Why Kamakura = best swords ever??

[Jussi Ekholm]

Heian and Kamakura period ubu tachi are very rare and precious items.

 

So do not think otherwise even if the number I will present next might seem large. So far I believe I have found 1238 of them (had to count them manually so it took some time). This number of course includes work and mumei attributions to smiths/schools that would have potentially worked into Nanbokuchō but I did not count any ubu dated tachi after end of Kamakura. And to be noted about 50% of this number are Bizen tachi.

[mas4t0]

14 minutes ago, Jussi Ekholm said:

So far I believe I have found 1238 of them (had to count them manually so it took some time).

 

Thank you for that information Jussi, I'm always amazed by your level of commitment and grateful for your contributions.

 

Whenever I try something like this (which is rare) I lose count or forget what I was doing. Invariably I end up writing some Python code to automate the process.

[Baba Yaga]

The Japanese have more than the ability to do none destructive metal analyses on all high end blades, but what then? Would they submit the findings and acknowledge there "best guesses" have been wrong? Hell no is the answer.     

[Jacques D.]

Mark 

 

Quote

 

In the image above they've delineated the three regions and you can visually observe the lamination layers. 1) The "sharp edge" 2) the "side plane" and 3) the "core region". This would seem to correspond to:

 

These swords are found to be composed of two kinds of middle carbon steel, outside [i.e. "sharp edge" and "side plane"] and low carbon steel, inside [i.e. "core region"]. In other words, Japanese sword is one of composite materials

 

No, re-read the title of this study it gives the purpose of the research, figure 2 is related to this text.

 

Quote

The carbon distribution of the cross section of both swords was analyzed by Electron Probe Micro-Analyze (EPMA) using JEOL JXA-8900R equipment. The microstructure was revealed with nital etchant and studied by optical microscopy (OM) and scanning electron microscopy (SEM, HitachiS-3500N). Three specific regions in the cross section i.e., (i) sharp edge, (ii) Hamon region (side plane) and (iii) core region were observed. Micro Vickers hardness was measured along the cross section through the center line in the both sword. The residual stress along the longitudinal direction on the surface has been measured by XRD. A special type of X-ray diffractometer (Rigaku, MSF-2M) having two-tilt facility was used for this purpose. 

 

[mas4t0]

6 hours ago, Jacques D. said:

Mark 

 

No, re-read the title of this study it gives the purpose of the research, figure 2 is related to this text.

 

 

 

Thank you Jacques.

 

I'm somewhat confused by what you're saying, could you please elaborate?

 

It seems quite clear that they're referring to three distinct regions, with different carbon content (and different microstructures), but which are each being treated as internally homogeneous.

 

You can see below that:

• the "sharp edge" has the highest carbon content on each sword and a fine, lath martensite microstructure
• the "side plane" has lower carbon content on each sword and a martensite + pearlite microstructure
• the "core region" has very low carbon content on each sword and a ferrite microstructure.

 

This is what would be expected for a differentially hardened laminated blade which was constructed in a Shihozume type way.

 

What's your explanation of this?

 

It very much seems like they are treating these regions as each being internally homogeneous but clearly distinct from each other as in a laminated blade (with no mention of hada, blending or pattern-welding).

 

 

Quote

3.1. Microstructure observations with SEM

 

The macro structure of the cross section in modern sword and old sword is shown in Fig. 2 and the carbon distribution of the cross section of both swords analyzed by EPMA is indicated in Table 1. Itis known that the carbon content of sharp edge especially influences the performance of Japanese sword and its amount is analyzed as 0.5–0.7 mass% in the greater part of Japanese swords [11,13]. These swords are found to be composed of two kinds of middle carbon steel, outside and low carbon steel, inside. In other words, Japanese sword is one of composite materials. There are hardly harmful impurities such as Si and Mn which decrease the sword quality. Fig. 3 shows the microstructures of the three specific regions in the cross section observed by SEM. Around the sharp edge, the microstructure is fully occupied with fine martensite. The morphology of martensite is lath [15–17]. This martensite is occurred by water quenching after hot forging of 10 several times in the process of sword making. The wavy pattern area in side plane contains hard martensite and semi-hard fine pearlite. The core region shows dominantly soft ferrite.

