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Toney Lauffer




Location: Virginia
Joined: 09 Aug 2008

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PostPosted: Sun 10 Aug, 2008 10:17 am    Post subject: Ancient "Steel"         Reply with quote

I open this topic out of curiosity brought about by my new hobby of making recreations of medieval armour, which I am only just beginning to study and pracitce, and from curiosity about some comments which I've read in various posts here at myArmoury.

Since by this definition: "Steel is an alloy consisting mostly of Iron with a Carbon content between 0.2% and 2.04% by weight." It would seem the only qualification for an armour to be identified as "Steel" would be if the overall carbon content met that criteria of percentage of carbon by weight.

According to this article which I found at The Oakeshott Institute web site entitled, "Some Aspects of the Metallurgy and Production of European Armor", by Craig Johnson, (first published in the Armored Proceedings Symposium Notes, 1999.)
Quote:
One of the main issues to arise from the metallurgical examination of period pieces is that steel was used for the construction of armor to a much greater extent than was previously thought. Many scholars up to a couple of decades ago were of the belief that the majority of armour was made from iron and not steel. The fact that steel was the material of choice for the majority of armor greatly affects the work process to make and maintain the armor. Iron was used for armor and weapons but it does not seem to have been the choice for even common objects and was reserved for the lowest quality munitions grade items. When the modern researcher comes across a piece of quality armor made of iron this can be seen as a red flag that the item may be a later reconstruction.


The author of this article goes on to describe the process of carurizing wrought iron and decarburizing cast iron. To carbuerize wrought iron, which seems the easier of the two options, the piece (iron bar, plate or perhaps even a finished piece of armour) and pack it in an organic material in a sealed vessel and bake at high temperature (red heat) for a long period of time. He then points out that the first mention of this process in Europe was in the late 12th Century, and then supplies us with a description of the process from Giambattista della Porta, Natural Magick, Book XIII, Ch IV, 1558;

Quote:

"Take soft iron armour of small price, and put it into a pot, strewing upon it [soot, and organic powders to supply carbon], cover it, and make a good fire about it: then at the time fit, take the pot with iron pinchers; and striking the pot with a hammer, quench the whole herness red hot in water; for so it becomes hard ... But, lest the rings of a coat of male should be broken, and flie in pieces, there must be strength added to hardness. Workman call it a return. Take it out of the water, shake it up and down in vinegar, that it may be polished and the colour be made perspicuous: than make red hot a plate of iron and lay upon the same: when it shows an ash colour, cast it again into water, and that hardness abated, and it will yield to the stroke more easily: so of a base coat of male, you shall have one that will resist all blows."


Since an Armourer makes his living selling "garments" to wear for protection in battle, those who produced harder, better protecting armours would garner the lion's share of business, and if a particular armourer was able to do this consistently then one can bet this was not by accident, that a process or processes were known to them which would improve the hardness and toughness of the armour they made. According to the author of this article, that process controllable by the armourer was heat treating.

Quote:
To harden steel, one needs to bring it above a critical temperature (usually a bright orange heat) for a certain amount of time and then cool it sufficiently fast, or quench it, to lock the crystalline structure in a form not usually created by a slower cooling process. Pure or wrought iron, a Ferrite crystalline structure, will not harden when quenched, and the majority of armor tested up to now have some form of heat treatment done to them. This indicates that the armorers tried to maximize their materials' qualities and it was the inconsistency of material and difficulty in controlling the process that separated the so-so from the masterful in creating hardened armors.


