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Kristjan Runarsson





Joined: 07 Nov 2015

Posts: 105

PostPosted: Sun 10 Sep, 2017 8:45 pm    Post subject: Modern equivalent steels for medieval armour plate         Reply with quote

Hi,
I want to build my own coat of plates and I was wondering what the modern equivalent of 13th, 14th and 15th century plate steels would have been.

The only stuff I can easily get in terms of carbon steel is 1, 1,5 and 2 mm mild (aka. low carbon) steel (EN 10130 cold rolled plate).

I experimented with this stuff by heating it red hot so that it lost its magnetic properties. When I quenched it, it does become tougher (due to the low carbon content) but EN 10130 does not by any means become so brittle that it shatters when you drop it like C75 would do (or so I'm told). Is 1,5 mm EN 10130 a good match for the stuff the Visby coats for example might have been made of? ... or did they already have something equivalent to EN C35-C75 high carbon steel plate by the late 13th and 14th centuries?

What grade of steel (modern equivalent) would reasonable quality 15th century armour have been made of? I.e. something:

(a) an average knight
(b) a well equipped foot soldier

... might have worn. Presumably the Knight would have worn high carbon armour but would the foot soldier have had a breastplate, helmet and other plate items of lower carbon steel?

I kind of suspect judging by what I have read about armour evolution that from the time they started making armour containing large plates in the mid 13th century and up to the mid 14th century, plate armour would have been made from something somewhat similar to EN1030. However by the late 14th and 15th centuries they would have had stuff much closer to EN C35-C75 and way more people (as in foot soldiers too) would have been wearing higher carbon steel plate by, say, the Burgundian wars than would have worn high carbon steel armour during, say the latter half of the 14th centrury when it would have been mostly worn by knights. But I'd like to hear an expert opinion.

Hardness conversion chart:
http://www.carbidedepot.com/formulas-hardness.htm

Steel type equivalencies:
http://www.mesteel.com/qualities/equivalentscs.htm


Last edited by Kristjan Runarsson on Mon 11 Sep, 2017 7:35 am; edited 2 times in total
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Philip Dyer





Joined: 25 Jul 2013

Posts: 475

PostPosted: Sun 10 Sep, 2017 9:12 pm    Post subject: Re: Modern equivalent steels for medieval armour plate         Reply with quote

Kristjan Runarsson wrote:
Hi,
I want to build my own coat of plates and I was wondering what the modern equivalent of 13th, 14th and 15th century plate steels would have been.

The only stuff I can easily get in terms of carbon steel is 1, 1,5 and 2 mm mild (aka. low carbon) steel (EN 10130 cold rolled plate).

I experimented with this stuff by heating it red hot so that it lost its magnetic properties. When I quenched it, it does become tougher (due to the low carbon content) but EN 10130 does not by any means become so brittle that it shatters when you drop it like C75 would do (or so I'm told). Is 1,5 mm EN 10130 a good match for the stuff the Visby coats for example might have been made of? ... or did they already have something equivalent to EN C35-C75 high carbon steel plate by the late 13th and 14th centuries?

What grade of steel (modern equivalent) would reasonable quality 15th century armour have been made of? I.e. something:

(a) an average knight
(b) a well equipped foot soldier

... might have worn. Presumably the Knight would have worn high carbon armour but would the foot soldier have had a breastplate, helmet and other plate items of lower carbon steel?

I kind of suspect judging by what I have read about armour evolution that from the time they started making armour containing large plates in the mid 13th century and up to the mid 14th century, plate armour would have been made from something somewhat similar to EN1030. However by the late 14th and 15th centuries they would have had stuff much closer to EN C35-C75 and way more people (as in foot soldiers too) would have been wearing higher carbon steel plate by, say, the Burgundian wars than would have worn high carbon steel armour during, say the latter half of the 14th centrury when it would have been mostly worn by knights. But I'd like to hear an expert opinion.
Honestly, I'm no metallurgist but I wouldn't be surprised if the visby pieces were made of iron, people often forget that the people massacred at Visby were very poor peasants wearing armor considered crude and dated by period standards.
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Kristjan Runarsson





Joined: 07 Nov 2015

Posts: 105

PostPosted: Mon 11 Sep, 2017 7:30 am    Post subject: Re: Modern equivalent steels for medieval armour plate         Reply with quote

Philip Dyer wrote:
Honestly, I'm no metallurgist but I wouldn't be surprised if the visby pieces were made of iron, people often forget that the people massacred at Visby were very poor peasants wearing armor considered crude and dated by period standards.


I might be mistaken here, but as peasants went during the Middle Ages, Gotlandic peasants were pretty well off since Gotland was generally a very rich place. As regards the material of the armours I thought the same thing you did but then I took a look at some of the ones with large highly curved plates and started wondering. Take this one for example:



If the original had been made of iron I would have expected these plates to be crumpled up after being buried in the ground with all that earth on top of the (Unless they were bent back into shape by a restorer which given the level of corrosion seems unlikely). I get told a lot that heat treating mild steel will do nothing which is not quite true, there is a noticeable reduction in the softness of the material and it bends less easily but it still bends and I would expect even plates like that to be constantly bending out of shape, but I suppose I'll be finding out soon enough since I'm going to use mild steel for my Visby armour. Maybe if I make the thing out of 2mm plates and harden them they'll be stiff enough that I won't have to bend the plates back into shape every time I take the brigantine off.

