CA1036806A - Method of producing anisotropic ferrite magnet - Google Patents
Method of producing anisotropic ferrite magnetInfo
- Publication number
- CA1036806A CA1036806A CA189,356A CA189356A CA1036806A CA 1036806 A CA1036806 A CA 1036806A CA 189356 A CA189356 A CA 189356A CA 1036806 A CA1036806 A CA 1036806A
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- CA
- Canada
- Prior art keywords
- ferrite
- sheet
- mass
- magnet
- pulverized
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
METHOD OF PRODUCING ANISOTROPIC
FERRITE MAGNET
Abstract A method is provided which comprises preparing pulverized ferrite having a magnetoplumbite type crystal structure of hexagonal system, mixing and kneading the ferrite with a viscous binding agent, subjecting the mixture to rolling to form a sheet-like mass with the easy axis being orientated in the direction perpendic-ular to the plane of the ferrite sheet by making use of anisotropic configuration of the crystal grains of the pulverized ferrite, forming the sheet-like mass into a desired shape, and sintering and magnetizing the shaped ferrite.
FERRITE MAGNET
Abstract A method is provided which comprises preparing pulverized ferrite having a magnetoplumbite type crystal structure of hexagonal system, mixing and kneading the ferrite with a viscous binding agent, subjecting the mixture to rolling to form a sheet-like mass with the easy axis being orientated in the direction perpendic-ular to the plane of the ferrite sheet by making use of anisotropic configuration of the crystal grains of the pulverized ferrite, forming the sheet-like mass into a desired shape, and sintering and magnetizing the shaped ferrite.
Description
Disclosure This invention relates to a method of producin~ anisotropic ferrite magnet, and more particularly to a method of producing a magnet of the type which has a so-called maQnetoplumbite type crvstal ~1~
structure of the hexagonal system composed from combination of an ~.
oxide of such material as barium, strontium, lead or the like and ferric oxide and which has the easy axis along the C-axis.
Generally, the ferrite powder composing the above-mentioned ferrite magnet has a magnetoplumbite type crystal structure of the hexaeonal system composed substantially from a chemical composition of M0-6Fe203 (where M is Ba, Sr, Pb or the like). This ferrite powdcr has the easy axis alons the C-axis and its crystal is apt to develop in the direction ver~ical to the C-axis. When sintered, it is t,~ ~ reduced into the flat ?~': shaped crystal srains.
If the powder of ~his tyl~e of f~rrite is simply subjected to .. ..
q~
, .;
, `, 1036~306 compression molding, the C-axis of the crystal runs in thc random directions, so that the material is worked into an isotropic magnet.
Such isotropic magnet is small in energy product as compared with anisotropic magnet which has been prepared from compression molding by orientating the C-axis of the crystal in a certain set direction, so that the former is less suited for use in various types of electric machines and instruments such as small-capacity motor, magnet for head-phone, etc. For instance, in the case of barium type ferrite magnet, if it is isotropic, its energy product (B-H)max is merely on the order of 0. 2 to 1. 2 x 106G Oe, whiie if it is made into aniso-tropic magnet, (B-H)max is raised to the order of 2.0 to 3.5 x 106G Oe.
Various methods have been proposed for inducing magnetic anisotropy during the compression molding. Among them, most typical is the ma gnetic field molding method. This magnetic field molding method is divided into two types, i . e. dry type and wet type. However, the ma nets produced by the dry type are inferior in magnetic properties to those produced by the wet type, so that the wet t~pe mcthod is uscd for producing thc magnets having excellent magnetic properties. This wet type magnetic field molding method comprises the steps of pulverizing barium ferrite which has been calcined with its crystal growth advanced to some extent, then mixing therein an organic binder and ~ solvent to form a slurry-like mixture, then applying thereto a magnetic field of a certain set direction from the outside to orientate the crystal grains in a predetermined direction while filtering them, and then subjecting them to compression molding.
