My Kobuse project

J

Joseph Gardner

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Oct 12, 2018
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Ok so this is a bit of a lengthy project of mine, I started forging the steels for this last year, its a bit of a slow and strenuous process too, everything is basically hand forged with a 4lb or sledge when I can get a striker. still currently working on the steels but I would like to share what I have been making and get some thoughts on it, there is a few complicated details and processes so bear with me.


I will use simplified terms instead of the proper Japanese terms for conversation simplicity.


The blade design will be a Kobuse with a complex skin steel made from about 10 different steels; the core and tusba, drag, sheath collar ring and pommel fitting will be wrought iron I forge welded together from my last bloomery.


So onto the skin steel which is the hard part.


Theres not a whole lot complicated about the steels but the way in which they are formed is, there is 6 general types of steel by grain structure (going off the way the elements are formed) and how they absorb, retain, transfer and diffuse shock.


The Goal is to make a steel with a complex internal structure as well as making enough of it for a 8 inch tang and 25 inch blade minimum with enough steel to preform an end cut on the tip. I will need a brick 5X3X3/8ths”. To fit a 1x3/4thsx4 Canoe shaped core.


-Bloom Steel made from manganese nails with deer bone and some added nickle. This section has been folded 17 times so its relatively homogeneous at this stage, it also has undergone a process where it was thinly painted with satanite and heated to 2400 degrees for about an hour to ensure even carbon distribution. It welds remarkably well and considerably tougher then steels such as 1095 but tends to be more plastic still instead of elastic. its not going to win any awards for being bent 180 and going back to form, it stays bent instead but also doesn't shatter when it hits something like a pig bone, chips less as well.
it's pretty close to .90% carbon, as for the nickle content of the deer bone its hard to say, I used an entire leg of bone and an entire lower jaw, teeth included.

-Cru Forge V which has a structure similar to cpm steels in that there is relatively low elemental segregation. as well as vanadium following John Verheoven's observations of Damascus blades, this provides my vanadium carbide banding.

-Iron Wire, made from my bloomery .05 thick ground to a round. This can be forged flat with a hammer cold, its pretty soft and ductile and has low slag content. (it’s basically just forge welded nails with some extra carbon)

-10XX series spring steels and small amounts of 5160

-15n20 for its shock reflection (as well to supplement the low amount of remaining bloom steel.

-W2 for its stability


So the form is as follows, I have made sections of steel starting with a 2 inch tall stack a inch wide by 4-6 inches long. This is about the limitations of my ability to forge weld with a 4lb, it takes me about 15 hours to convert this into a solid welded billet 3/8ths thick an inch and a half wide by about 8 inches long. I took the time to heat, reheat, flux, weld, reheat, flux, weld repeating about 5 times for 10 heats before drawing.


Any time I had a delam I would split the weld open flux it and scrub it out, add iron wire into the area seal and restart, so each section had about 13-20 heats before drawing to ensure my quality, the ends were also hot cut off to form a seal.


1 section W2, Cru Forge V with the outsides beign 15n20 to ensure welding, 9 layers.

1 section Cru forge v and 15n20, 12 layers.

1 section Bloom steel

1 section mixed from lots of smaller chunks of piled steel, 15n20,Cru Forge V,1085,5160,1045, 40 layers thick, alternating carbon content as well as chrome to non chrome as well as iron strips in non similar locations bewteen each layer, at odd angles. 15n20 on the outside and between for welding.


The bars will be thinned on the ends and formed into hooks, the hooks will be interlocked then I will use a spring swage to compress the center, repeating on either side and then forged flat, I will not work the sides but just mash it, slowly to ensure the weld and prevent the issue of a slip plane, keeping the order listed above.


Once the long bar is assembled I will hot cut with an axe and fold the end of the steel a half inch and then on the second fold and every fold after I will insert the iron wire cold against the fold line and then seal it by completing the fold.


I will continue to fold the steel beveling the bar down to match the widened folded section as I fold it up as it gets wider I will add quarter inch or wider sections of 1075 steel shim (.005 thick) with the edges sharpened. In principle the inserts will be reheated and welded with each further fold.


Once the block is rolled up it will be drawn and the process restarted. Figuring it might have 300 layers each fold might bring it up to 5000 layers at the end of the second time the billet is folded up. I might fold it 6 more times depending on how much steel I have and how close I am to the goal, I may have to forge cru forge V down to wire size and do inserts if I have to to increase my mass.


In theory since the inserts are always against the fold and the folds are on the outside, the ends of the U which form the spine will have more iron and spring steel wheras the blade section will have more high carbon steel content but still have micro layers of softer material inside, this folding process will also greatly reduce carbon diffusion because of the method the bars are assembled and folded together, as well there will be quite a bit of variance forming waves of differential. This method of folding should cause quite a bit of curvature in different directions and angles making wave patterns.


