon and to flux out unwanted elements. They make steel about as valuable as a precious metal, but they appear to be fun for some folks.

It's a good thing to be curious about. The history of steelmaking is fascinating. It's a good armchair study for metalworking hobbyists, and it will give you some very useful information to help you understand that incredibly diverse and versatile material -- steel.
Keep in mind that steel is nothing more than iron with a carbon content that falls into a specific range -- more or less, 0.08% - 2.1%, and that contains little or no sulfur, calcium, silicon, phosphorus, or some other elements. Some specialty steels add specific quantitites of these elements back in, to improve machineability, etc.
Beyond that, it's a study that can keep you occupied for a very long time.
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The number of people involved is not a good way to define small scale. I toured the Nucor steel mill in West Seattle and there were only about a dozen people working per shift.
Dan
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On Mon, 12 Mar 2012 20:17:03 -0700 (PDT), " snipped-for-privacy@krl.org"

For a highly automated, multi-million-dollar industrial plant. It appears that Tim is asking about a hobby-scale operation.
As someone pointed out, the fuel consumption, alone, is incredible in small-scale steel production. There is no way I've ever heard of to make an "efficient" setup on that scale.
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wrote:

Some ideas: http://www.consarc.com/brochures/var.pdf http://www.metallab.net/arcmelt.php http://www.sentrotech.com/vacuum-air-inert-all-in-one-furnace.php?gclid=CJG0rd7w464CFYNx4AodUklCWQ http://www.plasmalab.ru/metallurgy.htm http://blog.modernmechanix.com/2007/08/02/arc-furnace-incased-in-two-flowerpots / A modern flowerpot broke into small pieces when I made a charcoal forge from it.
jsw
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On Tue, 13 Mar 2012 08:47:10 -0400, "Jim Wilkins"

It probably got too hot too quickly to release the moisture within.
-- And the day came when the risk to remain tight in a bud was more painful than the risk it took to blossom. -- Anas Nin
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On 3/13/2012 6:52 AM, Larry Jaques wrote:

more likely it went through quartz inversion too fast. i fire them in my kiln and don't have problems if i raise the temps slow enough.
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Check out Wikipedia for "backyard furnace", which were used in the great Leap Forward in China.
i

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No. and Yes, as previously mentioned.
There is a a huge difference, though between wresting iron from iron ore and converting high carbon iron compounds (think cast iron) into "steel".
Folks that I hang around with are messing with these things on a regular basis. We have used processes, mostly, that were around as long as about 150 BCE, and well before. The largest bloom from one of these events that I have ever seen personally weighed in at under 100 pounds. Anything bigger than that is well out of the scope of the home shop, I'd say. These are always batch mode processes that no self respecting steel mill would put up with for 10 seconds.
Took at least 4 or 5 people, at lot of preparation, and then at least 4 hours in the furnace, but often 10 hours or more. And that's before forging the bloom into something you could actually call steel.
Tried to go continuous in 1992. Ran for 10 days X 24 hours. Burned 8 tons of charcoal and got maybe 800 pounds of questionable bloom.
They'll be doing this at the biannual ABANA conference in Rapid City, SD in mid July if you want to see it for yourself. (www.abana.org)
Pete Stanaitis ----------------
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On an extremely small home scale you can melt steel into a puddle and add whatever alloying elements you want with a TIG torch. Or you could try removing some of them by zone refining. http://en.wikipedia.org/wiki/Zone_melting
jsw
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IF you could get wrought iron, you could probably do the "crucible steel" process with a modern pottery kiln. The old-style steel-making process was to convert iron ore to cast iron in a blast furnace, cast iron to wrought iron by burning out the carbon during puddling, wrought iron to steel via the blister method or crucible method. Since wrought iron has been replaced with mild steel, it's unobtanium unless you'd like setting up your own puddling works. Some guys have. You have to have pretty pure ingredients to get decent metal out, sulphur and phosphorus will ruin your day come forging time. Really old-time smiths(medieval) could take bog-iron ore and charcoal(lots) and reduce it to iron of a sort in the forge. Took a lot of fuel and time to do it, though. So yes, you could probably do that in your backyard, assuming pollution regs and distant neighbors allow. Make money at it, probably not unless you could charge admission.
A more modern method would be to have an arc furnace to handle scrap and do steel founding using that. Arc furnaces can be had in small sizes, you'd need more than a household hookup to the power line, though. An induction furnace can be had in smaller sizes. Don't think you're going to be setting up a rolling or slitting mill in the garage, though. The main difference between modern steelmaking and ancient is the chemical control over the wanted and unwanted elements. In days of yore, the ironmaster just did the process by rote and hoped that everything would come out like the last successful batch.
Stan
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Here are two old textbooks on wet chemical analysis. Unlike modern instrumental methods the results are absolute quantities and don't require standard calibration samples for comparison.
http://www.archive.org/stream/standardmethods03scotgoog/standardmethods03scotgoog_djvu.txt http://www.archive.org/stream/semimicroquantit030896mbp/semimicroquantit030896mbp_djvu.txt
IIRC we were told that the chemist was expected to have the carbon percentage within 10 minutes and the full analysis in 30, since it took a lot of fuel to keep the metal molten while he worked.
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On Tue, 13 Mar 2012 09:01:23 -0700 (PDT), Stanley Schaefer