Such wet type magnetic field molding method, however, has the following disadvantages:
(1) Since the compression molding is perfcrmed after orien-tating the crystal grains in the direction of the easy axis by applying - from outside a masnetic field to the pulverized ferrite dispersed in the , t ~
~, J .
~o~a~
solvent solutiQn, the once attained ori~llt~ion of the crystal grains may be deranged to cause a change in directionality of the easy axis, resultin6 in dcteriorated magnetic properties. Especially, it is difficult to produce a cylindrical anisotropic ferrite magnet having the easy axis in the radial direction, because the crystal grains oriented in the radial direction are compressed perpendicularly and, thereby, the easy axis becomes random.
structure of the hexagonal system composed from combination of an ~.
oxide of such material as barium, strontium, lead or the like and ferric oxide and which has the easy axis along the C-axis.
Generally, the ferrite powder composing the above-mentioned ferrite magnet has a magnetoplumbite type crystal structure of the hexaeonal system composed substantially from a chemical composition of M0-6Fe203 (where M is Ba, Sr, Pb or the like). This ferrite powdcr has the easy axis alons the C-axis and its crystal is apt to develop in the direction ver~ical to the C-axis. When sintered, it is t,~ ~ reduced into the flat ?~': shaped crystal srains.
If the powder of ~his tyl~e of f~rrite is simply subjected to .. ..
q~
, .;
, `, 1036~306 compression molding, the C-axis of the crystal runs in thc random directions, so that the material is worked into an isotropic magnet.
Such isotropic magnet is small in energy product as compared with anisotropic magnet which has been prepared from compression molding by orientating the C-axis of the crystal in a certain set direction, so that the former is less suited for use in various types of electric machines and instruments such as small-capacity motor, magnet for head-phone, etc. For instance, in the case of barium type ferrite magnet, if it is isotropic, its energy product (B-H)max is merely on the order of 0. 2 to 1. 2 x 106G Oe, whiie if it is made into aniso-tropic magnet, (B-H)max is raised to the order of 2.0 to 3.5 x 106G Oe.
Various methods have been proposed for inducing magnetic anisotropy during the compression molding. Among them, most typical is the ma gnetic field molding method. This magnetic field molding method is divided into two types, i . e. dry type and wet type. However, the ma nets produced by the dry type are inferior in magnetic properties to those produced by the wet type, so that the wet t~pe mcthod is uscd for producing thc magnets having excellent magnetic properties. This wet type magnetic field molding method comprises the steps of pulverizing barium ferrite which has been calcined with its crystal growth advanced to some extent, then mixing therein an organic binder and ~ solvent to form a slurry-like mixture, then applying thereto a magnetic field of a certain set direction from the outside to orientate the crystal grains in a predetermined direction while filtering them, and then subjecting them to compression molding.
Such wet type magnetic field molding method, however, has the following disadvantages:
(1) Since the compression molding is perfcrmed after orien-tating the crystal grains in the direction of the easy axis by applying - from outside a masnetic field to the pulverized ferrite dispersed in the , t ~
~, J .
~o~a~
solvent solutiQn, the once attained ori~llt~ion of the crystal grains may be deranged to cause a change in directionality of the easy axis, resultin6 in dcteriorated magnetic properties. Especially, it is difficult to produce a cylindrical anisotropic ferrite magnet having the easy axis in the radial direction, because the crystal grains oriented in the radial direction are compressed perpendicularly and, thereby, the easy axis becomes random.
(2) As the product is molded from a slurry-like mass by gradualty removing the solvent, the entire process takes a long time and hence is not suited for mass production
(3) For producing a ferrite magnet of a desired configuration, it needs to prepare a mold that conforms to the particular configuration.
Therefore, it is extremely uneconomical to produce different shapes of magnets.
Therefore, it is extremely uneconomical to produce different shapes of magnets.
(4) As the compression force applied to every pulverized ferrite in the mold is not constant due to the shape of the mold; the product does not have uniform ferrite distribution.