 

Quote

3.2. Distribution of micro Vickers hardness in the cross section

 

In the cross section of both swords, micro Vickers hardness was measured along center line from the sharp edge. The hardness of sharp edge shows 830-880HV in Fig. 4 and this high hardness corresponds to the hardness of martensite which contains approximately 0.70 mass% carbon.

 

 

How do you reach the conclusion that they're referring to different layers in the hada?

[ROKUJURO]

17 hours ago, Jacques D. said:

Jean,

There is something that bothers me, on the one hand you say this :

.....Are you referring to the (wrong) theory that Damascus steel consists of layers of different hardness? This is certainly also not the case in Japanese blades....

and on the other you say that (picture below)

....Ebenso schmiede ich Damaszenerstahl aus verschiedenen Stählen, die so miteinander kombiniert werden, dass sich nach dem Ätzen der fertigen Klingen eine deutlich sichtbare Struktur ergibt.....

Wouldn't it be like a contradiction? ....

Jacques, 

first of all thank you for the little video which I did not see before!

Concerning your question: No, there is no contradiction which I will happily explain:

We have to go back a bit to explain that early Viking (6th century CE) so-called Damascus steel (correctly 'pattern-welded steel') consisted of two low-carbon iron components, one of which contained phosphorus, the other was free of it. The Viking smiths soon learned to use these materials in a way to produce predictable patterns instead of random ones in their famous sword blades. As this was non-hardenable iron, they welded a steel cutting edge onto the pattern-welded blade core. The result was a flexible blade with good cutting properties - and it looked stunning!

Leaving Wootz (or Bulat) - traditional crucible or 'crystalline' high-carbon steel made in India and Persia and traded via the famous city of Damascus - aside, I would like to explain that today's pattern-welded steel as used mainly in knives is made of two or more industrial steels that have similar hardness potential. The carbon content of both alloys is very close, so each steel could be used as single material for a blade.
I often use a manganese and a nickel containing steel.

The blades made with this technique are very durable and visually attractive.

This composite material has nothing to do with Wootz and should in fact not be called 'Damascus steel', but the market and habits stick to it.

On the other side, if you combine a (potentially) hard steel (= high carbon content) with another one of low carbon content (= sub 0,3% C), there are two possible scenarios:

Provided the steel layers are thick (sheet metal > 2 mm) and you only do a small number (< 3) of fire-weldings, time and temperature will not allow for a complete carbon diffusion throughout the layers. The result will be an edge that will show soft and hard spots. After some cutting work you will probably get a saw-toothed edge (depending on the pattern).
 
If you use the same material composition but your steel sheets are thin and/or you have a considerable number of foldings and fire-weldings, carbon migration through the layers will end up in an even carbon distribution. Provided you started with 0.7% C steel for the hardenable component and the same amount of carbon-free iron, your pattern-welded steel will have 0,35% of carbon throughout the billet (not calculating the loss of material and especially carbon because of the high temperature). 

These are metallurgical facts, nevertheless you will read everywhere about Damascus steel beinng made of soft and hard steel, thus combining flexibility and hardness.  Draw your own conlusions.

Jumping back to Japanese sword blades with steel layers of hair thickness and a considerable number of foldings/weldings, you can be sure that the carbon content in a carefully forged billet is homogeneous.

HEIAN and KAMAKURA era blades were made for combat, not for court presentation or decoration. The blades that survived the centuries have certainly been made with the utmost care and competence. As you may know, in a sandwich construction the outer (active) layers are most important, and so, by experience alone, the JIGANE in those old blades was made in the best possible way.   

I am not qualified to judge the overall quality of old Japanese sword blades, but I think that a number of aspects are involved. I think these swords were use on horseback, so this required a special SUGATA for a slicing cut.


 

 

[Alex A]

In this video and out of curiosity.

 

States "stacks differing wafers of varying carbon content".

