JPH04241402A - Permanent magnet - Google Patents

Abstract

PURPOSE:To provide a permanent magnet which has Th.Mn12 type crystal phase, where Curie temperature is improved without lowering magnetic property, for its main phase. CONSTITUTION:This permanent magnet is shown by the composition formula of RxMyAzFe100-x-y-z (R is at least one kind of element selected from rare earth elements including Y, M is at least one kind of element selected from Si, Cr, V, Mo, W, Ti, Zr, Hf, and A, and A is at least one kind of element selected from N and C, and by atom%, z is 4-20%, y is 20% or less, and z is 0.001-16%), and is constituted so that the main phase may have Th.Mn12 type crystal structure.

Description

[Detailed description of the invention]

[Object of the invention]

0002

[Industrial Application Field] The present invention relates to a permanent magnet, and the present invention relates to a permanent magnet that has an improved Curie temperature without deteriorating its magnetic properties compared to conventional Sm-Co-based or Nd-Fe-B-based magnets. Regarding.

0003

2. Description of the Related Art Conventionally known and mass-produced rare earth permanent magnets include Sm--Co magnets and Nd--Fe--B magnets. These magnets contain rare earth elements such as Sm and Nd as characteristic-producing components. That is, rare earth elements bring about extremely large magnetic anisotropy derived from the behavior of 4f electrons in a crystal field, which increases the coercive force and realizes a high-performance magnet. Such high-performance magnets are mainly used in electrical equipment such as speakers, motors, and measuring instruments.

However, rare earth elements are generally very expensive, and in order to reduce the cost of high-performance magnets as described above, it is necessary to reduce the content of rare earth elements.

Recently, 1-12 rare earth iron intermetallic compounds having a ThMn12 type crystal structure have attracted attention as magnetic materials with reduced rare earth content and high characteristics. Compared to the intermetallic compounds that constitute conventional Sm2Co17 magnets and Nd2Fe14B1 magnets, this intermetallic compound has a small stoichiometric rare earth content, so the raw material cost is low, and the Fe ratio is relatively high, so it has a large Saturation magnetic flux density Bs and high maximum energy product (BH) max
have.

[0006]

[Problems to be Solved by the Invention] However, permanent magnets formed from the above-mentioned 1-12 rare earth iron intermetallic compounds have a low Curie temperature (Tc) of about 300°C and are used under high-temperature conditions. The problem is that it is difficult to apply it to fields that require high magnetic stability against temperature, such as equipment, motors, and measuring instruments.

The present invention was made to solve the above problems, and an object of the present invention is to provide a permanent magnet with improved Curie temperature without reducing magnetic anisotropy. [Structure of the invention]

[0008]

[Means and effects for solving the problem] The present inventors suppressed the amount of expensive rare earth elements used as much as possible and raised the Curie temperature without impairing the magnetic anisotropy of the 1-12 series compound. As a result of continuing intensive research, we found that when a permanent magnet containing a predetermined amount of at least one of nitrogen and carbon and having a main phase of a tetragonal rare earth iron compound having a Th-Mn12 type crystal structure was formed, the Curie The present invention was completed based on the knowledge that it is possible to significantly increase the temperature.

That is, the permanent magnet according to the present invention has the composition formula R
xMyAzFe100-x-y-z (wherein R is at least one element selected from rare earth elements including Y, M
is at least one element selected from Si, Cr, V, Mo, W, Ti, Zr, Hf and Al, A is at least one element selected from N and C, and x is 4-20%, y is 20% or less, z is 0.001
~16%), and is characterized in that the main phase has a Th/Mn12 type crystal structure.

The reason why the composition of the permanent magnet according to the present invention is limited as described above is as follows.

[0011] The R mentioned above is La, Ce, Pr, Nd.
, Sm, Eu, Gd, Td, Dy, Ho, Er, Tm,
Examples include rare earth elements Yb, Lu, and Y, and one or a mixture of two or more of these may be used. R is added in a range of 4 to 20 at % in order to bring magnetic anisotropy to the material and impart high coercive force.

