JPH04356903A - Manufacture of direct current flow quenching magnet - Google Patents

Abstract

PURPOSE:To provide a manufacturing method capable of obtaining a quenching magnet, which is superior in magnetic characteristics and is stable, by a method wherein in the rare earth element-transition metal alloy quenching magnet, which is utilized for various motors, an actuator and the like, the problem of lowering and fluctuation of the intrinsic coercive force HCJ of the magnet are solved. CONSTITUTION:A rare earth element-iron alloy quenching magnet material having a value of 1/[1+(Ia/Ic)] (Ia is an amorphous diffraction peak area strength and Ic is a crystalline diffraction peak area strength), which is shown in the X-ray diffraction pattern and is specified in less than 0.60, or a billet consisting of the magnet material is hot-compressed rapidly by a compression using a rated load heavy load and a direct current flow, whereby a direct current flow quenching magnet having the value of an intrinsic coercive force HCJ made uniform to a level close to the maximum can be manufactured. In the case of the billet, it is desirable to set the ratio of a projected area S in the direction of a pressure axis of a cavity to a projected area So in the direction of the pressure axis to the billet in a ratio of (S/So)<=2.6.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to R2TM14B compound (
However, R is a rare earth element, TM is at least one element selected from Fe and Co), and the quenched magnet material or its billet, which has a specified metastable state, is compressed under a constant load and directly energized. The present invention relates to a method for manufacturing a compressed directly energized quenched magnet.

The directly energized quenched magnet thus obtained can stably generate a strong static magnetic field in the magnetic circuit gap, and can be used in various motors, actuators, and the like.

0003

[Prior Art] A method for manufacturing quenched magnetic materials is described, for example, in a paper published by Egami entitled "Low-Field Magnetic Properties of Amorphous Alloys".
Property of AmorphousA
lloys”Journal of The A
merican Ceramic Society
, vol. 60, No. 3 p. 128, 1977) as a continuous splat quenching method.

[0004] When an alloy bath containing a rare earth element R and typical transition metal elements Fe and B in a ratio close to 2:14:1 is rapidly cooled by a continuous splat process called melt spinning, R2T
A quenched magnet material that is magnetically isotropic in a metastable state and has an M14B compound as its main phase can be obtained (Japanese Patent Laid-Open No. 59-64739).
(Japanese Patent Application Laid-Open No. 60-9852). Quenched magnet materials have different metastable states depending on the degree of quenching, and are classified into underquench (UNDER-QUENCH), optimal quench (OPTIMUM-QUENCH), and overquench (OVER-QUENCH) states. Indicates the highest value of the characteristic. Optimum quench conditions are useful, for example alloy composition Nd13
．． The magnetic properties of the quenched magnet material in the optimal quench state, which is obtained by melt-spinning a rare earth-iron alloy of 5Fe81.7B4.8, are as follows: intrinsic coercive force HCJ = 14 kOe, residual magnetization 4πIr = 8 kG, energy product (BH) max = 1
4MGOe, J. F. Harvest (J.
F. Herbest et al. published a paper entitled “Rare Earth-Iron-Boro Materials”
n Materials”A new era i
n permanent magnets, Ann. R
ev. Sci. vol. 16 p475, 1984)
has been reported.

The magnetic properties of the optimally quenched quenched magnet material are based on a fine structure in which a 20-100 nm R2TM14B compound is dispersed in an amorphous Fe phase. In the under-quenched state, the R2TM14B compound is insufficiently crystallized and the HCJ is low. In the region from optimal quench state to overquench state, R2TM1
HCJ and 4πIr decrease due to coarsening of the 4B compound. Note that crystallization and coarsening of the R2TM14B compound occur not only by the degree of rapid cooling but also by heating the rapidly cooled magnet material to a temperature higher than the crystallization temperature (approximately 580° C.).

[0006] The material form of the above-mentioned quenched magnet material is limited to a powder form such as a thin band. Therefore, in order to make a general bulk magnet, it is necessary to change the material form, that is, to fix the thin band or thin piece by some method. The basic immobilization technology in powder metallurgy is pressureless sintering, but it is difficult to apply pressureless sintering to quenched magnet materials because it is necessary to prevent a decrease in HCJ due to the metastable state.

