JPH04318152A - Rare earth magnetic material and its manufacture - Google Patents

Abstract

PURPOSE:To provide a rare earth magnetic material having magnetic characteristics equivalent to Nd-Fe-B system permanent magnet and keeping excellent temp. characteristics better than the above magnet even when it does not contain hydrogen. CONSTITUTION:Metallic alloy power essentially consisting of a rare earth metal(R) and Fe or rare earth metal(R), Fe and Co is manufactured, and this metallic alloy powder is allowed to contact with cementating gas at 600-1200 deg.C to form a rare earth magnetic material consisting of 5-15% Sm-5-25% C - the balance Fe or 5-15% Sm-5-25% C-1-40% Co - the balance Fe.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth magnet material whose main components are rare earth metals, iron and carbon, and a method for producing the same.

0002

2. Description of the Related Art In recent years, with the miniaturization of various electronic components and equipment, high-performance permanent magnets have been required. The Nd-Fe-B permanent magnets developed in the 1980s have high magnetic performance and are made of abundant and inexpensive raw materials compared to the previous Sm-Co permanent magnets. It is being widely used industrially.

[0003] However, this Nd-Fe-B permanent magnet has poor corrosion resistance and easily rusts under high temperature and high humidity, leading to deterioration of magnetic properties. It is put into practical use by providing a coating film of nickel or epoxy resin. Another drawback is that it has poor temperature characteristics due to its low Curie point of about 300°C, making it unsuitable for use in an atmosphere where the temperature is 150°C or higher. As a countermeasure to this problem, replacing a portion of Fe with Co has been carried out, but although replacing Co increases the Curie point and slightly improves the temperature characteristics, it also causes a decrease in coercive force. There is a problem. As another measure, Nd
Although it has been attempted to partially replace Dy (dysprosium), even a small amount of substitution causes a decrease in the saturation magnetic flux density, making it difficult to improve the temperature characteristics in practice.

Recently, it has been reported that alloys containing rare earth metals, iron, nitrogen, and hydrogen as main components can be used as magnet materials (for example, see Japanese Patent Laid-Open No. 2-57663). According to this, when nitrogen and hydrogen coexist in the alloy, it can be expected to have a saturation magnetic flux density equivalent to that of Nd-Fe-B permanent magnets, as well as higher magnetocrystalline anisotropy and Curie point. It is said that

[0005]

However, according to the above-mentioned rare earth metal-iron-nitrogen-hydrogen permanent magnet, hydrogen in the alloy is relatively easily released due to changes in temperature and pressure.
There is a problem in that the magnetic properties tend to become unstable over a long period of time due to the occlusion phenomenon.Furthermore, there are difficulties in manufacturing as the manufacturing process involves handling hydrogen gas or ammonia decomposition gas, which has the risk of explosion. There was a problem.

The present invention has been made in view of the above-mentioned conventional problems, and provides a rare earth magnet that can secure magnetic performance equivalent to that of Nd-Fe-B permanent magnets and superior temperature characteristics even without hydrogen. The purpose is to provide materials and methods for their production.

[0007]

[Means for Solving the Problems] In order to achieve the above object, a rare earth magnet material according to the present invention is made of rare earth metal (R).
, carbon and iron in atomic percentage 5-15%R-5-
Contains 25% C-balance Fe, or contains rare earth metals (R), carbon, cobalt and iron in atomic percentages of 5 to 5%.
15%R-5~25%C-1~40%Co-Remainder F
It is characterized by being contained in a proportion of e.

[0008] Furthermore, the method for producing rare earth magnet materials according to the present invention involves obtaining rare earth metal (R) and iron, or alloy powder containing rare earth metal (R), cobalt, and iron as main components, and then producing this powder. It is characterized in that the alloy powder is brought into contact with carburizing gas at 600 to 1200°C.