[0012] When the amount of R added is less than 4 at %, α-
A large amount of Fe etc. precipitates and the coercive force (iHc) decreases significantly. On the other hand, if the amount of R added exceeds 20 atomic percent, the saturation magnetic flux density (Bs) will decrease significantly and a large amount of expensive rare earth elements will be used, leading to an increase in manufacturing costs. And you will be at a disadvantage.

[0013] M elements include Si, Cr, V, Mo, and W.
, Ti, Zr, Hf and Al, or a mixture of two or more thereof is used. Originally, a stable crystal structure cannot be formed only with the rare earth elements R and Fe, but
By adding the M element in an amount of 20 atomic % or less, a rare earth iron-based tetragonal compound having a stable ThMn12 type crystal structure can be formed. In addition, M
The above-mentioned effect can be obtained even if the element is added in a trace amount, but it is preferably 0.1 atomic % or more.

[0014] When the amount of M element added exceeds 20 atomic %,
Since the saturation magnetic flux density (Bs) will decrease significantly, M
The amount of the element added is set to 20 atomic % or less.

Element A, which is composed of at least one of C and N, is an effective element for improving the Curie temperature (Tc). In other words, C and N modulate the band structure of Fe, causing an increase in the magnetic polarization of d electrons and an exchange interaction between d electron spins, ultimately increasing the Curie temperature (T
c) is effective in increasing. However, it is difficult to form a solid solution in an amount exceeding 16 at %, and addition of an excessive amount beyond this leads to instability of the crystal structure, so it is unsuitable to add more than 16 at %. On the other hand, if the amount is 0.001 atomic % or less, the effect of improving the Curie temperature (Tc) is not significant, so the amount of element A added is set in the range of 0.001 to 16 atomic %.

Furthermore, by substituting a part of Fe with a transition metal other than Fe, such as Co--Ni, the Curie temperature of the magnet can be further improved and the coercive force can be increased. However, if 50 atomic % or more of iron is substituted, magnetic properties such as saturation magnetic flux density will be significantly deteriorated, so it is desirable that the amount of substitution be 50% or less of Fe in terms of atomic fraction. Furthermore, in order to suppress the amount of expensive Co used as much as possible, the amount of substitution is preferably within the above range.

Next, a method for manufacturing a permanent magnet according to the present invention will be explained.

First, when C is added alone as the A element, predetermined amounts of Fe, R, M, and A elements are melted by a method such as arc melting, and then cast to prepare an alloy having a predetermined composition.

On the other hand, when adding N alone as element A or when adding N and C in combination, first add N.
After preparing an alloy consisting of the components excluding the components by the above method, the prepared alloy is pulverized to a particle size of 1 mm or less, preferably 0.5 mm or less. Thereafter, the pulverized material is heat-treated at 300 to 1000 DEG C. in an N2 atmosphere of 20 to 1500 Torr to absorb N2 into the pulverized material, thereby producing an alloy of a predetermined composition. In this case, the molten alloy should be heated to
It may be heat-treated at ~1000°C to form a solution.

Next, the alloy thus obtained has an average grain size of 1 to 1.
After being finely pulverized to 50 μm, the obtained raw material powder is filled into a predetermined mold, hot pressed at a temperature of 400 to 1000° C., and integrally sintered. At this time, by preliminarily orienting the raw material powder in a magnetic field, a permanent magnet with higher anisotropy can be obtained. It is also possible to hot-work the obtained sintered body to develop anisotropy. The above hot press treatment is preferably carried out in an N2 gas atmosphere in order to prevent the dissipation of the N component once occluded in the alloy. It may be carried out in an inert gas or vacuum.

[0021] Furthermore, the coercive force can be increased by heat-treating the sintered body obtained by hot pressing at a temperature of 300 to 900°C for 0.1 to 5 hours.