Quote:
There are a couple of different methods one can use to attempt a quench. The full quench is where the steel is quickly cooled, creating a transformation to a 'Martensite structure' as fully as possible. This results in the steel being as hard as it can be and usually requires a quench in water for the materials it to achieve this state. This Martensite structure is a solid solution of carbon in iron which possess a distorted crystalline structure, this needs to be tempered to relieve stress and reduce some of the hardness by allowing some carbon to come out of the solution as iron carbide. A piece fully hardened could be tempered by heating to about 150°C to 260°C (300°F-500°F), to reduce brittleness and avoid cracking and breaks under use, by "relaxing" the martensite structure. The slack quench uses a slower quenching medium than water, such as brine, oil, boiling water, or some combination of materials which slows the cooling and results in a combined structure of Martensite and other constituents such as Bainite and Pearlite. Materials treated in this way will be harder than an air cooled item but not in need of a temper for performance as armor or a tool. This is the method used by the majority of armor makers. Interrupted, or timed quench is also a technique that was sometimes used. The item would be withdrawn from the quench medium before being fully cooled and the internal heat left in the item would temper the piece to some degree. The interrupted and delayed quenches are also called "slack quenching" today.


The author then points out that the processes involved in the production of the raw material and the hardening by the armourer were experiential processes, the mastery of which would have bordered on the magical since the real, scientific processes the metals were undergoing were not understood in the same way we "understand"them today. The results therefore would have been hit or miss and, as the author points out, ran the gamut of achievable results. The stats I found most interesting here were the relative hardnesses achieved by actual period pieces shown in the quote below;

Quote:

The results of heat treating ran the full spectrum of achievable results. Many munitions armors were iron or unhardened steel, while even some of the early examples of plate armor pieces were achieving 75-430 VPH (less than 6-44 Rc). The Pembridge helm (bef. 1375) testing at 430 VPH on the surface and the Küssnach Coat of Plates(c. 1352) Item No. LM 13367 in the Swiss National Museum, Zürich averaging 390 VPH (about 40 Rc). The Braybrook Helm (bef. 1405)Royal Armories No. AL.30 with less than .1% carbon and left without heat treating, averages 108 VPH.2

Later in the 15th and 16th C. armorers achieved more consistent results, such as the Helmshmied family of armorers in Augsburg who between c.1480 and 1551 averaged 240-441 VPH (20.3-44 Rc) on 17 items of their work sampled.4 Lorenz Helmschmied created one of the most consistent and well hardened pieces yet tested in an Armet (c. 1492), No. 66 Churburg which averaged 525 VPH (abt. 50 Rc).


In my opinion a hardness of 20-44 Rockwell (which is what I interpret that Rc to mean) is a very respectable result.

My questions and assumptions then are these;
1)If the carbon content of period armours was inconsistent, then am I wrong in assuming that any sheet of steel I get from a source like Lowes or Home Depot will have a better and more consistent distribution of carbon in it?

2)Am I wrong to assume that the overall content of carbon will also be, on average, higher than the average period piece?

3)Would modern steel used for reinforcing structures, like rebar, or plate steel be a better quality steel than that found in period pieces even though these types of steel are only required to meet "performance" standards and not "Materials" standards? The reason I ask this is that I have access to large quantities of this material for free and don't see any reason I need to spend alot of money on material at this stage of my new hobby.

To close, here is the link to the article from which I quoted; http://oakeshott.com/metal.html

Thanks in advance for any advice or other input/ sources which can be given.
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Jared Smith




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PostPosted: Sun 10 Aug, 2008 11:58 am    Post subject: Re: Ancient "Steel"         Reply with quote

Toney Lauffer wrote:


My questions and assumptions then are these;
1)If the carbon content of period armours was inconsistent, then am I wrong in assuming that any sheet of steel I get from a source like Lowes or Home Depot will have a better and more consistent distribution of carbon in it?

2)Am I wrong to assume that the overall content of carbon will also be, on average, higher than the average period piece?

3)Would modern steel used for reinforcing structures, like rebar, or plate steel be a better quality steel than that found in period pieces even though these types of steel are only required to meet "performance" standards and not "Materials" standards? The reason I ask this is that I have access to large quantities of this material for free and don't see any reason I need to spend alot of money on material at this stage of my new hobby.

To close, here is the link to the article from which I quoted; http://oakeshott.com/metal.html

Thanks in advance for any advice or other input/ sources which can be given.


