JP3105929B2 - Magnetostrictive material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Object of the invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-biased magnetic field type magnetostrictive material which is excellent in both magnetostriction and response of an applied magnetic field and has high mechanical strength.

[0003]

2. Description of the Related Art Since a magnetic substance is deformed by magnetostriction when a magnetic field is applied from the outside, the following magneto-mechanical displacement conversion device (hereinafter referred to as "device") has been developed by applying this magnetostriction. In other words, in the field of vibration, it can be applied to speakers, sonars, parts feeders, ultrasonic delay lines, ultrasonic processing machines, vibration isolation / vibration prevention mechanisms for motors, etc. in magnetostrictive transducers, and in precision positioning mechanisms as displacement control actuators in mechanical applications It can be applied to valve control valves, mechanical switches, micro pumps, printer heads, etc. Further, it can be used as a magnetostrictive sensor for a pressure sensor, a knock sensor, a sound pressure sensor, and the like, and is a very industrially useful material for application to a surface acoustic wave application element.

As magnetostrictive materials used for these devices, Ni-based alloys, Fe-Co alloys,
Although such a ferrite-based material has been known, much better (saturation magnetostriction lambda _s is 1000 × 10 ^-6 or higher) in the absolute amount of magnetostriction than these magnetostrictive materials recently (magnetostriction) rare earth - Laves ferrous Type intermetallic compound (general formula AB
₂ , MgCu ₂ (cubic system) or MgZn ₂ , Mg
An alloy phase having a crystal structure of Ni ₂ (both hexagonal systems and exhibiting magnetostriction) has been reported (JP-B-61-33).
No. 892).

[0005]

However, the above rare earth-iron giant magnetostrictive alloy has a low mechanical strength and is very brittle, so that it is liable to be cracked or chipped and has a poor shape arbitrarily. However, it is possible to mold only those having a given shape).

Further, since the rare earth-iron based magnetostrictive alloy has magnetostrictive characteristics as shown in FIG. 2, the applied magnetic field response near zero magnetic field is poor (magnetostriction when a fixed amount of magnetic field is applied). Is small). Further, positive magnetostriction occurs in both the positive magnetic field and the negative magnetic field, and the response of the applied magnetic field is not monotonically increasing or monotonically decreasing.

Therefore, if the applied magnetic field is changed so that the amount of magnetostriction when no magnetic field is applied becomes zero as expected, a desired amount of magnetostriction cannot be obtained, and the magnetostriction caused by the application of a magnetic field cannot be obtained. It is difficult to control the amount. For this reason, when used in the above-described magneto-mechanical displacement conversion device, a bias magnetic field is applied from the outside in addition to the magnetic field for controlling the magnetostriction, and the magnetic field is changed for control as shown by the broken line in the figure. Is shifted so as to include only the positive region, for example, without including the vicinity of zero.In the range of the magnetic field to be changed, the applied magnetic field response of magnetostriction is high, and the amount of magnetostriction changes monotonically with respect to the amount of applied magnetic field. I was

However, for this purpose, as shown in FIG. 3, in a device 1 using this magnetostrictive alloy, a magnetostrictive alloy piece 1 that expands and contracts in the direction of an arrow and a magnetostrictive alloy piece 1
In addition to the electromagnet 2 for applying a magnetic field for controlling the amount of magnetostriction, a magnetic circuit or the like including a permanent magnet 3 for forming an external bias magnetic field must be installed, so that high cost and large-sized device can be avoided. Did not.

The present invention has been made in view of the above circumstances, and has as its object to provide a magnetostrictive material having excellent mechanical strength and good magnetostriction characteristics. [Configuration of the invention]

[0010]

Means and operation for solving the problems The present invention in order to solve the above problems, for example, RFe x _(R is at least one rare earth element, 1.5 ≦ x ≦ 4) magnetostrictive alloy powder and permanent magnet powder A magnetostrictive material characterized by integrating a mixed powder of

[0011] In the magnetostrictive material of the present invention, first magnetostrictive alloy is super magnetostrictive alloy of the as RFe _x and the like,
When the R element constituting this is one kind of element, L
a, Ce, Pr, Nd, Pm, Sm, Eu, Gd, T
Rare earth elements such as b, Dy, Ho, Er, Tm, Yb, and Lu can be used. In addition, it can be R element,
When a combination of at least one kind of rare earth element is used, Tb-
Dy, Tb-Ho, Tb-Pr, Sm-Yb, Tb-D
Combinations of y-Ho, Tb-Dy-Pr, Tb-Pr-Ho and the like are conceivable.

