Whats happening to create a hamon?

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unky_gumbi

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Aug 28, 2009
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I have been playing a bit with temper lines for the last little bit on some 1084. I am getting nice lines, but never the nice wispy line that people get in W series steels. I know that is from the steel I have been using, but I do have a couple of W2 blanks waiting for my real forge to be finished.

I have read many tutorials on hamons, but what i am wondering is just what is going on in the steel that creates the hamon. I know it is a boundary of sorts between the fully hardened steel and the unhardened steel. I would also like to know what causes the wispy lines with the depth to them.

I am hoping that a bit of explaination of what is going on in the steel will hep me get it right the first time when I do move to the W2 blanks I made.

Thanks

Now its off to do some household chores before sanding out my latest temper line attempt. I know I have something there, just not how much:o
 
The wispy lines are called Ashi. They are formed by coating your clay in thin lines running from the main body of the clay towards the edge. They are small strips of steel caught between the hardened and unhardened state. I would be inclined to say that they are mostly hard, as the sections of steel we use are very thin compared to industry standard, and maybe it is mostly a surface thing, i am unsure. I know they sure do look good :)
 
OK, here it is in fairly plain metallurgical and hamon terms ( many hamon terms have no English word):

The blade must be made from a steel with medium carbon to higher carbon content, and there must be a low alloy content - especially low manganese. The steel is usually referred to as shallow hardening. Any steel with alloy ingredients high enough to affect the HT parameters will make the hamon weak or not there at all.

The blade is covered with a thin layer of clay, and the spine is covered with a slightly thicker layer. Often small lines of thicker clay are run from the spine coat to the edge.

Now, the blade is evenly heated to bring the entire blade about 50 degrees above Ac1, or non-magnetic. At this point all the steel is austenite.

The blade is quenched in a media that is fast enough to cool the edge in time to pass the pearlite nose, but slow enough to allow the clay coated spine hit the nose. This will send the edge on down toward the martensite start point (Ms) at around 400F. The spine goes straight into pearlite. Often the blade is pulled briefly from the quenchant to make sure the spine cools slower, and allow the heat from the spine to drive the hamon lower. This is called an "Interrupted quench".

The area where the thick clay meets the thin clay will be a border of these two structures. Since the two migrate from opposite directions, some of each goes into the other. This ghostly line of tiny martensite crystals ( called NIOI) dispersed in the pearlite compose the hamon. In places where the clay popped off the spine or was thinner, there may be pools of martensite crystals (NIOI), these pools are called NIE.

This mixture of martensite and pearlite was called troosite a long time ago, but now is just called the "martensite-pearlite transition zone".

In the area where the thin lines of clay go toward the edge, the Nioi crystals follow, making little wisps called Ashi.

The exact position of the hamon depends on many factors, but usually is just toward the edge from the thicker clay.

Just to explain the Nie vs Nioi:
Think of the nioi as fine ice crystals in the air - you might see the shimmer, but won't really see the individual crystals.
When the crystals clump together in the form of snow, they are clearly visible - that is the Nie.
I guess you could call the hamon a snowdrift.

Hows that for poetic, tai?
 
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bladsmth said:
OK, here it is in fairly plain metallurgical and hamon terms ( many hamon terms have no English word):

The blade must be made from a steel with medium carbon to higher carbon content, and there must be a low allow content - especially low manganese. The steel is usually referred to as shallow hardening. Any steel with alloy ingredients high enough to affect the HT parameters will make the hamon weak or not there at all.

The blade is covered with a thin layer of clay, and the spine is covered with a slightly thicker layer. Often small lines of thicker clay are run from the spine coat to the edge.

Now, the blade is evenly heated to bring the entire blade about 50 degrees above Ac1, or non-magnetic. At this point all the steel is austenite.

The blade is quenched in a media that is fast enough to cool the edge in time to pass the pearlite nose, but slow enough to allow the clay coated spine hit the nose. This will send the edge on down toward the martensite start point (Ms) at around 400F. The spine goes straight into pearlite. Often the blade is pulled briefly from the quenchant to make sure the spine cools slower, and allow the heat from the spine to drive the hamon lower. This is called an "Interrupted quench".

