MnZn-ferrite and its production method

Patent metadata

Field	Value
Publication number	US-10937579-B2
Application number	US-201515537688-A
Country	US
Kind code	B2
Filing date	Dec 24, 2015
Priority date	Dec 25, 2014
Publication date	Mar 2, 2021
Grant date	Mar 2, 2021

Abstract

A method for producing MnZn-ferrite comprising Fe, Mn and Zn as main components, and at least Co, Si and Ca as sub-components, the main components in the MnZn-ferrite comprising 53-56% by mol (as Fe2O3) of Fe, and 3-9% by mol (as ZnO) of Zn, the balance being Mn as MnO, comprising the step of sintering a green body to obtain MnZn-ferrite; the sintering comprising a temperature-elevating step, a high-temperature-keeping step, and a cooling step; the high-temperature-keeping step being conducted at a keeping temperature of higher than 1050° C. and lower than 1150° C. in an atmosphere having an oxygen concentration of 0.4-2% by volume; the oxygen concentration being in a range of 0.001-0.2% by volume during cooling from 900° C. to 400° C. in the cooling step; and the cooling speed between (Tc+70)° C. and 100° C. being 50° C./hour or more, wherein Tc represents a Curie temperature (° C.) calculated from % by mass of Fe2O3 and ZnO.

First claim

What is claimed is:

1. A method for producing MnZn-ferrite comprising Fe, Mn and Zn as main components, and at least Co, Si and Ca as sub-components,
the main components in said MnZn-ferrite comprising 53-56% by mol (as Fe 2 O 3 ) of Fe, and 3-9% by mol (as ZnO) of Zn, the balance being Mn as MnO, and
said sub-components comprising 0.05-0.4% by mass (as Co 3 O 4 ) of Co, 0.003-0.01% by mass (as SiO 2 ) of Si, 0.06-0.3% by mass (as CaCO 3 ) of Ca, 0-0.1% by mass (as V 2 O 5 ) of V, and 0-0.3% by mass in total of Nb (as Nb 2 O 5 ) and/or Ta (as Ta 2 O 5 ), per 100% by mass of oxides of said main components,
the method comprising the steps of
sintering a green body to obtain MnZn-ferrite;
said sintering comprising a temperature-elevating step, a high-temperature-keeping step, and a cooling step;
said high-temperature-keeping step being conducted at a keeping temperature of 1070-1090° C. in an atmosphere having an oxygen concentration of 0.6-2% by volume;
the concentration of oxygen being in a range of 0.001-0.2% by volume during cooling from 900° C. to 400° C. in said cooling step; and
a cooling speed between (Tc+70)° C. and 100° C. being 50° C./hour or more and 300° C./hour or less, wherein Tc represents a Curie temperature (° C.) calculated from the

percentages by mol of Fe 2 O 3 and ZnO contained in the main components in said MnZn-ferrite, and
said MnZn-ferrite having core loss Pcv of 2090 kW/m 3 or less between 0° C. and 140° C. at a frequency of 1 MHz and at an exciting magnetic flux density of 75 mT.

2. The method for producing MnZn-ferrite according to claim 1 , wherein said high-temperature-keeping step is conducted in an atmosphere having an oxygen concentration of 0.6-1.5% by volume.

3. The method for producing MnZn-ferrite according to claim 1 , wherein the cooling speed between (Tc+70) ° C. and 100° C. is 100° C./hour or more and 150° C./hour or less.

4. The method for producing MnZn-ferrite according to claim 1 , wherein the concentration of oxygen is 0.001-0.1% by volume at 900° C. in said cooling step.

5. The method for producing MnZn-ferrite according to claim 4 , wherein the concentration of oxygen is 0.01-0.1% by volume at 900° C. in said cooling step.

6. The method for producing MnZn-ferrite according to claim 1 , wherein the concentration of oxygen in an atmosphere is in a range of 0.4-2% by volume at least in a range of 900° C. or higher in said temperature-elevating step.

7. MnZn-ferrite comprising Fe, Mn and Zn as main components, and at least Co, Si and Ca as sub-components;
said main components comprising 53-56% by mol (as Fe 2 O 3 ) of Fe, and 3-9% by mol (as ZnO) of Zn, the balance being Mn as MnO;
said sub-components comprising 0.05-0.4% by mass (as Co 3 O 4 ) of Co, 0.003-0.015% by mass (as SiO 2 ) of Si, 0.06-0.3% by mass (as CaCO 3 ) of Ca, 0-0.1% by mass (as V 2 O 5 ) of V, and 0-0.3% by mass (as Nb 2 O 5 ) of Nb, per 100% by mass of oxides of said main components, with the proviso that Ta (as Ta 2 O 5 ) is not present; and
said MnZn-ferrite having core loss Pcv of less than 2180 kW/m 3 between 0° C. and 140° C. at a frequency of 1 MHz and at an exciting magnetic flux density of 75 mT.

8. The MnZn-ferrite according to claim 7 , wherein a core loss change ratio Ps1 determined by the formula 1 of Ps1(%)=[(Pcv max1 −Pcv min )/Pcv min ]×100 is 150% or less at a frequency of 1 MHz and at an exciting magnetic flux density of 75 mT, and a core loss change ratio Ps2 determined by the formula 2 of Ps2(%)=[(Pcv max2 −Pcv min )/Pcv min ]×100 is 200% or less at a frequency of 1 MHz and at an exciting magnetic flux density of 75 mT, wherein Pcv min represents core loss at a core-loss-minimizing temperature between 30° C. and 100° C., Pcv max1 represents the maximum core loss between 20° C. and 120° C., and Pcv max2 represents the maximum core loss between 0° C. and 140° C.

9. A method for producing the MnZn-ferrite according to claim 7 , the method comprising the steps of
sintering a green body to obtain MnZn-ferrite;
said sintering comprising a temperature-elevating step, a high-temperature-keeping step, and a cooling step;
said high-temperature-keeping step being conducted at a keeping temperature of higher than 1050° C. and lower than 1150° C. in an atmosphere having an oxygen concentration of 0.6-2% by volume;
the concentration of oxygen being in a range of 0.001-0.2% by volume during cooling from 900° C. to 400° C. in said cooling step; and
a cooling speed between (Tc+70) ° C. and 100° C. being 50° C./hour or more, wherein Tc represents a Curie temperature (° C.) calculated from the percentages by mol of Fe 2 O 3 and ZnO contained in the main components in said MnZn-ferrite.

Assignees

• Hitachi Metals Ltd

Inventors

• Koyuhara Norikazu
• Miyoshi Yasuharu
• Tada Tomoyuki
• Tanaka Satoru

Classifications

• H01F41/0246

  Manufacturing of magnetic circuits by moulding or by pressing powder (magnetic cores made by moulding or by pressing powder H01F27/255; soft magnetic particles H01F1/20, H01F1/36) · CPC title

• H01F1/344 Primary

  Ferrites, e.g. having a cubic spinel structure (X2+O)(Y23+O3), e.g. magnetite Fe3O4 · CPC title

• C22C38/04

  containing manganese · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• C22C1/10

  Alloys containing non-metals (C22C1/05, C22C1/08 take precedence) · CPC title