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Kenneth Armstrong




Location: Alexandria, VA (for the moment)
Joined: 24 Aug 2006

Posts: 13

PostPosted: Tue 19 Sep, 2006 1:11 pm    Post subject: forging techniques         Reply with quote

I'm aware of the "pattern welding" that was done on Viking and Celtic weaponry, but how was the medieval blade forged? Was it cast, pattern welded, or a combination of both?
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Nathan Robinson
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PostPosted: Tue 19 Sep, 2006 1:14 pm    Post subject:         Reply with quote

This might help:


Ground or Pound?
A Comparison of Forging and
Stock Removal
An article by by Patrick Kelly

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Arne Focke
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Location: near Munich, Germany
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PostPosted: Tue 19 Sep, 2006 1:55 pm    Post subject:         Reply with quote

A few rough points:

During the early medieval ages pattern welding was gradually abandoned simply because it was now possible to produce steel suitable for a blade. At the end of the "pattern welding era" very complex blades can be found in which bladesmiths show what they are capable of. At this point pattern welding is mainly used for pomp and not for use anymore.

It is not possible to cast a blade, because the casting process makes the material very brittle.

I hope I could help.


Greetings from Kiel, Germany.

So schön und inhaltsreich der Beruf eines Archäologen ist, so hart ist auch seine Arbeit, die keinen Achtstundentag kennt! (Wolfgang Kimmig in: Die Heuneburg an der oberen Donau, Stuttgart 1983)
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Geoff Wood




Location: UK
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PostPosted: Tue 19 Sep, 2006 2:17 pm    Post subject:         Reply with quote

Arne Focke wrote:

It is not possible to cast a blade, because the casting process makes the material very brittle.



Minor point. Generally I'm in agreement. Steel blades weren't cast (although most bronze blades were of course, in earlier times), and it probably wasn't possible to cast a decent steel blade then, but I think it could possibly be done now. It would be interesting to see what people could come up with in terms of properties with the benefits of such techniques as directional solidification.
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Arne Focke
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PostPosted: Tue 19 Sep, 2006 2:55 pm    Post subject:         Reply with quote

Of course, bronze blades were cast and then hardened with a hammer.

Geoff Wood wrote:
but I think it could possibly be done now.


That maybe, but I don't know since I tend to be very old-fashioned in the techniques I choose for my blades. Wink
And regarding the original question referring to medieval swords, I think it is sufficient to say that it is not possible to cast a steel blade. Also I personally would like to know in detail if there is or what kind of way there is today to cast a steel blade.

So schön und inhaltsreich der Beruf eines Archäologen ist, so hart ist auch seine Arbeit, die keinen Achtstundentag kennt! (Wolfgang Kimmig in: Die Heuneburg an der oberen Donau, Stuttgart 1983)
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Kenneth Armstrong




Location: Alexandria, VA (for the moment)
Joined: 24 Aug 2006

Posts: 13

PostPosted: Tue 19 Sep, 2006 3:15 pm    Post subject:         Reply with quote

Thanks for the replies!

The only reason why I brought up casting was because I've seen TV specials where experimental archaeologists cast bronze weapons, I had no Idea if that was eventually used for steel or not.

I'll read through that article, thanks for the link!

Read the article, now I have a couple of questions.

How is the steel itself created? I assume the swords are created from blocks of steel, but how are the blocks formed?
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Sam Barris




Location: San Diego, California
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PostPosted: Tue 19 Sep, 2006 5:01 pm    Post subject:         Reply with quote

Geoff Wood wrote:
I think it could possibly be done now. It would be interesting to see what people could come up with in terms of properties with the benefits of such techniques as directional solidification.


But... why?

Oh, and there's some stuff about the iron into steel question in here right at the beginning:
http://www.thearma.org/essays/How_Were_Swords_Made.htm

Pax,
Sam Barris

"Any nation that draws too great a distinction between its scholars and its warriors will have its thinking done by cowards, and its fighting done by fools." —Thucydides
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Geoff Wood




Location: UK
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Posts: 634

PostPosted: Wed 20 Sep, 2006 3:22 am    Post subject:         Reply with quote

Arne Focke wrote:


Also I personally would like to know in detail if there is or what kind of way there is today to cast a steel blade.


Sorry, can't do details, biology was my trade, not metallurgy. The point I was trying to make in my amateurish way was that a lot of the strength and toughness of forged blades (or of modern blades machined from rolled stock) appears to rely on the preferential mechanical elongation of the crystal structure along the axis of the blade that takes place during the forging or rolling. It just seemed to me that a similar effect could possibly be achieved with casting by directional solidification or directional recrystallization, which aim to achieve preferential elongation by controlling the direction of crystal growth. I'm probably way off the mark with this (a little learning is a dangerous thing, etc.etc..), but probably someone can correct me and then I'll know a little more.
regards
Geoff
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Ben Strickling




Location: Greenbelt, MD
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PostPosted: Wed 20 Sep, 2006 1:25 pm    Post subject:         Reply with quote

Geoff Wood wrote:

The point I was trying to make in my amateurish way was that a lot of the strength and toughness of forged blades (or of modern blades machined from rolled stock) appears to rely on the preferential mechanical elongation of the crystal structure along the axis of the blade that takes place during the forging or rolling.


