JPH04184901A - Rare earth iron based permanent magnet and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a magnet which is excellent in magnetic characteristics and has stable quality, by constituting a sintered body of permanent magnet alloy wherein a specified atomic % of rare earth metal R containing Nd, and a specified atomic % of B are contained and the residual part is constituted of iron, and including nonmagnetic rich phase in an alloy texture body. CONSTITUTION:A sintered body of permanent magnetic alloy is composed of the following: 10-25 atomic % of rare earth element R (where R is at least one or more kinds of elements out of rare earth elements containing Nd), 1-20 atomic % of boron, and iron of the residual part. Nonmagnetic R rich phase is included in an alloy texture body. Carbon content in the permanent magnet alloy is 0.03-0.11wt.%. In this permanent magnetic alloy composition, iron is substituted by 0-20 atomic % of at least one or more kinds of elements selected out of Co, Al, Nb, Mo, Ga, Ti, V, Ni, Si, Bi, Hf, W, Cr, etc., and the inclusion of O, N, H, Cl, F, S, etc., contains inevitable impurities. Thereby a magnet which is excellent in magnetic characteristics and has stable quality can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rare earth iron permanent magnet useful in the electrical and electronic fields and a method for manufacturing the same.

(Prior art) R-Fe-B rare earth iron permanent magnets have higher magnetic properties than R-Go rare earth iron permanent magnets, and have a maximum energy product (hereinafter referred to as (BH)). Looking at this, the basic composition of Nd+5FeyyBa reaches up to 35MGOe, and a mass-produced magnet with an improved composition of 37MGOe is available. Furthermore, now (BH)...
High-performance magnets of 40 MGOe or higher are being developed, and R
- This greatly exceeds 33MGOe obtained with Go-based magnets. In addition, the Curie temperature is improved by replacing a part of Fe with Co, and Al, Bi, Zr,
If, V, W, Mo, Cr, Ta, Sb
, Ge, Nb, Ni, Ti, Sn, etc., is known to improve coercive force (iHc).

(Problem to be solved by the invention) However, R-Fe-B having such high properties
Rare earth iron-based permanent magnets are made by mixing and melting raw metals and pulverizing the magnetic alloy powder, which is highly susceptible to oxidation. It must be carried out in an inert gas or in an organic solvent such as hexane. R-F
If impurity elements other than the above-mentioned additive elements are mixed into the e-B permanent magnet alloy, the magnetic properties may be significantly deteriorated. That is, these impurity elements are the main component elements R and F.
It is thought that a compound or solid solution is formed with e and B, and that when these compounds or solid solution precipitate in the magnet alloy, the magnetic properties are degraded. However, no matter how refined the elements are, impurities are inevitably mixed in during the magnet manufacturing process, causing deterioration of the magnetic properties.

The purpose of the present invention is to provide a rare earth iron-based permanent magnet with extremely minimal deterioration in magnetic properties by improving the composition and structure of a permanent magnet alloy, and to manufacture the same, in order to obtain magnetic properties that are effective against the contamination of these impurity elements. The purpose is to provide a method.

(Means for Solving the Problems) As a result of repeated research in order to solve these problems, the present inventors have found that R-Fe-B permanent magnet alloy sintered bodies contain rare earth elements and other raw material elements. The present invention was completed by discovering that magnetic properties are affected in various ways by the impurities contained, and by investigating the relationship between the content of these impurities and magnetic properties.

The gist of the present invention is that rare earth elements R10 to 25 at% (however, R is at least one rare earth element among rare earth elements including Nd);
A rare earth iron-based permanent magnet characterized by being a sintered body of a permanent magnet alloy consisting of 1-20 atomic percent of boron B and the balance being iron-Fe and containing a non-magnetic R-rich phase in the alloy structure, and a powder metallurgy method. In the production of rare earth iron permanent magnets, the heat treatment temperature of the shaped sintered body, which is the final step, is set at 500 to 500℃.
i, ooo "c, A method for producing a rare earth iron permanent magnet, characterized in that the processing time is 0.5 to 10 hours.

