JPS61281850A - Permanent magnet material - Google Patents

Abstract

PURPOSE:To improve coercive force and corrosion resistance by allowing a prescribed thin film layer to adhere to the surface to be ground of a sintered body containing prescribed percentage of rare earth elements such as Nd, Pr, Dy, etc., B, and Fe. CONSTITUTION:The Al thin film layer is allowed to adhere to the surface to be ground of the sintered magnetic body having a main phase composed of tetragonal crystal phase and also having a volume of <=2.5cm<3> or a thickness of <=5mm to form a permanent magnet material. The above sintered body is mainly composed of, by atom, 10-30% R (>=1 kind among Nd, Pr, Dy, Ho, La, Ce, Sm, etc.), 2-28% B, and 65-80% Fe and the above surface to be ground has a metallic thin film layer having body-centered cubic crystal structure mainly composed of Nd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application This invention is an Fa-BR-based magnet that prevents the deterioration of magnetic properties caused by grinding of the surface of a sintered permanent magnet and roughly improves the corrosion resistance of the magnet material. Regarding permanent magnets, especially those with a volume of 2.
501? The present invention relates to permanent magnet materials for small or thin objects with a thickness of 5.0 mm or less.

BACKGROUND ART Current typical permanent magnet materials are alnico, hard ferrite and rare earth cobalt magnets.

This rare earth cobalt magnet has extremely excellent magnetic properties and is used for a variety of purposes, but the main component is S.
, Co are both in short supply and expensive, and it will be difficult to supply them in large quantities stably over a long period of time.

Therefore, there has been a strong desire for a permanent 11-stone material that has excellent magnetic properties, is inexpensive, has abundant resources, and is composed of elements that can be stably supplied in the future.

The present applicant previously proposed a Fe-BR-based permanent magnet (R is at least one of rare earth elements including Y) as a new high-performance permanent magnet that does not contain expensive Sm (Japanese Patent Application Laid-Open No. 59-1991). -46008, JP-A-59-64733,
JP-A-59-89401@, JP-A-59-13210
No. 4).

This permanent magnet uses resource-rich light rare earth materials such as ceramics and circles as R, and uses 25MGO with Fe as the main component.
It is an excellent permanent magnet that exhibits an extremely high energy product of more than a.

Recently, with the improvement in performance and miniaturization of magnetic circuits, Fa-B
-R-based permanent magnet materials are attracting more and more attention, and the volume is 2
．． 5G+? There has been a demand for Fs-BR-based permanent magnet materials for small or thin items having a thickness of 5.0+ nm or less.

In order to manufacture permanent magnet materials for such uses, small or ultra-thin sintered magnets must be processed to remove surface irregularities and distortions, or to remove surface oxidation layers, and to remove magnetic In order to incorporate it into the circuit, it is necessary to cut the entire surface or the required surface of the magnet, and a peripheral blade cutting machine is used for the processing.

Internal blade cutting machine 2 surface grinding machine, centerless grinder,
A wrapping machine etc. are used.

However, when grinding the Fs-B-R permanent magnet material with the above-mentioned device, for example, the thickness of 1M~
When processed to a product thickness of 10 mm, there was a problem that various magnetic properties deteriorated, as shown by the curved line in FIG.

Furthermore, when a permanent magnet made of an FeBR-based magnetically anisotropic sintered body is incorporated into a magnetic circuit, oxides generated on the magnet surface may cause a decrease in the output of the magnetic circuit and variations between the magnetic circuits. However, there was also the problem of contamination of peripheral equipment due to shedding of surface oxides.

Therefore, in order to improve the corrosion resistance of the above-mentioned FeBR-based permanent magnet, the applicant first developed a permanent magnet (patent application filed in 1983) whose surface was coated with a corrosion-resistant metal plating layer by electroless plating or electrolytic plating. -162350) and proposed a permanent magnet in which the surface of the magnet body was coated with a corrosion-resistant resin layer by spraying or dipping (Japanese Patent Application No. 58-1719).
No. 07).

