JPS6174305A - Hot pressed permanent magnet having high and low coercive areas - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermally processed integrated permanent magnet having at least two distinct regions with different magnetic alignments. More specifically, the present invention specifically provides a method for thermally dispersing the heat to include regions with different orientations, one having a relatively high apparent coercivity and the other having a relatively high remanence. The present invention relates to a processed permanent magnet containing iron, neodymium and/or praseodymium, and boron.

For example, a high-energy, high-force permanent magnet made of iron, neodymium and/or praseodymium, and boron, and a method for manufacturing the same, are disclosed in European Official Patent No. 11 EP-A-01084.
74 and EP-A-0144112.

The composition of one of these in the form of atomic ratio is Ndo, +3(
FtO, 95Bo, os). , 87. This is a composition containing a specific stable intermetallic phase with a maximum dimension of about 2
It exhibits high coercive force when formed into fine crystallites of 0 to 400 nanometers.

A suitable melt of iron, light rare earth metal, and boron composition is quenched very rapidly by a method such as melt spinning.
It can be made into solid objects such as thin ribbons. Control the cooling rate to create a suitable microcrystalline microstructure (20-400nm)
The material exhibits excellent permanent magnetic properties.

On the other hand, if the cooling rate is increased (supercooling), the crystallites become smaller and the coercive force also decreases. However, as disclosed, such superquenched materials can also be annealed to suitably sized crystals with high coercivity and high energy product.

An interesting and useful property of the (for example) neodymium-iron-boron composition described above is that it is substantially magnetically isotropic.

The melt-spun ribbon of particulates can be crushed into fine tabular pieces. The fine pieces can be pressed with a die in a chamber to form a monolithic object with a density of about 85% of the material. A binder may be used before or after consolidation. This kind of bonded magnet (bvnded
The manufacturing method of magnet) is published in the European Patent Publication EP
-A-0125752.

Significantly, it has been found that this type of coupled magnet does not exhibit a preferential magnetic orientation. The direct or highest energy product of the intrinsic coercivity was independent of the direction of the applied magnetic field. There was no advantage to grinding the ribbon into very fine particles and magnetically aligning the trapped particles before consolidation.

Such isotropic materials are very useful because they can be easily pressed into composite shapes (without magnetic alignment). This shaped body can be magnetized in the most convenient direction.

Iron, neodymium, and boron based compositions have also been able to physically align at least some of the particles or crystallites, at least in part magnetically, by hot pressing or thermal processing. European Patent Publication εP-A-01
As disclosed in No. 33758 7C, such heat-processed materials,
The cry had an ai-destination magnetization direction. According to one embodiment disclosed in the above publication, Ndo, t3(/
A molten material containing 0.87% of ``io, ss Bo, os'' was cooled extremely quickly by melt spinning, etc., to form a thin ribbon-shaped solid material without permanent magnetic properties. The microstructure was amorphous.

This ribbon was ground into strips of convenient size for thermal processing operations. The strip is heated in an argon atmosphere to about 700°C or higher in a die to a temperature of at least 68947.6 KPa (
It was pressed with a punch in a die under a pressure of 10,000 psi). Through this hot pressing operation (hereinafter referred to as hot pressing), the pieces coagulated into a completely dense object.

If the thermal processing operation is stopped at the point where the material has agglomerated to saturation density, a slightly magnetically aligned magnet will result with the direction of easy magnetization parallel to the pressing direction. The demagnetization curve (room temperature, second quadrant, H vs. 4πM plot) of this type of densified magnet has the shape of line a A in FIG. 1 of the accompanying drawings.

When the sufficiently dense compact is pressed again in a larger die cavity under similar high temperature and pressure conditions,
The compact produces considerable plastic strain in the plane perpendicular to the pressing direction. This second stage heat processing operation is performed by die and upsetting (
die-upsetting), which results in
Substantial magnetic alignment occurs in the easy magnetization direction transverse to the direction of plastic strain. This type of die-upset
The demagnetization curve of the body ) is as shown by the white line B in FIG. 1 of the accompanying drawings. Looking at the demagnetization curves and curves in FIG. 1, it can be seen that the degree of magnetic alignment of the hot-pressed magnet (curve mA) and the die-upset magnet (curve B) is significantly different. Hot-pressed magnets have a relatively higher coercive force and lower residual magnetism in the pressing direction than die-upset magnets. Although the die-upset magnet has a higher maximum energy product, it is more easily demagnetized than a hot-pressed object of the same composition.

