DE2321368A1 - NEW SINTER PRODUCT MADE FROM AN INTERMETALLIC COBALT-NEODYME-SAMARIUM COMPOUND AND PERMANENT MAGNETS MANUFACTURED FROM IT - Google Patents

Description

1 River Road
SCHENECTADY, NY / USA

New Sin.terproduct from an intermetallic cobalt-neodymium-samarium compound and permanent magnets made therefrom

The present invention relates generally to permanent magnets and, more particularly, to new sintered products of cobalt-neodymium-samarium intermetallic compounds with unique properties and the invention further relates to those made from these new intermetallic Connections made permanent magnets.

Permanent magnets, i.e. so-called hard magnetic materials such as intermetallic cobalt-rare earth compounds, are from Technological importance as it has a high constant magnetic flux in the absence of an exciting magnetic field or be able to maintain an electric current generating such a field.

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Intermetallic cobalt-rare earth compounds exist in ■ a variety of phases. The permanent magnetic properties of the intermetallic cobalt-rare earth-materials with ■ Magnetic properties can generally be improved by crushing the coarser bodies into powders these materials are not stable in air in such a finely divided state and their magnetic properties are already becoming impaired after a short time.

There are already several intermetallic compounds made of cobalt ' and rare earths. So is the US patent Applicants' 3,695,945 in a method disclosed., Which comprises forming an alloy of cobalt and rare earth metal composed of plague particles, the content of rare earth metal is essentially the same as that desired in the sintered product. The obtained plague body particles are compressed into compact bodies and sintered to the desired density. The sintered product is made from a main amount of an intermetallic ϋο, -R phase and up to about 35 wt .- # from a second CoR phase, the content of Rare earth metal is larger than that of the COj-R phase. In both Cases, R is a rare earth metal. These sintered products are then magnetized to form new permanent magnets.

In applicant's US Pat. No. 3,682,715, there are new sintered products which consist of intermetallic compounds of cobalt and rare earth metals, namely samarium and Lant. ^ ui and the permanent magnets made from them.

In applicant's US Pat. No. 3,684,591, there are new sintered products Described from intermetallic compounds of cobalt and rare earth metals, referred to as rare earth metals Samarium and ger are present as well as those made from them; Permanent magnets.

In the applicant's US Pat. No. 3,682,716, new sin-

ter products disclosed from intermetallic compounds from cobalt and rare earth metals, the latter being composed of samarium and cerium mischmetal and those made therefrom Permanent magnets. j

In US Patent 3 682 71 ² * of the applicant are novel sintered products of intermetallic compounds of samarium and Prasedoym described as well as the permanent magnets prepared therefrom. . '■

In contrast, permanent magnets are made by the present invention created, 'which contain neodymium in a noticeable amount- " ten and the good permanent magnetic properties including have a satisfactory coercive force H.

In the following, the invention with reference to the drawing explained in more detail. Show in detail:

1 shows the cobalt-samarium phase diagram. It is assumed for the present application that each phase diagram at 300 ^° C., which is the lowest temperature shown in FIG. 1, is essentially the same as at room temperature. ·

Fig. 2 shows curves showing the magnetic properties: show the permanent magnets according to the invention. In particular Fig. 2 shows the positive values of magnetization; which are maintained in the presence of the demagnetizing field H. can be.

In short, the sintered product of the present invention comprises intermetallic compounds of cobalt and rare earth metals composed of samarium and neodymium. Cobalt in an amount of about 62 to 66 wt -% of the present product and the rare earth metals are present in an amount of about 3 ¹ I to 38 wt .- # of the product, wherein the neodymium.