However, in the former plating method, since the permanent magnet body is a sintered body and is porous, there is a risk that acidic or alkaline solutions may remain in the holes from the plating pretreatment, causing rust over time. Furthermore, since the chemical resistance of the magnet body is poor, there is a problem that the magnet surface is corroded during plating, resulting in poor adhesion and corrosion resistance.

Furthermore, since resin coating using the latter spray method is directional, it takes a lot of time and effort to apply a uniform resin coating to the entire surface of the object to be treated, and it is especially difficult to apply uniformly to odd-shaped magnets with complex shapes. It is difficult to apply a thick coating, and the dipping method has the problem of uneven resin coating thickness and poor product dimensional accuracy.

Purpose of the Invention The present invention prevents deterioration of magnetic properties associated with machining of sintered Wi magnets, especially for small or ultra-thin objects, in a new permanent magnet material mainly composed of rare earth elements, boron, and iron. In general, the purpose is to create a permanent magnet material on which a corrosion-resistant thin film layer with excellent adhesion and corrosion resistance is deposited without using or contacting with corrosive chemicals.

Structure and effect of the invention As a result of various studies on the coercive force of Fe-B-R permanent magnet materials, the inventors found that the magnitude of the coercive force of the magnet body is as follows:
This is due to differences in the grain boundary structure rather than within the crystal grains, and when the polished sintered magnet surface is examined in detail with an optical microscope using the Ke-rr effect, the magnetic domain reversal mechanism is found to be Magnetization reversal occurs in a very low magnetic field below the coercive force of 172 inside the magnet, and the reason why the coercive force of the crystal group in the first layer on the processed surface of the sintered magnet is low is because high coercive force appears. It has been found that this is due to the absence of a metal phase having the necessary optimal body-centered cubic structure (hereinafter referred to as body-centered cubic phase).

The body-centered cubic phase that exhibits high coercive force, which was first discovered by the inventor, is provided as a grain boundary phase with an optimal thickness and a special body-centered cubic phase structure on the crystal group on the surface of the processed sintered magnet. This is not easy to do using normal methods, but if the thickness is 1
It was discovered that the coercive force and squareness of the demagnetization curve of Fe-B-R permanent magnet materials can be improved by forming a body-centered cubic phase vapor deposited layer containing less than 1,000 Nd as a main component. This invention has now been completed.

Furthermore, M
The use of corrosive chemicals, etc. can be prevented by applying a Fil film.
It was discovered that there is no residue, the adhesion strength of the thin film is high, and excellent corrosion resistance can be stably obtained over a long period of time.

That is, the present invention provides at least one of R (R is m, Pr, Dy, )io, Tb, or roughly, La, Ce, Sm
, Cd, Er, Eu, Dingm.

consisting of at least one of Yb, La, Y)1
0% to 30 atomic%, □ B2 atomic% to 28 atomic%, 80 atomic% of 1"e6565 atoms as the main component, and the main phase is a tetragonal phase. The volume is 2.5a+? or less, or the thickness is 5.0mm or less. A thin film layer consisting of a body-centered cubic phase containing Nd as a main component is provided on the surface to be ground of the sintered magnet body, and an AI thin film layer is adhered to the surface of the magnet body including the thin film layer. It is a characteristic permanent magnetic material.

More specifically, on the surface to be ground of the above-mentioned sintered magnet body, a vapor deposited layer is formed, which is mainly composed of ceramic or Nd, and the remainder is made of at least one rare earth element, excluding Nd and including Y. After that, 700℃~1000℃ and 650℃~45
A two-stage aging treatment at 0°C is applied to deposit a thin film layer consisting of a body-centered cubic phase, imparting coercive force to the crystal group of the first layer on the processed surface, and preventing deterioration of magnetic properties due to grinding. Furthermore, this permanent magnet material is characterized in that an AI thin film layer is adhered to the entire surface of the sintered magnet body including a thin film layer consisting of a body-centered cubic phase.

Further, the permanent magnet material of the present invention has an average crystal grain size of 1 to a
It is characterized by having a main phase of a compound having a tetragonal crystal structure in the range of oljJn, and containing a nonmagnetic phase (excluding oxide phase) of 1% to 50% by volume.