With the higher layer content grinding of the edge will expose quite a bit of the content, as well the normal steel being on the spine section will aid in forming a hamon.


Thoughts?
 
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still figuring out this website for how to do that, im at the stage of forging in the hooks on the bars, just waiting on a new forge to come in the mail, previously was using charcoal.
 
So, I see you are still challenged in the presentation department.

I'm curious as to why you have chosen kobuse over all the other possibilities
M1TNdsJ.jpg


I'm also curious if you are differential hardening your blades and what hamon are showing when polished.
PeOCuu0.jpg


I'm no Einstein, in the computer or tech department and with so many just using their phones to interact on boards, it can be a problem but I have often freely offered to host photos, or otherwise get pictures up on the board, You are free to send them to me in email at
gcleeton@gmail.com
or send them to me at
https://www.facebook.com/profile.php?id=100000715996723
Cheers
GC
 
That is a really complicated question to answer. In short each of the materials have different thermal expansions, causing the sides of the billets to expand and delaminate, and thats why people do not attempt these sorts of things. My lamination process fixes this, just as well there is no point to cleaning the bars and etching them because its just going to warp again until all the seams are sealed.

Just as well those factors make alot of the other laminations even more difficult, there is however a primary goal with all japanese laminations and that is to have radial layers in the blade edge, they are never a san mai sort of stacking, and undernieth each layer is another layer, typically even a maru is folded into a U shape.
You can observe this with a folded peice of paper, even a single mono steel folded up with the edge section on the end of the U is harder mechanically. Compare a stack of paper glued together against the edge versus a stack of paper against the bend, the bend is stronger.

Additionally if it cracks, only a few layers ever crack, if it chips only a few layers can chip, This basic shape however isnt something people are doing these days, they just make stacks with a mono steel edge and so to say your welded face is your blade face. Twists overcome alot of those issues but not all of them, you get exposed welds at odd angles, and the main purpose of japanese laminations is actually to hide the welds and create geometric structures such as an I beam internally. Pure mechanical and less astetic.

Kobuse achieves all of that in one go, my lamination process quickly makes a large stack with internal variance slowing carbon dissolution and alloy thinning so to say, while also thinning the carbon content by adding soft steel on the back ends.

I will probally also clay up the spine, put the blade in a tube with charcoal powder seal it up and keep it in there for an hour to add extra carbon content on the edge.
 
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Goes as follows top left to right ect.
Damascus scraps, the mixed steels I might make another bar from, bloom steel, the two on the end are mixtures of spring steels with 15n20, W2/CRV, CRV/15n20, and a truck axel I will use for the handle, the bottom two are samples, the first is a minature of the blade profile I desire and the second is a to size sample of how I will do the tip.

Realistically, they look like burnt metal at this stage because that is what it is.
 
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I see where you're going with this, and it's a neat way to think about it, but there are numerous documentaries and books about the ways Japanese swords are forged, and it seems to be a straight-forward process after choosing which pieces of high and lower carbon steel to use. There are layers of steel with different properties in the right places. It seems that your billet project is taking that notion and expanding it ad absurdum.

The other thing is, generally speaking a proper weld isn't really a weak point; a bad one is.

"...main purpose of japanese laminations is actually to hide the welds and create geometric structures such as an I beam internally. Pure mechanical and less astetic."

Japanese swords and everything that surrounds them is seething with aesthetic detail. It's one of the definitive things about them.
 
Sort of, so when working with disimilar steels you end up using a variety of folding techniques, the removal of exposed welds during the process allows you to change the angles which it can be welded without running into problems.

In japanese forging centerline cuts are used down the piece of the steel long ways instead of a short fold. This method allows you to simply preform a normal short cut, fold the bar and do a light welding pass, it sticks reheat and then center line cut, the cut forms an extremely reliant weld and then the fold allows you to weld the bar more efficiently. In three heats you can go from 2 layers to 8, instead of needing 6 heats and having rough welds, your surface area also shrinks allowing for more consistent applica of force. The outside layer now covers 3 surfaces, the billet can then be turned 90 degrees and folded so all of the weld lines are in the center encased by a single type of steel. you now have Zero issues welding any face to any other face because of strangeness. further folding will cause stranding in the layers of steel, instead of flat layers you now have a wire structure, as the steel is drawn out it forms waves.

This could be said to be a way to do the same thing as the saxon methodology of twisting layers and then folding, essentially it forms a cable braid.

Welding temperature for iron-iron-carbon (steel) starts roughly at 1400 degrees where the material will bond and absorb other materials but the friction is what is required for a forge weld. each steel has its own welding temperature and preferred forging temp for existing welds and the issue then becomes that they retain heat differently.