There are several uses for magnets in which it is desirable to have both properties in an integrated magnet body.

It is an object of the present invention to provide a method of thermal processing of a permanent magnetic body that creates at least two cants disposed along a surface portion of the body and having different desired magnetic alignments. Generally speaking, one of the above regions has a higher apparent coercive force than the other regions, but a smaller residual magnetism.

It is specifically contemplated to apply this method to quenched compositions comprising iron, neodymium and/or praseodymium and boron.

It is another object of the present invention to provide an integrated magnetic structure that can be selectively thermally processed to include discrete regions of different magnetic alignment.

One line of its linear magnetic structure is the arcuate magnet for permanent magnet motors.

It is contemplated that one or both ends of the periphery of the arc may be processed so that the coercive force is relatively high, and the central portion of the arc is made to have a relatively large residual magnetism. In this case too, it is particularly contemplated that the magnet be of the iron/light rare earth/boron composition mentioned above.

In accordance with preferred embodiments of the invention, these and other objects and advantages are achieved as follows.

The starting material is a quenched composition of iron, neodymium and/or praseodymium and boron. An example of a suitable composition is NdO,13(/'110.9
The starting material is characterized by an amorphous microstructure or an extremely fine crystalline structure. It is desirable to be able to start with such an amorphous or particulate microstructure and to be able to carry out thermal processing without losing the appropriate coercivity of the final product.

A fine piece of melt-spun material is placed in the cavity of an open-ended die between two opposing punches. The fine pieces are heated in a die to a suitable temperature (suitably about 700° C. or higher) and compacted under a suitable pressure to form a sufficiently airtight object. As will be described later, a split ram punch (5p
lit-ram punch) can be used. Next, while the die is still hot, (split rum)
The ends of each punch are lined up in a row, and a portion of the agglomerated portion is simultaneously subjected to VC movement so as to undergo further heat processing.

In this case, during the thermal processing operation, the thicker portions in the irregularly agglomerated portions are subjected to different strains than the thinner portions. Due to the different degrees of strain across the cross-section, two regions with different magnetic alignments generally result. The area that suffered the strongest strain in the direction perpendicular to the pressing direction is arranged more strongly, and the song in Figure 1! !
Draw a demagnetization curve like B. A region that has not been deformed (or has been deformed to a small extent) by the secondary pressing operation has a low degree of magnetic alignment and exhibits magnetic properties as shown by curve A in FIG.

The above describes an example of creating different regions in a composition of iron, neodymium and/or praseodymium and boron by thermal processing operations, thus intentionally creating different magnetic alignments. A unified object with a unified area is formed. A typical field of application of the invention is arcuate magnets for motors, where the leading edge of the arcuate magnet (of a motor rotating in only one direction) is subject to a greater demagnetizing force than the rest of the arcuate magnet.

In such applications, the leading edge of the bow magnet is engineered to have a high apparent coercivity (measured radially with respect to the bow magnet), while the rest of the bow magnet has a relatively high remanence and high energy. It is heat processed to maximize the product.

The invention will be better understood from the detailed description thereof below. 1 is a plot of room temperature H versus 4πM in the second quadrant of a hot pressed magnet (curve MA) and a die upsetting magnet (curve aB). Figures 2(a) to 2(c) are schematic diagrams showing partial cross-sections of two different die combinations illustrating the sequence of die operations during the forming of a thermally processed arcuate magnet: Figures 3(a) and 2(c); (b) is a schematic diagram of a section of a split ram die showing the split ram die in two different operating states; FIGS. FIG. 5 is a schematic cross-sectional view of a fabricated die upsetting permanent magnet; FIG. 6(a) and (b) are shown in FIG. 5 according to an embodiment of the present invention.
[This is a schematic diagram illustrating the manufacturing method of a bow-shaped magnet similar to the one described in [1].

FIG. 7 further illustrates another die-forming process for forming a permanent magnet having at least two distinct magnetic alignment zones.

