JPH05315114A - Manufacture of rare earth magnet material - Google Patents

Abstract

PURPOSE:To prevent the drop of the crystal property of an ThMn12-type crystal structure of compound phase even if nitrogen penetrates into it. CONSTITUTION:Alloy contains N by 2-20% by getting alloy powder, which has a rare earth metal (R) consisting of at least one kind out of Nd, Pr, and Ce, Fe, and other metal consisting of at least one kind out of Ti, Mo, V, W, Cr, Mn, Al, and Si for its main ingredients and besides has a ThMn12-type compound for its main phase, and next, bringing the allay powder into contact with the nitriding gas at 200-600 deg.C thereby making nitrogen penetrate into it, and also, performing the diffusion heat treatment of nitrogen in the same temperature range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rare earth magnet material, and more particularly, a method for producing a rare earth-iron-nitrogen alloy powder as a magnet material having excellent magnetic characteristics and temperature characteristics. Regarding

[0002]

2. Description of the Related Art In recent years, high-performance Nd-Fe-B permanent magnets have been widely used as various electronic devices have been downsized. However, since this magnet has a low Curie point of 310 ° C, it has poor temperature characteristics and is difficult to use above 150 ° C.
On the other hand, by entering the nitrogen alloyed with rare earth metals and iron, for example, Th ₂ Zn ₁₇ type Sm -Fe -N-H-based permanent magnet of the compound as the main phase of crystal structure (alloy) is excellent It has been reported to have magnetic properties and a Curie point of about 470 ° C. However, this alloy has a problem that the cost is higher than that of the Nd-Fe-B-based alloy because Sm, which is rare even in rare earth metals, is used.

More recently, Nd-Fe-Ti-N system permanent magnets having a compound of Th Mn ₁₂ type crystal structure as a main phase have been developed and attracted attention (for example, JP-A-2-57663).
Publication). This alloy is expected to have excellent magnetic characteristics and temperature characteristics similar to the Sm-Fe-N-H alloy, and is inexpensive in terms of cost because it uses inexpensive Nd.

By the way, conventionally, the above-mentioned Nd-Fe-Ti-N is used.
Generally, Nd-Fe-Ti is used to produce a magnetic material.
A method has been adopted in which a powder containing a base alloy as a master alloy is obtained, and then a nitriding gas is brought into contact with the powder at an appropriate temperature to allow nitrogen to enter. According to this method, nitrogen penetrates into a predetermined position (2b site) in the crystal lattice of the Th Mn ₁₂ type main phase,
For example Nd nitride having a formula of _{Fe 11 Ti N x (x =} 0.2~2.5) is produced, it is that this nitride is to greatly contribute to improvement of magnetic properties and temperature characteristics.

[0005]

However, the above N
According to the method for producing a rare earth magnet material in which the nitriding gas is simply brought into contact with the d-Fe-Ti alloy powder and nitrogen is introduced,
There is a problem that not only the magnetic properties of the obtained powder become unstable, but also the magnetic long-term stability is lacking. This is because the intrusion position and amount of nitrogen taken into the crystal lattice are not constant, and there is a difference in the nitrogen content between the surface of the alloy powder and the inside. As a result, the Th Mn ₁₂ type main phase (nitride phase) It is considered that the crystallinity of) became unstable.

The present invention has been made on the basis of the above consideration. The purpose of the present invention is to prevent T even when nitrogen is penetrated.
An object of the present invention is to provide a method for producing a rare earth magnet material that does not lower the crystallinity of the h Mn ₁₂ type main phase and contributes to the improvement of magnetic properties and long-term stability.

[0007]

[Means for Solving the Problems] In order to solve the above problems,
The method for producing the rare earth alloy powder according to the present invention is based on Nd, P
Rare earth metal (R) consisting of at least one of r and Ce, Fe, and Ti, Mo, V, W, Cr and Mn
, Al, and Si, other alloys containing at least one metal (M) as a main component, and a compound having a Th Mn ₁₂ type crystal structure as a main phase are obtained as an alloy powder. The alloy is characterized in that 2 to 20 atomic% of nitrogen is contained in the alloy by contacting with a nitriding gas in a temperature range of 600 ° C. and then performing diffusion heat treatment of nitrogen in the same temperature range.