The area where the thick clay meets the thin clay will be a border of these two structures. Since the two migrate from opposite directions, some of each goes into the other. This ghostly line of tiny martensite crystals ( called NIOI) dispersed in the pearlite compose the hamon. In places where the clay popped off the spine or was thinner, there may be pools of martensite crystals (NIOI), these pools are called NIE.

This mixture of martensite and pearlite was called troosite a long time ago, but now is just called the "martensite-pearlite transition zone".

In the area where the thin lines of clay go toward the edge, the Nioi crystals follow, making little wisps called Ashi.

The exact position of the hamon depends on many factors, but usually is just toward the edge from the thicker clay.
Click to expand...

That's the sort of explanation I was looking for. I knew pretty much how to create one, I was just interested in what the crystalline structure was that caused it to stand out and you explained it well, thank you.

Danbo said:
And, it looks really cool! ;) :)
Click to expand...

Yes this too. Even though I still haven't achieved a true hamon, the temper lines I have gotten on 1084 shift and shimmer, almost as if you can see into the steel when the blade is twisted in the light. It is one of those things that you just can't see in a picture, you have to experience it in person. I can't wait to see a true hamon in person, hopefully it will be my own when I HT the W2 next month:D
 
George,
You have described exactly what the nioi is. You can't see it individually without magnification, but the movement of light across it makes the white look. That is also why it is so hard to photograph. Your eye/brain has a memory of the image you are seeing at about 200 frames per second. While you think you are looking at the knife and hamon as a static object, your brain sees the tiny changes every 5 milliseconds. The camera sees it one time, for about 1-4 milliseconds (shutter speed of 1000 to 250).
That is also why a curvaceous woman may look far better in person than in a photo....although Rick has only seen photos of curvaceous women.
 
Robert Dark said:
OR, she may look a whole lot worse. Folks can doctor photos, but you just can't doctor real-live-ugly.

Robert
Click to expand...

I really don't understand what you are talking about
goggles.jpg
 
If you expect the coolest looking hamon you have to polish the traditional way . Any attempt at fast polishing , power tools grinder , buffer etc will damage the delicate structures !!
 
I read an article that said the heat generated in grinding the blade post-HT would greatly change the structure of the hamon. The writer claimed the heat would change the delicate balance of structures.
 
I could see that happening if you let the blade get too hot to handle, but I am pretty sure that my blades get hotter during the temper cycles then they do when I am cleaning them up on the grinder. Even more so right now with the temps hovering around freezing most of the time. I don't go to heavy on the blades after HT, I use a very light touch, slow speeds and a Norax U264 X16 (aprox. 320g) belt followed by a Norax U264 X22 (aprox. 750g) to clean up any scale, clay and pits I may have. I also dip after every pass even if I don't feel and heat. After I finish the clean up I hand sand out to 2500g and start the etching process using the Nick Wheeler method.
 
I too agree with Danbo. Or maybe its I find his avatar agreeable. I know... both.
 
Unky, you should get a copy of The Craft of the Japanese Sword. Anyone interested by hamons will love this book. I've read it over and over, it's refreshingly free of the BS that can often be found in works about the Japanese sword. Lots of good pics.
 
I will have to look that up, thanks. I started looking into hamons as a whim, but quickly got caught up with what is going on with them. That and it is so much cheaper for me to buy a piece of W series steel that some Damascus to ass some flash to a special piece.



Just looked it up, it is available through Chapters for $38, but they only have 3 left so it looks like I will have to order it soon:eek:
 
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That is indeed a good book. Another is:
The Art of Japanese Sword Polishing ,by Setsuo Takaiwa. I find this book invaluable for togi.

