Kobe Steel, Ltd.

Tomotsuna Kamijo

Hirofumi Hojo

Hiroyuki Mitani

Wataru Urushihara

Takeshi Ohwaki

Mamoru Hosokawa

Mikako Takeda

Nobuaki Akagi

Masamichi Chiba

Takeo Miyamura

A powder for a powder magnetic core, being composed of iron-base soft magnetic powder particles which each have a phosphoric acid-based chemical conversion coating on the surface. In this powder, the maximum thickness of the phosphoric acid-based chemical conversion coating is 20 to 200 nm, and recessed portions are formed on the surface of the chemical conversion coating with the total area of openings of the recessed portions being 0.5 to 50% by area relative to the total area of the observation visual fields, as determined by observing ten or more parts of the surface of the phosphoric acid-based chemical conversion coating through a scanning electron microscope with a magnification of 10000&#xd7; or more.

Powder for powder magnetic core, and powder magnetic core

A powder magnetic core which exhibits a high compact density and a reduced iron loss can be obtained by compacting a soft magnetic powder in which the mass ratio of soft magnetic powder particles that pass through a filter having an opening of 75 &#x3bc;m is 95 mass % or higher relative to the whole amount of the soft magnetic powder and which has a mean strain of less than 0.100%.

Iron powder for powder magnetic core and process for producing powder magnetic core

Disclosed is an iron-based soft magnetic powder for dust core use, which includes an iron-based soft magnetic matrix powder and a phosphate conversion coating on a surface of the matrix powder. The phosphate conversion coating contains nickel element and has an aluminum content of equal to or less than that in the matrix powder. The iron-based soft magnetic powder has such excellent heat resistance as to maintain electrical insulation at satisfactory level even after subjected to a high-temperature heat treatment.

Iron-based soft magnetic powder for dust core use, manufacturing method thereof, and dust core

Provided is an iron-based soft magnetic powder for dust core having a less coercive force, which is obtained by specifying the amount of inclusions in the iron-based powder for dust core, and at the same time, capable of decreasing the coercive force of a dust core produced using the iron-based soft magnetic powder. The iron-based soft magnetic powder for dust core is characterized by that when the cross-section of the iron-based soft magnetic powder particle is observed with a scanning electron microscope, the number of inclusions having an equivalent circle diameter from 0.1 to 3 &#x3bc;m is 1&#xd7;10pieces/mmor less and the number of inclusions having an equivalent circle diameter exceeding 3 &#x3bc;m is 10 pieces/mmor less.

Iron-based soft magnetic powder for dust core, preparation process thereof, and dust core

Provided is a dust core excellent in flux density, iron loss, and mechanical strength. A production process of a dust core according to the invention includes a step of compacting a mixture obtained by mixing an iron-based soft magnetic powder for powder compact having a phosphate conversion coating film on the surface of an iron-based soft magnetic powder with a lubricant to obtain a powder compact, a heat treatment step of heating the resulting powder compact at 550&#xb0; C. or more but not more than 650&#xb0; C. in an inert atmosphere, and a heat treatment step of heating the heat-treated powder compact at 420&#xb0; C. or more but not more than 530&#xb0; C. in an oxidizing atmosphere.

Growing community of inventors

Takasago, Japan

Tomotsuna Kamijo