P.S. Why is it off topic to discuss what material Medieval arms and armour were made of for the purpose of creating accurate reproductions?
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Kristjan Runarsson





Joined: 07 Nov 2015

Posts: 105

PostPosted: Tue 12 Sep, 2017 3:29 am    Post subject:         Reply with quote

Well, to answer my own question in case it will help anybody in the future I found this thread with data that suggests that before the 15th century hardening or heat treatment was pretty un-common:

http://myArmoury.com/talk/viewtopic.20681.html

Mind you that is too small a small data set to draw sweeping conclusions from but the existence of what are basically air cooled Iron helmets in the 14th century indicates that most re-enactment gear today is of vastly better quality than the 'munitions grade' helmets/breastplates/limb armour of most of the Middle Ages as well as some of the higher grade Medieval stuff and this may have remained the case up to a point into the Renaissance.

Nota Bene, I'm no steel expert and I might be wrong about details so take the below with a certain amount of salt.

As for the steels it should be kept in mind that modern steels are much purer than medieval ones, specially pre-15th century steels, since it was only in the 15th century that large scale production of relatively pure steel started to take off in Europe. Early Medieval steel in particular was full of slag and other impurities which means that modern EN 10025 is probably significantly stronger than Medieval 0,2% carbon steel would have been due to it begin full of slag inclusions. Thus the below mappings are very approximate at best. You wont get a 0.2% carbon steel breast plate for your longbow armour penetration that is a real analogue for what would have been in use at Crecy in 1346 unless you make the steel from ore in a bloomery furnace and then work it and pound it into shape and harden it according to Medieval methods, slag inclusions and all. Furthermore don't forget to make your bodkins of at least 0.2% C steel and harden them, that's one thing (of many) that most of these longbow vs. armour tests get wrong.

  • EN 10130 is a low carbon steel with no more than 0.05% carbon in it so, it's basically iron as far as I can tell. This is an analog for the low carbon armour that you would find on the heads and chests of most Viking age warriors in the form of helmets and (possibly) lamellar armour as well as in poor 'munitions grade' breastplates and limb armour into the 14-15th century. Helmets made of, say 1-1,5 mm plates, which were in turn made of a slag a ridden version of this stuff would explain accounts in the Sagas of people occasionally stabbing spears, slashing swords, and shooting arrows through other peoples helmets. It also puts illustrations in medieval manuscripts of axes shearing through helmets in a new light, not to mention that story of William Marshall getting brained over the head so often his head got stuck in his helmet.

  • EN 10025 is a higher carbon mild steel with a carbon content of 0.18-0,24% carbon depending on the grade. This corresponds to the stuff used for better quality armour (starting in the 12th-13th centuries?) and it could be hardened up to a certain degree although that was apparently not done very often (statement subject to revision due to limited data set).

  • EN C35-C75 Are high carbon non alloy steels. The number after the C gives the median carbon content with C35, for example, meaning that the steel contains 0.35% carbon on average. The C50 to C75 steels in this range correspond to the really high quality properly heat treated Milanese and Augsburg armour you start to see in the late 14th and in the 15th centuries (statement subject to revision due to limited data set).
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Philip Dyer





Joined: 25 Jul 2013

Posts: 475

PostPosted: Tue 12 Sep, 2017 12:18 pm    Post subject:         Reply with quote

Kristjan Runarsson wrote:
Well, to answer my own question in case it will help anybody in the future I found this thread with data that suggests that before the 15th century hardening or heat treatment was pretty un-common:

http://myArmoury.com/talk/viewtopic.20681.html

Mind you that is too small a small data set to draw sweeping conclusions from but the existence of what are basically air cooled Iron helmets in the 14th century indicates that most re-enactment gear today is of vastly better quality than the 'munitions grade' helmets/breastplates/limb armour of most of the Middle Ages as well as some of the higher grade Medieval stuff and this may have remained the case up to a point into the Renaissance.

Nota Bene, I'm no steel expert and I might be wrong about details so take the below with a certain amount of salt.

As for the steels it should be kept in mind that modern steels are much purer than medieval ones, specially pre-15th century steels, since it was only in the 15th century that large scale production of relatively pure steel started to take off in Europe. Early Medieval steel in particular was full of slag and other impurities which means that modern EN 10025 is probably significantly stronger than Medieval 0,2% carbon steel would have been due to it begin full of slag inclusions. Thus the below mappings are very approximate at best. You wont get a 0.2% carbon steel breast plate for your longbow armour penetration that is a real analogue for what would have been in use at Crecy in 1346 unless you make the steel from ore in a bloomery furnace and then work it and pound it into shape and harden it according to Medieval methods, slag inclusions and all. Furthermore don't forget to make your bodkins of at least 0.2% C steel and harden them, that's one thing (of many) that most of these longbow vs. armour tests get wrong.