That's interesting info, Stan. I find it remarkable that anyone would engage in puddling iron as a hobby. It was one of the most physically destructive jobs a man could take. Puddlers were paid wages that were twice those of other iron-mill workers, and they seldom lived past age 45. Typically, they were physically broken down and had to leave the work by age 40.
A lot of that was the heat -- it was physically exhausting work done it an environment of toxic gases and constant exposure to radiant heat.
It's not my idea of a fun hobby. But then, I don't jump out of airplanes, either. d8-)
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I don't believe that is what is generally considered to be wrought iron. WI is produced by Hammering and forge welding on blooms ( The hammering being the "wrought"ing) And has a fibrous grainy texture due to slag inclusion. And what you are describing would be "bar iron" or "puddle steel" which is considerably closer to mild steel than it is to WI
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This is a *really* complicated subject, because there were so many different processes used to make "finery iron," "sponge iron," "bar iron," and so on. A bloom could be any of several products, usually low-carbon iron that could be forged or rolled into wrought iron, or steel. Some blooms were solid; others were spongy.
But the puddling method was the most common, if not the highest-volume, method for making wrought iron for at least a half-century before 1900. It also was used in Germany for making mild steel.
You can spend a lot of time studying old iron- and steel-making methods, and for metalworking hobbyists, it's an enjoyable study. At least, it was for me, back when I was Materials editor at American Machinist.
Here's a pretty good, if confusing, description of puddling from Wikipedia. I think it's accurate but I haven't studied it for decades:
http://en.wikipedia.org/wiki/Puddling_ (metallurgy)
Wrought iron is basically low-carbon iron with silicate slag inclusions, hammered out into a stringy composite.
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news:acdeaa7e-fb18-410b-aae6- -IF you could get wrought iron, you could probably do the "crucible -steel" process with a modern pottery kiln. The old-style steel-making -process was to convert iron ore to cast iron in a blast furnace, cast -iron to wrought iron by burning out the carbon during puddling, -wrought iron to steel via the blister method or crucible method. -Stan
A parallel process, if I remember correctly from a school trip to the Saugus Iron Works, reduces the iron ore to solid-state iron with CO from the fire, without reaching the ~1600C melting temperature of the nearly pure iron produced. The product is a dirty glob of sponge or bloom iron and slag, which they hammer out to compact it and squeeze out at least some of the slag. This is the classic"wrought iron" which is easier to forge-weld than the puddled version, they say
Their website currently says they produced wrought iron from cast pig iron, but I remember the guide talking about a slag-filled bloom that was displayed near the water-powered hammers. http://www.nps.gov/sair/index.htm
http://en.wikipedia.org/wiki/Bloomery
jsw
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