The present invention will be explained in detail below.

The composition of the rare earth iron-based permanent magnet of the present invention is the rare earth element R (
However, R is at least one rare earth element (including Nd), boron (B), and the balance is iron (F
e) A sintered body of a permanent magnet alloy consisting of: first, the magnet alloy components R include Y containing Nd, La, Ce,
Pr, Pm, Sm, Eu, Gd, Tb, Dy, Ho+E
r.

At least one of each of the rare earth elements T■, Yb and Lu
It is necessary to contain 10 to 25 at.% of rare earth elements. If it is less than 10 at.%, precipitation of α-Fe will occur, which disturbs the orientation of the particles in the magnet sintered body, and if it exceeds 25 at.%, it is not practical. A magnetic flux density cannot be obtained. B is required to be in the range of 1 to 20 at%, and if it is less than 1 at%, the soft magnetic phase of RaFe+
A compound precipitates out, deteriorating the magnetic properties, and if it exceeds 20 atomic %, a sufficient magnetic flux density cannot be obtained due to the precipitation of non-magnetic R+Fe4Ba. The rest except for R9B may be Fe (, Fe is Go, Al).

Nb, Zr, Mo, Ga, Ti, V, Ni
, Si, Bi, Hf, W.

Substituting O to 20 atomic % with at least one element selected from Cr, Ta, Sb, Ge, Sn, etc., and 0. The inclusion of unavoidable impurities such as N, H, C1, F, and S is optional as long as the magnetic properties are not impaired.

What is particularly noteworthy here is the impurity C contained in the rare earth element R1 and other raw material elements Fe and B. If a large amount of C is mixed in, it can significantly reduce the coercive force and cause damage to the sintered body during sintering. It was found that the density did not increase sufficiently, and for the reasons described later, the C content in the magnetic alloy sintered body was set at 0.03.
The essential requirement is ~0.11% by weight,
If it is less than 0.03% by weight, sufficient coercive force cannot be obtained;
If it exceeds 11% by weight, the density of the sintered body will decrease.

Hereinafter, the factors that determine the allowable amount of impurity C to be mixed will be explained in more detail. As a result of detailed research into the influence of impurity C on rare earth Fe-based permanent magnets, the present inventors found that C is dissolved throughout the main phase R, Fe, and 4B structures, and the RJe+40 It was found that as the C concentration increases, the saturation magnetic flux density and anisotropy magnetic field decrease. That is, when C is mixed into the main phase, the magnetic properties deteriorate.

In addition, regarding the metallographic structure, the sintered compact obtained by crushing the magnetic alloy ingot using the powder metallurgy method, forming and sintering the sintered compact after the final process of heat treatment (hereinafter referred to as the heat-treated sintered compact) is As a result of analysis using a needle analyzer, it was found that an intermetallic compound R-C of rare earth elements and carbon was formed in this heat-treated sintered body, and the amount of this R-C was determined by the C content in the magnetic alloy ingot. It was found that there is a tendency to increase. This R-C is hardly observed in the magnet alloy ingot or in the sintered body immediately after sintering, and exists in the form of solid solution in the R-rich phase, but at a specific heat treatment temperature, When the sintered body was heat-treated after sintering, it was found that this RC was also generated in the heat-treated sintered body. That is, according to the present invention, even if impurity C is mixed, C does not invade the main phase in the heat-treated sintered body, and the R-rich phase is separated into an R-rich phase containing Fe and an R-rich phase containing C. and R in the R-rich phase.
-C is characterized by its existence in isolation,
By effectively utilizing impurity C, which cannot be mixed in, as one component, it was possible to produce a permanent magnet whose magnetic properties are comparable to those of conventional methods.

