How/Why is there so many Hagire?

[Tensho]

Interesting Yari I came across. It suffers from at least 9 Hagire. Any thoughts on this? There is a large chunk taken out of the same side too. My thoughts were on tempering flaw, but seems to excessive 

 

 

 

[ROKUJURO]

In my experience this can happen in the quenching process if the heat was not evenly distributed throughout the workpiece.

 

There is a big difference in mass distribution in the cross-section of a YARI. Heating up such a blade to even temperature is extremely demanding as there is the risk of overheating the 'cutting edges' while the big mass in the core remains considerably cooler. When the thin HA area contracts in the quenching process, the YARI body remains rigid, causing a massive tension difference. This will often lead to HAGIRE.

An intense fire and a relatively short heating-up period before quenching could cause such flaws.

[1kinko]

Jean C- seems like I have questions for you on 2 subjects today-

1) I’ve only tried to make a kogatana once and when I quenched it I heard a distinct ping as the hagire occurred. That was the end of the effort for me, but I wonder how many hagire-flawed blades were polished in the old days (and this blade has way too many to miss).

2) In relation to the other subject today, have you seen hagire in kogatana made from layered forge-welded hard and soft steel?

[Tensho]

Thanks for the reply Jean. I seem to recall hearing Yari were a "challenge" to forge correctly.  

 

 

[Matsunoki]

Just a thought….to me those don’t look like “typical” hagire. Most hagire  I’ve seen are fine hairlines but these ones look as if they have opened quite a bit….and there are many of them.

I wonder if the large missing chunk is a clue? Could there have been (several?) severe sideways impact which caused that damage and at the same time caused the blade to “flex” thus causing the group of hagiri?

Never seen anything quite like it before.

Does it show any compression “wrinkles” elsewhere?

All the best

Colin

[ROKUJURO]

Hi Darrel,

I know the sound of a crack quite well. This happens from time to time when the heat-distribution in the workpiece is not correct just before quenching.
Cracks/HAGIRE are pre-determined breaking points, so a long bladed weapon for serious use would certainly fail in combat. I could imagine that poor SAMURAI sometimes carried such a flawed blade in later EDO JIDAI in the hope they would not have to use it. Of course a polisher would not miss a HAGIRE while working on a blade.

I have never seen HAGIRE in a KOGATANA, and I see no way to determine how such a blade was made (without damaging it). As Jacques mentioned, these blade were not made in composite construction, and it makes sense. But it could be done of course, and many fine kitchen knives are made that way. In Japan, HITACHI supplies a two-layered SHIRO-GAMI (plus iron) steel to knifemakers.

Get rid of the idea of combining 'hard and soft steel' to achieve a material with magic properties! In these combinations with very thin material layers, carbon diffusion is fast enough to come to a balance in the welding process. There are possibilities to test this yourself: Hold a simple nail (= very low carbon content) to your grinding wheel and observe the sparks. Now when you carbonize this nail in a good coal fire and let it soak for a short while at higher temperature, you can see the difference in the sparks later.  You can also make a test with a fine file. The carbonized outer layer will not be thick, but obvious.

 

[ROKUJURO]

Colin,

you are correct in that these HAGIRE (not hagiri) are extreme and are looking differently! We do not know what caused them; I can also think of a failed SAI HA (= retempering) attempt.

Thrusting weapons with an important cross-section are not so liable to break in action, so some poor ASHIGARU might have carried this YARI in best hope that it would not fail.

HAGIRE are always stress-related, caused by tensions in the steel. Often, they occur right after quenching, but they may appear at any time later, even when sitting in a TANSU. Of course a side impact will make them appear faster, but it is never the external force that creates them, but the mistakes made in the quenching process.

Cracks caused by mechanical failure (e.g. bending) are called SHINAE. They look different.  

[Matsunoki]

Hello Jean

I did spell it right in two places! Two out of three is pretty good for me nowadays!🙂

Thanks for the explanation. 
All the best

Colin

 

[ROKUJURO]

Congratulations Colin! 

For many new members NMB is a learning platform, and I feel it is important to present them the correct terms. 

[Jacques]

Hagire can occur at any time in the life of a sword, even during polishing.

[MarcoUdin]

1 hour ago, Jacques D. said:

Hagire can occur at any time in the life of a sword, even during polishing.

 

What about during a re-temper? Could that cause them as well?

[Mark S.]

I saw this yari on eBay as well.  I don’t mean any disrespect… but it sold (with shipping) for about $250???  Why?

[Matsunoki]

10 minutes ago, MarcoUdin said:

What about during a re-temper? Could that cause them as well?

See Jean’s comments above. I think he is suggesting that it is entirely possible.

[ROKUJURO]

42 minutes ago, MarcoUdin said:

What about during a re-temper? Could that cause them as well?

HI Marco,

as Jacques and me wrote separately, HAGIRE can appear at any time in a blade.

Re-tempering means going back to Zero with a blade. Heating it up to above 778°C erases all hardening features and tensions, but it does not bring back the basic shape of a sword which it had before the first YAKIIRE. So, SAI-HA sword blades often show a pronounced SORI.

A new tempering - be that on a sword-blade or on a YARI - can cause HAGIRE in case the above mentioned mistakes are committed. Existing HAGIRE won't of course disappear in a second tempering even if everything was made in a correct way. But it is almost certain that they will become more prominent.

[Matsunoki]

3 minutes ago, ROKUJURO said:

Re-tempering means going back to Zero with a blade. Heating it up to above 778°C erases all hardening features and tensions

Jean…..what happens to the hada and other hataraki…..is it affected by the re-hardening in any way? Do all the original nie/nioi disappear? Does the old hamon leave any trace?…..it’s interesting.

many thanks 

Colin

 

[Jacques]

What can cause a hagire during yaki-ire is the accentuation of the sori (to make it short) but there is no sori on a yari 

 

 

[Tensho]

6 hours ago, Mark S. said:

I saw this yari on eBay as well.  I don’t mean any disrespect… but it sold (with shipping) for about $250???  Why?

Thats a good question.  I was watching it as well. $250 was way too much in my opinion. I actually did not notice the large chunk taken out of the edge until I started this thread. I'm assuming someone believes it is "battle damage" Its a longer Yari with decent shirasaya and i don't see them pop up much. If it only had one Hagire $250 would have been okay imo. Yari are not as cheap to come across as they once were though.  

[ROKUJURO]

5 hours ago, Matsunoki said:

…..what happens to the hada and other hataraki…..is it affected by the re-hardening in any way? Do all the original nie/nioi disappear? Does the old hamon leave any trace?…..i

Hi Colin,

all hardening features (NIE, NIOI, HATARAKI, HAMON...) disappear, while the forging features (HADA, KITAE...) remain. There is an opinion that "shadows" of the first HAMON remain sometimes visible in a blade. 

[IBot]

The problem with yari is, unlike a sword, there is nowhere for the body of the blade to go. In other words, when a sword is quenched, the slower contraction of the body of the blade compared with that of the edge pulls it into a curve. In the case of a yari, both edges become rigid because they harden first whilst the body holds the heat longer and contracts later. If that contraction is powerful enough either the point pops off or hagire form as in the image. 

Ian Bottomley