[0009] In the rare earth magnet material according to the present invention,
Rare earth metals (R) include La, Ce, Pr, N
d, Sm, Eu, Gd, Tb, Dy, Ho
, Er, Tm, Yb and Lu. Among these, P
Particularly excellent magnetic properties can be obtained when r, Nd, Sm, etc. are selected. Regarding this rare earth metal (R),
If the content is less than 5% in atomic percent (at%), the coercive force will decrease, and if it exceeds 15%, the saturation magnetic flux density or residual magnetic flux density will decrease, making it difficult to make a practical permanent magnet. It was set to 15 at%. Regarding C, if the content is less than 5 at%, the crystal magnetic anisotropy will be small and the coercive force will be extremely small, and if it exceeds 25 at%, the coercive force will be small due to the increase in soft magnetic αFe. ~25at%.

[0010] Furthermore, Co has the effect of raising the Curie point, improving temperature characteristics, and improving corrosion resistance, but if it is less than 1 at%, the effect is small;
If it exceeds 0 at%, the magnetocrystalline anisotropy becomes small and sufficient coercive force cannot be obtained, so this should be set at 1 to 40 at%.
And so. Note that a part of Fe is replaced by Ti, V, Cr, M
n, Cu, Zn, Zr, Nb, Mo, W,
Substitution with other transition metals such as Hf, Ta, etc., or substituting a part of C with other elements such as B, N, O, Si, Al, etc. is also effective in slightly improving the magnetic properties. .

[0011] In the method for producing rare earth magnet materials according to the present invention, the above alloy powder can be obtained by any method. For example, rare earth metals and iron, or rare earth metals, iron, and cobalt are blended in a predetermined ratio. A pulverization method in which the raw material or master alloy is melted in a high-frequency induction furnace, the molten alloy is poured into a mold to form an alloy ingot, and then this alloy ingot is mechanically crushed using a jaw crusher, etc., and the molten alloy is rotated. Possible methods include a rapid cooling method in which the alloy is directly injected onto the roll surface, an atomization method in which the molten alloy is injected into a gas or liquid at high speed, and a mechanical alloying method in which interdiffusion between solid metals is used instead of melting. It is best to make the alloy powder as fine as possible in order to carry out the subsequent carburizing process efficiently, but if the powder is too fine, oxidation during handling and storage in the air will become a problem. It is desirable that the diameter be several tens to several hundred microns (μm). In addition, when using the pulverization method or the rapid cooling method, it is difficult to keep the particle size of the powder within this range as it is, so the powder is further pulverized by using, for example, a stamp mill or an attritor.

Furthermore, in the method for producing rare earth magnet materials according to the present invention, the method of bringing the alloy powder into contact with the carburizing gas is not particularly limited. A carburizing method using a carburizing agent, an organic solvent dropping carburizing method using an atmosphere generated by thermal decomposition of an organic solvent, a vacuum carburizing method using a vacuum furnace under reduced pressure, etc. can be employed. Carbon is R2 Fe 17, RFe 1
When entering the crystal lattice of intermetallic compounds such as 2,
It has the effect of significantly increasing the saturation magnetic flux density, Curie point, and crystal magnetic anisotropy. However, the temperature is 600℃
If it is less than 1,200°C, it will take time for carbon to penetrate, leading to a decrease in productivity, while if it exceeds 1,200°C, the alloy will begin to melt, so 600 to 1,200°C was selected as the carburizing temperature.

The rare earth magnet material according to the present invention is used as raw material powder for bonded magnets or sintered magnets. After the nitriding treatment, the material may be further pulverized using, for example, a jet mill or a ball mill, and, if desired, may be subjected to strain relief annealing at a temperature of 500° C. or less.

[0014]

[Operation] In the rare earth magnet material constructed as described above, carbon penetrates into the crystal lattice of the intermetallic compound of rare earth metal and iron, thereby enhancing the basic magnetic properties and raising the Curie point. Moreover, since it does not contain hydrogen, its magnetic properties are stable over a long period of time. Furthermore, according to the above manufacturing method, since the alloy powder is brought into contact with carburizing gas at high temperatures, it is easy for carbon to penetrate into the alloy.Furthermore, since hydrogen is not handled, there is no need to handle it during the manufacturing process. It also increases safety.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the accompanying drawings.