[0007] As a general method of converting the material form into a bulk magnet, there is a method of fixing quenched magnet material with resin. Since the resin can fix the quenched magnet material below its crystallization temperature, the HCJ is basically unchanged. Therefore, in this case, quenched magnet material in an optimally quenched state is used. However, with resin bonded rapidly cooled magnets, it is difficult to increase the density to 6 g/cm3 or more, and 4πIr is limited to ≦6.2 kG. Compared to 4πIr≈8kG of the quenched magnet material, 4πIr≦6.2kG of the resin-bonded quenched magnet becomes an obstacle that generates a strong static magnetic field in the magnetic circuit gap of various motors and actuators.

On the other hand, if the quenched magnet material is induction heated and hot compressed at a temperature higher than the crystallization temperature, the quenched magnet material can be directly fixed. According to this fixation technology, by using quenched magnetic material in an underquenched state, it is possible to increase the density to a state close to true density while maintaining the HCJ level to some extent, and hot compression of 4πIr≦8.4kG. It becomes a quenching magnet.

When the hot-compression quenched magnet is further induction-heated and hot-compressed above the crystallization temperature, the R2TM14B compound rotates in a specific direction depending on the degree of plastic deformation, inducing magnetic anisotropy and improving 4πIr. Then, Earl. Double. A paper published by R.W. Lee et al. “Hot-pressed neodymium-iron-boron magnet” (“Hot-pr
essed neodymium-iron-bor
on magnets”Applied Phys
ics Letters vol. 46 No. 8,
p790, 1985). This hot compression quenched magnet by induction heating is 4π depending on the degree of plastic deformation.
Since Ir=8 to 13 kG, it is possible to generate a strong static magnetic field in the magnetic circuit gap of various motors, actuators, etc.

0010

However, when a rapidly cooled magnet material is hot-compressed at a temperature higher than its crystallization temperature, particularly when it is subjected to two-step hot compression, the HCJ tends to decrease due to coarsening of the R2TM14B compound. Methods for suppressing the decrease in HCJ include methods related to alloy composition, such as adding Ga to the quenched magnet material, and methods of rapidly hot-compressing the quenched magnet material. As a rapid hot compression process, the present inventor has proposed a compression/direct energization method using a constant load (for example, Japanese Patent Application No. 2002-1
No. 41073). However, the region from the underquench state to the optimal quench state of the rapidly cooled magnet material is continuous. This means that even if it is a hot-compression quenched magnet in which additive elements such as Ga are added to the quenched magnet material, or a directly energized quenched magnet in which hot compression process control is quickly performed, the underquenching of the quenched magnet material will result. This means that HCJ varies depending on the degree of the condition. H.C.J.
This, together with the temperature coefficient of HCJ, has a significant effect on the thermal stability represented by irreversible demagnetization of the magnet. Therefore, it is important to stabilize the HCJ value of the magnet at a level close to the optimal quench state for various motors and actuators. This is necessary to stably generate a strong static magnetic field in the magnetic circuit air gap.

The present invention brings the HCJ value of a directly energized quenched magnet to an optimal quench state by combining a specific underquenched quenched magnet material with a constant load compression/direct energization method that enables a rapid hot compression process. The aim is to stabilize it at a similar level.

0012

[Means for Solving the Problems] The present invention provides a 1/[1+(Ia/Ic)] value (Ia is the amorphous diffraction peak area intensity, Ic is the crystalline diffraction peak area intensity) in an X-ray diffraction pattern. The HCJ value is brought close to the optimal quench state by quickly hot-compressing the rare earth-iron alloy quenched magnet material or its billet, which is specified to have a value (represented by each expression) of less than 0.60, by constant load compression and direct energization. This is a method of manufacturing directly energized quenched magnets that meet the standards. For billets, the ratio of the projected area S of the cavity in the pressure axis direction to the projected area So of the billet in the pressure axis direction (S/So)≦
2.6.

[0013]

[Operation] The present invention will be explained in more detail below.