Therefore, the permanent magnet material of the present invention mainly uses a light rare earth, which is rich in resources, mainly ceramics or rough circles as R, and has Fa, B, and R as the main components.
An Fa-B-R permanent magnet that has an extremely high energy product of 25 MGOa or more, high residual magnetic flux density, and high coercive force, prevents deterioration of magnetic properties due to grinding, and generally improves the corrosion resistance of the magnet material. Materials can be obtained at low cost.

In this invention, in order to deposit a thin film layer of body-centered cubic phase mainly composed of cation onto the surface of the sintered magnet to be ground,
Thin film forming methods such as vacuum evaporation, ion sputtering, ion blating, ion evaporation thin film formation (IVD), and plasma evaporation thin film formation (EVD) can be selected and used as appropriate. This is not preferable because it causes peeling of the deposited layer or a decrease in mechanical strength and does not form a body-centered cubic phase, and the layer thickness is preferably 1.J+ or less, and most preferably 0.5J or less.

In this invention, in order to deposit the M layer on the entire surface of the sintered magnet body, including the surface of the body-centered cubic phase thin film layer mainly composed of Nd, the above-mentioned methods such as vacuum evaporation, sputtering, ion blating, etc. can be used. The following thin film forming methods can be selected and used as appropriate. In addition, the thickness of the thin film layer is 30J, taking into account peeling of the thin film layer, reduction in mechanical strength, and ensuring corrosion resistance.
The following thicknesses are preferred, most preferably 5-25 layer thicknesses.

Reason for limiting the composition of the permanent magnet material The rare earth element R used in the permanent magnet of this invention has a composition of 1
It accounts for 0 atomic% to 30 atomic%, but ceramic, Pr.

~, Hb, and at least one of To, or in addition, Mu, Co, Sm, CA, Er, Eu, and D
, Yb, La, and Y are preferred.

Also, normally one type of R is sufficient, but in practice two types are sufficient.
A mixture of more than one species (Mitushmetal, Didim, etc.) can be used for reasons such as availability.

Note that this R does not have to be a pure rare earth element, and may contain impurities that are unavoidable in production within an industrially available range.

R is an essential element in the new above-mentioned permanent magnet material, and when IQJl is less than %, the crystal structure becomes a cubic structure that is the same as α-iron, so it has high magnetic properties, especially high coercive force. If the rare earth element is not obtained and exceeds 30 atomic %, the R-rich nonmagnetic phase increases, the residual magnetic flux density (B') decreases, and a permanent magnet with excellent characteristics cannot be obtained. The range is 10 atomic % to 30 atomic %.

B is an essential element in the permanent magnet material according to the present invention, and if it is less than 2 atomic %, the rhombohedral structure becomes the main phase and high coercive force (iHC) cannot be obtained, and if it exceeds 28 atomic %, B The rich nonmagnetic phase increases, and the residual magnetic flux density (
Br) decreases, making it impossible to obtain an excellent permanent magnet. Therefore, B should be in the range of 2 to 28 at%.

Fe is an essential element in the new above-mentioned permanent magnet, and if it is less than 65 at%, the residual magnetic flux density Br decreases, and the
If it exceeds 0 atom%, high coercive force cannot be obtained, so F
The content of e is 65 atomic % to 80 atomic %.

Furthermore, in the permanent magnet material according to the present invention, replacing a part of Fa with G can improve the temperature characteristics without impairing the magnetic properties of the resulting magnet.
If the amount of substitution exceeds 20% of Fa, the magnetic properties will deteriorate, which is not preferable. When the amount of substitution of B is 5 at % to 15 at % in the total amount of Fa and F, it is preferable to obtain a high magnetic flux density because (B'') increases compared to the case where no substitution is made.

In addition, the permanent magnet according to the present invention can tolerate the presence of impurities that are inevitable in industrial production in addition to R, B, and FEI;
Part of B is 4.0 at% or less of C13, 5 at% or less of P, 2.5 at% or less of S, 3.5 at% or less of 5, and the total amount is 4.0 By substituting at atomic % or less, it is possible to improve the manufacturability and reduce the cost of permanent magnets.

