JPS6393841A - Rare-earth permanent magnet alloy - Google Patents

Abstract

PURPOSE:To improve saturation magnetization and coercive force at room temp., by constituting by specifying the ratio of a low rare earth-B-Fe alloy with a specific composition to an alloy prepared by rapidly cooling a molten substance of high rare earth-Fe. CONSTITUTION:An alloy I consisting of, by weight, 20-35% R (Y, rare earth elements), 0.5-1.0% B, and the balance M (Fe, a mixture of Fe and Co) is prepared. On the other hand, an alloy II obtained by subjecting a molten substance consisting of 35-80% R and the balance X (Fe, a mixture of Fe and one or more elements among B, Al, Ti, V, Co, Zr, Nb, and Mo) to rapid cooling is prepared. Subsequently, the alloy I and the alloy II are blended in a ratio of 99.9:0.1-80:20, which is crushed and mixed and then is subjected to compacting and sintering to be formed into a permanent magnet. The alloy II provides a magnet having high saturation magnetization since it functions as a sintering auxiliary and causes reduction in oxygen content. Moreover, the alloy II has a coercive force-increasing effect and, when heavy rare earth elements are selected as the above R, the coercive force-increasing effect can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rare earth permanent magnet alloy that is useful as a material for various electrical and electronic appliances and has excellent magnetic properties, particularly excellent saturation magnetization and coercive force.

(Prior art and its problems) In recent years, Nd* has been used as a rare earth permanent magnet that does not require Co.
Fe/B magnets have been developed, and the residual magnetic flux density Br is 12.3 kG and the maximum energy product (BH) is due to powder or legal methods.
35) Peng ax magnets with the characteristics of IG fist Oe are being mass produced. However, the saturation magnetization 4πMs of the B phase of Nd2Fe, which is supposed to have the magnetism of this magnet, is 18k.
In contrast, the above Nd-Fe-B magnet has a considerably lower value than this. The reason is that the actual magnet composition has more Nd and B and less Fe than the stoichiometric composition of Nd2F014B, for example, Nd1
This is because s Fe 7 - t B s.

There are two reasons why this amount of Nd increases; one is that this magnet is densified by liquid phase sintering, which requires a liquid phase rich in Nd, and the other is that the magnet is densified during the manufacturing process. Nd
This is because the amount of Nd is increased in advance in anticipation of it being oxidized and wasted. Therefore, in order to obtain higher magnetic properties, the oxidation of the alloy powder during the process should be minimized, and the composition should be changed from the original Nd2Fe1. It is necessary to bring it close to H. Incidentally, a major cause of oxidation during the manufacturing process of Nd11Fe-B magnets is that the Nd-rich portion, which is present in the alloy powder at a volume percentage of about 20%, is very easily oxidized. Therefore, Nd2Fe1. It is conceivable to produce the matrix phase and the Nd-rich phase in separate processes, but since the Nd-rich phase is more easily oxidized than magnet powder, the first step is to find a method to suppress this.

On the other hand, the Curie point Tc of NdaFe@B magnets is approximately 31
Because it is as low as 0℃, the magnetic properties are greatly affected by temperature.
There are restrictions on the operating temperature. In particular, the shadow 1 of the coercive force iHc due to temperature is as large as -00B%/°C and is the most noticeable. For this reason, heavy rare earth elements such as Tb, Dy, and Ho, transition metals such as Ti, V, Zr, Nb, and Mo, and A
A method of increasing the coercive force value at room temperature by adding I has been proposed. However, as the content of these coercive force increasing elements increases, the saturation magnetization of the resulting magnet decreases, so there is a limit to the amount they can be added. Therefore, it is necessary to find additive elements that are less noisy and have the effect of increasing coercive force, and to develop a practical rare earth permanent magnet alloy.

(Means for Solving the Problems) The present invention aims to provide a rare earth permanent magnet alloy that has high saturation magnetization and maintains high coercive force even at room temperature.
R of 20 to 35% by weight percentage (however, R is at least one kind of rare earth element including Y) and 0.5 to 1.5
% of B and the balance M (however, M is Fe or Fe and Co
Alloy I consisting of 35 to 80% R (where R is the same as above) and the balance X (where X is Fe or a mixture of Fe and B, Al, Ti, V, Co.

Alloy I obtained by rapid cooling of a melt consisting of a mixture of Zr, Nb, and at least one of Mo! Toga,
The present invention relates to a rare earth permanent magnet alloy having a ratio of 99.5:0.1 to 80:20.