 

Now i suppose they could be close carbon content or miles apart.

 

Are you guys saying (in simple terms) that the carbon content after hammering and folding will be TOTALLY EVEN throughout the block ?

 

19.46 in this video.

 

Also, worth mentioning again that you will see some smiths do things differently, obviously a different hada is the result.

 

What im getting at, and the plasticine clay is a good analogy. Folk talk about “ The Japanese sword” like there was only ever one lol.

 

I wonder if the carbon content in a O-itame is as evenly distributed as that in a super fine Muji?

 

 

 

 

[ROKUJURO]

4 hours ago, Alex A said:

...Are you guys saying (in simple terms) that the carbon content after hammering and folding will be TOTALLY EVEN throughout the block ?....

Yes. Simple enough?

May I add that this depends of course - as I explained above - on the thickness of the layers and the number of foldings.

It is important to understand that ONLY homogeneous material can have predictable properties and be reliable in an application, whatever that is.

The demonstration with plasticine clay is helpful to understand the effects of homogenization. Of course you have to use different colours to show the process properly. That does not mean the steel wafers are of different carbon content!

As you may remember, the smith chooses his raw TAMAHAGANE first. Then he forges some of the lumps flat, cools them down quickly, and breaks them. The structure of the broken pieces (and the way they break) shows him what pieces are close in carbon content. These are then combined and fire-welded to form the initial billet. 

[Jacques D.]

   A lot of misunderstanding of what is really going on. Let's start with the beginning: the satetsu. In the ore, the iron oxide content is 1% and it is unevenly distributed. In the tatara, temperature and pressure are also unequal what makes that in the block of tamahagane that we recover at the end, the rate of carbon can vary from 0.2% to 1.4 or 1.5%. When the smith makes tsumiwakashi, he sorts the steel according to the hada he wants to obtain; if he wants a tight hada he will assemble pieces with a fairly close carbon content (0.1% or 0.2/% difference) if he wants a looser hada, he will increase this difference. What does hammering do? The more the smith folds his steel, the more layers are numerous, thin and close to each other. The carbon rate does not vary inside the layers (C has no legs and the temperature is too low) but as the layers are closer to each other there is homogenization (also loss of carbon) but not equalization of this carbon rate, which will make the hada visible, if the carbon rate was equal everywhere the hada would be invisible. It is important to understand that what we see is the steel layer and not the weld. Take an XC75 for example and fold it as many times as you want, you will never see the folds (I had it done by a smith).

To obtain an itame we choose the hammered side, to obtain a masame, we choose the non hammered side.

 

Mark,

 

First of all, learn to read a scientific study and the figures. Words have a meaning and it is not the one you want to see. The shihozume that you see comes from your imagination (or bad faith)

     

[Alex A]

Hi Jean

 

It states in the video the wafers are of differing carbon content.

 

Also, if carbon is always so evenly distributed, then why (as Jacques quoted the craft of the Japanese sword) does it state in that book

 

”The VARYING carbon content also produces etc etc”

 

Using the plasticine analogy , for perfect distribution i would expect the 2 colours to merge into 1 colour, as in extremely tight refined hada)

 

 

[Alex A]

Just as an example.

 

If you took two swords and did a carbon analysis on a dozen or so points on each blade and compared

 

1) Mass produced koto itame

 

2) Shinshinto refined Muji

 

On average, id bet my home 2 would show to have more consistent carbon 

 

Lots of swords and variations

 

 

 

 

[ROKUJURO]

1 hour ago, Alex A said:

.....Using the plasticine analogy , for perfect distribution i would expect the 2 colours to merge into 1 colour, as in extremely tight refined hada)...

Correct.

Again, HADA has no direct relation to carbon content

[Alex A]

Well, if the steel gets more evenly distributed when manipulated (as in plasticine analogy) how does that not distribute the carbon within the steel too?

[ROKUJURO]

As I tried to explain: the carbon content is indeed homogenized. HADA has nothing to do with carbon content.

