Iwasaki Tamahagane Information

I copied this post from the Buy/Sell/Trade section. I thought this forum would be a better place for discussion.

Here is the razor:

Attachment 294908

The tip was broken off by an accident involving a display cabinet.

These are my initial results from working with the tip of the broken Iwasaki Tamahagani razor. Please remember, this only shows the results involving this blade tip from this razor. These findings should not be taken as being representative of all Iwasaki tamahagane razors.

Attachment 294909

The sectioned tip. Sadly, the thinnest part broke off. I will try to make a sample from it in the future.
Honing angle - 17.6 degrees


Attachment 294910

Micro-hardness tester marks. These are shown through my regular microscope using an adapter from Amazon and my iPhone.
Hardness - 62.8 HRC (Converted from Knoop values). I was a little surprised by this. Iwasaki razors have a reputation of being very hard.


Attachment 294911

This is very fine martensite with a lot of excess carbides. In tamahagane, the carbides should be cementite. This much excess carbide in the martensite shows the steel is very high Carbon. My guess is 1%, or more.

The large dark spot is the only substantial inclusion in the entire blade section. It is likely Silica. The smaller dark spots are also inclusions. But, they are so small, they are inconsequential. There is no evidence of weld seams from folding and welding.


Attachment 294913

This also shows a lot of Carbon! There is laminar pearlite as well as spheroidal cementite. I shifted the light a bit to make the cementite stand out. As in the martensite photo, the steel is very clean. This leads me to think that Iwasaki came up with a way to refine the tamahagane that did not use the traditional folding and welding.

Overall, the steel is very high Carbon, and very clean. This is very uncharacteristic for forge welded tamahagane. There are very few inclusions of any kind.There is no evidence of forge welding. It is possible the raw tamahagane was re-melted in a crucible, and then forged to bars and blades. This is my current "guess".

That's all for now. More to follow.

I would guess that you're correct about the crucible, remember that Hitachi made a iron sand steel that was manufactured by modern methods. I'm reasonably sure Hitachi steel wan't forge-folded by hand. Maybe they copied whatever Iwasaki was doing?

Cheers, Steve

I was also led to believe that not all his Tamahagane razors were high Rockwell numbers, some of them were HV 900 Rockwell 67, and some were HV 860 Rockwell 66, some were HV 810 and 815 and HV 790, some of his Swedish steel razors are harder than his Tamahagane razors, all the info is on the original boxes, I have one of his early razors and that's Rockwell 64 and that's made from Swedish steel.

Like Jamie said, one tamahagane I have is HV 786 while the Iwasaki 30 swedish steel is listed on the box as HV 820.

I find it admirable (yet a little amazing) that you gents know so much about this subject. :chapeau

Quote:

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Originally Posted by Steve56

I would guess that you're correct about the crucible, remember that Hitachi made a iron sand steel that was manufactured by modern methods. I'm reasonably sure Hitachi steel wan't forge-folded by hand. Maybe they copied whatever Iwasaki was doing?

Cheers, Steve

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I believe the Tamahagane used by Iwasaki was from ancient Tamahagane.
　Hide's Export　　: Iwasaki and Tamahagane

A good read too

Hitachi Metals>Tale of tatara>Tama-hagane and the Japanese sword

Quote:

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Originally Posted by markbignosekelly

I believe the Tamahagane used by Iwasaki was from ancient Tamahagane.
　Hide's Export　　: Iwasaki and Tamahagane

A good read too

Hitachi Metals>Tale of tatara>Tama-hagane and the Japanese sword

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Thanks for putting that up Mark, it's always good to read something I've not seen before.

Hides Export is a great blog, he also talks to Iwasaki San about his honing methods and also talks with Iizuka San (student of Iwasaki) of Shigefusa knives.

Quote:

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Originally Posted by Steve56

I would guess that you're correct about the crucible, remember that Hitachi made a iron sand steel that was manufactured by modern methods. I'm reasonably sure Hitachi steel wan't forge-folded by hand. Maybe they copied whatever Iwasaki was doing?

Cheers, Steve

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More likely that this is a common process. Iwasaki was unlikely to be the first to think of this because it just makes sense. Folding is a very inefficient way to get rid of bloomery slag and inclusion. Plus, tamahagane starts out witha very high carbon content (the stuff for edge sections in any case) but after all the folding and forge welding, the carbon drops substantially if done by traditional methods. Mike Blue once told me that about 60% of tamahagane is lost as forging scale this way, and the carbon content drops from 1.4 to 0.7 to make sword grade steel.