Example 1 Samarium (Sm), electrolytic iron, and electrolytic cobalt, all with a purity of 99.9%, were mixed in a predetermined ratio, charged into an alumina crucible, melted in a high-frequency induction furnace, and poured into a mold. An alloy ingot was produced. Since component segregation is often observed inside this alloy ingot, it is held at 1000°C for 12 hours in an argon gas atmosphere.
After that, a heat treatment of rapid cooling was performed. Next, this alloy ingot was coarsely crushed into a size of several mm by using a jaw crusher, and then further crushed by a stamp mill.
This is sieved to obtain an average particle size of approximately 50 to 300 μm.
An alloy powder was obtained. Next, this alloy powder was placed in a small stainless steel plate and charged into a vacuum furnace, and methane gas was introduced into the vacuum furnace at 0.1 Torr.
Continuously introduced at a pressure of r and held at 1050°C for 2 hours,
After carbon was infiltrated into the alloy powder, it was ground again using a ball mill to obtain a magnet material with an average particle size of about 20 μm.

Next, 3% by weight of epoxy resin was blended into the magnet material obtained as described above, and the mixture was powder-molded at a pressure of 5Ton/cm2 while applying a magnetic field of 15kOe.
Subsequently, it was cured at 150 °C for 1 hour to form magnet samples 1 to 1.
3 were manufactured and subjected to tests to measure magnetic properties, Curie points, and components. Measurement of magnetic properties was performed at 60 kOe.
After applying a pulsed magnetic field, the Curie point was measured using a DC BH tracer.
The test was carried out by filling the powder sample into the holder M) and heating it. Component measurement (analysis) was performed for rare earth metals, iron, and cobalt by ICP emission spectrometry, and for carbon by combustion method.

[0018] The results of each test are summarized in Table 1. In the table, 4πIm represents the maximum magnetic flux density (G), iHc represents the coercive force, and Tc represents the Curie point. Furthermore, since it is difficult to measure the saturation magnetic flux density, the maximum magnetic flux density at the maximum measurement magnetic field of 20 kOe of the DC BH tracer was adopted. Furthermore, in the table, the symbol # attached to the sample number represents a comparative example.

[0019]

[Table 1]

As is clear from Table 1, magnet samples 3, 4, 5, 8, 9, and 10 according to the present invention all have lower coercive force iHc and Curie point Tc than those of the comparative examples. A high value was obtained. In particular, regarding the Curie point Tc, samples that do not contain carbon (comparative examples) 1 and 6 have a value of approximately 110 to 130°C, whereas those included in the scope of the present invention have a high value of approximately 350 to 600°C. The Curie point of the Nd-Fe-B permanent magnet is approximately 3.
It was confirmed that the value was sufficiently high compared to 10°C. In addition, comparative example sample 12 with low samarium content
The coercive force iHc is significantly smaller in
This is due to the presence of a large amount of αFe in the alloy, making it soft magnetic. Comparative sample 1 with high samarium content
In No. 3, the Curie point Tc was significantly lowered, and it became clear that there would be problems if the rare earth metal content was too small or too large. Furthermore, from a comparison of Samples 1 to 6, it is clear that carbon has an effect on raising the Curie point Tc, but if its content is too low (Sample 2) or too high (Sample 6), Coercive force iHc
has decreased significantly. This is presumed to be because when the carbon content is too low, the magnetocrystalline anisotropy becomes small, and when the carbon content is too high, the soft magnetic αFe increases. Furthermore, from a comparison of Samples 8 to 11, it is clear that replacing a part of iron with cobalt has an even greater effect on raising the Curie point Tc; however, Comparative Sample 11
Therefore, when the cobalt content is too large, the coercive force iHc decreases significantly. This is presumed to be because the magnetocrystalline anisotropy has become smaller.

Example 2 Sm, Pr, Nd, Ce, all with a purity of 99.9%
Alternatively, Dy and electrolytic iron are blended and melted in a predetermined ratio to obtain an alloy powder in the same manner as in Example 1, and then carburized and powder compacted in the same manner as in Example 1 to obtain a magnet sample. Nos. 21 to 27 were manufactured and subjected to tests to measure magnetic properties and components. Table 2 shows the measurement test results. From this, magnet samples 21 to 26 according to the present invention all exhibit high values of maximum magnetic flux density 4πIm and coercive force iHc, and have good magnetic properties even if a part of Sm is replaced with other rare earth metals. It has become clear that it can be obtained. Note that Comparative Example Sample 27 has an excessive content of rare earth metals, so the maximum magnetic flux density is 4πIm.
Also, a decrease in coercive force iHc is observed.