The present invention can be applied to a permanent magnet composition that can be magnetically aligned by plastic deformation of the material at high temperatures. An example of a preferred group of compositions to which the method of the invention can be applied are the transition metal/rare earth/boron materials described in the above-mentioned patent applications. In particular, the present invention is characterized in that the transition metal component is iron or iron and (
Compositions such as cobalt, nickel, chromium or manganese (one or more of them) are applicable. Cobalt is interchangeable with iron up to about 40 atomic percent. Chromium, manganese and nickel can be interchanged in smaller amounts, preferably up to 10 atomic percent. Zirconium and/or titanium can replace iron in small amounts (up to two atoms of iron). If the source of iron in the composition is a low carbon steel, the presence of very small amounts of carbon and silicon is acceptable. Preferably, the composition contains from about 50 atoms to about 90 atoms of the transition metal component - raw iron.

The composition also includes from about 50 atomic percent to about 50 atomic percent rare earth components. Neodymium and/or praseodymium are the basic rare earth constituents.

As mentioned above, these can be used interchangeably. Relatively small amounts of other rare earth elements such as samarium, lanthanum, cerium, terbium and dysprosium can also be mixed with neodymium and praseodymium without significantly detracting from the desirable magnetic properties. Preferably, these components do not constitute more than about 40 atomic percent of the rare earth component. It can be expected that the rare earth component contains a small amount of impurity elements.

The supercooled composition contains about 1 to 10 atoms of boron.

The overall 1 inhibition can be expressed as t−x 1−y7X by the formula RE (TM B). The rare earth (RE) component accounts for 10 to 50 fluorescence of the composition (x=0.5 to 0.9), and at least 60 atoms of the rare earth component are neodymium and/or praseodymium. The transition metals (TM) used in drums account for about 50-90 atoms of the total composition, with iron accounting for at least 60 atoms of the transition metal content. As far as the above empirical formula is concerned, other constituents such as cobalt, nickel, chromium and manganese are referred to as "transition metals".

Boron is present in the total composition in an amount of about 1 to 10 atomic percent (7=-about 0.601 to 0.11).For convenience, the composition is expressed in atomic percentages. It is clear that the numerical values in this case can be easily converted into weight ratios in preparing the mixed composition.

For purposes of illustration, the present invention is illustrated using a composition with the following atomic ratios: Ndo, r3 (Jno, gsBo, os) 0.117
However, it should be understood that the method of the present invention is also applicable to pond compositions such as those described above.

Depending on the cooling rate, the molten composition of transition metals, rare earths, and boron is solidified into a state with a microstructure in the following range.2a) Amorphous (glass-like) with extremely fine grain microstructure ( e.g., 20 nanometers or less in largest dimension) through b) microstructures containing very fine (micro) particles (e.g. 20 nm to about 400 nm) to C) fine aJ groove structures in seeds of larger size.

To date, no large-grained, 7-meter grooved material with useful permanent magnetic properties has been produced by rapid solidification methods from certain melts. Particulate structures possess useful permanent magnetic properties; amorphous materials do not; however, some glassy microchannel materials can be annealed to give them isotropic magnetic properties. The present invention is capable of converting microparticles into permanent magnets with such over-quenching.
nch) applied to glassy materials. The present invention is also applicable to high coercivity, fine particle materials "as quenched" where the material is exposed to high temperatures above 700° C. for a short period of time, i.e. 5 minutes or less, during thermal processing. .

Suitable superquench compositions are prepared by melt spinning.

The melt spinning method by which strings can be made is described in the above-mentioned application and will not be repeated for strings. This method is also used industrially to produce non-magnetic or soft magnetic alloys. Speed 1 such that an amorphous or extremely fine crystal structure is produced
In the case of iron-neodymium-boron compositions, it is preferable to start with a rapidly solidifying structure with particle sizes of less than about 20 nanometers. The material is heated and processed in a die at about 700-750 degrees Celsius to agglomerate the material particles into a completely dense mass and then selectively (plastically deformed) to transform the agglomerated object into different magnetic fields. These operations are carried out fairly quickly, so that no excessive particle growth occurs and the permanent magnetic properties are not lost.