For Jacques:

....Japanese iron sands are usually really low, about 2% to 5% (yet it is fair to highlight that the iron sand found in the Chugoku region, which was known to be the top quality, has a 58% iron content).....

 

from Gunbai military blogspot

[mas4t0]

7 hours ago, Jacques D. said:

Mark,

 

First of all, learn to read a scientific study and the figures. Words have a meaning and it is not the one you want to see. The shihozume that you see comes from your imagination (or bad faith)

 

(Professor) Jacques,

 

Thank you for so generously sharing your great wealth of knowledge.

 

If I can't read a simple paper, I clearly have nothing of value to say here, so I'll bow out and avoid further comment.

 

I know that the word "Shihozume" is not mentioned in the study, but a similar type of lamination is shown and described. I used the word and provided an illustration for added clarity as it is a term that all here will be familiar with.

 

Why in your (expert) opinion do those regions have differing carbon content, and why is lamination visible in the cross section if the blade is not in fact laminated?

 

This thread has reminded me of an old acquaintance (a physicist) who wrote a simulation and a paper modelling the economy on ideal gas laws. It was a masterpiece, complete with references to papers which had no relevance to what he was using the reference to support and to (unpublished) papers he had written (which obviously only referenced other papers he had written and which had not been accepted for publication, a closed system as it were); always a lovely flourish, showing true mastery of the scientific process. His conclusions were predictably absurd. In effect he concluded that if someone wealthy were to interact with someone less well off, the wealthier party should give the other party half of their net worth - in so doing, it would naturally follow that all societal problems and political differences would resolve themselves in a matter of days (remember that this was a serious piece of academic work and was not intended as satire). He also considered (entirely arbitrarily) that this should only apply when the wealth of the wealthier party was above a certain threshold, which he was of course below. He was angry and upset that no major economics journal was interested in publishing his groundbreaking magnum opus. His more recent extra-curricular activities have involved carrying out a study on bus punctuality, which had major methodological flaws (which is quite impressive for such a simple project).

 

I don't grasp your meaning of "bad-faith", so I suppose I'll go re-read some work by Sartre (maybe when I'm done and have thoroughly misunderstood his meaning you'll be so kind as to help me with that too).

 

The below is from a class on Mathematics for Computer Science. It's been quite a few years since I took the class, but I like to keep a copy on hand. I think we're approaching a full-house (a rare accomplishment for a single thread), if we keep this going I'm confident we can get there!

 

Popular Proof Techniques NOT Allowed

 

Spoiler

Proof by throwing in the kitchen sink:

The author writes down every theorem or result known to mankind and then adds a few more just for good measure. When questioned later, the author correctly observes that the proof contains all the key facts.

Proof by example:

The author gives only the case n = 2 and suggests that it contains most of the ideas of the general proof.

Proof by vigorous hand waving:

A faculty favorite. Works well in any classroom or seminar setting.
 

Proof by cumbersome notation:

Best done with access to at least four alphabets and special symbols. Helps to speak several foreign languages.

Proof by exhaustion:

An issue or two of a journal devoted to your proof is useful. Works well in combination with proof by throwing in the kitchen sink and proof by cumbersome notation.

Proof by omission:

“The reader may easily supply the details.”
“The other 253 cases are analogous.”
“...”

 

Proof by picture:

A more convincing form of proof by example. Combines well with proof by omission.

Proof by vehement assertion:

It is useful to have some kind of authority in relation to the audience.
 

Proof by appeal to intuition:

Cloud-shaped drawings frequently help here. 

Proof by reference to eminent authority:

“I saw Fermat in the elevator and he said he had a proof . . .”

 

Proof by intimidation:

Can involve phrases such as: “Any moron knows that...” or “You know the Zorac Theorem of Hyperbolic Manifold Theory, right?”

Proof by intimidation (alternate form):

Consists of a single word: “Trivial.” Often used by faculty who don’t know the proof.

Proof by reference to inaccessible literature:

The author cites a simple corollary of a theorem to be found in a privately circulated memoir of the Slovenian Philological Society, 1883. It helps if the issue has not been translated.