Quote:

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Originally Posted by Bruno

More likely that this is a common process. Iwasaki was unlikely to be the first to think of this because it just makes sense. Folding is a very inefficient way to get rid of bloomery slag and inclusion. Plus, tamahagane starts out witha very high carbon content (the stuff for edge sections in any case) but after all the folding and forge welding, the carbon drops substantially if done by traditional methods. Mike Blue once told me that about 60% of tamahagane is lost as forging scale this way, and the carbon content drops from 1.4 to 0.7 to make sword grade steel.

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Bruno,

Those are very good general numbers. I typically lose 50% over 13 folds. The highest Carbon content I have ever had is about 1% in the finished steel. Usually, I end up with about 8% Carbon. Plus, the Silica never completely goes away. The more I look at the micrographs, the more I think the Iwasaki steel was melted, at some point.

Very intersting thread.
It is well known that Dr. Kosuke Iwasaki, the father of Shigeoshi Iwasaki, did a special refining of traditional tamahagane to adapt the steel properties and characteristics from traditional katana sword steel to razor tamahagane, which need different charateristics. It is also known that Shigeoshi Iwasaki sent out razors with different hardening to Barbers all around Japan to get feedback of their performance. A lot of the Barbers were not able to sharpen the very hard razors successfully. So they sent it back to Iwasaki. With a new heat treatment at lower Rockwell numbers most of the Barbers did manage the sharpening much better. This might be one reason why some Iwasaki razors are reaching hardness beyond 65 HRC, others stay below.
Also this leds Iwasaki to write his essay about sharpening razors and Nihon kamisoris.

Here is a quick update. For the last five weeks, I have had the pleasure of shaving with an Iwasaki tamahagane razor. I can understand why they are so sought after. It is truly a special razor. Here is a photo of the Iwasaki razor, with my Jnats as background props.

Attachment 304570

I was able to do some micro-hardness tests along the hone wear zone near the spine. I got a consistent reading of 63.5HRC (converted from Knoop values). I am guessing the edge hardness will be 64 - 65HRC.

The honing angle is just under 19 degrees. It does seem like Iwasaki liked honing angles on the obtuse side. But, it certainly hasn't effected the shave. Every shave has been splendid.

I finish honed it on a vintage Nakayama Kiita Naishi (bottom left in photo). Stropping has been with Kanayama canvas and cordovan.

More to follow...

Tim, I'd be hard pressed to choose a favorite razor between my Iwasaki Tamahagane and my custom Zowada. While one shaves like no other in my collection, the other produces an excellent shave in addition to being the an exceptionally beautiful razor that I'll always treasure. One thing I've enjoyed about this hobby is that there is always something new to learn, and I'm impressed with some of your new adventures and your obvious enjoyment in them.

Tim, I don't want to put you on the spot, but I'd think that all of us would love to hear exactly why you think the Iwasaki tamahagane is so special. You're in a pretty unique position as a no-shi!t razorsmith who makes his own steel to tell us what is so special about Iwasaki razors, beyond the interesting HRC values.

It's unlikely I'll ever own one. But living vicariously through you, it would be nice to have a detailed insider's take.

(I met you years ago at an SRP meet-up in Asheville, NC, and you were gracious to me and everybody else, answering every question we all had. It was great, a very fond memory.)

So let's start with the 19 degree bevel angle (!?) and just work back from there, in glorious detail. :beer1:

Ashvlle, North Carolina .... wow, that was a long time ago. :)

I'm pretty busy for the next couple days. I have a funeral to attend...

I'll give it some thought and get back to you.

Quote:

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Originally Posted by FatboySlim

Tim, I don't want to put you on the spot, but I'd think that all of us would love to hear exactly why you think the Iwasaki tamahagane is so special. You're in a pretty unique position as a no-shi!t razorsmith who makes his own steel to tell us what is so special about Iwasaki razors, beyond the interesting HRC values.

It's unlikely I'll ever own one. But living vicariously through you, it would be nice to have a detailed insider's take.

(I met you years ago at an SRP meet-up in Asheville, NC, and you were gracious to me and everybody else, answering every question we all had. It was great, a very fond memory.)

So let's start with the 19 degree bevel angle (!?) and just work back from there, in glorious detail. :beer1:

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Quote:

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Originally Posted by Tim Zowada

Usually, I end up with about 8% Carbon. Plus, the Silica never completely goes away.

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Did you mean 0.8%, as a typical range for high carbon steel would be 0.3-1.7%, or did I miss something here?


B.

Oops! I’m sorry. I missed the decimal point. I’ll. Get it fixed.

Thank you.


Update: The post, #10, is too old to edit. The correct value is 0.80% Carbon.

Thank you for your understanding regarding my poor typing skills.

