Here my source of knowledges. It is in google cache right now. Let it stay here:
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Rich　Wulf
yasuki@seki-cut.com Sun Jul 6 20:20:38 PDT 2003
Background of premium steels including ATS-34
Yasuki hagane(preimium steel group in Japan) are used for most cutlerys respectfully in Japan. It is called YSS(Yasuki Speciality Steel) too. Although tamahagane(jewel steel for samurai sword), Sweden steel, Phenix steel born in British, etc are used also, but these are special case. Japanese blacksmiths all over Japan make the cutlery with forging Yasuki steel unexceptionally. Yasuki steel is produced at the Yasugi works of Hitachi Metals, Ltd. The predecessor of Hitachi Metals, Ltd. is Unpaku steel company founded on the background in Yasugi in 1891. A subsidiary of yasugi works has the technology of the wakou(Japan steel) production which obtains raw steel of swords,etc from the premium iron sand of the Izumo. Yasugi works was absorbed by Hitachi and the company name was changed as Hitachi Metals, Ltd. in 1967. So it is said that yasugi works is the oldest works in Hiatchi group.
The land of Izumo of Shimane province with the Yasugi works was famous as a place of production of ancient tamahagane from ancient times. Tamahagane is made from iron sand with the high purity called "Masa" which can be taken at a mountain or a river abundantly. And also the way of taking sand is called "canna nagashi" using the flow of a river, and iron specific gravity -- it is simple, but it was able to extract in large quantities by the skillful method.
Furthermore, the rich forest resources of a mountains turned into a source of supply to which charcoal required for iron manufacture is not exhausted. tamahagane of Izumo produced by the "tatara steelmaking process" which became famous for the movie "Princess Mononoke" was very good, and was shipped all over Japan as raw materials for edged tools including Japanese swords. And the market shear of steels was more than 80% till Edo period. When the modernistic steelmaking method which obtains iron from an iron ore stone was introduced using the huge blast furnace, the "tatara furnaces" which existed in Japanese every place declined quickly. However, only tamahagane of Izumo survived till the early stages of 1900s. Hitachi Metals, Ltd. which absorbed Unpaku steel company inherited the process of wako which used "Masa" sand as materials taking advantage of such a geographical advantage, and it has resulted by the end of today. The wakou museum in yasugi can be asked about the history of such iron manufacture, and it is said that Hayao Miyazaki also got the inspiration of the people of tatara steel making of "Princess Mononoke" from these exhibition things.
After that, Yasugi works had developed same directly deoxidation method as tatara without using charcoal made from woods. And also they had developed modern steelmaking process one after another. For example, ESR had been developed by USSR(now Ukuraine) under the Cold War period. ESR means Electro-Slag Remelting method. Fine solidification structure of steels can be formed without using vacuum process by this method. It put in practical use at Yasugi works as next case of USSR and the first case of western side countries. This was secret, so it was second case in Japan on official memorial. But a part of Russian people have known this fact. So yasuki steels are also now famous special steels for cutlery, auto motive parts, razor blade, heat resistance turbine blade of jet engines, tool steels because of high qualities. ATS-34, SLD(D2) are most famous and premium steel for cutlery blade all over the world. Gingami(GIN) is one of most famous grade for razor blade steel too.
And also high carbon pure steels like a tamahagane, Shirogami,Aogami are famous as professional wood-craftmen or chefs cutlery use in Japan. It is considered that these steels become a good fine microstructure at the time of use. However, also edge-performance is greatly dependent on skills of craftsmen who makes them from such steels,etc. That status can be felt by beauty of blade surface. Excellent craftmen or merchants using Yasuki steel are Toyokuni, Misuzu, Hiro, Munemitsu, Masutaro, Okatsune, Tadafusa Saji, Okuda, Takeuchi, Okayasu, Yamashita, Ito, Yoshiharu, Sasada, Minegishi, Totsuka, Kato, Ohgi, Umetoku, Aoyama, Nichiei, Koyama, Hiyoshi, Takefu Tajima, Kawai, Sandoh, Kamishima, Futaba, Kyoshin, Daido, Aichi, Koshiha Sanyo, Tosen, Sakaguchi, Furuichi, Nichidai, OSG and Kanesane, etc. in Japan. And also yasugi works is famous as metal supplier for electronics now.
By the way, in case of steels indication, it is called "Yasuki". And also in case of place indication, it is called "Yasugi" historically.
(refference)
http://www.nausicaa.net/miyazaki/mh/MakingOfMH/Part1.html
http://www.joho-shimane.or.jp/dentou/hagane/giho_e.htm
http://www.hitachi-metals.co.jp/e/corp/corp07/s_yasu.html
http://www.joho-shimane.or.jp/dentou/hagane/index_e.htm
http://www.japanese-knife.com/steel/
http://www.thesushibar.com/sushi_chipcolumn.shtml
http://www.hks.co.jp/english/sentan.asp
http://www.misuzu-hasami.co.jp/yasukikou.html
http://www.hitachi-metals.co.jp/tatara/
http://www.wakou-museum.gr.jp/
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