A reverence for steel. . . .

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coffeecup
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A reverence for steel. . . .

Post by coffeecup » Mon Jan 05, 2015 2:58 am

For some time now, I’ve been planning a series of posts discussing steels: what’s known about the early days of iron and steel use, composition, micro-structure, carbides, and what it all means. The problem has been the question of where to start. . . . The answer is obvious: start at the beginning. I’m posting them here because I’d rather tell a story than write a research paper.

We know people have been using iron, in one form or another, for at least 75,000 years: engraved pieces of ochre—an iron ore—were found in Blombos Cave in South Africa, an early occupation site. It has probably been used as a pigment for almost that long. The Khormusan culture, in Egypt, was making beads of hematite about 35,000 years ago. Nickel-iron meteors provided the raw material for beads in Iran about 5,000 years ago, and the earliest known iron weapon is a spearpoint from Egypt dating from about 6,000 years ago.

Smelting—the process of using heat under controlled conditions to extract iron from ores—was probably discovered about 5,000 or more years ago. But until about 3,200 years or so ago, ornamentation and occasional tools/weapons were the primary uses of iron. The reason for this seems to be that bronze was a "known quantity":cheaper to make and cheaper/easier to work, and that people tend to stay with what they know.

We’re in a similar situation today, in regard to various sources of power. There are arguably “better” (however you want to define “better”) sources of power. The problem is that we don’t know that choosing those power sources will give us more-desirable outcomes. Then and now, switching to a new unproven resource requires some consideration and preparation, and convincing a lot of people that it is worth the change.

It is hard for us today to really comprehend the slowness of technological change in the past. Things have changed so rapidly in our lifetimes that we find a lack of technological progress to be baffling. We forget many times that there are factors—often, seemingly unrelated—that confound the adoption of new technology.

For example, in Europe a great many people drive small, highly-efficient diesel vehicles. They just haven’t caught on here in the US. Part of this is due to fuel being cheaper here, so it isn’t worth the investment. Part of it is due to tighter emissions standards here. Part of it is due to our preference for larger, more-powerful vehicles, and part of that preference has evolved from the different driving conditions many of us face here.

Most of Europe and Asia went from the Bronze Age to the Iron Age, and in many places it took hundreds of years for the change-over to be complete. The use of iron wasn’t a “mature technology”; the technology to refine and work iron had to develop while the cultures changed to accept the new technology. In other places—North America is a good example—iron tools (by then a “mature technology”) displaced the use of stone tools in a single lifetime.

Next post we’ll look at what constituted a “mature technology” for almost 2,800 years. I’ve got some experimental data on time/energy requirements, and yields of iron and steel, that make it clear that this was hardly a “mature technology” from our perspective today.

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Re: A reverence for steel. . . .

Post by Colonel26 » Mon Jan 05, 2015 3:01 am

Very interesting! I look forward to reading more.
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Re: A reverence for steel. . . .

Post by FRJ » Mon Jan 05, 2015 3:16 am

This is very interesting to me, coffeecup. I know nothing about steel/iron, but it never kept me from buying knives.
Thank you for this important information. I'm looking forward to more of your posts.
Joe

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Re: A reverence for steel. . . .

Post by philco » Mon Jan 05, 2015 3:25 am

Jim I always know when you post information you've done your homework and you're going to teach me things. I enjoy that. ::tu::
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Re: A reverence for steel. . . .

Post by coffeecup » Mon Jan 05, 2015 5:00 am

Thanks guys. I figured to get this started tonight and will try to add a post every week or so. One more for tonight.

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Re: A reverence for steel. . . .

Post by coffeecup » Mon Jan 05, 2015 5:03 am

(I sometimes joke about the local volunteer fire departments having requested that I not be allowed to weld, or use a torch, or play with fire. . . or even convert motor vehicles to large wood-lathes. I think that as you read through this, you may understand why they would do this.)

