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Post by razorseal on Nov 17, 2018 3:00:28 GMT
Hey guys,
I've been watching some youtube videos on the Ulfberht sword and how it was so ahead of it's time using crucible steel. I'm curious how this compares to our steel that is now used in modern swords (1075 1566 high carbon, and tool steel).
If I remember correctly, the last two in the 1075 is the carbon content (.75 carbon content)
If someone could shed some basic light, I'd appreciate it.
THanks!
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Post by Timo Nieminen on Nov 17, 2018 3:47:51 GMT
Most traditional crucible steels were ultra-high carbon steels, with carbon contents between 1% and 2%. About 1.5% was common. So it's a quite different steel from 1075 etc. For comparable modern steels, look at modern UHC steels. Roselli uses such steels for a range of knives: www.roselli.fi/UHC-knives and gets about 65HRC. However, getting the heat treatment done right isn't an easy thing, and could be very difficult with pre-modern technology. So a very common traditional heat treatment for crucible steel was to air-cool it (and not quench and temper). This would leave the steel quite soft (somewhere around 30HRC) and tough. The sword would have reasonable good edge retention, however, since at these carbon contents, the steel ends up full of carbides (which, if the forging has been done right (i.e., not too hot), will be in tiny grains) which are very hard, and provide good wear resistance. Quenched and tempered crucible steel swords can be brittle, which might be why more than one of the crucible steel Ulfberhts were found broken. Traditional crucible steels were better than bloomery steels in that they were lower in slag, and could be more homogeneous. Also easier to make very high in carbon. Not necessarily any better than steel made by decarburising cast iron.
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Post by razorseal on Nov 17, 2018 13:43:44 GMT
Thanks for that. That is pretty high in carbon content (and not ideal in today's standards I think?) so mono tempered 1075 steel (or something similar) is probably going to hold up better vs a crucible steel from few to several centuries ago...
I wonder what kind of luck they would have had if they discovered high carbon steel back in the day. (not sure when that got introduced)
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Post by bluetrain on Nov 17, 2018 14:06:29 GMT
I think early metalworkers didn't know that much about content in the metal, although they knew more than that statement might suggest. But what they did know was that some combinations and techniques worked well or at least better than others, so they stuck with it. They learned their trades by the apprentice method of working with a master or journeyman for a long time. I expect different techniques were developed in different places. They all worked more or less well but differently. Besides, not everyone wanted the same characteristics or qualities. I'm referring to things a very long time ago.
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Post by Timo Nieminen on Nov 18, 2018 0:20:18 GMT
I wonder what kind of luck they would have had if they discovered high carbon steel back in the day. (not sure when that got introduced) They did discover high carbon steel back in the day. Not that they understood it as high carbon steel, but they made it and used it. For example, lots of pattern-welded swords have high carbon steel edges, quench-hardened. High carbon steel edges are normal for swords in China, from the Han Dynasty onwards, and are common in Europe from early Medieval onwards. High carbon steel edges on a laminated or pattern-welded sword were common. This type of construction makes pre-modern heat treatment more reliable.
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Post by AndiTheBarvarian on Nov 18, 2018 0:45:18 GMT
The way of making iron and steel out of ore since the 14th cent. BC in bloomeries produces pieces of iron and steel with different carbon content. There always was some high carbon steel. The problem was to produce more of it.
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Post by bluetrain on Nov 18, 2018 12:11:30 GMT
I'd say the problem was quality control. They knew what they wanted but they may not have been able to control the production well enough to produce consistent results. Of course, quality control seems to still be a problem for any product.
An interesting exercise would be to dig the ore, melt it to produce pig iron and from there, make a usable object: in this case, some kind of blade. That's still the basic process. The only difference between what is done now and what was done five hundred years ago is the scale of production and refinements in the basic output. Primitive ironworking is still done in a few places where they make their own spearheads. But large scale (relatively speaking) production of iron was already around 250 years ago in this country.
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Post by Timo Nieminen on Nov 18, 2018 20:23:04 GMT
Modern heat treatment makes an enormous difference. This is helped by consistency of the steel - by being able to buy steel that's made to spec, so that you know how to heat treat it. Or, at least being able to measure the composition of steel (with your handy mass spectrometer, which at least medium/large foundries will have (or should have)).
With low alloy steels, the main thing is the carbon content, and the primitive smith can judge to a reasonable degree. For example, the number of times the steel is folded for the edge of a katana is determined by the carbon content - a good smith would stop folding when it hit about 0.7% (it drops during the folding).
The primitive smith can quench successfully enough. Primitive tempering, OTOH, is much more hit-and-miss. Thus, techniques such as lamination, pattern-welding, differential quenching (at least 3 different methods for that out there - Japanese-style clay coating, multiple methods for edge-only quenching), etc. which all reduce or eliminate the need for tempering after quenching.
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Post by bluetrain on Nov 18, 2018 21:59:19 GMT
All of this would have meant that testing of the final product would have been more important. In fact, I think that cutting tests were made on finished Japanese swords, were they not? In the West, there came to be proofing of swords. I don't when that practice began although the sorts of tests applied do not seem to have been that extensive. Some firearms are still proofed and so marked.
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