First, 1/[1+(Ia/I
c)] Explain the values. Here, the formula 1/[1+(Ia
/Ic)] is the quenched magnet material in the underquenched state.
In the line diffraction pattern, P. Naughty. Hermans (P.
H. Hermans) crystallinity calculation method (P.H.
Hermans et al; macromol.
chem. vol. 50, No. 98, 1961). In the present invention, 1/[1+(Ia/Ic)
] Specify the value to be less than 0.60.

The quenched magnet material referred to in the present invention is a typical transition metal element F with a rare earth element R13 to 14 atomic % as a standard.
At least one element among e and Co and B are 2:
A molten alloy containing a ratio close to 14:1 is rapidly cooled by a continuous splat process called melt spinning, and it is an irregularly shaped ribbon or flake with a thickness of about 30 μm. In addition, as an additive element to the alloy, element Z suppresses grain growth and increases HCJ.
n, Al, Si, Nb, Ta, Ti, Zr, Hf, W, etc. may be used as long as the residual magnetization does not decrease. However, at the stage of continuous splat rapid cooling, 1/[1+(Ia/
Ic)] value is required to be less than 0.60.

[0016] The billet referred to in the present invention is 1/[1
+(Ia/Ic)] A rapidly cooled magnet material with a value of less than 0.60 is hot-compressed by applying a constant load and directly energized to form a billet, and the density is 80 to 95 of the true density.
% is preferable.

Next, the structure and operation of a hot compression process in which the quenched magnet material or its billet is compressed under a constant load and directly energized to form a quenched magnet will be described.

FIG. 1 is a sectional view of a main part in which a quenched magnetic material or a billet thereof is hot-compressed by compression under a constant load and direct energization. In the figure, 1 is a die, 2a and 2b are a pair of electrodes corresponding to the die 1, and form a cavity with the die 1. 3a and 3b are a pair of thermal compensators placed on the anti-cavity surfaces of the electrodes 2a and 2b. 4 is a quenched magnet material or a billet thereof that becomes a predetermined quenched magnet. 5a and 5b are constant load pressurization systems, 6a is a discharge processing power source, and 6b is a DC constant current power source. Note that these power sources 6a and 6b are electrically connected to the pressure shaft rods of the pressurizing systems 5a and 5b.

In the hot compression process in which the quenched magnet material is directly energized and made into a quenched magnet, first a constant load of 200 to 500 kgf/cm2 is applied to the quenched magnet material 4 from the end faces of a pair of thermal compensators 3a and 3b via electrodes 2a and 2b. Add compression due to load. The compression reduces the potential energy of the quenched magnet material 4. Subsequently, the quenched magnet material 4 is subjected to electric discharge. An etching effect in which active chemical species such as electrons, ions, and excited species due to discharge collide with the surface of the quenched magnet material 4 with a certain amount of kinetic energy, thereby reacting with contaminants and low-molecular compounds attached to the surface of the quenched magnet material. The potential energy decreases further.

After the above-described discharge treatment, current is applied directly to the quenched magnet material 4 via the pair of thermal compensators 3a and 3b and the electrodes 2a and 2b while maintaining the compression pressure due to the constant load applied to the quenched magnet material 4. do. The temperature begins to rise with the generation of Joule heat proportional to both the square of the current density ΔI at each part and ρ/sc (ρ is specific resistance, s is specific gravity, c is specific heat, and s×c is volumetric specific heat).

[0021] ρ/sc in the initial state of the rapidly solidified magnet material 4 is 1
It is about 0-4. There, the electrode 2 that forms the cavity
The ρ/sc of a and 2b is set to about 10 −4 or a slightly lower level of 10 −5. The ρ/sc of the pair of thermal compensators 3a and 3b which are in contact with the anti-cavity surfaces of the electrodes 2a and 2b is set at the 10-3 level. Thereby, the temperature rise of the rapidly cooled magnet material 4 can be corrected by heat transfer from the thermal compensators 4a and 4b. When the quenched magnet material 4 in the cavity whose temperature rise has been corrected is heated to a temperature higher than the crystallization temperature of the quenched magnet material 4 under compression pressure by constant load loading, the temperature rise is 10
- Plastically deformed and densified at a strain rate of -1 to 10-2 mm/sec or more. The strain rate is accelerated by a decrease in viscosity as the temperature of the rapidly cooled magnet material 4 increases, but as densification progresses, the strain rate shows a peak and gradually decreases to a smaller value. Strain rate 1
If the current is cut off when the current reaches about 0-3 to 0 mm/sec, the quenched magnet material 4 becomes a directly energized quenched magnet whose HCJ value is close to the optimal quench state and is highly densified to almost true density. In addition, in order to bring the HCJ value to a level close to the optimal quench state, the heating peak should be set at the crystallization temperature ~75
Keep the temperature below 0℃ and increase the temperature to 10-1 to 10-3 Torr.
It is desirable to perform this in a vacuum atmosphere of r.