Proof by semantic shift:

Some standard but inconvenient definitions are changed for the statement of the result.

Proof by cosmology:

The negation of the proposition is unimaginable or meaning­less. Popular for proofs of the existence of God.

Proof by obfuscation:

A long plotless sequence of true and/or meaningless syntac­tically related statements.

Proof by wishful citation:

The author cites the negation, converse, or generalization of a theorem from the literature to support his claims.

Proof by funding:

How could three different government agencies be wrong?
 

Proof by personal communication:

“xn + yn = zn for n > 2” [Fermat, personal communication].

Proof by importance:

A large body of useful consequences all follow from the proposition in question.
 

Proof by accumulated evidence:

Long and diligent search has not revealed a counterexample.
 

Proof by mutual reference:

In reference A, Theorem 5 is said to follow from The­orem 3 in reference B, which is shown from Corollary 6.2 in reference C, which is an easy consequence of Theorem 5 in reference A.

Proof by ghost reference:

Nothing even remotely resembling the cited theorem appears in the reference given.

Proof by forward reference:

Reference is usually to a forthcoming paper of the author, which is often not as forthcoming as the first.

Proof by metaproof:

A method is given to construct the desired proof. The cor­rectness of the method is proved by any of the above techniques.

 

[Alex A]

Going around in circles here

 

Back to Kamakura

[Baba Yaga]

3 hours ago, mas4t0 said:

 

(Professor) Jacques,

 

Thank you for so generously sharing your great wealth of knowledge.

 

If I can't read a simple paper, I clearly have nothing of value to say here, so I'll bow out and avoid further comment.

 

I know that the word "Shihozume" is not mentioned in the study, but a similar type of lamination is shown and described. I used the word and provided an illustration for added clarity as it is a term that all here will be familiar with.

 

Why in your (expert) opinion do those regions have differing carbon content, and why is lamination visible in the cross section if the blade is not in fact laminated?

 

This thread has reminded me of an old acquaintance (a physicist) who wrote a simulation and a paper modelling the economy on ideal gas laws. It was a masterpiece, complete with references to papers which had no relevance to what he was using the reference to support and to (unpublished) papers he had written (which obviously only referenced other papers he had written and which had not been accepted for publication, a closed system as it were); always a lovely flourish, showing true mastery of the scientific process. His conclusions were predictably absurd. In effect he concluded that if someone wealthy were to interact with someone less well off, the wealthier party should give the other party half of their net worth - in so doing, it would naturally follow that all societal problems and political differences would resolve themselves in a matter of days (remember that this was a serious piece of academic work and was not intended as satire). He also considered (entirely arbitrarily) that this should only apply when the wealth of the wealthier party was above a certain threshold, which he was of course below. He was angry and upset that no major economics journal was interested in publishing his groundbreaking magnum opus. His more recent extra-curricular activities have involved carrying out a study on bus punctuality, which had major methodological flaws (which is quite impressive for such a simple project).

 

I don't grasp your meaning of "bad-faith", so I suppose I'll go re-read some work by Sartre (maybe when I'm done and have thoroughly misunderstood his meaning you'll be so kind as to help me with that too).

 

The below is from a class on Mathematics for Computer Science. It's been quite a few years since I took the class, but I like to keep a copy on hand. I think we're approaching a full-house (a rare accomplishment for a single thread), if we keep this going I'm confident we can get there!

 

Top 10 Proof Techniques NOT Allowed

 

  Reveal hidden contents

Proof by throwing in the kitchen sink:

The author writes down every theorem or result known to mankind and then adds a few more just for good measure. When questioned later, the author correctly observes that the proof contains all the key facts.

Proof by example:

The author gives only the case n = 2 and suggests that it contains most of the ideas of the general proof.

Proof by vigorous hand waving:

A faculty favorite. Works well in any classroom or seminar setting.
 

Proof by cumbersome notation:

Best done with access to at least four alphabets and special symbols. Helps to speak several foreign languages.