Conventionally, an alloy having a compound of a Th Mn ₁₂ type crystal structure as a main phase and having a composition of 11% Fe -1% Ti-balance (bal.) Sm in atomic% has been known. This alloy has a low saturation magnetic flux density and is not suitable for practical use. Therefore, it is considered that nitrogen is simply allowed to penetrate into this alloy, but in this case, the crystal magnetic anisotropy becomes in-plane anisotropy and cannot be a magnet material. However, in the case of an alloy using any one of Nd, Pr and Ce as the rare earth metal (R),
Uniaxial anisotropy can be imparted, and other magnetic properties are also excellent. By the way, 11% Fe -1% T before nitrogen invasion
The saturation magnetic flux density, crystal magnetic anisotropy and Curie point of i-bal.Nd alloy are 12.5 kG, 10 kOe and 270 ° C, respectively.
Whereas those of the alloys after nitrogen infiltration are 13.7
kG, 60kOe, 460 ℃ significantly improved. In order to adjust the magnetic performance and the cost of raw materials, Nd, Pr, Ce
There is no problem in substituting some of the above with other rare earth metals.

For other metals (M), Ti, M
Any one of o, V, W, Cr, Mn, Al and Si is Th.
It is essential for stabilizing the Mn ₁₂ type crystal structure, and is required in the alloy in an amount of about 5 to 20 atom%. Further, in the present invention, by substituting a part of Fe in the alloy with Co,
Further, the saturation magnetic flux density and the Curie point can be increased. However, when the substitution rate of Co for Fe is 50% or more, the decrease in magnetocrystalline anisotropy becomes large.
It should be less than 50%.

In the present invention, the method for obtaining the alloy powder is arbitrary. For example, raw materials prepared by mixing rare earth metals, iron and other metals in a predetermined ratio are subjected to high frequency melting, and the molten alloy is poured into a mold to form an alloy ingot, which is then homogenized at high temperature and then the ingot May be crushed by a jaw crusher, a ball mill, a jet mill, or the like, or the molten alloy may be directly cooled to obtain a powder.

Further, the penetration of nitrogen into the alloy powder is carried out by bringing this powder into contact with a nitriding gas at a high temperature. In this case, if the particle size of the powder is 1 μm or less, it is easy to oxidize, and nitrogen is not sufficiently penetrated in a unit of several mm. As the nitriding gas, nitrogen, ammonia, or a mixed gas of nitrogen and hydrogen can be used. Further, regarding the nitrogen penetration temperature, if the temperature is less than 200 ° C, the penetration of nitrogen is insufficient.
If it exceeds the above range, the Th Mn ₁₂ type crystal structure is easily decomposed.

By the way, a difference in the amount of nitrogen invasion occurs between the surface and the inside of the nitride powder obtained above, and the crystallinity is likely to be lowered due to nitriding. Therefore, in the present invention, the nitrogen diffusion heat treatment is performed after the nitriding treatment, but this diffusion heat treatment is performed in a vacuum or in an inert gas atmosphere in the same temperature range as the nitriding treatment. By this heat treatment, the amount of nitrogen on the surface of the powder is made uniform, and the crystallinity characteristic of the present alloy is recovered.

The amount of nitrogen penetrating into the present alloy is 2 to 20 atomic%, that is, when expressed as a typical nitride Nd Fe _{1 1} Ti N _x, it is preferable that x = 0.2 to 2.5. The reason for this is that if it is less than 2 atom%, the crystalline magnetic anisotropy is small and the magnetic properties are not excellent, and if it exceeds 20 atom%, the Th Mn ₁₂ crystalline phase becomes unstable and the crystallinity and magnetic properties are deteriorated. This is to bring.

The rare earth magnet material produced according to the present invention can generally be solidified with a binder to form a so-called bonded magnet. In this case, a metal such as zinc or tin, a thermosetting resin such as an epoxy resin or a phenol resin, or a thermoplastic resin such as nylon can be used as the binder, and the molding method includes compression, injection,
Various methods such as extrusion and hot pressing can be used.

[0015]

According to the above-described method for producing rare earth alloy powder, the nitrogen atoms freely penetrating into the alloy are transformed into T by the diffusion heat treatment.
It fits into a predetermined position (2b site) in the hMn ₁₂ type crystal lattice, and the crystal structure of the Th Mn ₁₂ type main phase is stabilized.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Example 1 Metal neodymium (Nd), electrolytic iron, and ferrotitanium were blended in a predetermined ratio, and the mixture was melted at a high frequency to form a component composition formula Nd ₁ Fe.
An alloy ingot having a composition of ₁₁ Ti ₁ (atomic ratio of Nd: Fe: Ti = 1: 11: 1) was produced, and this ingot was made into 1200
Diffusion heat treatment is performed at 12 ℃ for 12 hours in Ar gas atmosphere, and then the average particle size is 10 with a stamp mill and a jet mill.
A μm alloy powder was obtained. Next, this alloy powder was kept in nitrogen gas at 5 atm at 350 ° C. for 1 to 36 hours to infiltrate nitrogen, and subsequently kept at 400 ° C. in vacuum for 4 hours to perform diffusion heat treatment of nitrogen. .. The nitrogen content of the obtained nitriding powder was measured by TC-436 of LECO analyzer, and it was confirmed by X-ray diffraction method whether or not the ThMn ₁₂ type main phase was formed. The magnetic characteristics were measured by a vibrating sample magnetometer. The test results are shown in FIGS. 1 and 2.