I just thought I'd mention that a similar point was made in this thread: http://www.thearma.org/forum/viewtopic.php?t=21746 in a discussion about the ARMA article mentioned above.

Ben
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Geoff Wood




Location: UK
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PostPosted: Wed 20 Sep, 2006 3:59 pm    Post subject:         Reply with quote

Sam Barris wrote:
Geoff Wood wrote:
I think it could possibly be done now. It would be interesting to see what people could come up with in terms of properties with the benefits of such techniques as directional solidification.


But... why?



But .... why not? I will qualify, it would be interesting to me. If you are only concerned with historical accuracy, my point has nothing to do with it. I was commenting on casting being no good (or otherwise) for blades as an absolute, not as a historical issue, and on whether one could achieve desirable properties with cast steel using the techniques now available. It is a largely academic point, since i don't think anyone who has the technology available is going to bother making sword blades with it. If raising such issues is incorrect for the forum, I'm sure the mods will tell me and I can remove the posts in question.
Geoff
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Geoff Wood




Location: UK
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PostPosted: Wed 20 Sep, 2006 4:16 pm    Post subject:         Reply with quote

Ben Strickling wrote:
Geoff Wood wrote:

The point I was trying to make in my amateurish way was that a lot of the strength and toughness of forged blades (or of modern blades machined from rolled stock) appears to rely on the preferential mechanical elongation of the crystal structure along the axis of the blade that takes place during the forging or rolling.


I just thought I'd mention that a similar point was made in this thread: http://www.thearma.org/forum/viewtopic.php?t=21746 in a discussion about the ARMA article mentioned above.

Ben


Thanks. I've now read the article and thread. I found the strongly expressed emotion in the latter made it a distractingly uncomfortable read, so i possibly missed the point you are making.
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Kjell Magnusson




Location: Sweden
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Posts: 123

PostPosted: Thu 21 Sep, 2006 5:49 am    Post subject:         Reply with quote

Geoff Wood wrote:
The point I was trying to make in my amateurish way was that a lot of the strength and toughness of forged blades (or of modern blades machined from rolled stock) appears to rely on the preferential mechanical elongation of the crystal structure along the axis of the blade that takes place during the forging or rolling. It just seemed to me that a similar effect could possibly be achieved with casting by directional solidification or directional recrystallization, which aim to achieve preferential elongation by controlling the direction of crystal growth.


Hm, are we sure of the presence of a pronounced texture in sword blades (texture = the microstructure is elongated in certain direction)? It would seem tot me that the hardening of the blade would at least have the possibility of overwriting the previous microstructure as first the austenite nucleates and grows in the perlite, and then the martensite does the same in the austenite. I won't even try to say if this process partially or fully does remove the texture though, so, does anyone know (either form sticking a sword under a microscope or from doing the math) to what extent this happens?

Now, if the texture isn't the cause, my guess is that the beneficent mechanism here is the recrystallisation instead, as the cast microstructure (especially in the case of slow, uncontrolled solidification, which would seem to be the case during "the old days") would probably tend to be very coarse, so giving the steel a good beating and then keeping it hot for a while would seem a good idea (as this can result in a refinement of the microstructure).

As for controlled, directional solidification, hm. From what I've understood, grains will tend to grow in the direction of the thermal gradient (ie, cool on one side, and the grains will nucleate there, and then grow towards the hot side). So, if we want our grains to go flat-to-flat in the blade, then that shouldn't be too hard. Going edge-to-edge would be a bit more troublesome, and point-to-tang would be the most difficult case. Also, as we want high rates of solidification (in order to avoid a too coarse microstructure), which would probably make the point-to-tang case effectively impossible (as the heat would have to conduct along the length of the blade). Now, one can refine the grain size simply in the hardening/tempering heat-treat,but as per above, I'm not sure to what extent the texture would survive this. Also, at lower solidifications peeds, segregation could give us problems with alloying agents being enriched in the last solidified parts, something which would then have to be heat-treated away through keeping the blade hot for a long time ( probably unrealistically long times if we need to move large alloying atoms from one end of the sword to another). This could also weaken/erase the texture left from the solidification, as grains will tend to change towards rounder shapes if given the chance (ie if the material is kept hot).

Now, as for directional recrystallisation, I'm afraid I simply don't know anything really there (can't even recall if I've ever heard of it), so to what extent that is a possible route, well, I don't know.

Now then, long-winded, perhaps somewhat incoherent, probably rather technical (I'll be happy to explain, well, anything really, if anyone wonders, though I can't promise that it'd lessen the confusion...), and most me trying to remember what I've read in my textbooks a year or three ago, so the accuracy may be a bit so-so. Never did too well on the texture-coarse either. WTF?! Hopefully I haven't slipped too bad at least.
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Jesse Frank
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Location: Tallahassee, Fl
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PostPosted: Fri 22 Sep, 2006 5:52 am    Post subject:         Reply with quote

Hi all,

Been a while since I've posted.