Quote:

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Originally Posted by beluga

Did you mean 0.8%, as a typical range for high carbon steel wouold be 0.3-1.7%, or did I miss something here?


B.

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Okay. Here we go. Rather than write a long essay, I'll make a list of points why I think the Iwasaki tamahagane razors are so special.

1. Exceptional craftsmanship. This encompasses a lot of things. The most notably, the care taken to do things well. Iwasaki took the time and effort to do things like hardness testing. Doing a micro-hardness test on a finished razor is extremely difficult. Most likely, they took the time to prepare a metallurgical sample for each steel and heat treat batch. My procedures are probably pretty similar. It takes about an hour to make and polish a sample for micro-hardness testing. Also, the grinding and evenness of the honing bevel is wonderful.

2. Doing something difficult. Traditional forge welded tamahagane usually has too many Silica inclusions to make a good razor. To provide consistency in his steel, Iwasaki took the time to melt the tamahagane in a crucible. This is a complex process as well. This removed much of the Silica. What was left became so small as to be inconsequential. With traditional forge welded tamahagane, every batch can be quite different in Carbon content, Silica content, and other properties.

Tamahagane is very "fussy" in heat treatment. Even the best Japanese smiths lose about 30% of their blades, due to cracking during heat treatment. Most of us have seen the photo of Iwasaki's scrap pile. Those blades most likely cracked during heat treatment. Yet, they were kept, most likely for re-melting. The commercial steels of the time could have been hardened in oil, eliminating the cracking problem. A tamahagane razor was worth the cost of losing about 30% of his production. All of this during a time when straight razor popularity was decreasing!

3. Melding the ancient with the modern. This is an area where one could wax poetic for hours. Iwasaki took the best from ancient Japanese steel making and melded it with modern metallurgy to produce an exceptional product.

4. Unique functional properties. The most notable is the low abrasion resistance of tamahagane. It is possible to keep an Iwasaki tamahagane razor sharp for a very long time, with just canvas and leather stropping. This is amazing. The closest modern steel would be 1095. But, it's not the same at all. 1095 has a much higher abrasion resistance, at the same hardness. I'm hoping to work with a local metallurgy lab, to quantify some of this. If you ever have the opportunity to hand sand a piece of hardened tamahagane and a piece of hardened 1095, the difference is easy to feel.

5. Limited availability. Supply and demand...

I don't think the honing angles are anything special. My guess is Iwasaki simply found the angles that worked best with his steel and heat treatment. Seeing this does tempt me to tinker with my Timahagane honing angles.

I'm sure there is more I will come up with. But, this is a start. Studying these razors and their makers has shown me the potential of what can be achieved with ancient steels. It is certainly motivation to get out in the shop and smelt some steel.

More to follow...

Tim Z.

Quote:

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Originally Posted by FatboySlim

Tim, I don't want to put you on the spot, but I'd think that all of us would love to hear exactly why you think the Iwasaki tamahagane is so special. You're in a pretty unique position as a no-shi!t razorsmith who makes his own steel to tell us what is so special about Iwasaki razors, beyond the interesting HRC values.

It's unlikely I'll ever own one. But living vicariously through you, it would be nice to have a detailed insider's take.

(I met you years ago at an SRP meet-up in Asheville, NC, and you were gracious to me and everybody else, answering every question we all had. It was great, a very fond memory.)

So let's start with the 19 degree bevel angle (!?) and just work back from there, in glorious detail. :beer1:

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Great post Tim!
Let me add something to the list that is somehow special in my eyes.
This is producing a razor in total and really from the beginning on. Not starting with a blanket and simply grinding and finishing. Starting with the original material that was given from nature - iron ore. Refining this pure natural material to get something special - adopted to the max to what it should be used for. Than forging, heat treatment, grinding, finishing. So doing the whole process from beginning to the end. And putting together the best knowledge of all simple steps. Dr. Kosuke Iwasaki was a master of metallurgie and history of ancient tamahagane swords.
Shigeoshi Iwasaki learned bladesmithing from the best bladesmith of his time and region. With the great master in producing western straights at this time - Yukio Kamijou, Iwasaki learned forging and heat treatment of western straight razors. The collaboration with Tanifuji brought the finishing and everything else to get a perfect product.
So the last steps might have nothing to do especially with the tamahagane razors. But it rounds up the whole process, since Iwasaki brought together the best of all - knowledge, skill and experience. And this in all steps of producing a razor.

Regards Peter

I'll add that Shigeyoshi Iwasaki also puts back into his community, he teaches young smithys his skills. He has also passed on his knowledge to developing countries,
a very noble thing to do.

That it an incredible amount of thought/skill/care put into their razors. Thanks for the information.