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Stephen Jones
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 Posted: Thu 16 Apr, 2015 10:53 am Post subject: European Shift To Homogeneous Steel Date? |
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When did Europeans shift from pattern welded sword blades to predominantly homogeneous steel blades? Who made the first homogeneous steel blades in Europe?
I'm not sure I have my terms right. If not thanks for your patience.
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Jared Smith
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| Posted: Thu 16 Apr, 2015 6:46 pm Post subject: |
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I would have to do a lot of checking to give you a great answer. Some concepts to consider though.
Large billets of material, enough so as to make a whole blade, were exported by around the 11th century. There are variations by region, but we can say prior economic and material availability conditions that could have favored piled construction really changed.
Some authors, I believe Verhoeven included, have mentioned frequency or percentage of swords from various eras that appeared "pattern welded" by which I mean to have deliberate mechanical manipulation of the piled construction so as to contain elaborate geometric designs if contrasting materials were used. Just swagging it ... I the peak of this was around 7th to 10th century. There was still historic demand and replication or reinvention of the attractive geometry "pattern welded" blade long after, including amongst current day collectors. It is fairly difficult to say it "ended" other than to say it appears it was both unnecessary and progressively less common as steel production method and export industry increased.
Absence of evidence is not necessarily evidence of absence!
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Bartek Strojek
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| Posted: Fri 17 Apr, 2015 11:24 am Post subject: |
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It's worth considering that 'homogeneous' steel weren't all that common up to the 16th century, though mostly in smaller workshops.
Just items out of rather homogeneous iron 'steeled', so roasted in coal powder until outer layers would get to desirable levels of carbonization, and then properly tempered and generally treated to achieve desired characteristics.
So while it obviously wouldn't be any pattern welding, it wouldn't be homogeneous steel either.
Bigger manufactures, particularly huge industries in Northen Italy or in modern Austria would already have a lot of billets that would be mostly steel, of course.
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Dan Howard
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| Posted: Fri 17 Apr, 2015 3:01 pm Post subject: |
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Most people define homogenous steel as "not pattern welded", but Bartek's defintion is more accurate. You would probably have to clarify what you mean to get a useful answer.
Author: Bronze Age Military Equipment, Pen and Sword Books
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Stephen Jones
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| Posted: Fri 17 Apr, 2015 4:31 pm Post subject: |
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I'm using the only definition I know, the one used in physics and chemistry. A homogeneous material or system has the same properties at every point; it is uniform.
I realize few materials have the same properties at every point. I mean reasonably homogeneous. I also understand that a reasonably homogeneous steel can have a differential crystalline structure due to the tempering.
I guess my question might have better phrased. How about: When did pattern welding stop being used as the predominate method of sword making in Europe?
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Glen A Cleeton
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| Posted: Fri 17 Apr, 2015 4:52 pm Post subject: |
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In Europe, blister steel (heterogeneous) was further refined to shear steel, with the English then refining some steel further in crucibles by the mid 18th century. The blister to shear steels continued well into the 19th century, even past Bessemer's "innovations". My understanding of it anyway. There is an article somewhere regarding some furnace slag was decarbed going back to the medieval centuries and furnaces in Scandinavia.
Cheers
GC
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Scott Roush
Industry Professional
Location: Washburn, WI Joined: 27 Jan 2011
Posts: 452
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| Posted: Sat 18 Apr, 2015 3:57 am Post subject: |
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Pattern welding is the deliberate combination of at least two different materials that show contrast when etched in acid. Heterogenous. As people have alluded to... due to the available technology many swords were composed of multiple layers of the SAME material just to get a large enough billet to make a sword. So in this sense.. it could be seen as 'homogenous' to some extent. Sword blades were made like this since the beginning of the iron age and all through the middle ages.
The only truly homogenous steel would originate in a molten form.. and the first examples of this were made in crucibles. So the shift to using crucible steel in England might be your best line of research. I'm assuming you mean a European scenario and don't need to consider Persian crucible-made steel, wootz, etc.
http://www.bigrockforge.com
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Pieter B.