Furthermore, at least one of the following additional elements is R-B-
It can be added to Fa-based permanent magnets because it is effective in improving the coercive force and squareness of the demagnetization curve, improving manufacturability, and reducing costs. However, addition to improve coercive force causes a decrease in residual magnetic flux density (Br), so it is desirable to add in a range that is equal to or higher than the residual magnetic flux density of conventional hard ferrite magnets.

A1 of 9.5 atom% or less; D119 of 4.5 atom% or less
．． V at 5 atomic % or less, Cr at 8.5 atomic % or less.

8, O atomic % or less) In, 5.0 atomic % or less B
119.5 atomic % or less of Nb, 9.5 atomic % or less of Dye a.

No less than 9.5 atom%, Edge less than 9.5 atom%,
2.5 atomic % or less of sb, 7 atomic % or less of Ge, 3.
Sn of 5 atomic% or less, Zr of 5.5 atomic% or less, 9.0
Ni at % or less, Si at 9.0 atomic % or less, 1.
At least one of Zn of 1 atomic % or less and Hf of 5.5 atomic % or less is added. However, if two or more types are contained, the maximum content is the maximum value of the added elements. By containing atomic percent or less, it becomes possible to increase the coercive force of the permanent magnet.

It is essential that the main phase of the crystalline phase is a tetragonal one in order to produce a sintered permanent magnet having superior magnetic properties than a fine and uniform alloy powder.

Further, the permanent magnet of the present invention can be press-molded in a magnetic field to obtain a magnetically anisotropic magnet, and can be press-molded in a non-magnetic field to obtain a magnetically isotropic magnet.

Permanence according to this invention [i is coercive force (08 for HC≧1,
The residual magnetic flux density Br>4 kG, and the maximum energy product (Btl) max is, in the most preferred composition range,
(BH) maX≧108GOe, maximum value is 25H
Reach GOa or higher.

In addition, in the case where the main component of R in the alloy powder for permanent magnets of this invention is light rare earth metals mainly composed of dynamic and circular elements, R12 to 20 at%, B44 to 24 at.
When the main component is (BH) max 358 GOs or more, especially when the light rare earth metal is ceramic, the maximum value is 428 GOa or more. reach

Example Example 1 As starting materials, electrolytic iron with a purity of 99.9%, ferroboron alloy, and Nd with a purity of 99.7% or more were used. After mixing these, they were high-frequency melted, and then cast in a water-cooled copper mold. 15
．． An ingot having a composition of 5Nd 7.5B 77Fg was obtained.

Thereafter, this ingot was coarsely ground using a stamp mill, and then finely ground using a ball mill to obtain a fine powder with an average particle size of 3.0 items.

This fine powder was inserted into a mold, oriented in a magnetic field of 20 koe, and molded at a pressure of 1.5 tJ in a direction parallel to the magnetic field.

The obtained molded body was sintered at 1100° C. for 1 hour in an Ar atmosphere to obtain a sintered body having dimensions of 20 mm in length, 10 mm in width, and 10 mm in thickness.

And from the sintered body, length 20mm x width 5mm x thickness 10
After obtaining various test pieces whose thickness was temporarily reduced by cutting them into test pieces of mm size, they were inserted into a quartz tube with a vacuum level of 2 x 10-4 Torr together with the extracted metal, and heated at 1000°C for 5 hours to completely remove the entire surface of the sample. Between 100 and 2,000 people were deposited in the membrane layer.

Roughly 800℃, 1 hour and 630℃, 1.5 in Ar
A permanent magnet according to the present invention was fabricated by performing a two-step aging treatment to form a body-centered cubic phase on the surface to be ground.

Comparative test pieces were also prepared by immediately aging the above-mentioned test pieces having various thicknesses without providing a dynamic membrane layer.

3r, iHc and (BH
) The maX value was measured using a vibrating sample magnetometer (VSH), and the results are shown in FIG. Curve a is for the permanent magnet of the present invention having a 111 ki thin IiU layer, and curve a is for the comparative permanent magnet.

Example 2 As starting materials, electrolytic iron with a purity of 99.9%, ferroboron alloy, and Nd with a purity of 99.7% or more were used, and after blending these, they were high-frequency melted, and then cast in a water-cooled copper mold.
．． An ingot having a composition of 5Nd 9.0B75.5Fe was obtained.