(5) In manufacture of a cylindrical anisotroplc ferrite magnet havlng the eAsy axis in the radial direction, if a tOO strong magnetic field is applied during the magnetic field molding, the iron core of the molding machine may be brought into a magnetically saturated state to cause reduction of magnetic permeability of the iron core, so that it becomes difficult to correctly orientate the easy axis in the radial direction. If the magnetic field applied is too weak, it is aiso impossible to correctly direct the easy axis in the radial direction. Particularly, extreme difficulty attends in orientating the easy axis in the radial direction when molding a mass having a height more than five times as ~long as its diamcter.
With a view to finding out a solution to the above problems, t~.e prescnt inventors have pursued extensive studies and experiments '., ' ~i .
~ `
toward that end, and as an ~co~me thereof, has found the fact that if said pulverized ferrite mixéd up with a binder is rolled with a roll or such, the crystal grains of ferrite are spontaneous-ly laid one upon the other in regular order and the easy axis, which has been random, is forcibly orientated in the direction vertical to the sheet face. The present invention has been accomplished on the basis of such finding.
The primary object of the present invention, therefore, is to provide a novel method of producing anisotropic ferrite magnet which has excellent magnetic properties.
Another object of the present invention is to provide a méthod of producing anisotropic ferrite magnet with easy molding and economically on a mass-production scale.
Another object of the present invention is to provide a method suited for producing cylindrical anisotropic ferrite magnet having the eas~ axis in the radial direction.
According to the present invention there is provided a method of producing an anisotropic ferrite mag4n~t having a C radial particle orientation comprising~mixing puiverized ferrite particles with an organic binder suïtable for forming ferrite maqnets to develop the particles in the planar direction per-pendicular to~the C-axis, said pulverized ferrite particles having~
a hexagonal crystal structure of the magnetoplumbite type and comprising a substance having the chemical composition MO:6Fe2O3 in which M is Ba, Sr or ~, said pulverized ferrite having been calcined and having a well-advanced crystal growth, rolling said mixture between calender rollers to form a ferrite sheet, said calender rollers being driven at substantially the same - speed to align the particles with their easy axis oriented in a direction perpendicular to the plane of the ferrite Yheet, winding said sheet convolutely and tightly under pressure to form a cylindrical shaped integral mass, sintering said mass at about 1,100 to 1,300C and applying a magnetic field to .
said sintered mass to com lete~said anisotropic ferrite magnet A~ ~
103~;~06 ` ~ ~
- having said radial particle orientation.
To produce a flat ferrite magnet, the rolled ferrite &heet is stamped to punch out a flat mass, which is then -sintered and ma~netized ~, ` . , ~,- .
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~036806 by applying a magnetic field. -~
For obtaining a ferrite magnet with a desired thickness, several ferrite sheet obtained by rolling is laminated in layers, and then pressed into an integral lamination. The lamination is then stamped ~
to punch out a ferrite mass of desired shape, followed by sintering and ~,.
magnetization with application of a magnetic field. ~ -Shaping of a cylindrical anisotropic ferrite magnet having the easy axis in the radial direction can be accomplished by convolutely and tightly winding the ferrite sheet so that no space will be present between the adjacent layers and then pressing the wound sheet into a integral cylindrical mass, which is then sintered and magnetized by applying a magnetic field.
, The aforementioned and other objects and features of the present invention will be apparent from the following detailed description of specific embodiments thereof, when read in conjunction with the .
4ccompanying drawings, in which Figure 1 is a sectional view showing one step in the process of the present invention in which a knead mixture of pulverized ferrite and a viscouse binder is rolled down into a sheet with a roll;
.i . .
Figures 2a and 2b are perspective view showing the cylindrical anisotropic ferrite magnets obtained by winding the ferrite sheets formed by rolling in the manner as shown in Fig. 1, according to the different embodiments of the present invention; and Figures 3a and 3b are viewS showing by arrows the directions of the magnetic field of the cylindrical anisotropic ferrite magnets produced according to the method of the present invention.
The preseslt invention is now described in detail by- way of embodiments thereof.