The permanent magnet according to the present invention is manufactured by melting, casting, pulverizing, and heat-sintering the predetermined composition as described above, and also by making the mixed powder of the raw materials react in solid phase with each other to form an alloy. It can also be manufactured by a method, and the manufacturing method will be explained below.

First, when adding C alone as the A element, a mixture of powders containing predetermined amounts of R, Fe, M, and A components is alloyed by solid phase reaction. As a method for causing a solid phase reaction, for example, a mechanical alloying method is adopted in which a raw material mixture is introduced into a planetary ball mill, a rotary ball mill, an attritor, a vibrating ball mill, a screw ball mill, etc., and the powder particles are mechanically alloyed. can.

[0024] According to this mechanical alloying method, raw material powder particles are crushed into flakes, and the raw material mixture is homogeneously integrated by dispersing different types of atoms in the areas where the flakes are in surface contact with each other. Ru.

[0025] When N is included as the A component, the solid phase reaction described above is carried out in an N2 gas atmosphere to occlude N2 gas in the raw material mixture, thereby preparing an alloy powder having a predetermined composition. be able to.

The coercive force of the alloy powder prepared by the above-mentioned solid phase reaction can be significantly increased by subjecting it to heat treatment at a temperature of 300 to 1000° C. for 0.02 to 5 hours. In this case, in order to prevent the occluded N2 component from dissipating, it is desirable to perform the heat treatment in an N2 gas atmosphere. Note that alloy systems that do not contain N may be treated in another inert gas or in vacuum.

[0027] Instead of the heat treatment for integrating the alloy materials as described above, hot pressing treatment may be performed. Even when performing this hot press treatment, it is desirable to perform it in an N2 gas atmosphere in order to prevent the N2 component from dissipating. Similarly, alloy systems that do not contain an N component can be treated in another inert gas or in vacuum.

[0028] By performing hot press treatment instead of such heat treatment, the alloy obtained by solid phase reaction can be more firmly integrated.

Furthermore, in order to further improve the magnetic properties of the permanent magnet, the sintered body formed by hot pressing may be further heat treated at the above temperature. Further, by applying pressure to the sintered body and subjecting it to plastic working, the magnetic orientation can be further enhanced.

In addition to the above two manufacturing methods, it is also possible to prepare an alloy powder of a predetermined composition by a liquid quenching method, and then sinter and integrate the obtained powder to form a permanent magnet. In this case, by the liquid quenching method, an alloy powder having a particularly high coercive force can be obtained, and a permanent magnet with excellent magnetic properties can be obtained.

[0031] In order to manufacture a bonded magnet from the above-mentioned heat-treated alloy, a method is employed in which a powdered alloy is mixed with an epoxy resin, a nylon resin, or the like, and then molded. As a molding method, when the resin is an epoxy-based thermosetting resin, curing treatment is performed at a temperature of 100 to 200° C. after compression molding, and when the resin is a nylon-based thermoplastic resin, injection molding may be used.

The permanent magnet according to the present invention is mainly composed of a compound phase having a stable tetragonal ThMn12 type crystal structure, and in particular, since at least one of N and C is added, the Curie temperature (Tc) is high. , exhibits extremely superior magnetic properties compared to conventional binary or ternary compounds.

[0033]

EXAMPLES Next, the present invention will be explained in more detail based on the following examples.

Examples 1-3, Comparative Examples 1-3 Examples 1-3
High-purity Sm, Ti, Si, and Fe powders were mixed into the composition shown in Table 1, melted in a high-frequency melting furnace, and then poured into a mold to prepare each ingot. Next, each ingot was pulverized by a jet mill to an average particle size of 150 to 200 μm. Next, 750To for each alloy powder obtained
Heat treatment was performed at a temperature of 500° C. for 1 hour in an N2 gas atmosphere of rr. Furthermore, each alloy powder was finely pulverized to an average particle size of 3 μm, oriented in a magnetic field of 20 KOe to form a green compact, and each green compact was further pulverized at a temperature of 800°C and 600 T.
Hot press treatment was carried out in an N2 gas atmosphere of 0.05 mm. Each hot-pressed sintered body obtained was heat-treated at a temperature of 600°C for 1 hour in a 600-Torr N2 gas atmosphere to determine the residual magnetic flux density (Br) and coercive force (iH) of the sintered body after the treatment.
c), and the maximum energy product (BH) max and Curie temperature (Tc) were measured to obtain the results shown in Table 1.