FIG. 1 shows the test results of magnetic properties and Curie points. In FIG. 1, white marks represent the test results of the powder before the diffusion heat treatment, and black marks represent the test results after the diffusion heat treatment. In the figure, 4πIm represents the maximum magnetic flux density at the maximum applied magnetic field of 20 kOe, and Ha represents the anisotropic magnetic field. From the results shown in FIG. 1, the nitride N as the main phase of Th Mn ₁₂ type
The alloy powder according to the present invention containing d Fe ₁₁ Ti N _x (where x is not a constant and can take an unspecified value) has a maximum magnetic flux density of 4πIm and an anisotropic magnetic field due to nitrogen infiltration and its diffusion heat treatment. It has been found that all of Ha are improved and excellent magnetic characteristic values are obtained. The amount of nitrogen in the alloy powder is 2
When it is less than 20 atomic% or less than 20 atomic%, the magnetic properties are not significantly improved.

FIG. 2 shows the X-ray diffraction results of the powder sample before and after the diffusion heat treatment. In addition, this X
The line diffraction was performed on a powder sample containing 6 atomic% of nitrogen, and FIG. 2 shows an X-ray diffraction pattern of the (002) plane. From the results shown in the figure, the diffraction pattern of the powder sample after the diffusion heat treatment represented by the curve b is sharper than that of the powder sample before the diffusion heat treatment represented by a, and the crystallinity of the nitride is increased by the diffusion heat treatment. It is clearly improved. From this, it is considered that the magnetic properties after the diffusion heat treatment are improved because the crystallinity of the nitride is improved.

Example 2 As a rare earth metal, any one of Nd, Pr, Ce, Sm and Dy, electrolytic iron and ferro titanium were used as a melting raw material, and melting and pulverization were carried out in the same manner as in Example 1. Next, this alloy powder was kept in an ammonia gas stream at 350 ° C. for 2 hours to allow nitrogen to infiltrate therein, and subsequently kept in vacuum at 400 ° C. for 4 hours for diffusion heat treatment of nitrogen. Table 1 collectively shows the composition and magnetic properties of the obtained nitride powder samples No. 1 to 7. In the table, the numerical value attached to each element represents the atomic ratio,
The # symbol added to the sample number represents a comparative example.

[0021]

[Table 1]

As is clear from the results shown in Table 1, good magnetic properties were obtained for Sample Nos. 2 to 7 according to the present invention. On the other hand, in the comparative sample No. 1, since the rare earth metal is Sm, the crystal magnetic anisotropy becomes in-plane anisotropy, and the anisotropic magnetic field required as a magnet material cannot be obtained.

EXAMPLE 3 Metal neodymium, electrolytic iron, and T as other metals
A ferroalloy of any one of i, Mo, V, W, Cr, Mn, Al and Si was used as a raw material, and dissolved and pulverized in the same manner as in Example 1. Next, this alloy powder was kept under a nitrogen gas atmosphere of 5 atm at 400 ° C. for 2 hours to allow nitrogen to infiltrate, and subsequently kept at 350 ° C. for 6 hours in vacuum to carry out nitrogen diffusion heat treatment. The obtained nitride powder sample No. 11
Table 2 collectively shows the composition and magnetic properties of 20.

[0024]

[Table 2]

As is clear from the results shown in Table 2, good magnetic properties were obtained for samples No. 12 to 20 according to the present invention. On the other hand, Comparative sample No. 11 does not contain a metal element that stabilizes the Th Mn ₁₂ type crystal structure, and therefore Th ₂
The Zn ₁₇ phase is generated, and therefore the magnetic properties are low.

Example 4 Metal neodymium, electrolytic iron, electrolytic cobalt, and ferrotitanium were mixed in a predetermined ratio and were subjected to high frequency melting to produce an alloy ingot having a compositional formula Nd ₁ Fe ₉ Co ₂ Ti ₁ . This was subjected to diffusion heat treatment at 1100 ° C. for 12 hours in an Ar gas atmosphere, and then a stamp mill and a ball mill were used to obtain a powder having an average particle size of 50 μm. Next, this alloy powder is kept in nitrogen gas at 5 atm at a temperature of 100 to 700 ° C. for 16 hours to allow nitrogen to infiltrate, and then in an Ar gas stream.
This was held at 350 ° C for 12 hours to perform nitrogen diffusion heat treatment. The obtained nitriding powder was subjected to measurement of magnetic properties in the same manner as in Example 1. Results are shown in FIG.