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ι content in the range of 20 to 90% of the amount Gew.r rare earth metals is and the preferred range, the Neodymgehaltes ^be-. 40 and see "60 wt -% of the quantity of rare earths is of the.
sintered product will be permanent magnets in the form of coarser ~! Parts and formed in the form of solid particles. \

The sintered product of the present invention can be made by a number of different methods, but is _; preferably that described in US Pat. No. 3,655,464 of the applicant "!

procedures are used. This process according to US Pat. No. 3,655,464 comprises the formation of a mixture of solid particles from a base alloy of cobalt and rare
Earth metal and an additional alloy of cobalt and rare earth \ metal. The base alloy is one which at Sintertempe- \ temperature intermetallic as a single solid phase exists COj-R, wherein R represents a rare earth metal. The additional alloy '; made of cobalt and rare. Earth metal is richer in rare earths. metal as the base alloy and at the sintering temperature it is at least partially liquid and thus increases the sintering; speed. The mixture is then formed to form a green \

Body pressed, which to the desired density and phase co-

Settlement is sintered. In the present invention, ';

j the final sintered product has a major amount of the intermetallic = j "COj-R phase and a minor amount of the Co-Rp phase. In general, the Co ₇ Rp phase is in an amount in the range of 0.1

j to 5 wt -.% of the sintered product present. ^:

j ■;

The sintered product of the present invention is also in

t usable form by the method of U.S. Patent 3,655,463

available from the applicant. '

:

The method of this US Pat. No. 3,655,463 is essentially the same as that of US Pat. No. 3,655,464 with the difference that an additive Co-R is used
is solid at the sintering temperature and a higher content of \ _ rare earth metal than said base alloy used.

For the manufacture of the new products of the present invention, the process is carried out with a base alloy which is described in
the sintering temperature is fixed and at this temperature in the we-; sent or completely composed of the intermetallic Co._R phase: where R is samarium, neodymium or preferably a mixture of samarium and neodymium. In general, the base alloy used in the present invention consists of about
65 to 68 Qew .-% cobalt and about 32 to 35 wt -.% Rare earth "metal or rare earth metals, although the base alloy in.
the composition may vary, it should be such an addition | have composition, which together with the addition to
the claimed composition of the sintered product according to the invention. - '

The additional alloy used in the context of the present invention is one made of cobalt and rare earth metal with one:

higher content of rare earth metal than the base alloy ^; having. The additional alloy is preferably one which is at least partially in liquid form at the sintering temperature, but it can also be a solid. The additional alloys used are those made from cobalt samarium, cobalt | Neodymium or Cobalt Samarium Neodymium. :

The additive alloy may vary in composition and "j, this composition may after Phaseηdiagramm for jewei- j celled cobalt-rare earth metal system can be determined or one;., The composition may also determine empirically When a sintering \ tern in the presence of a liquid 1 shows for the cobalt-samarium system that phases which are partially or completely liquid occur in the temperature range from 950 to 1200 C. Any alloy within the range shown in FIG The area shown, which at least partially forms a liquid phase at the special sintering temperature, could therefore be used as an additional alloy. As can be seen from FIG .-SS of Z us at ζ alloy upwards varying-;

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If it is desired, an additional alloy ι at the sintering temperature determined, then this can] riieren also va- in the composition and they may be from the phase diagram for the correspond: sponding cobalt-rare earth metal-System determine or empirical i riseh determine. For example, FIG. 1 shows for the cobalt samarium; System that there is a solid phase with a samarium content of more; % are at a temperature in the range of 950 to 1200 g - as a 36 wt.. In a temperature range from 950 to 1075 ⁰ C there is a _: solid alloy for. the cobalt samarium system with a samarium content of about 36 to about 55 wt. from the additional alloy; and at temperatures in the range from 950 to 1200 ° C., the solid additive alloy can have a saraarium content of about 36 to about
.% Have the additional alloy - 45 wt. Any additional alloy \ within these ranges could therefore be used as a solid additional alloy i. '>

If desired, the sintered additive alloy can be made after a; A number of methods can be selected empirically, so by j samples of different compositions of the additional alloy up to "j heated to the desired sintering temperature in order to determine which j before compositions are solid and which at the sintering temperature ^l at least partially liquid. · T