As a matter of designation/ specification tolerances on sheet steel grades, most modern sheet steels as you would pick up in a hardware store with an AISI or ASTM marking are more consistent than historical material (modern carbon content varying by less than 0.1 % .) A lot of the mild steel sheet material may only be 0.18% carbon to 0.4% carbon depending on what you are looking at, and may be lower strength than the average composition of historical pieces you referenced on the Oakshotte site articles. You need to examine the specific grade of sheet you are considering for purchase. It is possible that you may need to special order something with a more accurate carbon content of 0.4% (1040 series carbon steel sheet, my opinionated approximation of a high quality historical armour piece that may have been carburized with various heats in conjunction with organic material.)

There are a lot of other variables involved too. Differential thickness and cold working varied according to areas of most harsh stress and impact, and even suggestions of differential quench/ hardness treatments of the pieces was discussed in the Oakshotte articles on historical metallurgy. The carbon content alone does not tell the whole story.

Absence of evidence is not necessarily evidence of absence!
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Sean Manning




Location: Austria
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PostPosted: Sun 10 Aug, 2008 12:53 pm    Post subject:         Reply with quote

A book by Alan Williams, The Knight and the Blast Furnace (Brill Academic Publishers: Leiden, 2003)is the definitive place to go for things like this. Its a coffee-table sized book worth about US$250 new, though, so I hope you have access to a good library system! He doesn't cover ancient armour, though, just medieval.
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Toney Lauffer




Location: Virginia
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PostPosted: Sun 10 Aug, 2008 2:06 pm    Post subject:         Reply with quote

Sean Manning wrote:
A book by Alan Williams, The Knight and the Blast Furnace (Brill Academic Publishers: Leiden, 2003)is the definitive place to go for things like this. Its a coffee-table sized book worth about US$250 new, though, so I hope you have access to a good library system! He doesn't cover ancient armour, though, just medieval.


Thanks for the book idea Sean. Actually Medieval would cover it for me. I consider anything over 300 years old ancient anyway. Some things are just ancienter Happy
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Toney Lauffer




Location: Virginia
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PostPosted: Sun 10 Aug, 2008 2:12 pm    Post subject:         Reply with quote

WHOOAAAA MY God! I just looked up "The Knight and the Blast Furnace" on Amazon, kinda hoping it would be a LIttle cheaper, but WTF?! It's 370.00 Eek! Eek! and it's out of stock. Unfortunatly my local library didn't even have titles like "The New edge of the Anvil" or the "Complete Modern Blacksmith". So, I ordered those books and they came in. I'm still waiting on the "Techniques of Medieval Armour Reproduction".
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Dan Howard




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PostPosted: Sun 10 Aug, 2008 5:53 pm    Post subject:         Reply with quote

Dr Williams' book is the definitive work. If you can't get a copy then there is not much point persuing this subject.
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Chris Fields




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PostPosted: Sun 10 Aug, 2008 9:47 pm    Post subject:         Reply with quote

Just an FYI, if you plan on carburizing the pieces, it may not matter what the initial carbon content is, as long as you know what specific steel you have. If you take it to a heat treating facility, and tell them what Rc level you want, along with the grade of steel, they'll know exactly how much carbon to force into the surfaces of the steel and adjust their furnaces to have the right atmosphere to allow for the carbon migration happen. You can carburize almost any steel, and by doing so you change the carbon content on the surface layers, so initial carbon content may not matter. IE.. if you start with 1020, and carburize it to RC50, it's outer surfaces may end up as 1070 up to .030" deep. (You can also specify how deep of a carburization you want.)

So, long story short, yes, you can use the steel you have lying around.
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Toney Lauffer




Location: Virginia
Joined: 09 Aug 2008

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PostPosted: Mon 11 Aug, 2008 3:14 am    Post subject:         Reply with quote

Dan Howard wrote:
Dr Williams' book is the definitive work. If you can't get a copy then there is not much point persuing this subject.


Forgive me Dan, I may be misunderstanding this response, but, are you saying that if one cannot afford to purchase this book, or does not live close to a library which has a copy, that such a person should remain forever in ignorance regarding this subject?