  • EN 10130 is a low carbon steel with no more than 0.05% carbon in it so, it's basically iron as far as I can tell. This is an analog for the low carbon armour that you would find on the heads and chests of most Viking age warriors in the form of helmets and (possibly) lamellar armour as well as in poor 'munitions grade' breastplates and limb armour into the 14-15th century. Helmets made of, say 1-1,5 mm plates, which were in turn made of a slag a ridden version of this stuff would explain accounts in the Sagas of people occasionally stabbing spears, slashing swords, and shooting arrows through other peoples helmets. It also puts illustrations in medieval manuscripts of axes shearing through helmets in a new light, not to mention that story of William Marshall getting brained over the head so often his head got stuck in his helmet.

  • EN 10025 is a higher carbon mild steel with a carbon content of 0.18-0,24% carbon depending on the grade. This corresponds to the stuff used for better quality armour (starting in the 12th-13th centuries?) and it could be hardened up to a certain degree although that was apparently not done very often (statement subject to revision due to limited data set).

  • EN C35-C75 Are high carbon non alloy steels. The number after the C gives the median carbon content with C35, for example, meaning that the steel contains 0.35% carbon on average. The C50 to C75 steels in this range correspond to the really high quality properly heat treated Milanese and Augsburg armour you start to see in the late 14th and in the 15th centuries (statement subject to revision due to limited data set).

It doesn't shed any new light. Allot of helmets were with space between the helmet and the skull, you wouldn't be able to shear through a crappy with a sword or a axe. People have tested this with swords and axes made of much better steel and helmets allot thinner than originals and the best you can do is clobbering the hell out of someone with a sword or axe through their helmet. https://www.youtube.com/watch?v=Z1KJAeJj3Pc https://www.youtube.com/watch?v=VOSmJbzUgCA Armorsmiths knew they had crap in their and worked hard to compensate for that.
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Timo Nieminen




Location: Brisbane, Australia
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PostPosted: Tue 12 Sep, 2017 4:10 pm    Post subject: Re: Modern equivalent steels for medieval armour plate         Reply with quote

Kristjan Runarsson wrote:
and it bends less easily but it still bends and I would expect even plates like that to be constantly bending out of shape, but I suppose I'll be finding out soon enough since I'm going to use mild steel for my Visby armour. Maybe if I make the thing out of 2mm plates and harden them they'll be stiff enough that I won't have to bend the plates back into shape every time I take the brigantine off.


What are you planning to use the armour for? Unhardened 2mm mild steel should be more than thick enough. When I was fighting in the SCA with 1.6mm mild steel armour, only once was there any damage to the armour (a bent-in fan on a knee cop). 1.5mm should be sufficient for that kind of thing (maybe HMB/BotN is harder on armour and you want to be a little thicker), for a Visby-style coat of plates. But if you want 2mm thick, to have arrow-proof armour, that'll work too.

Plates for brigandine can be thinner. 1.2mm dents/bends rather more easily, but note that HMB/BothN people will use that kind of thickness for brigandine. Original brigandines could be thinner than that - arrows/spears will need to get through multiple thicknesses, and 1mm brigandine will work well.

"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
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Mike O'Hara




Location: New Zealand
Joined: 10 Jul 2010
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Posts: 106

PostPosted: Wed 13 Sep, 2017 3:17 pm    Post subject: Mild steel for coat of plates         Reply with quote

Hi Kristjan

I've made several coats of plates on the Wisby design from 1.6mm mild and they serve very well as protective armour, just as Timo says.

What actually matters are the curves you put on the plates. Even the relatively large plates are much stiffer once you have hammered them to shape. Perhaps a litlle of this is work hardening but most is just the shape itself. You can back-curve the edges to make them stiffer again and I also have found this helps the plates 'move' over one another in the armour.

Once you rivet the plates to leather with the proper overlap and fit, the whole armour re-inforces itself and becomes much stiffer. It is not plate armour but is resistant to blows and damage. We tested it by hitting me with a blunt pollaxe. Definitely felt it but the plates didn't deform.

I made one set of 2mm plates and found it heavier than I really wanted and didn't give me than much extra protection.

cheers
mike

MIke O'Hara
Location: Plimmerton, New Zealand
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Mark Moore




Location: East backwoods-assed Texas
Joined: 01 Oct 2003
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PostPosted: Wed 13 Sep, 2017 3:49 pm    Post subject:         Reply with quote

Weird as this may sound, you can pick up used steel road signs from your local DoT equipment yard. They are at least 12ga....maybe even thicker. And...if you play your cards right, they're FREE. A large one ought to be enough for a CoP. Happy ....McM
''Life is like a box of chocolates...'' --- F. Gump
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M. Eversberg II




Location: California, Maryland, USA
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PostPosted: Fri 15 Sep, 2017 11:57 am    Post subject:         Reply with quote

They are aluminum, however.

M.

This space for rent or lease.
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