Although useful sintering additive alloys in a general
Composition range fall, the preferred additional alloys have a relatively low content of rare earth metals, so that the undesirable properties of pure rare earth metals in the additional alloy are kept to a minimum.
For example, pure samarium is pyrophoric and very ductile and therefore
difficult to crush and mix with the base alloy as it has a tendency to separate out and onto the
To drop bottom of container. A sintering additive alloy
Cobalt and samarium with a samarium content of preferably
less than 70 wt. ~% is not reactive at room temperature in Luft-.im essential and it may decompose by conventional methods are kleinert • "Since the additional alloy of such a cooperation
-_ .. - - - ' -2QBMLUQJlB- -

Settlement is also slightly magnetic, it adheres to the base alloy and results in an essentially thorough stable mixture. The higher the cobalt content of the addition is, the * stronger are their magnetic properties and the more stable is the mixture of solid particles that it is with the Base alloy forms.

For making the sintered product of the present invention The base alloy and the additional alloy of cobalt and rare earth metals can be produced using a number of processes will. E.g. one can use an electric arc or induction melting for the production of both cobalt and rare earth metal melt together in the appropriate amounts under a substantially inert atmosphere such as argon and solidify the melt permit. The melt is preferably poured into an ingot.

The solid base alloy and additive alloy can be converted into particulate form in a conventional manner. Such conversion can can be carried out in air at room temperature since the alloys are essentially non-reactive. E.g. you can use any alloy comminute with a mortar and pestle in air and then using a jet mill in an essentially inert atmosphere pulverize into a finer form. .

The particle size of the base alloy and the addition alloy which are used to produce the mixture according to the invention can vary. Each can be used in as finely divided a form as desired. For most applications, the average particle size will range from about 1 micron or less to about 10 microns. It can also larger particles are used, but with increasing particle size, the maximum obtainable coercive force is reduced because the coercive force is generally inversely proportional to the particle \ - - ■ size changes. In addition, a lower sintering temperature can be used for smaller particles. !

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To prepare the starting mixture of the present invention, the base alloy and the sintering additive alloy are each used in such an amount that the mixture obtained has a cobalt and rare earth metal content which essentially corresponds to that which is desired in the sintered end product. ; However, in making the mixture, the additive alloy should be used in an amount sufficient to facilitate sintering. This amount depends essentially on the specific composition of the additional alloy and can. be determined empirically, but the sintering additive alloy generally used in an amount of at least 0.5 weight should -% of the. mixture of basic and are Zusatζlegierung used. For sintering when a liquid phase occurs, it should be noted that the greater the proportion of rare earth metal in the sintered: additional alloy, the more liquid this alloy is in the! Sintering temperature. In detail is therefore a liquid phase for sintering at Aufj enter the sintering additive alloy of UO: wt -% cobalt and 60 weight -% composed samarium and preference;.. wisely, the additional alloy is present in an amount of 4 to 25 wt .- # i of the mixture of base and additional alloy.

¹ To carry out the method of the present invention,

I the base alloy with the additional alloy in any suitable; neten manner blended to form an essentially thorough partial; to obtain a mixture of ingredients. The particle mixture can then become a; green bodies of the desired size and density by any of the known methods such as hydrostatic pressing or methods using steel tools. The mixture is generated in the presence of an aligning magnetic field! compresses to magnetically align the particles along their easy axes or, if desired, the mixture can be compressed after the particles have been magnetically aligned. The greater the magnetic alignment of the particles, the better the magnetic properties obtained. The pressing is preferably carried out in such a way that a green body is obtained with the greatest possible density, since the sintering

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speed increases, preference will be given to green bodies with
: a density of about 40 % or more of the theoretical density
\ manufactured. - · ·

; The green body is desired to form a sintered body.
; sintered density. The green body is preferably sintered

so that a sintered body is created in which the pores are essentially
; are not related to each other. This noninver-; ; bonding of the pores stabilizes the permanent magnetic \ ; Properties of the product, since the inside of the sintered product ji or magnets against the external atmosphere in this way ge j

protects is. ;

