Thread: 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:



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.



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




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.




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.




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.

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

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

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

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.

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

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.

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.

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.