In order to control the amount of C mixed within the allowable range, it is necessary to carefully select the raw material metal, but usually rare earth metals containing about 0.02 to 0.1% by weight are used.
When ferroboron (FeB) is used, the amount is about 2% by weight if it is high carbon, and about 0.2% by weight if it is low carbon. Moreover, the content in electrolytic Fe is about 0.01% by weight or less. Furthermore, after finely pulverizing a magnetic alloy ingot, during press forming in a magnetic field, a lubricant containing carbon may be mixed into the fine magnetic powder to improve the magnetic field orientation of the compact, so the quantitative relationship between these is This will determine the carbon content of the final magnet product.

The rare earth iron-based permanent magnet of the present invention is produced by a powder metallurgy method. That is, a magnetic alloy ingot is produced by blending raw metals, melting and cooling, and is manufactured through the steps of pulverization, forming in a magnetic field, heat treatment, and processing. The melting of raw metal is
High frequency melting is performed in argon or vacuum using the usual method, and the rare earth elements are added last. The pulverization is divided into coarse pulverization and fine pulverization, and the coarse pulverization is performed using a stamp mill, a Ziggy crusher, or a Braun mill, and the fine pulverization is performed using a jet mill, a ball mill, etc. to an average particle size of about 3 μm. In order to prevent oxidation, both are carried out in a non-oxidizing atmosphere, and organic solvents and inert gases are also used. The molding is carried out by molding in a magnetic field of approximately 0.
Press molding at a pressure of 8 ton/cm'' is then carried out in vacuum, in an inert gas such as argon or nitrogen, or in a non-oxidizing atmosphere at a predetermined temperature within the range of 1,000 to 1,200°C. 30 to 120 minutes for sintering, and then sintered at a temperature of 350°C to sintering temperature for 30 minutes to 10 hours, preferably 500 to 1,000°C, 0.
Heat treat for 5-4 hours.

In order to make the C of the present invention exist in an isolated form as R-C in the structure of the non-magnetic R-rich phase, it is necessary to strictly control the heat treatment conditions of this final step, and the C content of the magnetic alloy ingot must be controlled strictly. Measure the temperature and time to determine the treatment temperature and time. Outside the above range, i.e. less than 350°C or less than 30 minutes? A sufficient heat treatment effect cannot be obtained, and if the temperature exceeds the sintering temperature or exceeds 10 hours, the main phase particles will react and grow, resulting in a decrease in coercive force.

Hereinafter, specific embodiments of the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

(Example 1.2, Comparative Example 1.2) As a starting material, Nd with a purity of 99.7% by weight or more, where the carbon content is 0.061% by weight, 0.102% by weight,
Using four types of 0.280% by weight and 0.412% by weight, electrolytic Fe with a purity of 99.9% by weight and boron with a purity of 99.5% by weight, these were melted at high frequency and cast into a mold. A magnetic alloy ingot having a composition of NdtsFeysBa was obtained. The carbon content of these ingots was 0.021% by weight (Comparative Example 1), 0.035% by weight (Example 1), and
0.096% by weight (Example 2), 0.141% by weight (
Comparative Example 2). Each of these ingots was coarsely crushed to 32 meshes or less using a show crusher and a brown mill, and then crushed in a nitrogen stream using a jet mill to obtain raw material magnet powder with an average particle size of 3 μm. Using this magnetic powder,
The molding is performed by press molding in a magnetic field of approximately I teala at approximately 0.8 ton/cm''.Then, the obtained molded body is placed in a vacuum, an inert gas such as argon or nitrogen, or a non-oxidizing atmosphere. The sintered bodies were held at a temperature of 1,100°C for 60 minutes, and then heat-treated at 650°C for 2 hours to prepare samples.The sintered bodies with these four types of carbon content were subjected to electron beam microprobing. When the R-rich phase was observed using a needle analyzer, it was found that the R-rich phase of Example 1.2 and Comparative Example 2 was
An R-rich phase containing a large amount of R-C intermetallic compound and a small amount of Fe was observed in the rich phase, and especially in Examples 1 and 2, the intermetallic compound R-C phase was isolated in the nonmagnetic R-rich phase. It existed. Also. Regarding Comparative Example 1, only an R-rich phase containing Fe was observed.