The sintering temperature used in the method according to the invention

: door may vary. However, the sintering temperature must be at least \

^{1 must be} high enough that sintering in the special system of '

! Cobalt and rare earth metal takes place, i.e. it must be high; . be enough to combine the particles of the constituents

: melt. In the present process has a sintering temperature;

door in the range of about 1050 to 1150 C as suitable, ■

where a sintering range of 1100 to 1125 ° C is particularly satisfactory ^!

provides positive results. ^:

Preferably, the sintering is carried out so that the pores of the '· sintered product does not communicate with each other. A ! Sintered bodies with a density of at least 87 % of the theoretical density generally have pores which are essentially>

■ are not connected to each other. This disconnected-

; standing can be determined using customary metallographic methods; e.g. through electron transmission recordings of a cross-section! of the sintered product. The maximum sintering temperature is before:

: preferably those in which a noticeable growth of the particles or: Grains of the constituents not yet taking place because too large a ί

; Increasing the particle size the magnetic properties,
like the coercive force. The green body is in
sintered in a substantially inert atmosphere such as argon

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j ■ '■■'. '. ■■ '■': ■ - ίο -

and after sintering it becomes substantially inert
Atmosphere cooled to room temperature.

The density of the sintered product can vary. The specific density depends largely on the desired permanent magnetic properties. In order to obtain a product with substantially stable permanent magnetic properties, the density of the sintered product should preferably be such that the pores are substantially non-communicating, and this is generally at a density of about 87 % of theoretical
Density the case. For a number of uses, the density can
range from about 80 to 100 % of theoretical density. For lower temperature applications, sintered bodies with a density down to 80 % of the theoretical density can be satisfactory. The preferred density of the sintered product is
the one that is maximally available without a growth in grain size
which, as already mentioned, would noticeably impair the magnetic properties. The higher density is
desirable because the higher the density, the improved the magnetic properties. For the sintered products of the present
Invention is a density of at least 87 % of theoretical
j density, ie full density and up to 96 % of theoretical; Density preferred in order to arrive at permanent magnets with useful magnetic properties that are essentially stable ..

The sintering of the "green body leads to a sintered product \ essentially the same weight as does the green body.
This shows that no weight loss or at least no noticeable loss of cobalt and rare earth metal has taken place. With the usual chemical analyzes of the sintered product it could be determined that the content of rare earth metals and cobalt remains essentially unaffected by the sintering process. !

The magnetic properties of the sintered products according to the invention can be improved if they are used for production; new permanent magnets are subjected to a heat aging process «.

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This heat aging process is deeply borne in the US patent 3 684 593 of the applicant.

For application to the production of new permanent magnets according to the present invention, the heat-aging process involves heating the sintered products of the present invention to a temperature within 400 ⁰ C below its sintering temperature for a time up to 24 hours in a substantially inert atmosphere, such as e.g. argon. The specific aging temperature and aging time can be determined empirically and depends on the desired improvement in the magnetic properties. -

The magnetization of the sintered products according to the invention from Ko-; bait, samarium and neodymium lead to permanent magnets with magnetic

- table properties which make them useful for a wide variety ' of making applications. A particular advantage of the invention Sintered products is that neodymium is a much more common element than samarium and thus the invention

^: moderate permanent magnets for a greater variety of applications than the known magnets. Neodymium also potentially creates the highest saturation induction.

The permanent magnets of the present invention are substantially stable in air and have a wide variety of uses. For example, they can be used in telephones, electric bells, radios, televisions, and record players. they are : Also useful in portable devices such as electric toothbrushes and electric knives and for operating car accessories. In Industrial equipment can use the permanent magnets of the the invention can be used in such diverse applications., ■ such as measuring devices and instruments, magnetic separators, data processing machines and microwave devices.