Proof by exhaustion:

An issue or two of a journal devoted to your proof is useful. Works well in combination with proof by throwing in the kitchen sink and proof by cumbersome notation.

Proof by omission:

“The reader may easily supply the details.”
“The other 253 cases are analogous.”
“...”

 

Proof by picture:

A more convincing form of proof by example. Combines well with proof by omission.

Proof by vehement assertion:

It is useful to have some kind of authority in relation to the audience.
 

Proof by appeal to intuition:

Cloud-shaped drawings frequently help here. 

Proof by reference to eminent authority:

“I saw Fermat in the elevator and he said he had a proof . . .”

 

Proof by intimidation:

Can involve phrases such as: “Any moron knows that...” or “You know the Zorac Theorem of Hyperbolic Manifold Theory, right?”

Proof by intimidation (alternate form):

Consists of a single word: “Trivial.” Often used by faculty who don’t know the proof.

Proof by reference to inaccessible literature:

The author cites a simple corollary of a theorem to be found in a privately circulated memoir of the Slovenian Philological Society, 1883. It helps if the issue has not been translated.

Proof by semantic shift:

Some standard but inconvenient definitions are changed for the statement of the result.

Proof by cosmology:

The negation of the proposition is unimaginable or meaning­less. Popular for proofs of the existence of God.

Proof by obfuscation:

A long plotless sequence of true and/or meaningless syntac­tically related statements.

Proof by wishful citation:

The author cites the negation, converse, or generalization of a theorem from the literature to support his claims.

Proof by funding:

How could three different government agencies be wrong?
 

Proof by personal communication:

“xn + yn = zn for n > 2” [Fermat, personal communication].

Proof by importance:

A large body of useful consequences all follow from the proposition in question.
 

Proof by accumulated evidence:

Long and diligent search has not revealed a counterexample.
 

Proof by mutual reference:

In reference A, Theorem 5 is said to follow from The­orem 3 in reference B, which is shown from Corollary 6.2 in reference C, which is an easy consequence of Theorem 5 in reference A.

Proof by ghost reference:

Nothing even remotely resembling the cited theorem appears in the reference given.

Proof by forward reference:

Reference is usually to a forthcoming paper of the author, which is often not as forthcoming as the first.

Proof by metaproof:

A method is given to construct the desired proof. The cor­rectness of the method is proved by any of the above techniques.

 

 

If you keep it up Jesus Christ himself will post the real answers. This was something I actually found interesting until it went sideways. 

[Jacques D.]

6 hours ago, ROKUJURO said:

Correct.

Again, HADA has no direct relation to carbon content

Prove it by describing the physical process that takes place at the level of the molecules; nothing else.

 

Mark.

 

 

 

Quote

I know that the word "Shihozume" is not mentioned in the study, but a similar type of lamination is shown and described

No, no and no. There is no suggestion of lamination in this figure.
By the way, what does the 1mm scale we can see on it mean ? 

 

 

[Alex A]

I don't see how Hada cannot be related to carbon content when the steel made to create the Hada pattern is made from carbon steel/steels.

 

Think maybe this deserved its own thread.

 

Sorry, again.

 

[Alex A]

Actually, ive said sorry a few times but in reality if one cant get their head around this then this then there is no hope to understand Japanese swords, If your serious about Japanese swords and find this boring then i would go back and re-read what has been talked about. Again, this is fundamental to the hobby and there is little chance of remotely understanding any sword construction , let alone what makes Kamakura swords interesting.

 

Reading what Mark, Jean and Jacques have said has been very interesting . As said, this is not what i have neen learning about, been mainly Kantei type stuff.

 

So excuse my basic thoughts with regards this particular part of the hobby, im no blacksmith, just a guy trying to get his head around it

 

The interesting part for me, the plasticine analogy,  struck a nerve and i will tell you why. Very similar, years ago working as a printer i mixed more different coloured inks then i care to remember to create other colours, reds and yellows to create orange and so on.