On the other hand, the other element constituting the magnetostrictive alloy is Fe
However, it is possible to partially replace Fe with Co for improving corrosion resistance. However, if the substitution amount is too large, the magnetostriction characteristics are reduced (the magnetostriction amount is reduced and the response to the applied magnetic field is reduced). Therefore, the substitution amount of Fe by Co is 95 at%.
(95 atomic%) or less.

Further, if necessary, a part of Fe may be further substituted with Mn. The R-Fe magnetostrictive alloy is Mn.
When the element is contained, the magnetic anisotropy of the rare earth element changes, and excellent magnetostriction characteristics can be obtained not only in a high magnetic field but also in a low magnetic field. The upper limit of the amount of Fe replaced by Mn is 50 at%. If the upper limit is exceeded, the Curie temperature decreases, and the magnetostriction characteristics deteriorate.

In addition, Fe is the mechanical strength of the magnetostrictive material,
For the purpose of improving corrosion resistance and saturation magnetostriction, Ni, Mg,
Al, Ga, Zn, V, Zr, Hf, Ti, Nb, C
u, Ag, Sn, Mo, Cr, Ta, Pd, In, S
It may be further substituted with b, Ir, Pt, Au, Pb, W, Si, B or the like. However, the amount of these substitution elements is M
The limit is up to about 50 at% of Fe, including the amount of substitution by n. If it exceeds this, the amount of magnetostriction decreases.

The atomic ratio x between the R element and Fe is 1.5
When x is less than 1.5, sufficient magnetostriction characteristics cannot be obtained, and when x is more than 4, toughness is significantly reduced and the film becomes brittle.

On the other hand, as the permanent magnet powder, powders such as ferrite magnets, Sm-Co magnets, and Nd-Fe-B magnets can be used. -Co and Nd-Fe-B magnet powders are preferred.

The mixing ratio of the permanent magnet powder is preferably 5 to 50% by weight based on the magnetostrictive alloy powder. If the content is less than 5% by weight, it is difficult to obtain a sufficient self-bias magnetic field even when the permanent magnet powder is magnetized, and if it exceeds 50% by weight, it is difficult to obtain a sufficient magnetostriction for the magnetostrictive alloy. This mixing ratio is more preferably 10 to
30% by weight.

The particle size of the magnetostrictive alloy powder and the permanent magnet powder is preferably from 1 to 800 μm. If it is less than 1 μm, the surface area of the whole powder becomes too large, which tends to cause deterioration of the magnetostriction characteristics and magnet characteristics due to oxidation, and 800 μm
If it exceeds, the mechanical strength of the magnetostrictive material is reduced, and it is difficult to mold the material into ultra-thin flakes.

Next, a method for producing the magnetostrictive material of the present invention will be described.

First, an R element and Fe having a predetermined atomic ratio and, if necessary, the above-mentioned Co, Mn, etc. are prepared and melted by arc melting or the like, and then a magnetostrictive alloy powder is obtained by a super-quenching method, a hydrogen absorbing method or the like. Get. The rapid quenching method is a single-roll method, a twin-roll method, a gas atomizing method, a RDP (Rotating Disk Pr
ocess; a method in which a molten metal is jetted onto a rotating disk) to rapidly quench the molten alloy to form a powder.
It is preferable that the super-quenching is performed in an atmosphere of an inert gas such as Ar or He from the viewpoint of preventing oxidation.

Further, after cooling the melt of the magnetostrictive alloy into an alloy ingot having a shape that can be pulverized by a mechanical means such as a ball mill, a brown mill, a stamp mill, and the like, the alloy ingot is subjected to the mechanical pulverization means described above. Even if it is pulverized, a magnetostrictive alloy powder can be obtained.

In the case of pulverizing from an alloy ingot, the magnetostrictive properties can be improved by performing a heat treatment before and after the pulverization at 300 ° C. or a temperature range of the melting point of the giant magnetostrictive alloy for about 0.1 to 500 hours. .

After the powder of the magnetostrictive alloy is obtained, the powder of the permanent magnet is obtained in the same manner, and the two powders are mixed. Then, after inserting the mixed powder into a mold having a desired shape, for example, hot pressing or HIP (hot isostatic pressing) is performed.
To obtain a magnetostrictive material. The mixed powder integrated in the present invention refers to a powder in which the magnetostrictive alloy powder and the permanent magnet powder are aggregated at a high density while maintaining the powder shape with each other.