Related matters have already been shown in Figure 1, which graphically explains the custom demagnetization of hot-pressed iron/neodymium/boron magnets (curve aA) and die upsetting magnets (curve @B) of the same composition. Hot pressed magnets are only moderately aligned magnetically and have a relatively high coercive force in the pressing direction. The die upsetting magnet has been significantly plastically deformed. wood,
14 has reached a relatively high alignment state. For this reason, the coercive force in the pressing direction is reduced, but the residual aeration is increased.

In this work, it was observed that the heat-processed magnets exhibited magnetic alignment in the direction perpendicular to the direction of plastic flow. When such plastic flow occurs perpendicular to the pressing direction (the direction of movement of the punch), the magnetic alignment state is parallel to the pressing direction.

When measuring the magnetic properties of such anisotropic magnets, such as coercive force and remanence, unless otherwise specified, the measured values in the preferred (alignment) direction are detected and recorded.

A method of forming magnetically aligned arcuate permanent magnets by die upsetting is illustrated in FIG.

A fine piece of melt-spun material is charged into a cavity consisting of a through die 10 and vertically aligned opposed punches 12 and 14 as shown in FIG. 2(a). Heat the die and its contacts with an induction heater (not shown).
Heat to or near 00°C. The pressure exerted by the punches 12 and 14, for example, 103421.4KPa (1500
Figure 2.
(a) into the substantially fully densified object shown within the die cavity.

The arrow within the outline of object 16 indicates that the densified compact is substantially unoriented. However, there is a slight selectivity in the direction of arrangement in the direction of compaction. The magnetic properties of this compact are as shown in curve A of FIG.

The compact 16 is then transferred to a larger die 18 having opposed punches 20 and 22, as shown in FIG. 2(b). The cavity is similarly heated 7JO to maintain compact 16 at a temperature at or near 700°C. The compact 16 is then plastically deformed with punches 20 and 22 into a die-upset arcuate object 24. The material flows laterally, but in the direction of alignment, perpendicular to the easy magnetization direction I'i plastic flow, ie, generally in the direction of pressing, as indicated by the arrows in FIG. 2(C). The resulting arcuate magnet 24 is wider and thinner than the compact 16. The magnets 24 are arranged highly uniformly and radially with respect to the center of curvature. A cross section of the magnet 24 is shown in FIG. 2(c).

If shown in perspective, it would look like the magnet 36 shown in FIG. 4(b). Such an arcuate magnet 24 could be made in a manner similar to that described in European patent application EP-A-0133758 mentioned above.

In accordance with the present invention, an integrated arcuate magnet or other permanent magnet structure is created having at least two regions of different magnetic alignment. In one embodiment of the invention, densified compacts of varying cross-sectional thickness are first hot pressed. One convenient procedure is to mold compacts with abrupt or stepwise differences in thickness. The excellent split ram die shown in FIG. 3 can be used for this purpose.

At the depth shown, a die body 25 conventional for this type of die is used, but the upper and lower punches 26 and 28 are divided into two parts of each punch (26', 26').
", 28', 28' can move simultaneously as shown in FIG. 3(a) or separately as shown in FIG. 3(b). Such a split punch or・Using a ram-die arrangement in hot pressing, the molten spun material made into fine pieces can be solidified and molded into a compact shape as shown in Figure 4(a).

The hot-pressed arcuate compact 30 in FIG. 4(a) has uniform occlusion and random magnetic alignment (
In other words, the thickness K has a stepwise difference.

A perspective view of the arcuate compact 30 (FIG. 4(a)) shows a relatively thick section 32 and an adjacent thin section 34. The length of the string of Compact 30 is L.

This arc can be made with a split lamb die with a moving split punch as shown in Figure 3(b). By making the hot-pressed densified compact 30 with this loose configuration, it is possible to create a die-cut curved agglomerate that has uniform thickness but regions with different magnetic alignment states. As shown in Figure 4(b),
(The compact of (a) is pressed in a die with a wide cross-sectional area in a cavity, heated to a temperature of approximately 700°C, and heat-processed to make it long (as shown in Figure 4, the length of the string is L'). L) Use a thin arcuate magnet 36. Since the cross section 32 of the compact 30 in FIG. 4(a) was thicker than the cross section 34, the extent of plastic deformation and flow is greater at the portion of the cross section 32. Therefore, the above-mentioned point a 32 of the compact 30 undergoes significant lateral distortion, resulting in a curved region 38 of the die upsetting magnet 36 in FIG. 4(b).
become.