From the results shown in FIG. 3, the Th M according to the present invention is
It has been clarified that the alloy containing the n ₁₂ type main phase exhibits excellent magnetic properties by nitriding treatment in the temperature range of 200 to 600 ° C. If the nitriding temperature is less than 200 ° C, it is not easy for nitrogen to enter. On the other hand, if the nitriding temperature exceeds 600 ° C, the magnetism deteriorates due to decomposition of the nitride crystal.

Example 5 As in Example 4, the chemical composition formula of Nd ₁ Fe ₉ Co ₂ Ti was used.
The alloy powder of _{No. 1} was charged into an autoclave and kept in nitrogen gas at 40 atm at 350 ° C for 12 hours to allow nitrogen to infiltrate. Subsequently, this powder was held in vacuum at 100 to 700 ° C. for 12 hours to perform a nitrogen diffusion heat treatment. The magnetic characteristics of the obtained nitride powder sample were measured in the same manner as in Example 1. The result is shown in Figure 4.
Shown in. From the results shown in FIG. 4, it has been clarified that the alloy powder according to the present invention has improved magnetic properties by performing the heat treatment in the temperature range of 200 to 600 ° C.

Example 6 Using metal praseodymium, electrolytic iron, electrolytic cobalt, ferrotitanium, and ferrochrome as raw materials, component composition formula P
An alloy ingot of r ₁ (Fe, Co) _10.8 Ti _0.8 Cr _0.4 was produced. Next, after homogenizing treatment at 1100 ° C. for 12 hours, a powder having an average particle size of 6 μm was obtained by a jet mill. This alloy powder is heated to 350 to 4 in nitrogen gas at 5 atm.
The temperature was kept at 00 ° C. for 12 hours to allow nitrogen to infiltrate, and subsequently, the temperature was kept at 350 ° C. for 6 hours in vacuum to carry out nitrogen diffusion heat treatment. The nitrogen content of the obtained nitriding powder is 5 to 9 atom%.
The same was subjected to the magnetic property test as in Example 1.
Results are shown in FIG.

From FIG. 5, it has been clarified that the maximum magnetic flux density is increased by substituting Fe with Co at a constant ratio among the composite components in the present invention. However, if the substitution rate is 60% or more, the improvement of the magnetic flux density cannot be seen, so the Co substitution rate must be less than 50%.

[0031]

As described above in detail, according to the method for manufacturing a rare earth magnet material of the present invention, nitrogen atoms freely penetrating into the alloy are diffused and heat-treated to a predetermined amount in the Th Mn ₁₂ type crystal lattice. Since it fits in the position, the crystallinity of the Th Mn ₁₂ type main phase is stabilized, the magnetic characteristics and temperature characteristics are improved, and a rare earth magnet material excellent in long-term stability can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing the influence of the amount of nitrogen on the magnetic properties of the rare earth magnet material obtained in Example 1 of the present invention.

FIG. 2 is a graph showing an X-ray diffraction result of the rare earth magnet material obtained in Example 1 of the present invention.

FIG. 3 is a graph showing the effect of nitriding temperature on the magnetic properties of the rare earth magnet material obtained in Example 4 of the present invention.

FIG. 4 is a graph showing the effect of diffusion heat treatment temperature on the magnetic properties of the rare earth magnet material obtained in Example 4 of the present invention.

FIG. 5 is a graph showing the influence of the Co / Fe ratio on the magnetic characteristics of the rare earth magnet material obtained in Example 6 of the present invention.

Claims (2)

[Claims] 1. A rare earth metal (R) comprising at least one of Nd, Pr, and Ce, Fe, and Ti, Mo.
, V, W, Cr, Mn, Al, Si, other metal (M) consisting of at least one of the main components, and an alloy powder containing a compound of the Th Mn ₁₂ type crystal structure as the main phase is obtained. Then, this alloy powder was brought into contact with a nitriding gas in the temperature range of 200 to 600 ° C., and then nitrogen diffusion heat treatment was carried out in the same temperature range so that the alloy contained 2 to 20 atomic% of nitrogen. A method for producing a rare earth magnet material, comprising: 2. The method for producing a rare earth magnet material according to claim 1, wherein a part of Fe is replaced with less than 50% of Co.