If desired, that of the present invention; obtained sintered bodies to a desired particle size,

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preferably a powder, which is used for the alignment ...

. ·: ■ tion and binding in a matrix to produce a stable

j permanent magnets are particularly suitable. The matrix material can

I vary within wide limits and it can be a plastic,

I be a rubber or a metal, such as lead, tin, zinc, copper

! or aluminum. The powder-containing matrix can then be poured, poured

j, pressed or extruded to obtain the desired permanent

I surrender magnets. ;

ι ■ - ^:

! The invention will now be explained in more detail by means of examples, in

I denote the terms and procedures, if nothing else-!

I, the following are:

! All parts and percentages are parts by weight or percentages by weight

I cent.

j The compositions of the base alloy and the sintering additive-I alloy were determined on a nominal weight basis.

I.

The orientation is the ratio of the magnetization with the field zero to that with a field of 60 kOe, ie A = B / 4IfJg ₀ .

The particle size was determined using a Fischer sieve sizer determined.

The sintering furnace was an electrically heated ceramic tube. -

The sintering was carried out in an inert atmosphere from! j purified argon and after the completion of the sintering, the sintered product was removed in the same atmosphere of purified argon.

! cools. ;

The percent packing density was calculated from the measured density of the sample divided by the full density of the corresponding Alloy determined. The full densities of the alloys used are as follows:

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Alloy ' g / cm ;

Co ₁ -Sm 8.6

: ^Co 5 ^Nd O, 5 ^Sm O, 5 · ⁸ >⁵;

B is the induction of saturation.

B is the residual or remanent induction, i.e. the flow »of the previous ; is present when the applied magnetic field is reduced to zero '

will. '■

! • t

The normal coercive force H is the field strength at which the Induction B becomes zero. j

The maximum energy product (BH) is the maximum product

iuclX

the magnetic field strength H and the induction B on the ■ ^! Demagnetization curve is determined. ;

is the magnetization.

example

In the experiments in the following table, each alloy melt was passed under purified argon. Manufactured by induction melting and poured into an ingot. The ingot was then ground in air with a mortar and pestle or in a jaw crusher under nitrogen and then further ground under nitrogen with a jet mill to a powder having an average particle size of 6 to 8 microns. The sintering additive alloy was then mixed with the base alloy in a drum to form an essentially thorough mixture which was stable because the additive alloy was essentially non-reactive in air and was slightly magnetic. In experiments 1 to 4 of ^the: following table shows the composition of the base alloy '66.7% cobalt, 16.6% samarium and neodymium was 16.6%. The composition of the additional alloy was kO% cobalt and 60 % samarium. j Base and additional alloys were used in such quantities that the combination given in the following table

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placement of the green body was obtained. In Experiment No. 5 of the following table, the composition of the base alloy was 68 % cobalt and 32 % samarium, and the composition of the auxiliary alloy was 40 % cobalt and 60 % samarium, and the magnetic properties were determined after all of the treatment was completed.

"The green body of the experiments 1 to 5, inclusive, were prepared by placing the mixture into a rubber tube having a working space of about 9 _S 5 mm (corresponding to 3/8 inch) in diameter and about 44.5 mm (corresponding to 1 3/4 inch) Length. The tube was: placed in an axial magnetic field of 60,000 Oersted to align the particles along their preferred axes. After alignment, the powder was pressed and then the sample was hydrostatically pressed at a pressure of about 14,000 kp / cm (corresponding to 200,000 US pounds / inch). The pressed samples, ie j the green bodies, had a packing density of about 80 %. The, ί green bodies were cylindrical in shape and j diameter in the range from about 6 to 9, 5 mm (corresponding to 1/4 to 3/8 inches) and a length of about 18 to 37 mm (corresponding to 3/4 to 1 1/2 inches), In general, the green bodies were machined to form a right-angled cylinder suitable dimensions for testing purposes th. The green bodies were then treated as shown in the following table. The magnetic properties of the bodies of experiments 1 to "5 were determined after magnetization at room temperature in a field of 60,000 Oersted.