Thus, the area 38 of the final arcuate magnet 36 is shown in FIG. 4(b).
), they become highly aligned magnetically. In contrast, the region 34 of the compact 30 undergoes relatively little deformation, and therefore the region 40 of the magnet 36 is hardly aligned. Region 40 has a magnetization characteristic similar to that of curved gland A in FIG. 1, and region 38 exhibits a magnetic characteristic similar to curved dB. Thus, as seen in FIG. 4(b), the right peripheral portion 40 of the arcuate magnet 36 has a higher coercive force than the remainder of the single magnet. Such customization is particularly useful for arcuate pole pieces of DC motors where the demagnetizing force acts most strongly on the leading edge of the magnet.

FIG. 5 illustrates the general principles of the invention in two areas: a stone 42.
This is a side view. One (or both) of the curved ends of the magnet 42 (region 46) is shown schematically in the direction of the arrow in the figure oriented at an angle θ (θ y O) with respect to the radial direction of this arcuate curve. It has a certain magnetic orientation state.

The remaining portion 44 of the magnet is machined to be oriented magnetically radially with respect to the center of the curved line as indicated by the arrow in region 44. Thus, regions 44 and 46 are both highly oriented and exhibit relatively high remanence in the alignment direction. However, the magnetic field 46 is relatively difficult to demagnetize due to the reverse magnetic field generated by the motor's mirror.

There is a two-area magnet of this type which constitutes another embodiment of the present invention. A two-area magnet such as that shown in FIG. 5 can be made by the procedure illustrated in FIGS. 6(a) and (b). Figure 6 (a
) A die upsetting permanent magnet 48 having a warped shape is manufactured.

First, a hot press compact is made, and then a strain force is generated in the indicated direction to form a die into the shape shown in FIG. 6(a). Although the die upsetting magnet 48 is warped, its magnetic orientation is parallel across its entire cross-section. By bending the warped original magnet in the opposite direction, a different region of horizontal magnetic alignment (44) as shown in FIG. and a bow-shaped magnet (such as 42) with a
is completed.

FIG. 7 also illustrates another die forming procedure for manufacturing a two-pole permanent magnet in accordance with the present invention. First, a non-curved compact 56 having graduated thicknesses is hot pressed.The compact 56 has a relatively thick portion 58 and a thin portion 60. This compact is made in the die 62! It is made using split punches 64 and 66 that operate in the young condition. Next, the punches are moved back four times and used side by side to thin the thick portion 58 of the compact and thicken the thin portion 60 of the compact 56. This example results in a flat body 68 (dashed line) with regions of different magnetic alignment due to different plastic flows. In FIG. 7, the arrows indicate the direction of strain rather than the direction of magnetization. The magnetization direction will be perpendicular to the strain as mentioned before.

As described above, according to the present invention, an integrated magnetic material having two or more regions of different magnetic alignment can be produced. It is preferable for the regions to be separated in the direction of the surface rather than for one region to be wrapped around the other. This separation of regions along the surface dimension is illustrated by regions 38 and 40 of arcuate magnet 36 and regions 44 and 46 of arcuate magnet 42. In both cases, the regions are separated in the circumferential direction of the archwire.

Regions of different magnetic alignment can be created by selectively thermally processing magnetic material objects in a variety of ways. Different parts of an object will strain to different degrees or in different directions at high temperatures. Such an effect is achieved by starting from densified compacts of different thicknesses and molding them into a product of uniform thickness using a die upsetting operation.

In another embodiment, a d1 uniform parallel array of magnetic material bodies may be bent at high temperature (as shown in FIG. 6) to create two magnet structures.

The invention can still be practiced using fine J1 pieces from ribbons obtained by melt spinning in combination with pre-hot pressed compacts. Compacts and fine pieces from different parts of the same die are hot-pressed, the compact is (for example) die-upset, the fine pieces are hot-pressed, and the fine pieces are hot-pressed together with them to maximum density (or near maximum density). Press to form an integrated object having regions with different arrangements. In this embodiment, different compositions could be used for the initial compact and addition@side pieces.

The present invention is particularly useful in the production of transition metal, rare earth, and boron based magnets of the type described above. However, other magnetic compositions that can be magnetically aligned by plastic deformation at suitable high temperatures can also be used.