Thereafter, this ingot was coarsely ground using a stamp mill and then finely ground using a ball mill to obtain a fine powder with an average particle size of 3.2 tons.

This fine powder was inserted into a mold, oriented in a magnetic field of 10 kOa, and molded at a pressure of i, ot, g in a direction parallel to the magnetic field.

The obtained molded body was sintered at 1100°C for 1 hour in an Ar atmosphere to a length of 10 W + m x width of 15 mm.
A sintered body with a thickness of 8 mm was obtained.

And from the sintered body, length 2.75 mtn x width 0.7 m
After cutting into a test piece with w +
Between 100 and 2000 Nd thin film layers were deposited.

A two-stage aging treatment of 800° C. for 2 hours and 630° C. for 4 hours in Ar was performed to produce a permanent magnet with a body-centered cubic phase formed on the surface to be ground.

Comparative test pieces were also prepared by immediately aging the above test pieces of various thicknesses without providing a Nd thin film layer.

Next, the above sample was placed in a vacuum container with a vacuum degree of 5 x 10-5 Torr, Ar gas was introduced, and the vacuum was heated to 1 x lO-2 Torr.
After discharging for 20 minutes at a voltage of 400 V in Ar gas at R, then using 1-515M powder with a purity of 99.99% as a coating material, it was heated to ionize the evaporated N, These ionized particles were attracted by the electric field and adhered to the test piece constituting the cathode, forming an AI thin film. The thickness of the thin film formed on the surface of the test piece was 20 mm. The above ion brating conditions are voltage 1.
The treatment was at 8 kV for 12 minutes.

In addition, for comparison, the test piece having the above Nd thin film layer was
Solvent degreasing for 3 minutes with trichloride, and 6 minutes with 5% NaOH.
After alkaline degreasing at 0°C for 3 minutes, pickling with 2% HCf at room temperature for 10 seconds in a Watts bath at a current density of 4A/d.
Electrolytic nickel plating was performed under the conditions of m', bath temperature of 60'C, and 20 minutes to obtain a comparative test piece (comparative example) having a nickel plating layer with a thickness of 201 An on the surface.

This test piece was subjected to a corrosion resistance test and a thin film adhesion strength test after the corrosion resistance test. In addition, the magnetic properties before and after the corrosion resistance test were measured. The test results and measurement results are shown in Table 1.

The corrosion resistance test was evaluated based on the appearance of the test piece when the test piece was left in an atmosphere of 60° C., 90% humidity, and 90% humidity for 500 hours.

In addition, in the adhesion strength test, the above test piece after the corrosion resistance test was
Using adhesive tape, pull the squares at 11Tlff1 intervals,
Evaluation was made based on whether or not the thin film layer peeled (no peeling Ii! = number of squares/number of total squares).

As is clear from the results in Figure 1 and Table 1 below, the deposited layer consisting of a body-centered cubic phase containing Nd as a main component is extremely effective in preventing deterioration of the magnetic properties of the ground surface, and is particularly effective in preventing the deterioration of the magnetic properties of the ground surface. It can be seen that the thinner the thickness, the more remarkable the effect is, and the adhesion strength of the corrosion-resistant M thin film layer is extremely high, indicating that the corrosion resistance is stable.

[Brief explanation of drawings]

Figure 1 shows the thickness of a permanent magnet material test piece and Br. It is a graph showing the relationship between iHC and (BH)max.

Claims (1)

[Claims] 1 R (R is at least one of Nd, Pr, Dy, Hb, Tb, or furthermore, La, Ce, Sm, Cd,
At least one of Er, Eu, Tm, Yb, La, Y
The main components are 10% to 30 atomic% (consisting of seeds), 28 atomic% to B2 atomic%, and 65 atomic% to 80 atomic% Fe, and the main phase is a tetragonal phase with a volume of 2.5 cm^3 or less or a thickness of A thin film layer made of a metal phase having a body-centered cubic structure containing Nd as a main component is provided on the surface to be ground of a sintered magnet body of 5.0 mm or less, and the surface of the magnet body including the thin film layer is coated. A permanent magnetic material characterized in that it has a deposited Al thin film layer.