Hitachi Metals, Ltd.

Masahiro Takahashi

Kimio Uchida

Fumitake Taniguchi

Shigeho Tanigawa

Masaaki Tokunaga

Masahide Kawabata

Katsuhiko Kojo

Akira Kikuchi

Senri Okada

Yoshio Igarashi

Toshiki Yoshida

Syuichi Takano

Kenya Matsuyama

Hideharu Nakano

Masamichi Ozaki

A sintered ferrite body having a main composition comprising 63-80% by mol of FeO, and 3-15% by mol of ZnO, the balance being manganese oxide; Rdetermined from the FeOcontent X (% by mol) by the formula (1) of R=[200(X&#x2212;50)]/(3X), and the ratio R (%) of Feper the total amount of Fe in the sintered body meeting the condition of R&#x2212;2.0&#x2266;R&#x2266;R+0.3; and the sintered body having a density of 4.9 g/cmor more.

Sintered ferrite and its production method and electronic part using same

A method of producing an R--Fe--B-based, sintered permanent magnet, wherein R is at least one rare earth element including Y, having a small oxygen content. A coarse alloy powder prepared by a reductive diffusion method is milled and recovered into a solvent to form a slurry. The slurry is wet-compacted to form a green body which is then sintered after removing the solvent. The milling, recovering, wet-compacting, solvent-removing and sintering steps are carried out while preventing the powder, slurry and green body from being brought into contact with air to minimize the oxygen content in the final sintered permanent magnet. The sintered permanent magnet produced has a high density and a high magnetic properties due to a low oxygen content.

Rare earth permanent magnet and production method thereof

An additive for use in producing spheroidal graphite cast iron of the present invention contains a fine particle of magnesium oxide having a purity of 90 weight % or more and at least one selected from the group consisting of a graphite-spheroidizing material, an inoculant and a graphite-spheroidizing inoculant. The fine particle of highly pure magnesium oxide increases the number of nuclei in a melt, and as a result thereof, increases the graphite spheroid count of a spheroidal graphite cast iron being produced. Another additive for use in producing spheroidal graphite cast iron of the present invention contains at least one selected from the group consisting of a graphite-spheroidizing material, an inoculant and a graphite-spheroidizing inoculant, and an oxide of a metal which has, at a temperature of a melt at a time when subjected to a graphite-spheroidizing treatment, an affinity for oxygen smaller than that of a graphite-spheroidizing element being used in the graphite-spheroidizing treatment. By adding to the melt the metal oxide which oxidizes the graphite-spheroidizing element in the melt to an oxide thereof, a great number of fine oxide particles of the graphite-spheroidizing element is dispersed in the melt to provide a spheroidal graphite cast iron having a great number of fine graphite spheroids and a small chill area ratio.

Additive for use in producing spheroidal graphite cast iron

A rare earth permanent magnet consisting essentially, by weight, of 27.0-31.0 % of at least one rare earth element including Y, 0.5-2.0 % of B, 0.02-0.15 % of N, 0.25 % or less of O, 0.15 % or less of C, at least one optional element selected from the group consisting of 0.1-2.0 % of Nb, 0.02-2.0 % of Al, 0.3-5.0 % of Co, 0.01-0.5 % of Ga and 0.01-1.0 % of Cu, and a balance of Fe, and a production method thereof. The contents of rare earth element, oxygen, carbon and oxygen in the magnet are regulated within the specific ranges.

Rare earth permanent magnet and method for producing the same

A rare earth permanent magnet consisting essentially, by weight, of 27.0-31.0% of at least one rare earth element including Y, 0.5-2.0% of B, 0.02-0.15% of N, 0.25% or less of O, 0.15% or less of C, at least one optional element selected from the group consisting of 0.1-2.0% of Nb, 0.02-2.0% of Al, 0.3-5.0% of Co, 0.01-0.5% of Ga and 0.01-1.0% of Cu, and a balance of Fe, and a production method thereof. The contents of rare earth element, oxygen, carbon and oxygen in the magnet are regulated within the specific ranges.

An R-Fe-B-based, sintered magnet, wherein R is one or more of rare earth elements including Y, is produced by the method including the steps of mixing fine R-Fe-B-based magnet powder with a mineral oil and/or a synthetic oil having a fractional distillation temperature range of 150.degree.-400.degree. C. and a kinetic viscosity of 10 cSt or less to prepare a mixture; charging the mixture under pressure into a die cavity equipped with a filter, to which an orientated magnetic field is applied, while removing a mineral oil and/or a synthetic oil from the mixture; compressing the mixture in the die cavity to carry out a wet molding while orientating the powder to prepare a green body; heating the green body to a temperature up to 500.degree. C. at a speed of 10.degree. C./min or less under pressure of 10.sup.-1 Torr or less for 30 minutes or more to remove a mineral oil and/or a synthetic oil from the green body; and then sintering the green body.

Method for producing R-Fe-B-based, sintered magnet

Disclosed is a Nd-Fe-B system magnet having coercive force iHc of 12 KOe or more and high maximum energy product (BH)max of 42 MGOe or more. The permanent magnet consists of 28 to 32 wt. % of Nd and Dy (Dy ranges from 0.4 to 3 wt. %), 6 wt. % or less of Co, 0.5 wt. % or less of Al, 0.9 to 1.3 wt. % of B, at least one of 0.05 to 2.0 wt. % of Nb and 0.05 to 2.0 wt. % of V, 0.02 to 0.5 wt. % of Ga, Fe and unavoidable impurities, having coercive force iHc of 12 KOe or more and maximum energy product (BH)max of 42 MGOe or more.

Growing community of inventors

Kumagaya, Japan

Masahiro Takahashi