First! pulverized anisotropic ferrite is prepared which has a magnetoplumbite type crystal structure of the hexagonal system ` ~ 3~
~.
~ i03~B06 ~
composed mainly Or a chcmical composition MO6~:~2O3 (wl~ere M is Ba, Sr, Pb or such). The ferrite has the easy axis in the direction of the C-~s and-ha~s been calcined ~vith its c~rystal gro~vthwell advanced. The -ferrite is added with an organic binder such as polyvinyl butyral, a plasticizer ~ a solvent, etc ., and the mixture 1, after well knead, is rolled into a sheet with a calender roll 2 as shown in Fig. 1. The ferrite according to the present invention is a hexagonal crystal having the ' easy axis alonc the C-axis, so that the crystal tends to develop in the planar direction perpendicular to the C-axis and is apt to be made into thin and flat plate-shaped crystal grains. When these flat plate-shaped ~' crystal grains are subjected to rolling with a roll under a tension applied in the direction perpendicular to the direction of rolling, the crystal grains are laid one on the other in a natural way and in regular order.
Thus, the easy axis, which has been directed randomly, is now forcedly j orientated in a set direction. In'this way, owing to the configuration of the crystal grains, there can be formed with ease an anisotropic ferrite ;
sheet having the easy axis in the direction perpendicular to the sheet face by merely rolling down the ferrite sheets 3. 'l'he more the degree of rolllng is increased, thé more correct becomes the orientation of the C-axis. - If rolling is carried out while aE?plying a magnetic field `~.-vertically to the sheet face from the outside, the C-axis is forcedly orientated by the action of said magnetic field, resulting in further improved magnetic properties. More preferably, heating in the range of about 50 - 100C is applied while rolling so as to further impro~te the magnetic :
properties .
For obtaining a ~lat ferrite magnet, the rolled ferrite sheet is formed into a desired shape by suitable punching-out and then subjected tO sintering at 1,100 to 1 ,300C, followed by calcination and magnetization with application of a magnetic field.
For forming a ferrite magnet with a desired thicl;ness, '-'. ~, ' ~,`, : , .
.
_ _ 1036~
scveral ferritc sheets obtained from rolling are laid one upon thc other in layers to a desired thickness and then subjected to heating press to ;
make an integral ferrite magnct plate havins crystal anisotropy This is shaped into a desired form by suitable punching-out and sintered at l,100 to 1,300 C. After sintering, a magnetic field is applied to ~ ,.
effect ma~netization .
For shaping a cylindrical anisotropic ferrite magnet having the easy axis in the radial direction, a ferrite sheet 3 obtained from rolling is convolutely and tightly wound about a core 4 so that no space will be produced between the ad3acent layers as shown in Fig. 2(a).
Alternatively, the ferrite sheet 3 is convolutely and-tightly wound up, without using any core, so that no space will be created between the layers as shown in Fig. 2~b). The wound-up sheet Is then subjected to, for example, hydrostatic press to form an integral mass. The thus shaped cyiindrical mass is then sintered at 1,100 to 1,300C. After sintering a ma8netic field is applied in a known method to thereby obtain a ferrite magnet which has the easy axis in the radiai direction and which has been magnetized to have two poles as shown in Fig. 3(a) or four polcs as shown ln Fig. 3(b).
Thus, according to the method of the present invention, a knead mixture of pulverized ferrite and a viscous- binding agent i5 rolled with a roll or other suitable means to make~ anisotropic ferrite magnet plate having the easy axis directed in the direction perpendicular to the plane of the ferrite sheet. So, for obtaining a flat magnet, a desired shaped is punched out from said magnet plate or a lamination of such plates, and for obtainin~g a cylindrical magnet, such magnet plate is wound up to form the desired product. Thus, the present method permits easy shaping of the products and is suited for mass production. Also, it becomes possible to produce an extremely thin flat magnet on the order of 0. 1 mm thick. Particu'arly, in case of forming cylindrical m~gnets, ~ .