George,
Believe it or not, even sharpening a knife on a stone will create an amazing amount of heat at the junction of the stone and the steel. If the metal is contacting a moving abrasive belt, the amount can be well above the tempering point at the junction. The blade may only get barely warm, because the heat is drawn into the cooler mass of the core, but the skin on the surface can be affected. This can be a big deal on a very fine edge. On a hamon, there is the added mechanical process of dragging one structure into the other. This "blending" along with the surface heating to temos approaching the upper pearlite range can wipe out a weak hamon, and greatly diminish a bold one.
Roman Landes has done extensive study on unintended tempering during sharpening.

If you need a real time example to show the amount of heat generated, take a piece of 1084 and shape the end to a sword tip shape. Harden the bar and temper it. Now lean into the grinder for just a second on the tip. It will turn dark blue instantly. The bar still is in your bare hands and didn't get warm. The tip went to 500-600F in a split second.
Now lean in hard and watch the tip turn red. If you do this quickly, and pull it off fast, the bar won't even get warm. The tip edge got about 1000F, but the bar is still 80F.
 
bladsmth said:
Harden the bar and temper it. Now lean into the grinder for just a second on the tip. It will turn dark blue instantly. The bar still is in your bare hands and didn't get warm. The tip went to 500-600F in a split second.
Now lean in hard and watch the tip turn red. If you do this quickly, and pull it off fast, the bar won't even get warm. The tip edge got about 1000F, but the bar is still 80F.
Click to expand...

All my first grind attempts on my 1x42" resulted in blue or disappearing tips.. the heat is very quick indeed.
What do you suggest for post HT grinding when you're going for a hamon, hand sanding only?
 
bladsmth said:
That is indeed a good book. Another is:
The Art of Japanese Sword Polishing ,by Setsuo Takaiwa. I find this book invaluable for togi.

George,
Believe it or not, even sharpening a knife on a stone will create an amazing amount of heat at the junction of the stone and the steel. If the metal is contacting a moving abrasive belt, the amount can be well above the tempering point at the junction. The blade may only get barely warm, because the heat is drawn into the cooler mass of the core, but the skin on the surface can be affected. This can be a big deal on a very fine edge. On a hamon, there is the added mechanical process of dragging one structure into the other. This "blending" along with the surface heating to temos approaching the upper pearlite range can wipe out a weak hamon, and greatly diminish a bold one.
Roman Landes has done extensive study on unintended tempering during sharpening.

If you need a real time example to show the amount of heat generated, take a piece of 1084 and shape the end to a sword tip shape. Harden the bar and temper it. Now lean into the grinder for just a second on the tip. It will turn dark blue instantly. The bar still is in your bare hands and didn't get warm. The tip went to 500-600F in a split second.
Now lean in hard and watch the tip turn red. If you do this quickly, and pull it off fast, the bar won't even get warm. The tip edge got about 1000F, but the bar is still 80F.
Click to expand...

I realize just how quickly the steel can heat up, I have the burn scars to prove it:o When I am cleaning up a HT'd blade my bare fingers are right over the part of the blade that is on the belt and I am looking for that instant bluing affect. What I didn't realize is that even though my fingers are right over top of the part that is on the belt at all times is that there was a considerable amount of heat there that I am not feeling. I also touch the side of the blade that was on the belt to check the temp as soon as I finish a pass and it is on the way to the dip bucket. Being that I send most of my blades out for HT I am always concerned about screwing up the HT.

On a related note Stacy, I have been reading pretty much every hamon thread that has come up and I see it suggested to those that are doing a brine quench to leave the edges extra thick. If grinding can ruin your hamon wouldn't grinding through the extra material left for a brine quench be risking ruining your work? I have no intentions of trying a brine quench BTW I am not that daring:eek:
 
mgysgthath said:
All my first grind attempts on my 1x42" resulted in blue or disappearing tips.. the heat is very quick indeed.
What do you suggest for post HT grinding when you're going for a hamon, hand sanding only?
Click to expand...

My grinder is a GIB with a VFD and when I am doing my clean up I have it slowed right down to about 25% so that would be in the range of 900 SFP
 
When you ruin your first really good hamon, please remember that you were told not to use a grinder to clean it up. ;)
 
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