Carbon Loss During Folding

[DruSmithing]

Hi guys,

I know there's carbon loss during folding, especially multiple times, as in Japanese bladesmithing, but is there enough loss for it to be a concern? Kapp in "The Craft of the Japanese Sword" throws a number of .03% carbon loss per fold, so after 10 folds, a 1%C stock would retain .7% but the question is how does it relate to carbon loss in modern stock steel like 1095? I'm not taking other factors into account, like forge environment or oxygen exposure, only multiple folding, say, 1024 layers after 10 foldings.

In other words, if I forge a blade from 1095 and fold it 10 times, am I going to end up with ~.6%C?

[Steve Sells]

Yes, No, Maybe. 

How good are you at forge welding? How do you run your fire, what steels are you using ?  Personally I find that 10 folds to get 1024 layers is doing it the hard way, and will likely have a mess of mild steel when done, so much less waste to scale and fuels  if you do it in 4 folds, using quarters to get your 1024 layers in 4 folds.

As you read and you'll learn more, Welcome to IFI

[ThomasPowers]

 So what gas mileage will I get with my pickup truck?  Will I get the same as someone else driving a different truck? Is this not a reasonable question?

What I generally do is to start with thin layers, say 25:  1=50, 2=100, 3=200, 4=400, 5=800, 6=1600  or z fold: 1=75, 2=225, 3=675, 4=2025

For high fold projects I also tend to raid my stash of old black diamond files from back when they were 1.2% carbon.  You can also use can welding to help preserve the carbon content, use san mai to get around the lower C higher level, etc and so on. Starting so all layers are high carbon helps a lot---why 15N20 is prefered to pure nickel for example.

[wicon]

I don't understand your arithmetics. If you loose 0.03% per fold, you would end at around 0.97%C.

If you loose 3% per fold you would end up at 0.74%C. 

[DruSmithing]

Thank you Steve, and thanks for the replies, I guess I'm just gathering info, trying to understand the process as I find it fascinating. At this point I'm not sure I'm getting it right, so here's a quote from Kapp on Japanese swordsmithing.

"[...] Each successive fold causes a loss of 0.03% as large carbon crystals continue to be broken up. Suppose the starting tamahagane has a carbon content of 1.4%. By the time of the first fold, this has already been reduced to 1.1%. Thirteen more folds causes a loss of 0.03% x 13 = 0.39%. This leaves the final steel with a carbon content of about 0.7%."

How come a .3% loss upon the first fold?

Very interesting about starting with a stack of thin layers to drastically minimize the number of folds. Would it work to combine two different steels, say, 1095 with a 2%Si spring steel?

[ThomasPowers]

If you are working on a pattern you choose steels that will contrast when etched.  For general stuff I often use bandsaw blades for their nickel content and pallet strapping---selecting the type that have an appreciable carbon content to them, (heat/quench/break test)  Another technique is to keep adding a layer inside each fold.

Have you read any books on this subject like "The Pattern Welded Blade"?  Ort attended any of the ABS classes?

One question why forge a monosteel blade with folding?  You get all the possible weaknesses of that process without the beauty to counteract them.  Folding does not usually make the material stronger than it would be in an unfolded state you know.

[DruSmithing]

I'm barely getting into the subject, long before any blade will get forged successfully, so I'm asking out of curiosity to understand some major problems I am new to. I'm talking mostly about the way they used to make laminated blades and the problems of folding two different steels for combined properties rather than beauty, including calculating for certain degree of carbon loss in the process. The last part is what I'm not at all clear about.

[jmccustomknives]

Like Steve said, there are a lot of mitigating factors concerning carbon loss.  The 3 main factors are the billet materials, forging time and forge atmospher.  The billet materials can have the largest impact, if you use a high/low steel mix not only do you fight carbon loss to oxidization but to diffusion through the material.  The longer the billet is worked (number of heats) + the forge atmosphere will combine increase the loss.  So if you are hand forging carbon loss will have a larger impact than if you have a power hammer.

There is a technique I've been working on to mitigate this, by adding charcoal to the borax flux.  I haven't tested it on pattern welded material yet but on cable Damascus I've seen a 15% increase in edge holding.  I think it works with cable due to the large surface area it starts with, I don't expect those results with a pattern welded billet but it will take several billets to test.

[SLAG]

J. M.

Capital idea.

But, I think charcoal is not necessarily pure carbon. There may be a small amount of other mineral in it. Powdered graphite should be pure carbon. This can be substituted for charcoal powder. Powdered graphite is on sale in auto supply stores and costs little. Such a switch should save labor graphite is already powered but charcoal requires grinding.

My thoughts,

SLAG.

[gote]

I think there is a certain amount of cross purpose here. The Japanese katana maker does not aim to make a nice damascus pattern he is aiming to homogenize a very uneven mix of materials into a usable steel. He sorts his bits and pieces after how they look since high carbon ones look different from low carbon. He choses the mixture he thinks will eventually yield the right compostion and forges them into a billet. This billet is of course very uneven in quality but after sufficient numer of folds it has been homogenied and in the process excess carbon has burnt off and slag inclusions have been squeezed out. He is doing what a baker does to his kokkie dough. There might be a pattern that is visible after polishing but that is not the purpose. The pattern the Katana smith is after is that created at the edge by the diffeent degree of temper.

If you use a modern steel the Japanese smith's reason for folding obviously does not exist. It seems that Kapp is talking through his hat since there is not a well defined carbon content at the start and there are no carbon crystals to be broken up. Crystalline carbon is usually referred to as diamonds. Obviously carbon rich parts like cementite are "broken up" but that in itself does not make the carbon atoms disappear. They diffuse into carbon poor parts as already pointed out and those on the surface may burn.

Yes charcoal may have traces of other elements (mainly potassium) but if you are a Japanes charcoal smith your steel is made with charcoal anyway. The ash content in charcoal is also not very high and if you add some charcoal to get the carbon content up by a small fracion of  percent I think it can be ignored - especially since it will dissolve into the borax.

[JHCC]

6 hours ago, gote said:

Crystalline carbon is usually referred to as diamonds. 

Well, just to be pedantic, there are other forms of crystalline carbon, such as graphite, graphene, and the various fullerenes. 

[Steve Sells]

its sad to see a a topic posted only to later learn the OP never returns to IFI.. like why do they bother?

[Frosty]

5 hours ago, Steve Sells said:

its sad to see a a topic posted only to later learn the OP never returns to IFI.. like why do they bother?

See Steve, Chechakos are EVERYWHERE!

Frosty The Lucky.

[SLAG]

Frosty San,

But are they endangered creatures?

Somehow, I think not,

SLAG.

[Frosty]

On 10/30/2016 at 4:00 PM, SLAG said:

 

Oh yes, Chechakos are self endangered, are willing to share but breed faster than they chlorinate themselves. Any idea how to get them to self chlorinate BEFORE passing on the stupid gene?

Frosty The Lucky.

[Steve Sells]

I am 100% in favor of removing silly warning lables

[Frosty]

Same for enforcing seat belt laws, except in the case of small children, car seats, etc.

Frosty The Lucky.

[bluerooster]

In some instances, whether the OP comes back or not is immaterial to me. The answer to the question posed, is what I'm after, and haven't been dissapointed yet.

Thanx for the help. And I didn't need to ask, it was already answered.  :D