 

How is this relevant, you may ask. Well, when i watch the guy in the vid fold the steel it takes me back to that time stood folding 2 blocks of ink together. I can tell you this for sure, 12 folds isn't enough to turn 2 colours into 1 colour. I would be there ages folding many times to see the final 1 colour and even then you would find the odd streak.

 

 When i see a smith in a video talking about steels of different carbon content being stacked, heated, hammered and folded, it takes me back. I watch him hammer and fold. I don't see steel, i see colours being mixed.

 

Its been stated that steels of different carbon go in to the block, sometimes close and sometimes not so close.

 

When i watch a smith in the video fold the steel, lets say 2 steels of varying carbon. I imagine 2 different colours., 

 

Even if those 2 steels are close in carbon content then even after 12 folds im still assuming a difference within that block. 

 

We have HADA!

 

The only way to produce a block of pure equal carbon steel would be to really refine. Im talking melt it down as in at steelworks molten metal, no ?

 

Muji hada is the result of much folding/refining, O-itame not so much

 

Its been said varying carbon levels makes the hada more distinct by a few sources.

 

Lets remember that folding steel is not always perfect, also. Look at how many delamination's we see in blades, impurities and so on, flaws etc

 

As for this carbon migration, i dont know anything about it but wonder how much of an effect there might be ?.

 

An image of a reasonably tight hada below, to look at, is that just the result of heat, hammer and folding and not material differences, i find it hard to believe.

 

As mentioned, there is a molecular level, i aint going there haha. Think maybe that is the only way to settle it.

 

Gone on a bit.

 

Great thread, cheers.

 

 

 

 

[Jacques D.]

Alex, 

 

Quote

As for this carbon migration, i dont know anything about it but wonder how much of an effect there might be ?

Carbon migration does not exist, the laws of physics prohibit it at these temperature and pressure conditions. Carbon migration can only occur in liquid steel when convection starts. Carbon can also be migrated with the use of a laser or in the heating of a steel with a high chromium content but this is not the subject here. Many people confuse carbon migration with carbon diffusion which is not the same . The speed of displacement of atom depends on the temperature , for example at 1000° a carbon atom will move 0.75mm/hour. The higher the temperature is, the faster the atoms move. But, a carbon atom will not be able to cross the barrier of the weld, it can only move in its layer.

 

hs : I specify that the temperature is nothing else than the measure of the molecular agitation at equal pressure and volume and that a thermometer measures only the temperature of the thermometer; that's why it is necessary to wait that the temperature of the thermometer is at the thermodynamic equilibrium with its environment so that we can know the temperature of what we want to measure.

 

 

ps However, I wonder if it is necessary to continue as people seem to be so attached to their certainties...

[Alex A]

Folk disagree then that's fair enough, im happy just to pick up on a things that i wouldn't normally look into and gain a bit more understanding of the full picture.

 

Cheers.

[DoTanuki yokai]

I think that the temperature is more then high enough for Carburizing when forging swords. 
I don’t know if the carbon can go through the welds but I can imagine this if it can on the surface. 

https://www.efunda.com/processes/heat_treat/hardening/diffusion.cfm?search_string=Diffusion hardening
 

[Alex A]

Hi Christian, but it states this about carburizing.

 

"This diffusion will work only if the steel has low carbon content, because diffusion works on the differential of concentration principle"

 

 

[Jacques D.]

Burning charcoal to heat the steel compensates in part for the loss of carbon due to hammering this process is called cementation. 

[mas4t0]

As promised, I'm going to try and avoid any opinions or analysis of my own (they'd surely be incorrect), but this carbon diffusion denial is quite ridiculous.

 

It's been well known and well studied for decades. It's well known because it's the root cause of many problems in industrial applications.

 

I understand your doubts Alex and your reasoning, but this is a diffusion process which takes place in addition to the mixing effect you described - to observe diffusion in your inks you'd probably need to dilute them significantly with a solvent. This isn't an unfounded belief, it's based on a huge body of empirical evidence.

 

I'm not going to type up entire chapters from text books on the topic, but I would encourage people to read some relevant books.