-7- ~
,.
, ~ . .
.
~'J` ~0368~)6 there is no necd of preparinS a diîfcrent mold for every different size ,. .
of m~gnet to be produced, so that the method oî the present invention proves extremcly economical in manufacture of the magnets. Moreover, since the ~cnead Ir.ixture of the pulverized ferrite is rolled by a roll or such, the ferritc distribution in the product is very uniform, so that, after magnetization, the magnetic flux density becomes~uniform. Thereby, ~' many types of magnetization may be used such as pulse type magnetiza- -tion, multipoles magnetization, one-side magnetization and the like.
Furthermore, the ferrite masnet produced in accordance with the present invention has higher density and stronger mechanical strength than the conventional ones. g~
Although the present invention has been disclosed with reference to preferred embodiments thereof, many modifications and alterations may bè made within the spirit of the present invention.
. . - ~
~, . h s .j .,'' ,"'~ '' '''' ~
"' ' "~
- ~,, - , '~
~, ,, . ., ~
, . .
-,
With a view to finding out a solution to the above problems, t~.e prescnt inventors have pursued extensive studies and experiments '., ' ~i .
~ `
toward that end, and as an ~co~me thereof, has found the fact that if said pulverized ferrite mixéd up with a binder is rolled with a roll or such, the crystal grains of ferrite are spontaneous-ly laid one upon the other in regular order and the easy axis, which has been random, is forcibly orientated in the direction vertical to the sheet face. The present invention has been accomplished on the basis of such finding.
The primary object of the present invention, therefore, is to provide a novel method of producing anisotropic ferrite magnet which has excellent magnetic properties.
Another object of the present invention is to provide a méthod of producing anisotropic ferrite magnet with easy molding and economically on a mass-production scale.
Another object of the present invention is to provide a method suited for producing cylindrical anisotropic ferrite magnet having the eas~ axis in the radial direction.
According to the present invention there is provided a method of producing an anisotropic ferrite mag4n~t having a C radial particle orientation comprising~mixing puiverized ferrite particles with an organic binder suïtable for forming ferrite maqnets to develop the particles in the planar direction per-pendicular to~the C-axis, said pulverized ferrite particles having~
a hexagonal crystal structure of the magnetoplumbite type and comprising a substance having the chemical composition MO:6Fe2O3 in which M is Ba, Sr or ~, said pulverized ferrite having been calcined and having a well-advanced crystal growth, rolling said mixture between calender rollers to form a ferrite sheet, said calender rollers being driven at substantially the same - speed to align the particles with their easy axis oriented in a direction perpendicular to the plane of the ferrite Yheet, winding said sheet convolutely and tightly under pressure to form a cylindrical shaped integral mass, sintering said mass at about 1,100 to 1,300C and applying a magnetic field to .
said sintered mass to com lete~said anisotropic ferrite magnet A~ ~
103~;~06 ` ~ ~
- having said radial particle orientation.
To produce a flat ferrite magnet, the rolled ferrite &heet is stamped to punch out a flat mass, which is then -sintered and ma~netized ~, ` . , ~,- .
. ' , , . ' , ,. .
.': ' ' ''' 0 ,. . '. ' . , ~
. ., , ' . ', ~ . ' . ' ' ' ~ .
' . ' . ` . ', ~ , ', ' ',: ' ` ~ ".;, .
" . . " ,,, .~,.
,, ,. , ... .
:', ,' ', , ,, . ' ` ~ ~
,~
' : , ' , - - - ~,,~
- ~e , .^3' ~ - ' ' ' ' ' ' ` ' `
' ' " ~" ' ' ' . - ' ' , ~- .
:' ` ' '' - ' ' . . ' ~
. '~
.. :
.
~ ' ` "' ' ' ' ' ".