The terms ``permanent stone'' or ``hard stone'' used in strings refer to materials that have a sufficiently large intrinsic coercive force at room temperature, for example, a coercive force of 1000 Oe or more.

[Brief explanation of the drawing]

FIG. 1 is a plot of second quadrant room temperature H versus 4πM for a hot-pressed magnet (curved line A) and a die-upset magnet (curved line B). FIGS. 2(a) to 2(c) are schematic diagrams showing partial cross-sections of two different die combinations illustrating a series of die operations during molding of an H-thermally processed arcuate magnet. 3(a) and (b) are schematic diagrams showing the split ram die in two different operating states. FIGS. 4(a) and 4(b) are schematic cross-sectional views of a hot-pressed compact and a die-upset permanent magnet fabricated according to the invention. FIG. 5 shows a cross-section of a thermally processed arcuate magnet with adjacent regions of different magnetic alignments according to the invention. FIGS. 6(a) and 6(b) are one embodiment of the present invention, and thus FIG.
FIG. 2 is a schematic diagram illustrating a method of manufacturing an arcuate magnet similar to that described in FIG. FIG. 7 further illustrates another die forming process for forming a permanent magnet having regions with at least two different magnetic orientations. [Suspicious amount of main parts] 36.42.68...Object

Claims (1)

[Claims] 1. In a permanent magnet body having first and second regions having different magnetic properties, the object (36; 42:68) is one or more of iron, neodymium, and/or praseodymium and boron. The first and second regions (38; 40; 44; 46; 58; 60) are arranged along the surface direction of the object (36; 42; 68), and the magnetic alignment A permanent magnetic body characterized in that the objects (36; 42; 68) are heat-processed so that their states are different from each other. 2. The arcuate object (36; 42) has the first region located at one end (40; 46) and the second region located at the center of the surface of the arcuate object (36; 42). Consists of area (38; 44),
The object (36; 42) is characterized by being thermally processed so that the first region has a higher coercive force than the second region when measured in the radial direction of the arcuate object (36; 42). Permanent magnetic body according to claim 1, wherein said object is an arcuate object (36; 42). 3. The object (36; 42) is connected to one end of the arcuate pole magnet (40; 4
6), and the second region located at the center of the surface of the arcuate pole magnet, and the area is measured in the radial direction of the arcuate pole magnet in the first region (40; 46). The object is arranged such that the coercive force is larger than that of the second region, and the residual magnetism measured in the radial direction is larger in the second region (38; 44) than in the first region (40; 46). 2. A permanent magnet body according to claim 1, which is formed into the shape of an arcuate pole magnet for an electric motor, and is non-uniformly heat-processed. 4. A permanent magnetic body having first and second regions having different magnetic properties, wherein the object (36; 42; 68) comprises one or more compositions consisting of iron, neodymium and/or praseodymium and boron. The first and second regions (38; 40; 44; 46; 58; 60) are arranged along the surface direction of the object (36; 42: 68) and have different magnetic alignment states. In the method for producing a permanent magnetic body, wherein the body (36; 42; 68) is thermally processed, the composition comprises iron, neodymium and/or praseodymium and boron, and has an inherent room temperature coercive force of more than about 1000 Oe. to form a substantially fully densified object (30; 48; 56) of the same composition, which is then non-uniformly thermally processed. At least two types of regions (38; 40; 44; 46; 58; 60) A method for manufacturing a permanent magnet body, characterized by manufacturing. 5. The substantially fully densified object (30; 56) has at least two parts (32; 34; 58; 60) with different cross-sectional thicknesses, and the object (30;
; 56) is thermally processed to reduce the thickness of the thick portion (32; 58), and at least two of the above regions (38; 40; 58; 60) having mutually different magnetic alignment states form a thermally processed product. 5. The method of manufacturing a permanent magnet according to claim 4, wherein the permanent magnet is heat-processed so as to be arranged along the surface direction of the magnet. 6. The substantially fully densified object is charged into a die with fine pieces of a composition comprising iron, neodymium and/or praseodymium and boron and having an intrinsic room temperature coercivity greater than about 1000 Oe; is hot-pressed, and the object is heat-processed so as to produce an integrated object having the first and second regions having mutually different magnetic alignment states. A method for manufacturing a permanent magnet according to claim 4.