 

Anyhow:

 

From Elements of Metallurgy and Engineering Alloys (link):

 

Chapter 5: Diffusion:

 

Abstract:

 

Diffusion is the movement of atoms through the crystalline lattice. This chapter discusses the two main types of diffusion that can occur in solids: interstitial diffusion and substitutional diffusion. It describes Fick's first and second laws of diffusion, with emphasis on several applications of the latter. The chapter also provides information on the temperature dependence of diffusion, intrinsic diffusion coefficients (Kirkendall effect), and high diffusion paths.

 

From Steel Metallurgy for the Non-Metallurgist (link):

 

Chapter 7: Diffusion—A Mechanism for Atom Migration within a Metal:

 

Abstract:

 

Diffusion is the primary mechanism by which carbon atoms move or migrate in iron. It is driven by concentration gradients and aided by heat. This chapter provides a practical understanding of the diffusion process and its role in the production and treatment of steel. It discusses the factors that determine diffusion rates and distances, including time, temperature, and the relative size of the atoms involved. It also describes two heat treating methods, carburizing and decarburizing, where carbon diffusion plays a central role.

 

 

Are we happy now?

[Alex A]

Hi Mark, cheers

 

Im just wondering whether that is relevant here?, and i say that because of TIME.

 

Just been watching another video about what Jacques said and this guy states that carbon travels at approx 0.005" or in our terms 0.127mm per HOUR

 

If its the case, would it make much difference?

 

Ps Christian, i get the point of your post now, cheers

 

2.15 in this vid 

 

[mas4t0]

4 hours ago, Alex A said:

Hi Mark, cheers

 

Im just wondering whether that is relevant here?, and i say that because of TIME.

 

Just been watching another video about what Jacques said and this guy states that carbon travels at approx 0.005" or in our terms 0.127mm per HOUR

 

If its the case, would it make much difference?

 

Ps Christian, i get the point of your post now, cheers

 

2.15 in this vid 

 

 

Hi Alex,

 

Jean did some simple calculations earlier in the thread. I think the key point is that this is happening at each layer where there's a diffusion gradient. If the layers are 0.06mm thick (for example) and there's a diffusion gradient on both sides, it only has to diffuse across 0.03mm (0.06/2), which by the above numbers would take ~15 minutes. Clearly the billet spends a lot longer than 15 minutes at forge welding temperature, so we would expect full homogenisation of carbon as a result of the refining process.

 

It's not particularly relevant when considering lamination (i.e. san-mai) as there are orders of magnitude fewer layers, and they are orders of magnitude thicker. But even in that case smiths will generally forge weld a short, stout laminated billet (to maximize layer thickness and minimise diffusion) and then draw that out to form the blade.

[Alex A]

The other thing is PRESSURE, Jacques mentioned it,

 

The guy in the vid seals the tube.

 

Also says its an all day process

 

Need an honours in metallurgy to work out what is what   

 

Heading out now, will catch up later, cheers.

[Jacques D.]

20 minutes ago, mas4t0 said:

 

Hi Alex,

 

Jean did some simple calculations earlier in the thread. I think the key point is that this is happening at each layer where there's a diffusion gradient. If the layers are 0.06mm thick (for example) and there's a diffusion gradient on both sides, it only has to diffuse across 0.03mm (0.006/2), which by the above numbers would take ~15 minutes. Clearly the billet spends a lot longer than 15 minutes at forge welding temperature, so we would expect full homogenisation of carbon as a result of the refining process.

 

It's not particularly relevant when considering lamination (i.e. san-mai) as there are orders of magnitude fewer layers, and they are orders of magnitude thicker. But even in that case smiths will generally forge weld a short, stout laminated billet (to maximize layer thickness and minimise diffusion) and then draw that out to form the blade.

 

You should learn the basis of physic before talking, such the conservation mass law. Each layer of steel is a body independent of the others. The law of conservation of mass obliges you to preserve the same number of molecules or atoms in this body (constant of Avogadro). If you remove an atom you must replace it, then explain me how and by what.

 

ps your links makes me laugh a lot, thank you for that.