Since my pursuit of this subject in this forum thus far really only consists of the asking of three relatively simple questions, which have been answered by some very helpful persons to my satisfaction, I consider my pursuit of this subject, to this point, successfully completed. I will of course check back periodically to see if any other helpful information is provided by other Forumites.

Thank you for your help and input,
Toney
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Toney Lauffer




Location: Virginia
Joined: 09 Aug 2008

Posts: 16

PostPosted: Mon 11 Aug, 2008 3:15 am    Post subject:         Reply with quote

Chris Fields wrote:
Just an FYI, if you plan on carburizing the pieces, it may not matter what the initial carbon content is, as long as you know what specific steel you have. If you take it to a heat treating facility, and tell them what Rc level you want, along with the grade of steel, they'll know exactly how much carbon to force into the surfaces of the steel and adjust their furnaces to have the right atmosphere to allow for the carbon migration happen. You can carburize almost any steel, and by doing so you change the carbon content on the surface layers, so initial carbon content may not matter. IE.. if you start with 1020, and carburize it to RC50, it's outer surfaces may end up as 1070 up to .030" deep. (You can also specify how deep of a carburization you want.)

So, long story short, yes, you can use the steel you have lying around.


Thanks Chris, this if very good to know.
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Lafayette C Curtis




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PostPosted: Mon 11 Aug, 2008 7:19 am    Post subject:         Reply with quote

This might be worth checking:

http://www.the-orb.net/encyclop/culture/scitech/iron_steel.html
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Craig Johnson
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PostPosted: Mon 11 Aug, 2008 9:23 am    Post subject: Iron and Steel the early years         Reply with quote

Hi Toney

I am glad my article was helpful and generated your excellent questions. I will try to add a bit to the good info people have contributed already.


Quote:
My questions and assumptions then are these;
1)If the carbon content of period armours was inconsistent, then am I wrong in assuming that any sheet of steel I get from a source like Lowes or Home Depot will have a better and more consistent distribution of carbon in it?


In most cases any modern production steel will have a consistent carbon content that is much closer in tolerance than period steels would be. The chief thing to remember is that the majority of steel in period would vary throughout the piece. To say that medieval steel had an average carbon content even in a single piece would be difficult to compare to modern steels as the range of carbon in that medieval piece would be far greater and have much more effect on how hard the heat treatment could make it than most of the other factors in any given situation.

Quote:
2)Am I wrong to assume that the overall content of carbon will also be, on average, higher than the average period piece?


I would not say higher, but more consistent as was mentioned in other posts. The content in many cases may range higher than what we would want in a piece today that was being constructed for durability. The crucial aspects of medieval metal working is that is was done experientially. They did not have the concept of seconds or degrees. It was done by eye and passed on knowledge and the ability to know what should happen if such and such was done. There are many today that can testify to the difficulty of getting a good heat treat with the help of all our scientific knowledge. Back then it was a different challenge as they were working in the realm of repeated procedures developed over long life times of work.

Quote:
3)Would modern steel used for reinforcing structures, like rebar, or plate steel be a better quality steel than that found in period pieces even though these types of steel are only required to meet "performance" standards and not "Materials" standards? The reason I ask this is that I have access to large quantities of this material for free and don't see any reason I need to spend alot of money on material at this stage of my new hobby.


The consistency of almost all modern steels will far surpass that of period examples. Using the right type of material for the piece you want is, as it was then, the first choice a smith must make and a very important one. The production of weapons and armor in period show us a great range of material choices being made and if anything one of the mistakes made today in replicating the items of the past is the desire to maximize some attribute in a piece as opposed to finding the balance in material and intended use that seems to have been a very conscious choice by the period makers.

Hope that helps.

Best
Craig
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Toney Lauffer




Location: Virginia
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PostPosted: Mon 11 Aug, 2008 2:06 pm    Post subject:         Reply with quote

Thanks Craig and Lafayette. This additional info is most helpful. One day I'm sure I will purchase the book "The Knight and the Blast Furnace", I just can't do it for now. Unfortunatly for me it is also most unlikely that any library near me will have a copy as the one nearest me only had one volume on Blacksmithing period. Oh well Sad
Thanks again to all,
Toney
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Dan Howard




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PostPosted: Mon 11 Aug, 2008 3:22 pm    Post subject:         Reply with quote

A few points relating to the original questions.