Re: caststeel blades.

David Boye started doing that back in the early 80's.

http://www.boyeknivesgallery.com/ Check out the "dendritic steel" section. Pretty neat stuff Happy

Re: grain structure/elongation

You will pretty much always have a grain direction, even with modern crucible steels. I've got a bar of W1 that I forgot in a vinegar etch for a couple months, and it looks just like old wrought iron now. I had that thing a 2300f for quite a while. The exceptions to this are the CPM (particle metallurgy), which are mixed in a powder form and compressed.


RE: how steel was made.

Lot's of different ways to go about that, but they are all basically the same, at least in these periods.
Here is a thread that I posted a while back:
http://www.myArmoury.com/talk/viewtopic.php?t...ight=bloom

I've also got a section on forging the bloom here:
http://jfmetalsmith.com/smelting2.html
I don't know if that helps or not, but I hope it does!

Jesse

http://jfmetalsmith.com/
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Kjell Magnusson




Location: Sweden
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Posts: 123

PostPosted: Fri 22 Sep, 2006 7:36 pm    Post subject:         Reply with quote

Jesse Frank wrote:

I've got a bar of W1 that I forgot in a vinegar etch for a couple months, and it looks just like old wrought iron now.


Any details on the history of that piece, ie what forging, heat treatment, and such it had been subjected to between the original casting and the etch? Primarily whether or not there had been any heat treatment resulting in phase change or recrystallisation after any texture/grain elongation was "put into" the steel (as the main thing I'm wondering about is to what extent such a structure in the steel would survive the hardening of a blade).
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Jesse Frank
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Location: Tallahassee, Fl
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PostPosted: Mon 25 Sep, 2006 6:42 am    Post subject:         Reply with quote

The bar was bought as cold drawn square. It was kept at a welding heat for several minutes and air cooled. I had welded it into a billet to make some knives out of. Others that I have made from the same batch have all shown the same marked grain pattern when polished and etched, regardless of prior/current microstructure. It's one of those things that isn't apparent when you polish it like normal with sandpaper, but when you go at it with a very long, slow etch, or hit it with powdered abrasives with the correct backing will jump right out at you. Happy
http://jfmetalsmith.com/
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Kjell Magnusson




Location: Sweden
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PostPosted: Mon 25 Sep, 2006 7:07 am    Post subject:         Reply with quote

In that case, could it perhaps be that what the etch brought out was chemical inhomogeneities, instead of the grain structure itself?
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Jesse Frank
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PostPosted: Tue 26 Sep, 2006 8:13 am    Post subject:         Reply with quote

The alloy banding will follow the grain flow. Happy

Grain flow is just a fact of life when dealing with crucible steels.

http://jfmetalsmith.com/
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Kjell Magnusson




Location: Sweden
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PostPosted: Wed 27 Sep, 2006 6:11 am    Post subject:         Reply with quote

Initially the grain size and alloy segregation would go hand in hand, yes, my thought was though that later treatment might produce a new grain structure which didn't follow the alloy banding quite so close? (Though, with the alloy content affecting surface tension and such, I guess some dependance will always be there.) In this case for example, the possibilities I see would be recrystallisation (if the deformation during cold drawing or welding was sufficient), grain growth, and transformation perlite->austenite->perlite (partially, at least) if the temperature is high enough (welding temperature should be over 1000K or so I guess).

The first two processes would tend to "round off" grains (minimising the surface tension, as round shapes gives us the least amount of surface per volume), unless the surface tension varies much with the crystalline directions, in a homogenous material. Not sure to what extent alloy banding would chance that. Also, the phase transformation could, at least potentially, recreate the grain structure entirely. Not sure how the concentration differences will affect this either, but as we no longer have the huge difference in alloy transport rate which was present during solidification, I don't see any need for the new structure to mimic the structure achieved during the original solidification at least (which should be when the alloy banding was initially created iirc).

So, taken together, it would seem to me that there is the possibility of the grain structure diverging (at least in part) from the alloy banding after the original billet has been processed a bit. Looking back to what I initially wondered/suggested, this could indicate that grain flow doesn't necessarily survive phase changes, recrystallisation and such during the forging of a blade, in which case the impact of such factors on the final properties of a blade might be neglible.

Anyway, the chance to compare my scraps of theoretical knowledge here with actual experience with these materials is greatly appreciated, so thanks for mustering the patience to deal with me.
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Geoff Wood




Location: UK
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PostPosted: Wed 27 Sep, 2006 6:59 am    Post subject:         Reply with quote

Kjell Magnusson wrote:



Now, as for directional recrystallisation, I'm afraid I simply don't know anything really there (can't even recall if I've ever heard of it), so to what extent that is a possible route, well, I don't know.



Mr Magnusson
Not sure if the attached description explains the process helpfully?

http://www.dartmouth.edu/~ianbaker/DR/DR.htm

Regards
Geoff
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Kjell Magnusson




Location: Sweden
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PostPosted: Wed 27 Sep, 2006 7:50 am    Post subject:         Reply with quote

That cleared it up, yes. Thank you very much for the link.
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