To explain this, the present inventors have conducted various studies to solve the above-mentioned problems, and as a result, (1) Fe or Fe! : The above-mentioned alloy I whose main component is a mixture with Co to form a matrix, and Y
The above-mentioned alloy as a sintering aid whose main component is a rare earth element containing! When a permanent magnetic alloy is produced by the so-called two-reserve method, in which alloy I and I are individually melted, solidified, and pulverized, and then sintered in a mixing chamber, alloy II, which serves as a sintering aid, is mixed with alloy I, which forms the matrix. Lll of the element distribution in the crystal grain structure using an electron probe microanalyzer revealed that R,,Ml, forms a heterogeneous structure unevenly distributed near the grain boundaries in the crystal grains of the parent phase and in the R-rich phase. As a result, the coercive force can be effectively improved to the conventional amount -L, and the use of heavy rare earth elements and transition metals as additive elements can be reduced. (2) By rapidly cooling and solidifying the molten alloy II, the oxidation of rare earth elements during the manufacturing process is suppressed, and the amount of oxygen in the entire magnetic alloy is reduced, making it possible to reduce the amount of oxygen in the entire magnetic alloy. It is possible to improve the saturation magnetization by making the composition closer to the stoichiometric ratio than (3).
) As the rare earth elements used in this permanent magnet alloy, we have discovered that all rare earth elements other than the above-mentioned Nd and Y can be similarly applied, and have arrived at the present invention.

As described above, the alloy I used in the present invention contains at least one rare earth element containing Y represented by R of 20 to 35% in deuterium percentage, 0.5 to 1.5% of B, and the balance. M is composed of Fe or a mixture of Fe and Co, but if R is 20% or less in this composition, the coercive force is low, and if R is 35% or more or B is outside the above range. In this case, only magnets with low coercive force and saturation magnetization equivalent to those obtained by the -alloy method can be obtained.

These rare earth elements include La, Ce, Pr, Nd, and Sm.
It is preferable to select at least one of -L light rare earth elements, especially Nd or Pr elements, which has the advantage of further improving the saturation magnetization of the permanent magnet as the final product.

In preparing this alloy I, the ratio of rare earth elements in the ingredients is low, and there is little influence from this oxidation, so the above ingredients are put into a commonly used high frequency furnace, melted, poured into a mold, coarsely pulverized, This is achieved by fine pulverization or the like.

On the other hand, Alloy II contains at least i! i or more, and the remainder X is Fe or Fe and B, AI, Ti, V, Co, Z
It is composed of a mixture with at least one of r, Nb, and Mo (7), but if R is 35% or less, the amount of liquid phase in the sintering temperature range is small and it is effective as a sintering aid. becomes small, and if it exceeds 80%, oxidation will be severe even during rapid cooling, making handling difficult.

Furthermore, this alloy I! When selecting a light rare earth element similar to that used as a rare earth element in the above, it serves as a sintering aid in the magnet structure, resulting in a decrease in the amount of oxygen, thereby providing a magnet with high saturation magnetization.

On the other hand, as this rare earth element, Gd, Tb%D? ,Ho,E
r, Tm, Yb, Lu, and Y (7) When at least one heavy rare earth element is selected, it has an effect of increasing coercive force in addition to the effect as a sintering aid.

In addition, the component defined by the multiple X is Fe or Fe and B
, Al, Ti, V, Co, Zr, Nb, Mo.
This has the effect of increasing the coercive force of.

This molten alloy, which is used as a sintering aid and contains a large amount of rare earth elements that are easily oxidized, is rapidly solidified to make it easier to crush and to suppress the oxidation of rare earth elements by imparting oxidation resistance to the surface. However, in this case, the cooling rate is preferably 1000°C/see or higher, and it is desirable to solidify into a ribbon or powder.
If the cooling rate is less than this, the ribbon becomes thick, the powder becomes coarse, and the amount of oxygen adsorbed during pulverization or mixing with Alloy I increases, which is not preferable.

1- Solidification into a thin strip or powder by rapid cooling can be easily achieved by forming a thin strip by a single roll method, a twin roll method, etc., or into a powder by a gas atomization method, a powdering method using a roll, etc. be able to.

In this way, 1! ) Alloy II melts in the sintering temperature range and acts as a sintering aid, so it has a melting temperature similar to that of Alloy I (~3
It is not necessary to make the powder into fine particles, and the particle size of the powder may be coarser than that of the residual powder, which has the advantage of suppressing the oxidation of Alloy II.

In addition, alloys Ⅰ and II are 99.5:0-1 to 80:2
A permanent magnet can be obtained by mixing, pulverizing, mixing, molding, and sintering using a conventional method. Alloy I in this formulation
If the amount of I added is less than 0.1%, it will not be effective as a sintering aid, and if it is more than 20%, the saturation magnetization will decrease significantly, which is not preferable.

When mixing the remaining material II, when Alloy 11 is in the form of 8 strips, it is first mixed with the powder of Alloy I made into coarse particles by coarse pulverization, or mixed with the powder of Alloy I in the form of a pJ strip, and then mixed with the powder of Alloy I. (or while mixing), and if Alloy II is a powder with a particle size of about 20 mesh or less, it can be mixed with the remaining powder as it is, and in this case there is no need to grind it again. Therefore, it has the advantage of suppressing oxygen adsorption.