Today any steel you buy at Home Depot will have been recycled many many times from virtually any source of steel scrap. The quality varies considerably. Some batches are excellent for making armour and swords, others are useless.

Carbon content is not the only property to consider. Bloomery iron is far far different mechanically to modern mild steel. I'm not saying whether it is better or worse, just different (Williams discusses it in detail). It is very difficult to find a source of modern steel that mechanically resembles the material used to make historical amrour. The closest modern approximation would be charcoal-rolled iron.

The carbon content of the best examples of plate armour from Augsberg, Innsbruck, Milan, etc easily equal anything that modern armourers can make today with regular high carbon steel. You'd need to source a very specific steel and quench harden it using the most modern of technologies to better them.

What is your intent by asking these questions? If you are trying to make a replica that closely resembles historical plate then you need to approximate bloomery iron - such as charcoal rolled iron. Home Depot won't cut it. If you just want to make a suit that offers practical protection for modern combat simulation then mild steel is fine.
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Thomas Watt




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PostPosted: Tue 12 Aug, 2008 5:10 am    Post subject:         Reply with quote

Toney Lauffer wrote:
Thanks Craig and Lafayette. This additional info is most helpful. One day I'm sure I will purchase the book "The Knight and the Blast Furnace", I just can't do it for now. Unfortunatly for me it is also most unlikely that any library near me will have a copy as the one nearest me only had one volume on Blacksmithing period. Oh well Sad
Thanks again to all,
Toney

Sounds like a topic to bring up with your reference librarian (preferably at your college or university)...
inter-library loan or other possible outlets are both possible (including electronic transmission of relevant sections in the case of oversized or rare/fragile texts).
Having done a couple of semesters' stints as a library flunky, I can promise you that the reference librarian is probably dieing to show how capable they can be, as they are usually bored out of their skulls.

Have 11 swords, 2 dirks, half a dozen tomahawks and 2 Jeeps - seem to be a magnet for more of all.
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Craig Johnson
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PostPosted: Tue 12 Aug, 2008 7:50 am    Post subject: KatBF and Armor making         Reply with quote

Hi Toney

The book should be able to find its way to your local Library as Thomas has indicated. I would follow his advise and persue this line. It would be very difficult to convey the wealth of information that it contains on this subject via posts.

Dan is correct in his comments on the best armor of the period being very well made from the best materials they had to hand. It is also crucial to remember that most armor was not made by these makers. This would be the very high end of the market. There where other production centers as well that turned out high end product but in many of these same locations large amounts of medium and low grade armor would be produced. The quality of material and skill of manufacture would have varied to what the customer was willing to pay. The structure of the armor industry at that time was geared to this simple economic structure.

There are examples from this period where armor is made from wrought iron to very well made steel. (This steel would still have a wider range of carbon content than modern made material) The choice to heat treat was not always made or always successful when the attempt was made. There are many interesting examples of what was achieved and choices made by armorers throughout the period and it is an area of study that Dr. Williams has really pioneered. With out him there would still be many great misperceptions about weapons and armor.

The article I wrote was finished before KatBF was published and could use a revamp in light of this important work. I hope to work on that in the future Happy Dr. Williams was gracious enough to critique my article before I published it and has always been very supportive of our efforts at the Oakeshott Inst. and furthering the dissemination of this important information.

Best
Craig
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Chad Arnow
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PostPosted: Tue 12 Aug, 2008 9:49 am    Post subject:         Reply with quote

Alan William wrote an article on the metallurgy of 4 14th century helms in the June, 1981 issue of the Journal of the Arms & Armour Society. It's interesting reading. It won't be anywhere as in-depth as the Knight and the Blast Furnace, but it's much cheaper. Happy
Happy

ChadA

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