Low carbon likes 2000, high carbon and hyper eutechtoid tool steels might prefer 1700, There isnt a set point on what welds to what, its largely based on carbon differential, and what bonds to what, as well as where the steels like to compress in a similar manner.

the faster you can eliminate any surface welds the better you can weld it to other bars of differently aligned material, your good refined steel will shrink so you might add other bars of content in different arrangements. The direction of the internal layers matters in conjunction to its purpose and where the steel is going to be laminated, as well as how the carbon will diffuse.

The get the best welds steel has to have a long soak time at 2000 degrees or higher, the weld lines vanish and any slag and cold shuts will get reabsorbed into the steel (your scale inside bad welds goes away) but now you face the challenge that your materials lose any benefit from dissimilar carbon content and differential hardening, so staggering the layers in such a way that the carbon cant transfer is important.

In a simple phrase: 7 and 9 makes 8, so if your layers are 8, 10, 8, 10, 8, 10, 13, 2, 6, 2, 6, 2, 6 the end result eventually might become 9999(10)(9)(6)4444. The steel will want to continue to balance out between the layers but has to start the process all over again. In hopes by the time the steel is done being forged there is enough carbon differential to maintain different properties giving the damascus its pattern welded effect in micro layers without becoming a single steel, adding new material also changes this effect and starts the calculation.
 
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its not a japanese method of folding but it was my answer to how to get vanadium chromium banding as well as isolation of elements, which has been the bitch of it all. The W2/Cru forge V didnt want to weld at any temperature but the moment I let it cool it self welded. None of these steels like to play together and I dont have a power hammer to do this work, but I can promise my quality with a sledge hammer one inch at a time.

Being a blacksmith is all about creating your own solutions to problems. need a tool make a tool, face an obstacle improvise.
 
As for the pattern i have no idea. working on the closed fold will cause the steel next to it to compress thinning around the end of the fold, since its going to get wider Ile be forging bevels into the sides of the main bar to get it to match but its going to have a convex shape with the material but also will be slanted to the side each time, and then of coarse it get flipped, the stack will have a flat face from being welded together but the convex flips, so while I might have W2Cru to W2Cru, the convexes are opposed internally.

And then it forms a bar to be lengthened and repeated, eventually being bent into a U. So the grain line, I have no fucking clue
 
Monday is my next forge day, im hoping to get at least 3 of the bars hooked together im still debating how much more steel i will have to add to it though, im thinking at least 2 more segments
 
Fair enough. Lots of good ways to make a sword blade, laminations are a fantastic way to do it. So the goal of all this steel welding, it's to take the idea of zones of harder and softer steels and extend it into the realm of micro layers of various different alloys and elements? What advantages or differences are you expecting to see when the process is done?

Keep going with the photos, plox.

I see what you're talking about with the huge thick tang as a handle, for balance. If that works out then great, but contrary to what you were saying before about how good/real swords used to be made, it's nearly universal that they have small tangs and the weight distribution of the hilt and it's parts brings the long blade, however it's shaped, into balance.
 
So for that distribution i could have easily taken that section and forged it into a rat rail, as long as its thickness remains the same as before the taper it doesnt matter how long you draw it out. This works for long swords too, you just taper the bar all the way down to a quarter inch and sand that down into a round, you can slide a pommel up it and peen it. Some smiths just left it a stub like this knife was some prefer to thin it down and draw it out. Really its just a distrubition but it makes excellent blades doing it that way because you get pure leverage this isnt practical for knives you want to be tip heavy its almost advantageous to flip the bar around the other way to get a more efficient chopper, its just centering mass.

Generally i try to aim for an inch or two above the taper because as i draw it out i increase the stock removal needs and that countermands the balance point. Also given the portion of the hot cut at the tip so the edging bevels bring the tip back in line with the spine hiding the core so all the exposed welds are in the spine.

I get most of my blades balanced right on the index finger because im more fond of fast parrying.

The big advantage of the preform bar is you can make any sword from there and go anywhere with it, broad sword, long sword, rapier, katana, saber, great sword doesnt matter. For a broke back seax or arabic blades you simplely flip the bar over so the heavy end is on the tip
 
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And im going for a battle sword so ile need the ending portion of 4lbs and .3 thickness, but with the balance exactly on the index finger it will feel perfectly light. Give or take i may need a scale and weigh out 10 pounds on the bar, wel see how much more I need to add.
 
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In theory this is the iron and 1075 content added on each fold the first time forming.

https://goo.gl/images/NDmQbs I pulled this one off google, but basically yeah, theres an aweful lot of steel there.

and on another note its traditional to file the tang?... doing that with cru forge V is gonna fucking suck.
 
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