ι p ^e i ρ α ι / η 11

Ver Co , green_ body. Sm % Nd % Alignment treatment H pressed H and 1100 ⁰ C H and 1100 "G H and 1100 ^ C 1100 "C , there- and 16 a at Sintered product_ _ Pack magnetic Properties according to B ■ H * Λ C \ Ό 5 Q * V * search tion H at H 1100 ⁰ C H 1100 ⁰ C H 1100 C 1100 C on share % of magnetization gSuss O§ 10 Gauss Oe) No. 62 % 19th 19th at cooling down cooling down cooling down cooling down at density B. 6.7 1.6 14th 0.92 a) how oven 1 1/2 h 1 1/2 h 1 1/2 h 1 1/2 h 81.0 Gauss 7.8 3.4 1 0.956 b) 1 o ^C 6.88 89.7 9.1 7.96 5.0 0.944 c) 1 ⁰ C pressed _Λ pressed pressed _Λ at 1130 ^° C, 1 7.62 90.8 9.1 after a) how at at at , there- 7.72 9.3 1} 900 b) 1 at at at on 10 62, 18.75 18.75 900 c) 1 oven oven oven at 6.1 1.5 Ί4 0.88 after ° C o ^C 80.6 7.5 3.4 , 5 to 2 5 0.917 900 ° C ⁰ C 6.85 89.8 8.96 7.86 5.2 O 0.926 900 a) how a) how ,and 7.63 93.3 9.12 (D b) 1 b) 1 , there- 7.93 9.10 5 GO c) 1 c) 1 on 11 * "* 63 18.5 18.5 after after at 6.8 1.6 16 ■ <! 0.915 900 900 80.0 8.13 2.9 O 3 0.948 900 QOO 6.80 89.7 9.37 8.59 5.0 0.950 1 h 7.62 93.2 9.57 -4 1100 , there- 7.92 9.71 4th CO on on 12th 63, 18.25 3B, 25 900 at 6.3 1.6 17th , 5 0.874 80.2 7.9 3.8 4th 5 0.929 h at 6.82 89.8 9.20 8.4 5.9 0.936 J. ^ Cool the furnace 7.64, 93.3 9.45 900 ' ^W C 7.93 9.6 16 ⁰ C 62, 37.5 -._ 8.1 6.2 , 0 0.95 93 5 5 9.1.

Experiments No. 1 to 4 show the properties of the permanent j magnets of the present invention. In particular, the magnets according to the invention have permanent magnetic properties that they are useful for a variety of applications, e.g. for measuring instruments do.

Fig. 2 shows which positive values of the magnetization 41Tj in Presence of the demagnetizing field for the product of • Experiment No. 4 can be maintained.

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Claims (6)

Claims Permanent magnet with essentially stable permanent-magnetic properties, characterized in that it contains, as an active magnetic component, a sintered product of compressed intermetallic cobalt-rare earth material in particle form, that the sintered product has pores which . are essentially not in connection with each other, has a packing density of at least 87 % and a composition which consists essentially of cobalt in an amount of 62 to 66% by weight of the sintered product and the rare earth metals samarium and neodymium in an amount of ~ $ h to 38 wt. JC of the sintered product, the neodymium content being in the range of about 20 to 90 wt. JS of the total amount of the rare earth metals. 2. Magnet according to claim 1, characterized in that the neodymium content is in the range of about 40 to 60 wt. Si of the total amount of the rare earth metals. 3. Magnet according to claim 1, characterized in that the sintered product is in the form of particles is present, which are bound with a matrix material. 4. Magnet according to claim 3 »characterized in that the matrix material is a metal. 5. Magnet according to claim 3 »characterized by the
draws that / matrix material is a plastic. 6. Magnet according to claim 3 »characterized that the matrix material is a rubber. 309847/0776