~ - 4a -4 ~ ~
~036806 by applying a magnetic field. -~
For obtaining a ferrite magnet with a desired thickness, several ferrite sheet obtained by rolling is laminated in layers, and then pressed into an integral lamination. The lamination is then stamped ~
to punch out a ferrite mass of desired shape, followed by sintering and ~,.
magnetization with application of a magnetic field. ~ -Shaping of a cylindrical anisotropic ferrite magnet having the easy axis in the radial direction can be accomplished by convolutely and tightly winding the ferrite sheet so that no space will be present between the adjacent layers and then pressing the wound sheet into a integral cylindrical mass, which is then sintered and magnetized by applying a magnetic field.
, The aforementioned and other objects and features of the present invention will be apparent from the following detailed description of specific embodiments thereof, when read in conjunction with the .
4ccompanying drawings, in which Figure 1 is a sectional view showing one step in the process of the present invention in which a knead mixture of pulverized ferrite and a viscouse binder is rolled down into a sheet with a roll;
.i . .
Figures 2a and 2b are perspective view showing the cylindrical anisotropic ferrite magnets obtained by winding the ferrite sheets formed by rolling in the manner as shown in Fig. 1, according to the different embodiments of the present invention; and Figures 3a and 3b are viewS showing by arrows the directions of the magnetic field of the cylindrical anisotropic ferrite magnets produced according to the method of the present invention.
The preseslt invention is now described in detail by- way of embodiments thereof.
First! pulverized anisotropic ferrite is prepared which has a magnetoplumbite type crystal structure of the hexagonal system ` ~ 3~
~.
~ i03~B06 ~
composed mainly Or a chcmical composition MO6~:~2O3 (wl~ere M is Ba, Sr, Pb or such). The ferrite has the easy axis in the direction of the C-~s and-ha~s been calcined ~vith its c~rystal gro~vthwell advanced. The -ferrite is added with an organic binder such as polyvinyl butyral, a plasticizer ~ a solvent, etc ., and the mixture 1, after well knead, is rolled into a sheet with a calender roll 2 as shown in Fig. 1. The ferrite according to the present invention is a hexagonal crystal having the ' easy axis alonc the C-axis, so that the crystal tends to develop in the planar direction perpendicular to the C-axis and is apt to be made into thin and flat plate-shaped crystal grains. When these flat plate-shaped ~' crystal grains are subjected to rolling with a roll under a tension applied in the direction perpendicular to the direction of rolling, the crystal grains are laid one on the other in a natural way and in regular order.
Thus, the easy axis, which has been directed randomly, is now forcedly j orientated in a set direction. In'this way, owing to the configuration of the crystal grains, there can be formed with ease an anisotropic ferrite ;
sheet having the easy axis in the direction perpendicular to the sheet face by merely rolling down the ferrite sheets 3. 'l'he more the degree of rolllng is increased, thé more correct becomes the orientation of the C-axis. - If rolling is carried out while aE?plying a magnetic field `~.-vertically to the sheet face from the outside, the C-axis is forcedly orientated by the action of said magnetic field, resulting in further improved magnetic properties. More preferably, heating in the range of about 50 - 100C is applied while rolling so as to further impro~te the magnetic :
properties .
For obtaining a ~lat ferrite magnet, the rolled ferrite sheet is formed into a desired shape by suitable punching-out and then subjected tO sintering at 1,100 to 1 ,300C, followed by calcination and magnetization with application of a magnetic field.
For forming a ferrite magnet with a desired thicl;ness, '-'. ~, ' ~,`, : , .
.
_ _ 1036~
scveral ferritc sheets obtained from rolling are laid one upon thc other in layers to a desired thickness and then subjected to heating press to ;
make an integral ferrite magnct plate havins crystal anisotropy This is shaped into a desired form by suitable punching-out and sintered at l,100 to 1,300 C. After sintering, a magnetic field is applied to ~ ,.
effect ma~netization .
For shaping a cylindrical anisotropic ferrite magnet having the easy axis in the radial direction, a ferrite sheet 3 obtained from rolling is convolutely and tightly wound about a core 4 so that no space will be produced between the ad3acent layers as shown in Fig. 2(a).