On the other hand, as Comparative Examples 1 to 3, Examples 1 to 3
A magnet body was prepared in the same manner using the ingot prepared in the above without occluding the N component, and its magnetic properties were measured. That is, each ingot used in Examples 1 to 3 was finely pulverized to an average particle size of 3 μm, and each of the obtained powders was pulverized to 20 KO
After being oriented in a magnetic field of e and made into a green compact, it was
Hot press treatment was performed in an Ar gas atmosphere of 00 Torr. Next, each obtained sintered body was heated to 400T at 600℃.
After heat treatment for 1 hour under orrAr gas atmosphere,
When the magnetic properties were measured, the results shown in Table 1 below were obtained.

[Margin below]

[0037]

[Table 1]

As is clear from the results shown in Table 1, according to Examples 1 to 3, the rare earth iron-based tetragonal compound constituting the magnet is stabilized by N, and therefore, compared to Comparative Examples 1 to 3, It was found that the magnetic properties were excellent, and in particular, the Curie temperature (Tc) was significantly improved.

When the crystal structures of the magnet bodies prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were measured by X-ray diffraction, it was confirmed that a ThMn12 type crystal structure existed in each case. It was done.

Examples 4 to 9 As Examples 4 to 6, rare earth powder with an average particle size of 0.5 mm, Fe, Mo,
A raw material mixture was prepared by blending Si, Ti, and C powders to the compositions shown in Table 2, and each of the obtained raw material mixtures was put into a ball mill and pulverized and mixed for 60 hours in an Ar gas atmosphere. The raw material powder was alloyed by mechanical alloying.

Next, each of the obtained alloy powders was filled into a mold and hot pressed at 800° C. in an Ar gas atmosphere to form a magnet body. The magnetic properties of each of the obtained magnet bodies were measured in the same manner as in Examples 1 to 3, and the results shown in Table 2 were obtained.

[0042] Also, as Examples 7 to 9, each element powder is shown in Table 2.
A raw material mixture was prepared by blending the composition shown in , and each of the obtained raw material mixtures was put into a ball mill and heated at 760 Torr of N.
2. Pulverization and mixing treatment was performed for 180 hours in a gas atmosphere to allow each raw material powder to absorb N2 gas, while being alloyed by mechanical alloying.

Next, each of the obtained alloy powders was filled into a mold and hot-pressed at 800° C. in a 600 Torr N2 gas atmosphere to form a magnet body. The magnetic properties of each of the obtained magnet bodies were measured in the same manner as in Examples 4 to 6, and the results shown in Table 2 below were obtained.

[0044]

[Table 2]

As is clear from the results shown in Table 2, in Examples 4 to 6, C was added to stabilize the crystal composition and raise the Curie temperature, and in Examples 7 to 9, C was added.
Since N and N are added in a composite manner, a magnet with excellent magnetic properties and a high Curie temperature (Tc) can be obtained.

[0046]

As explained above, according to the present invention, since a rare earth iron-based tetragonal compound having a stable ThMn12 type crystal structure containing at least one of N and C is formed as the main phase, magnetic properties are improved. It is possible to provide a permanent magnet with a high Curie temperature without damaging the temperature.

Claims (1)

[Claims] [Claim 1] Compositional formula RxMyAzFe100-x-
y-z (wherein R is at least one element selected from rare earth elements including Y, M is Si, Cr, V, Mo, W
, Ti, Zr, Hf, and Al, A is at least one element selected from N and C, x is 4 to 20%, and y is 2
0% or less, z is 0.001 to 16%),
A permanent magnet characterized in that the main phase has a Th/Mn12 type crystal structure.