Remember as a little kid, finding a fruit tree with ripe fruit, what did you do first? You picked the low-hanging fruit, right? Then you climbed the tree as high as you could, maybe fell out of the tree and broke your arm or something, but you picked the low-hanging fruit first because it was easy to get to. The low-hanging fruit of the iron ore world—widely distributed, easy to find, easy to refine, and renewable—is bog iron.

Bog iron is an impure iron oxide, typically found in swamps and bogs. The formation of bog iron begins when subterranean streams dissolve iron-bearing ore. When the streams break the surface and become springs, the iron in solution becomes iron oxides. When the water enters a swamp or bog, anaerobic bacteria that grow in the acidic water concentrate the iron, resulting in the formation of pea-sized lumps or nodules. Folks harvesting peat from bogs discovered the stuff. There’s never a lot in any one place, but if you are harvesting peat to burn for heating and cooking, you cut a lot of peat and find a fair amount of iron . . . and it is renewable in that you can go back to the same area in 20-30 years and find newly-formed nodules.

But finding and gathering bog iron is the easiest part of refining it. The next step is to heat it in a fire to dry it out and burn off organic contaminants. You can do this while burning the charcoal—and you’re going to use a lot of charcoal. . . . Coal would have been a more-efficient fuel, but charcoal was preferred for a couple of reasons. Iron refining seems to have developed from earlier refining of copper/tin/bronze, and charcoal was the preferred fuel for this because anywhere there are trees, charcoal can be made. They knew how to use charcoal, and it worked with the tools and technology they had then. Coal burns hotter, which can create problems of its own.

For about 2,500 years, Iron refining was done in bloomeries. A bloomery is rather like a chimney, in which charcoal and iron are mixed, and then the charcoal is burned in the presence of an air blast to increase temperatures. The burning charcoal generates carbon monoxide, which reduces the iron oxides in the ore into metallic iron. There are problems with this approach: the most obvious from a modern perspective being that the iron doesn’t really get hot enough to melt completely, so instead of an ingot of cast iron, your get a foul mass of iron and slag, commonly called a “bloom” or “sponge iron”.

I’m not so sure that is a problem, at least from the perspective of the early workers. A more-modern way is to process ore into cast iron (which is iron and various impurities including a very high level of carbon), and then further refine the cast iron by sorting out the impurities and burning off the carbon. Way-back-when, they didn’t really have a way of further refining cast iron, but they could convert the bloom into wrought iron. They used some of the impurities to their advantage, and worked out ways to convert the iron to steel. Granted, they were very labor- and energy-intensive ways to do so, but they were ways that worked on a small scale. Modern ways are more efficient, but only on a large scale.

Early bloomeries were small, producing a couple pounds of iron with each firing. By early medieval times in Europe, they were producing up to 25-30 pounds per firing. When the loads got larger, the extended time involved meant that some of the iron got hot enough to melt. This resulted in cast iron, which they saw as a waste product because they didn’t know what to do with it!

In the early ‘90s, I got my hands on a couple gunny-sacks of bog iron. Of course, when you’ve got something like this, you have to build a bloomery. Maybe that’s just me. Half of that bog iron was wasted when I made a series of stupid mistakes. I thought I—a product of the 20th century—knew more than the folks who invented the process.

I scaled up the bloomery to yield a roughly-25 pound bloom. I used coal, because it was “more efficient” (and available). And because I’d always used a blower on a coal forge, I brought that degree of forced air into the picture.

According to the probes I had in place on the bloomery, internal temperatures exceeded 1,300 degrees C (about 2,400 degrees F). The bonded-clay bloomery cracked. All I had to show for it were a twisted mass of useless cast iron and slag, and a request to move my experiments out of the city where I lived then. Oh well, I was going to have to make charcoal anyhow. . . . Before I was done, I’d converted a cord of mixed hardwoods—not a “face cord” but an actual 4’x4’x8’ cord—to charcoal.

My Mark II bloomery was smaller, with a projected yield of a 2 pound bloom. Air supply was via a single-chamber bellows, and the fuel was charcoal. The probes said the temps never exceeded 1,100 degrees C (roughly 2,000 degrees F). I still ran out of charcoal, but by the time I was done I’d converted over 200 pounds of bog iron to about 40 pounds of sponge iron.

