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'''KS Steel''' is a permanent [[magnetic]] [[steel]] with three times the [[magnetic reluctance]] of [[tungsten steel]], which was developed in 1917 by the Japanese scientist and inventor [[Kotaro Honda]]. "KS" stands for [[Kichizaemon Sumitomo]], the head of the family-run conglomerate, who provided financial support for the research leading to KS Steel's invention. Honda would go on to invent [[NKS steel]] in 1933 whose magnetic resistance is several times higher than that of KS Steel.<ref>{{cite web |title=KS steel |url=http://www.riken.jp/en/research/inventions/ks/ |publisher=Riken |access-date=16 December 2018}}</ref>
== History ==
After World War one, when Japan had to cope with painful restrictions on imports of materials from foreign countries such as Germany, physicist Kotaro Honda was motivated to study alloys due to the need of a domestic steel production. He opened up his RIKEN-Honda Laboratory at Tohoku Imperial University in 1922 after he invented KS steel in 1917; it is a permanent magnetic steel with three times the magnetic resistance of [[tungsten steel]].<ref>{{cite web |title=KS steel |url=http://www.riken.jp/en/research/inventions/ks/ |website=Riken |accessdate=16 December 2018}}</ref> The initials KS in the name of the steel come from Kichizaemon Sumitomo, who was the head of the family that provided financial support for the research leading to the invention.
== Material properties ==
The composition of KS steel is 0.4–0.8 percent [[carbon]]; 30–40 percent [[cobalt]]; 5–9 percent [[tungsten]]; and 1.5–3 percent [[chromium]]. KS steel is best tempered when heated to 950&nbsp;°C and then quenched in heavy oil. The residual magnetism is reduced by only 6 percent when artificially aged.<ref>{{cite journal |title=On K. S. Magnet Steel |journal=Physical Review |volume=16 |issue=6 |pages=495–500 |doi=10.1103/PhysRev.16.495 |year=1920 |last1=Honda |first1=Kôtarô |last2=Saitô |first2=Shôzô |bibcode=1920PhRv...16..495H }}</ref> The yield strength of KS steel is above 500 and tensile strength is above 620 and elongation is above 14. The [[maximum energy product]] (BH)max of KS steel is 30 kJ/m^3.<ref>{{cite book|author1=R. E. Smallman|author2=A.H.W. Ngan|title=Physical Metallurgy and Advanced Materials|url=https://books.google.com/books?id=fHFogyL7VlkC|year=2011|publisher=Elsevier|isbn=978-0-08-055286-6}}</ref>
==See also==
* [[MKM steel]]
* [[RIKEN]]
* [[Ten Japanese Great Inventors]]
==References==
{{reflist}}
[[Category:Steels]]
[[Category:Japanese inventions]]
[[Category:1917 introductions]]
[[Category:Magnetic alloys]]
[[Category:Ferromagnetic materials]]
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