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| Posted: Sat 18 Apr, 2015 11:12 am Post subject: |
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| Stephen Jones wrote: | I'm using the only definition I know, the one used in physics and chemistry. A homogeneous material or system has the same properties at every point; it is uniform.
I realize few materials have the same properties at every point. I mean reasonably homogeneous. I also understand that a reasonably homogeneous steel can have a differential crystalline structure due to the tempering.
I guess my question might have better phrased. How about: When did pattern welding stop being used as the predominate method of sword making in Europe? |
A commonly cited time is the end of the viking era or the beginning of the first crusade, this would place it somewhere in the 11th century. However I don't believe any kind of research was done in this area.
The homogeneous and heterogeneous terms being thrown around could be read as two different things. Homogeneous iron can be read as chemically pure as in only containing Fe(iron) atoms and steel would be iron atoms with carbon in it. However this kind of purity is something we only really see after the industrial revolution. Bloomery iron/steel is direct reduced metal and contains many trace elements and has slag inclusions, folding it a few times can spread these trace elements and slag inclusions out a little but one end of the steel billet might still differ from the other end in chemical makeup. The same goes for the carbon content which could be 0.7% at one place and 0.5% a few inches further. This is all due to the way iron and steel was produced back in the day, in essence no piece of metal before the industrial revolution was chemically pure and therefore even blades which appear to be made out of one type of steel are heterogeneous in chemical makeup. Effort was made to make it as homogeneous as possible so that the carbon content across the whole billet was more or less equal and that slag was spread out across it too to make sure it wouldn't cause a catastrophic failure.
The crystalline structures within carbon steel which are most important are Ferrite, Pearlite, Cementite Austenite and Martensite. When you heat carbon steel above a certain temperature (730 Celsius) Austenite will start to form/exist (the longer you keep it at that temperature the more will form). When you drop below this temperature it will transform into other Crystalline structures which each have their own properties. If cooled rapidly (few hundred degrees per second) the Austenite will (for a part) transform into martensite which makes the steel hard and brittle, this transformation is usually achieved by quenching a hot piece of steel in a liquid. If hot metal is cooled slowly Pearlite will form which is a Crystalline structure made up out of Ferrite(pure Iron I believe) and cementite, the degree of pearlite formation is influenced by how fast the piece of steel is cooled. Letting it cool down in a hot oven will cool it really slow while letting it cool in air is somewhat faster.
If you heat a piece of quenched carbon steel (containing Martensite) below the temperature at which Austenite will form and then let it air cool you will get tempered martensite which is what you generally want for a blade.
As you see the eventual formation of tempered martensite is influenced by the tempering temperature and time, the initial amount of martensite which in term is influenced by the cooling time and initial amount of Austenite which in term is influenced by heating duration and a myriad of other factors. Besides the large variation possible in this process there is also the chemical makeup of the steel we just talked about above. But I see I really drifted off from the initial topic of heterogeneous en homogeneous construction of swords which is what you are talking about 
PS, I have no background in Chemistry whatsoever so this is all just information from books, articles etc. If anyone more qualified (and that would be everyone) noticed a mistake please correct me.
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Stephen Jones
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| Posted: Sat 18 Apr, 2015 12:28 pm Post subject: |
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Thanks for all of your well thought out answers.
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Mart Shearer
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| Posted: Sat 18 Apr, 2015 12:39 pm Post subject: |
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Certainly better answers than the facetious, "14:00 on 12 November 1193".
ferrum ferro acuitur et homo exacuit faciem amici sui
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James Arlen Gillaspie
Industry Professional
Location: upstate NY Joined: 10 Nov 2005
Posts: 587
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| Posted: Thu 23 Apr, 2015 8:13 pm Post subject: |
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Plate armour often shows differing layers, welded together to get steel that has the desired characteristics, essentially adjusting the average carbon content by layering. Swords seem to be the same till industrial processes make homogeneous steels possible. Not that they really are; a piece of 1050 can vary from 0.45% to 0.55% carbon, last I knew.
jamesarlen.com
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This is a standard topic