Alternatively, the ferrite sheet 3 is convolutely and-tightly wound up, without using any core, so that no space will be created between the layers as shown in Fig. 2~b). The wound-up sheet Is then subjected to, for example, hydrostatic press to form an integral mass. The thus shaped cyiindrical mass is then sintered at 1,100 to 1,300C. After sintering a ma8netic field is applied in a known method to thereby obtain a ferrite magnet which has the easy axis in the radiai direction and which has been magnetized to have two poles as shown in Fig. 3(a) or four polcs as shown ln Fig. 3(b).
Thus, according to the method of the present invention, a knead mixture of pulverized ferrite and a viscous- binding agent i5 rolled with a roll or other suitable means to make~ anisotropic ferrite magnet plate having the easy axis directed in the direction perpendicular to the plane of the ferrite sheet. So, for obtaining a flat magnet, a desired shaped is punched out from said magnet plate or a lamination of such plates, and for obtainin~g a cylindrical magnet, such magnet plate is wound up to form the desired product. Thus, the present method permits easy shaping of the products and is suited for mass production. Also, it becomes possible to produce an extremely thin flat magnet on the order of 0. 1 mm thick. Particu'arly, in case of forming cylindrical m~gnets, ~ .
-7- ~
,.
, ~ . .
.
~'J` ~0368~)6 there is no necd of preparinS a diîfcrent mold for every different size ,. .
of m~gnet to be produced, so that the method oî the present invention proves extremcly economical in manufacture of the magnets. Moreover, since the ~cnead Ir.ixture of the pulverized ferrite is rolled by a roll or such, the ferritc distribution in the product is very uniform, so that, after magnetization, the magnetic flux density becomes~uniform. Thereby, ~' many types of magnetization may be used such as pulse type magnetiza- -tion, multipoles magnetization, one-side magnetization and the like.
Furthermore, the ferrite masnet produced in accordance with the present invention has higher density and stronger mechanical strength than the conventional ones. g~
Although the present invention has been disclosed with reference to preferred embodiments thereof, many modifications and alterations may bè made within the spirit of the present invention.
. . - ~
~, . h s .j .,'' ,"'~ '' '''' ~
"' ' "~
- ~,, - , '~
~, ,, . ., ~
, . .
-,
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for producing an anisotropic ferrite magnet having a radial particle orientation comprising the steps of mixing pulverized ferrite particles with an organic binder suitable for forming ferrite magnets to develop the particles in the planar direction perpendicular to the C-axis, said pulverized ferrite particles having a hexagonal crystal structure of the magnetoplumbite type and comprising a substance having the chemical composition MO:6Fe2O3 in which M is Ba, Sr or Pb, said pulverized ferrite having been calcined and having a well-advanced crystal growth, rolling said mixture between calender rollers to form a ferrite sheet, said calender rollers being driven at substantially the same speed to align the particles with their easy axis oriented in a direction perpendicular to the plane of the ferrite sheet, winding said sheet convolutely and tightly under pressure to form a cylindrical shaped integral mass, sintering said mass at about 1,100 to 1,300°C and applying a magnetic field to said sintered mass to complete said aniso-tropic ferrite magnet having said radical particle orientation.
2. The method according to claim 1 in which said mixture is heated to about 50°-100°C during said rolling.
3. A method according to claim 1 in which said ferrite sheet is wound around a core.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA189,356A CA1036806A (en) | 1974-01-02 | 1974-01-02 | Method of producing anisotropic ferrite magnet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA189,356A CA1036806A (en) | 1974-01-02 | 1974-01-02 | Method of producing anisotropic ferrite magnet |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1036806A true CA1036806A (en) | 1978-08-22 |
Family
ID=4098830
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA189,356A Expired CA1036806A (en) | 1974-01-02 | 1974-01-02 | Method of producing anisotropic ferrite magnet |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1036806A (en) |
-
1974
- 1974-01-02 CA CA189,356A patent/CA1036806A/en not_active Expired
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