From start to finish, my hypothetical umpty-great-grandpa who ran a bloomery 2,500 years ago would have had about 120 hours in producing that 40 pounds of sponge iron. And the work only gets harder from here. . . .

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Re: A reverence for steel. . . .

Post by jerryd6818 » Mon Jan 05, 2015 5:10 pm

Please continue. I am at the very least being entertained. The writing is pleasant to the mind and flows freely. I'm not sure I'm really learning anything because my exposure to the sciences involved is very limited so my understanding of the material is very limited but I am enjoying your posts. Maybe I'll learn something by accident. :)
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Re: A reverence for steel. . . .

Post by Dinadan » Mon Jan 05, 2015 11:24 pm

A nice thread, Coffeecup. Talking of bog iron, here along the Alabama coast we have a rock which we call ironstone, which is believed to be formed by repeated rising and dropping water tables. Sometimes very dense heavy nodules form, an inch or two in diameter, they trigger magnetic locator. I have guessed that they are pretty similar to bog iron but I have never tried to smelt them. That is something I keep thinking that I want to try. I would imagine that someone has tried it somewhere as an experiment but I am not aware of it. The really heavy nodules are not at all common but I have found a few along the beds of clay bottom streams at times. Wish I had a few on hand and I would post some photos.

I am curious where you got your bog iron. Any photos of the raw stuff?

Oh yes - as a man who grew up in a house where we heated with wood, I think your 120 hours estimate may be a bit, or even a lot low. No saws, poor axes by our standards, just getting the wood for the charcoal burning would have been quite a task.
Mel

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Re: A reverence for steel. . . .

Post by rangerbluedog » Tue Jan 06, 2015 12:55 am

Jim, You sound like an old foundry guy. ::nod::
I am addicted to the liquid iron science myself!
Don't do it for a living anymore, but I still dabble in the backyard with my little charcoal furnace.
Keep talking, we're a listening!
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Re: A reverence for steel. . . .

Post by coffeecup » Tue Jan 06, 2015 4:52 am

Jerry, if you enjoy it as much as a series of campfire stories, then I'm doing it right.

Dinadan, the ironstone I'm familiar with from that area is a sedimentary stone; it underlies much of the coastal plain. Generally grey on the inside, but lumps exposed to seawater turn black--black oxides of the ferrous component. The Brits used it as a source for iron, but most of the stuff is fairly low-grade, and it isn't economical to use today. The bog iron I got came from Massachusetts I think, I got it in a trade from someone back east.

As for the charcoal, part of that cord-worth was used in the bloomery, and part of it was used to further refine the sponge iron. I did a trial run producing charcoal based on written accounts of the old methods of production. Old method was to cut the trees, stack and bury them (leaving a small tunnel for air), then fire it up. Stuff didn't have to be cut to length, which saved a lot of time. The burn took a few days, but a guy could do other work while watching the burn--and he could burn a cord or more at a time. I'm firmly convinced that someone who knew what they were doing could have done it quicker and more efficiently. On a small scale like I was doing, it would have been more practical to burn the charcoal at the tree source, and set up the bloomery there. Most of the charcoal I used was produced in a retort improvised from a 55 gallon drum.

Blue, as the screwup with coal shows, I really had no idea what I was doing at first. I just wanted to understand how it all worked. One of the things that frustrated me as a kid was that it always seemed there were pieces missing in what I knew. I learned to forge weld before I was 10 years old, a knife-maker friend explained how to make pattern-welded steel when I was 17 or so, but I always wanted to know where and how they got the iron in the first place, and then I wanted to know how and why they did what they did. . . . The more answers I got, the more questions I had.

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Re: A reverence for steel. . . .

Post by jerryd6818 » Tue Jan 06, 2015 5:04 am

As Blue said. Keep talking. We're listening.
Forged on the anvil of discipline.
The Few. The Proud.
Jerry D.

This country has become more about sub-groups than about it's unity as a nation.

"The #72 pattern has got to be pretty close to the perfect knife."
--T.J. Murphy 2012

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