(Effect of fi light) According to the present invention, "1) (by forming a unevenly distributed structure of the sintering aid alloy in the matrix forming alloy by the second life method, the coercive force of the permanent magnet to be rubbed is This can be improved even more effectively.

2) The use of heavy rare earth elements and transition metals as additive elements is small, and a decrease in saturation magnetization can be suppressed.

2. By reducing the amount of oxidation during the manufacturing process, l) the composition of the permanent magnet alloy can be changed to the R2M
14B phase, resulting in increased saturation magnetization and a permanent magnet with a higher maximum energy product.

2) Loss due to oxidation of R element, which is the most expensive of the three main elements R, Fe, and H, is reduced.

3) The time constraints for handling conventional 1-alloy powder in air are relaxed, reducing manufacturing costs.

4) The risk of alloy powder ignition is lowered, and the yield is improved. ” and other effects.

(Example) Next, specific aspects of the present invention will be explained using examples.

Example 1 Using electrolytic iron, B or ferropolone with a purity of 93.5% or more, and Nd with a purity of 99.5% or more as starting materials, the compositions and mixing ratios of alloys I and II were respectively shown in Table 1. Alloys were weighed, put into a high frequency melting furnace, melted in vacuum or in an Ar atmosphere, poured into an SI mold, and cooled to obtain an ingot. Alloy 0 was pulverized into particles of 500μ or less using a disk mill, and then melted in a ball mill. 0 alloy If used for pulverization was melted in the same manner, and the melting rate was approximately 301/s.
It was rapidly quenched by jetting it onto a copper roll rotating at a speed of ee (quenching rate: about 10,000°C/5ec) to form a thin strip. The average particle diameters of alloys I and II thus obtained were 1 to 10 bar 1 and 1 to 500 B m, respectively.
Alloy II was added during the grinding of Alloy I, and the mixture was mixed and ground in a ball mill in n-hexane while adjusting the respective grinding times. After removing n-hexane and drying, it was molded at a press pressure of 1 t/crn' in a magnetic field of 1 koe, sintered at 1000 to 1200°C, and further
They were heat-treated at 0°C for 1 hour to form permanent magnets, and their magnetic properties were measured, and the results shown in the table were obtained.

In the same table, Experiment No. 1 to 3 are the present invention, No. 4
-5 are comparative examples with different compositions, No. 6-7 are alloy II
Comparative examples No. 8 to No. 9 are those of the compositions shown in the table, which were not quenched. They were melted, solidified, and pulverized by the over-life method under the same conditions as Alloy I above, and then permanently cured in the same manner as above. This is a comparative example using a magnet. The compositions in the table are expressed as atomic percentages,
The mixing ratio represents the percentage of heavy noise.

Example 2 Electrolytic iron as a starting material, B, Co with a purity of 39.5% or more
, Al, Nb, Ce, Pr, Nd, Td, and Dy were weighed so as to have the compositions and mixing ratios of Alloys I and II shown in Table 2, respectively, and melted in the same manner as in Example 1. Anisotropic sintered bodies (experiment Nos. 10 to 14) were created using the fine powder obtained by solidification, mixing, and pulverization. When the magnetic properties of each sintered body were measured, the results shown in the table were obtained.

For comparison, the final composition of the sintered body of Experiment No. 13 (Nd
An ingot having the same composition as 13-3Fe72.8CO8, OB5.9) was prepared and wet-pulverized using a ball mill in n-hexane according to the -alloy method to obtain a powder with an average grain size of 3.5μ. When this was pressed, sintered, and heat treated under the same conditions as Example 1, and its magnetic properties were examined, the residual magnetization was 1.
．． It was very low, with a coercive force of 5 kG or less, a coercive force of 0.2 kG or less, and a maximum energy product of 1) less than IC.08.

The reason for this is thought to be that the samples prepared by the after-life method were not sufficiently sintered and had a low apparent density of 8.23/cc or less. On the other hand, Experiment No. 13 created using the 2-alloy method
It was confirmed that the sample according to the above had an apparent density of 7.433/cc and was baked to 38% or more of the true density.

Claims (1)

[Claims] 1. R of 20 to 35% by weight percentage (however, R is at least one kind of rare earth element including Y) and 0.5 to 1
．． Alloy I consisting of 5% B, the balance M (where M is Fe or a mixture of Fe and Co), and 35 to 80% R
(However, R is the same as above) and the remainder X (However, X is F
e or Fe and B, Al, Ti, V, Co, Zr, Nb
, a mixture with at least one or more of the following:
A rare earth permanent magnet alloy having a ratio of 0.1 to 80:20.