Table 1 shows the magnetic properties of these sintered bodies. Comparative example 1,
and Example 1.2 had no decrease in density and was 7.4 g/c
However, when the carbon concentration reached Comparative Example 2, the density decreased (6.8 g/cc) and the magnetic properties deteriorated.

(Example 1, Comparative Examples 3.4) Regarding Example 1, Table 2 shows changes in magnetic properties with respect to heat treatment temperature. The coercive force shows a peak at a heat treatment temperature of 650° C. for 2 hours, and decreases at temperatures higher or lower than that. Moreover, when observing the structure of the sintered body, Example 1, Comparative Examples 3 (550°C), 4 (750°C)
Compared to the above, isolation of the R-C phase in the R-rich phase was promoted.

(Example 3, Comparative Example 5) As starting materials, Nd and Dy with a purity of 99.7% by weight or more, where the carbon content of all rare earth elements is 0.085%.
% by weight (Example 4) and 0.042% by weight (Comparative Example 5)
) using two types of electrolytic F with a purity of 99.9% by weight.
e and cobalt (CO), boron (B) with a purity of 99.5% by weight, A1. Using Nb, these were melted by high frequency and cast into a mold to produce Nd+s, oaDyo, t4F.
etr, *aCOs, 114B, Al+Nbo,
An ingot having a composition of 4 was obtained. The carbon content of the obtained ingot was 0.060% by weight and 0.021% by weight, respectively, based on the results of analysis using a non-dispersive infrared method. This ingot was subjected to the same process as in Example 1 to obtain a magnet sintered body. However, the heat treatment temperature was 570°C. As a result of observing the structure of this sintered body using an electron beam microprobe analyzer, it was found that the phase state of the R-rich phase in the sintered body was more complicated due to the inclusion of various additive elements. The magnetic properties of these sintered bodies are shown in Table 3.

(Effects of the Invention) According to the present invention, the structure of a magnet sintered body made by legally crushing, forming, sintering, and heat treating a magnet alloy ingot contains R. The -C intermetallic compound exists isolated in the R-rich phase, and there is no decrease in density or orientation, and a rare earth iron permanent magnet with excellent magnetic properties and constant quality can be obtained, and its utility value in industry. is extremely high.

Patent applicant: Shin-Etsu Chemical Co., Ltd. Agent/Patent Attorney Ryo Yamamoto - Agent/Patent Attorney Tsukasa Arai

Claims (6)

[Claims] 1. A sintered body of a permanent magnet alloy consisting of 10 to 25 at.% of rare earth element R (wherein R is at least one rare earth element among rare earth elements including Nd), 1 to 20 at.% of boron B, and the balance being iron-Fe, and A rare earth iron permanent magnet characterized by containing a non-magnetic R-rich phase in its alloy structure. 2. The carbon C content in the permanent magnet alloy is 0.03 to 0.
2. The rare earth iron permanent magnet according to claim 1, wherein the content is 11% by weight. 3. In the permanent magnet alloy composition, Fe is replaced by Co, Al,
Nb, Zr, Mo, Ga, Ti, V, Ni, Si, Bi
, Hf, W, Cr, Ta, Sb, Ge, Sn by 0 to 20 atomic %, and mixing of O, N, H, Cl, F, S, etc. The rare earth iron-based permanent magnet according to claim 1 or 2, characterized in that it contains unavoidable impurities. 4. Claims 1 to 3, characterized in that an intermetallic compound of a rare earth element and carbon C is present in the nonmagnetic R-rich phase.
A rare earth iron permanent magnet as described in any of the above. 5. The rare earth according to any one of claims 1 to 4, wherein an R-rich phase containing Fe and an R-rich phase containing C are separately precipitated in a nonmagnetic R-rich phase. Iron-based permanent magnet. 6. In the production of the rare earth iron permanent magnet according to any one of claims 1 to 5 by a powder metallurgy method, the heat treatment temperature of the shaped sintered body in the final step is 500 to 1,000 °C.
A method for producing a rare earth iron permanent magnet, characterized in that the treatment time is 0.5 to 10 hours.