[0022]

[Table 2]

Example 3 Similar to Example 1, samarium and electrolytic iron were mixed in a predetermined ratio and melted to produce an alloy ingot.Then, this alloy ingot was charged into a quartz tube and recycled in a high frequency furnace. After melting, the molten alloy was injected from the pores at the bottom of the quartz tube onto the surface of a rotating copper roll and rapidly cooled. The obtained rapidly solidified alloy has a thickness of about 0.05 mm, a width of about 2 mm, and a length of 20 to 100 mm.
It was flaky. In addition, since the rotational speed of the roll is closely related to the crystallinity and magnetic properties of the obtained alloy flakes, the peripheral speed of the roll was varied in the range of 20 to 35 m/s, and the X-ray diffraction method and SEM observation were performed. Therefore, the grain size is 0.1
The alloy flakes having a diameter of ~5 μm were classified and used in Example 1.
Magnet samples 31 to 34 were produced by carburizing and powder compacting in the same manner as above, and were subjected to tests to measure magnetic properties, Curie points, and components. In this example, since the alloy flakes are magnetically isotropic, powder compaction was performed without applying a magnetic field. Table 3 shows the measurement test results. From this, all of the magnet samples 32 to 34 according to the present invention have a maximum magnetic flux density of 4πIm,
High values were obtained for both the coercive force iHc and the Curie point Tc, and it became clear that there would be no problem even if the rapid cooling method was applied to the production of alloy powder. In addition, since Comparative Example Sample 31 does not contain nitrogen, the coercive force iHc and Curie point Tc
Both are significantly smaller.

[0024]

[Table 3]

Example 4 From a master alloy of 12% Sm - 88% Fe in atomic percentage, the particle size was 50 to 300 μm using the same procedure as in Example 1.
An alloy powder of 400-1200℃, time 1-36 hours (h)
Carburizing was carried out with various changes within the range, followed by heat treatment at 550° C. for 2 hours in vacuum to release the hydrogen occluded in the alloy powder. Next, magnet samples 41 to 45 were manufactured by the same procedure as in Example 1, and subjected to tests to measure magnetic properties and components. Table 4 shows the measurement test results. From this, it is clear that the carburizing temperature must be at least 600° C. in order to ensure desired magnetic properties and productivity.

[0026]

[Table 4]

[0027]

Effects of the Invention As explained in detail above, the rare earth magnet material according to the present invention not only ensures magnetic properties equivalent to those of Nd-Fe-B permanent magnets, but also has significantly improved temperature characteristics. Furthermore, since the alloy does not contain hydrogen, it has excellent long-term stability and has the effect of expanding the range of applications. Further, according to the method for manufacturing rare earth magnet materials according to the present invention, carbon can easily penetrate into the alloy, thereby achieving the effect of ensuring desired productivity.

Claims (4)

[Claims] Claim 1: Rare earth metal (R), carbon and iron in atomic percentage: 5-15%R- 5-25%C-balance Fe
A rare earth magnetic material characterized by containing a proportion of . 2. Obtain an alloy powder containing rare earth metal (R) and iron as main components, and then add this alloy powder to 600-1
A method for producing a rare earth magnet material, the method comprising obtaining the rare earth magnet material according to claim 1 by contacting it with a carburizing gas at 200°C. 3. Rare earth metal (R), carbon, cobalt and iron in atomic percentages of 5 to 15% R- 5 to 25% C-
A rare earth magnet material containing 1 to 40% Co and the balance Fe. 4. Obtain an alloy powder containing rare earth metal (R), cobalt and iron as main components, and then process this alloy powder
A method for producing a rare earth magnet material, which comprises contacting with a carburizing gas at 600 to 1200°C to obtain the rare earth magnet material according to claim 3.