The method of hot-compressing the quenched magnet material by compression under a constant load and direct energization has been described above.A billet of the quenched magnet material is hot-compressed by compression under a constant load and direct energization to create a magnetic It is also possible to induce anisotropy. In this standard operation, both the compression pressure P due to constant load application and the current I are stepped up during hot compression. Specifically, after discharging for about 15 seconds under the primary pressure P1 ((0.2 to 1.0) .0)×I2)
Add. Plastic deformation of the billet starts after about 20 seconds, and the billet plastic deformation peak under P1 is observed after about 40 seconds. When the peak has passed, the secondary pressure P2 (250 to 300 per projected area in the pressure axis direction of the cavity)
kgf/cm2), and finally the secondary current I2 (250 to 350 per projected area in the pressure axis direction of the cavity).
A/cm2) for about 10 to 20 seconds to form the final shape. The total energization time is about 80 seconds. Note that the ratio (S/So) of the projected area S of the cavity in the pressure axis direction and the projected area So of the billet in the pressure axis direction must be 2.6.

[0023]

EXAMPLE Hereinafter, the present invention will be explained in more detail by way of an example. However, the magnetic property values shown below are based on a 50 kOe pulse magnetized self-recording flux meter (RFM) or a vibrating magnetometer (V
SM).

Alloy composition Nbx (Fe0.80Co0.2
0) 94-xB6, the density of the quenched magnet material in the optimal quench state reaches the true density of 8 by applying pressure and direct current in the configuration shown in Figure 1.
0 to 95%, outer diameter 16 mm, weight 16.9 g (pressure 250 kg/cm2, current density 280 A/
cm2, atmosphere 10-1 to 10-2 Torr). This billet was compressed and hot-compressed by direct energization into a directly energized quenching magnet (S/So=
2.25) (P1=0.4×P2, P2=280
kg/cm2, I1=0.5×I2, I2=260A/
cm2).

FIG. 2 is a characteristic diagram showing the magnetic characteristics of the above-mentioned magnet with respect to the amount of Nd. As shown in Figure 2, the amount of Nd is 13~
The range of 14 atomic % shows high values for both HCJ and 4πIr. Furthermore, the HCJ value is greatly influenced by the alloy composition, such as the amount of Nd, as well as the material condition. This suggests that it is difficult to specify the material state based on the HCJ value of the quenched magnet material.

FIGS. 3(a) to 3(f) show alloy composition Nd13.
FIG. 6 is a characteristic diagram showing the X-ray diffraction patterns of six types of quenched magnet materials with different underquench states of 6Pr0.15Fe77.5Co3.0B5.8. X-ray source is Cu-Kα, 40k
V-30mA, scanning speed 0.5°/min, scanning range (
2θ=20 to 60°). Figure 3(a) shows P. Naughty. 1 by the method of P.H. Hermans
/[1+(Ia/Ic)] value is calculated, Ia=0
．． 393(kcps×deg), Ic=0.330(k
cps×deg), 1/[1+(Ia/Ic)]=0.
It is 45. (b) to (f) 1/[1+(Ia/Ic
)] values are also shown in the figure.

[0027] The above alloy composition Nd13.6Pr0.15F
e77.5Co3.0B5.8 1/[1+(Ia/I
c)] Six types of quenched magnet materials with different values were compressed under a constant load and directly energized in the configuration shown in Figure 1 to create a directly energized quenched magnet (S/So = 1 magnet) with an outer diameter of 16 mm and a weight of 16.9 g.
(pressure 250 kg/cm2, current density 280 A/
cm2, atmosphere 10-1 to 10-2 Torr).

