Mitsubishi Materials Corporation

Nissan Motor Company Limited

Koichiro Morimoto

Ryoji Nakayama

Muneaki Watanabe

Makoto Kano

Tetsurou Tayu

Kinya Kawase

Yoshio Kawashita

Katsuhiko Mori

Yoshinari Ishii

Kazunori Igarashi

Norihito Fukatsu

This rare earth magnet having high strength and high electrical resistance has a structure including an R&#x2014;Fe&#x2014;B-based rare earth magnet particleswhich are enclosed with a high strength and high electrical resistance composite layer. The high strength and high electrical resistance composite layeris constituted from a glass-based layerthat has a structure comprising a glass phase or R oxide particlesdispersed in glass phase, and R oxide particle-based mixture layersthat are formed on both sides of the glass-based layerand contain an R-rich alloy phasewhich contains 50 atomic % or more of R in the grain boundary of the R oxide particles.

Rare earth magnet having high strength and high electrical resistance

This rare earth magnet having high strength and high electrical resistance has a structure including an R&#x2014;Fe&#x2014;B-based rare earth magnet particleswhich are enclosed with a high strength and high electrical resistance composite layer. The high strength and high electrical resistance composite layeris constituted from a glass-based layerthat has a structure comprising a glass phase or R oxide particlesdispersed in glass phase, and R oxide particle-based mixture layersthat are formed on both sides of the glass-based layerand contain an R-rich alloy phasewhich containsatomic % or more of R in the grain boundary of the R oxide particles.

An object of the present invention is to provide a composite soft magnetic sintered material that has high density, high mechanical strength and high relative magnetic permeability at high frequencies and, in order to achieve this object, the present invention provides a method of producing the composite soft magnetic sintered material, which comprises mixing a composite soft magnetic powder, that consists of iron powder, Fe&#x2014;Si based soft magnetic iron alloy powder, Fe&#x2014;Al based soft magnetic iron alloy powder, Fe&#x2014;Si&#x2014;Al based soft magnetic iron alloy powder, Fe&#x2014;Cr based soft magnetic iron alloy powder or nickel-based soft magnetic alloy powder (hereinafter these powders are referred to as soft magnetic metal powder) of which particles arc coated with a ferrite layer which has a spinel structure, with 0.05 to 1.0% by weight of silicon dioxide powder having a mean powder particle size of 100 nm or less and sintering the mixed powder after compression molding, or processing two or more kinds of the composite soft magnetic powders, of which particles are coated with ferrite layer having a spinel structure of a different compositions, by compression molding and sintering.

Composite soft magnetic sintered material having high density and high magnetic permeability and method for preparation thereof

A valve seat made of an Fe-based sintered alloy excellent in wear resistance and having a reduced counterpart valve attack property is disclosed, which comprises a base comprising 15-40% by weight of Cu, 0.3-12% by weight of Ni and 0.0005-3.0% by weight of C, and further comprising 0.1-10% by weight of Co and 0.1-10% by weight of Cr when necessary, with the balance being Fe and inevitable impurities, the base having a structure which comprises an Fe-based alloy phase composed of Fe as a main component combined by a Cu-based alloy phase composed of Cu as a main component, wherein hard particles phase having MHV of 500-1700 is dispersed in the base. The Fe-based alloy phase is an Fe alloy phase which comprises Ni, Cu and C with Fe having more than 50% by weight, while the Cu-based alloy phase is a Cu alloy phase which comprises Ni, Fe and C with Cu having more than 50% by weight. At the same time, the contents of Ni and C included in the Fe-based alloy phase are more than those of Ni and C included in the Cu-based alloy phase.

Fe-based sintered valve seat having high strength and method for producing the same

A valve seat made of an Fe-based sintered alloy excellent in wear resistance and having a reduced counterpart valve attack property is disclosed, which comprises a base comprising 15-40% by weight of Cu, 0.3-12% by weight of Ni and 0.0005-3.0% by weight of C, and further comprising 0.1-10% by weight of Co and 0.1-10% by weight of Cr when necessary, with the balance being Fe and inevitable impurities, the base having a structure which comprises an Fe-based alloy phase 1 composed of Fe as a main component combined by a Cu-based alloy phase 2 composed of Cu as a main component, wherein hard particles phase 3 having MHV of 500-1700 is dispersed in the base. The Fe-based alloy phase 1 is an Fe alloy phase which comprises Ni, Cu and C with Fe having more than 50% by weight, while the Cu-based alloy phase 2 is a Cu alloy phase which comprises Ni, Fe and C with Cu having more than 50% by weight. At the same time, the contents of Ni and C included in the Fe-based alloy phase are more than those of Ni and C included in the Cu-based alloy phase.

An R--T--M alloy material, wherein R is at least one rare earth metal including Y, T is Fe or an Fe component partially replaced by Co or Ni, M is B or a B component partially replaced by C as primary components is prepared by heating the alloy at a temperature from room temperature to a specific temperature of less than 500.degree. C. in a non-oxidizing atmosphere and holding it at the given temperature, if necessary; performing hydrogenation by holding the alloy in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and an inert gas at a specific temperature in the range of 500-1,000.degree. C.; medial annealing the alloy by holding the R--T--M alloy after the hydrogenation step in an inert gas atmosphere at a specific temperature in the range of 500-1,000.degree. C.; and dehydrogenating the alloy by holding the alloy in a vacuum of less than 1 Torr for dehydrogenation, and then cooling the alloy.

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Niigata, Japan

Koichiro Morimoto