FIG. 4 is a characteristic diagram showing the relationship between the HCJ of the quenched magnet material and the directly energized quenched magnet with S/So=1 for the 1/[1+(Ia/Ic)] value. 1 as shown in Figure 4
/[1+(Ia/Ic)] When the value is around 0.60, both the material and the HCJ of the magnet change significantly. 1/[1+(I
a/Ic)] value of 0.60 or more, a decrease in the HCJ of the magnet is observed, and the state begins to shift from the optimal quench state to the overquench state. However, 1/[1+(Ia/Ic)
] When the value is less than 0.60, the HCJ of the magnet increases in proportion to the 1/[1+(Ia/Ic)] value, and although it is an underquench state, it can be said to be at a level extremely close to an optimal quench state. The 4πIr of the directly energized quenched magnet is 8.2 to 8.3 kG, which is equivalent to the quenched magnet material itself. Therefore, it is suggested that the static magnetic field of the magnetic circuit air gap is improved by 30% or more compared to a resin-bonded quenched magnet.

Next, 1/[1+(Ia/Ic)] value 0.5
9 and 0.65 were made into cylindrical billets with densities of 80 to 95% of the true density and different outer diameters, and these were made into magnets with an outer diameter of 24 mm and a height of 5 mm (P1 = 0
．． 4×P2, P2=280kg/cm2, I1=0.5
×I2, I2=260A/cm2).

FIG. 5 is a characteristic diagram showing the magnetic characteristics for S/So. As shown in Figure 5, S/So≒2 and 4πIr
exceeds 11 kG and (BH) max reaches approximately 30 MGOe, but HCJ has a 1/[1+(Ia/Ic)] value of 0.
The manner of decline is different between 59 and 0.65. 1/[1+(
Ia/Ic)] value of 0.59, that is, less than 0.60, no significant decrease in HCJ was observed, and S/So was 2.40.
The maximum value of (BH)max can be obtained at a maximum value of (BH)max.

[0031] Note that if S/So exceeds 2.60, 1/[
1+(Ia/Ic)] Even if the value is less than 0.60, HC
Since J starts to decrease, it is preferable that S/So≦2.6.

[0032]

Effects of the Invention The present invention optimizes the HCJ value of a directly energized quenched magnet by combining a specific underquenched quenched magnet material with a constant load compression/direct energization method that enables a rapid hot compression process. It is stabilized at a level close to the current state, and has the effect of stably generating a strong static magnetic field in the magnetic circuit gap of various motors and actuators.

[Brief explanation of drawings]

[Figure 1] Cross-sectional view of main parts showing the process of compression and direct energization

[
Figure 2: Characteristic diagram showing the relationship between the amount of Nd in a magnet and its magnetic properties

[
Figure 3: Characteristic diagram showing the X-ray diffraction patterns of six types of quenched magnet materials

[
Figure 4: Characteristic diagram showing changes in HCJ of materials and magnets with respect to 1/[1+(Ia/Ic)] value

[Figure 5] Characteristic diagram showing changes in magnetic properties with respect to S/So

[Explanation of symbols]

1 Die 2a, 2b A pair of electrodes 3a, 3b A pair of thermal compensators 4 Quenched magnet material or billet 5a, 5b Pressure system 6a　Discharge processing power supply 6b DC constant current power supply

Claims (2)

[Claims] Claim 1: 1/[1+(Ia/
Ic)] value (Ia is the amorphous diffraction peak area intensity, Ic
(represents the diffraction peak area intensity of crystalline material) is 0.
．． A method for producing a directly energized quenched magnet, in which a quenched magnet material of a rare earth-iron alloy having a particle diameter of less than 60% or a billet thereof is hot-compressed by constant load application and direct energization. [Claim 2] Ratio between the projected area S of the cavity in the pressure axis direction and the projected area So of the billet in the pressure axis direction (S/So)
2. The method for producing a directly energized quenched magnet according to claim 1, wherein: 1.0 to 2.6.