When hot pressing is performed at the time of integration, the hot pressing temperature is preferably 600 to 1200 ° C., and the pressing pressure is preferably 1 t / cm ² or more. 60
If the temperature is lower than 0 ° C., it is difficult to generate a liquid phase, and it is difficult to increase the density.
This leads to a decrease in mechanical strength. On the other hand, when the temperature exceeds 1200 ° C., the magnetostrictive alloy and the permanent magnet do not maintain the shape of the powder and are solidified.
This is because the co-solved material deteriorates the coercive force of the permanent magnet and the magnetostrictive characteristics of the magnetostrictive alloy. Also, if the pressing pressure is 1
Even when it is less than t / cm ^2, high density is difficult. Further, when hot pressing is performed, it is preferable to perform hot pressing in an atmosphere of an inert gas such as Ar or He so that the magnetostrictive alloy powder is not oxidized and the magnetostriction characteristics are not deteriorated.

As described above, if the magnetostrictive alloy is once powdered and then molded and integrated by hot pressing, the crystal grain size is made uniform and the segregation of the composition is prevented, so that good magnetostrictive characteristics are stabilized. And the mechanical strength is also improved. In addition, since the powder is molded, it is excellent in arbitrary shape.

By the way, if R element comprises two or more elements, e.g. _{R1 p R2 1-p Fe x} (R1 and R2 mutually different rare earth elements, 0 <p <1) in the case of the above to follow the alloy ingot to a method of grinding, first R1 _p F
An alloy powder is manufactured from an alloy ingot having a composition of e _x1 and R2 _1-p Fe _x2 (x1 + x2 = x). When the two powders are mixed at the stage of the integration, the desired composition is obtained by grain growth during hot pressing. The magnetostrictive material can be formed while obtaining the magnetostrictive alloy powder.

In hot press molding, when a magnetic field is applied to make the magnetostrictive alloy magnetically anisotropic in the direction of the axis of easy magnetization, the magnetostriction characteristics can be improved. In the case where the R element contains two or more elements and the alloys containing each R element have different magnetic anisotropy directions, two or more rare earth-iron alloys are formed so as to have a desired composition as described above. System alloy powder,
After magnetically forming this mixed powder (forming a compact in a magnetic field) and achieving magnetic anisotropy for each alloy,
When hot pressing is performed, a magnetostrictive alloy having the same magnetic anisotropy direction can be obtained as a whole, and a magnetostrictive material having excellent magnetostrictive properties can be formed.

Further, when hot pressing is performed after adding a low melting point metal or alloy such as Al to the magnetostrictive alloy powder or coating the powder surface, the hot pressing temperature can be lowered, and the cost associated with hot pressing can be reduced. Can save. In addition, when the heat treatment is performed at a temperature of 300 ° C. to the melting point of the magnetostrictive alloy after the hot pressing, the magnetostriction characteristics can be improved, similarly to the heat treatment after the alloy ingot pulverization.

The magnetostrictive material of the present invention comprises a self-biased magnetic field type having a bias magnetic field in the magnetostrictive material by applying a magnetic field to the magnetostrictive material and magnetizing the permanent magnet powder before device formation after the integration. It can be a magnetostrictive material. The self-biased magnetic field and the initial magnetostriction due to the self-biased magnetic field (for example, the magnetostriction before the magnetostriction is appropriately changed by the electromagnet 2 in FIG. 3) can be adjusted by adjusting the amount of the permanent magnet powder.

The magnetostrictive material of the present invention is desirably improved in weather resistance such as rust prevention by coating the surface with a metal coating such as Ni plating or resin coating with an epoxy resin or the like.

In the magnetostrictive material of the present invention, the mixed powder of the magnetostrictive alloy powder and the permanent magnet powder is integrated by hot pressing or the like. The magnet powder can be magnetized and act as a bias magnetic field. Therefore,
In the device using the magnetostrictive material of the present invention, a permanent magnet or the like for applying a bias magnetic field from the outside is unnecessary.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

Example 1 First, Tb _0.35 Dy in atomic ratio
After preparing each atom so as to be _0.65 (Fe _0.85 Mn _0.15 ) ₂ , arc melting was performed in a water-cooled copper boat under an Ar atmosphere to obtain an alloy ingot having the above composition. Then, the alloy ingot was brown-milled to have an average particle size of 30.
It was pulverized to μm to obtain a magnetostrictive alloy powder. Then, 20% by weight of an Nd—Fe—B-based permanent magnet powder (average particle diameter: 100 μm) was mixed with the magnetostrictive alloy powder.

Next, after filling the above mixed powder into a mold, hot pressing was performed in an argon atmosphere at 900 ° C. and 1.5 t / cm ² to obtain a cylindrical magnetostrictive alloy rod having a diameter of 6 mm and a length of 30 mm. I got Finally, add 3 to this magnetostrictive alloy rod.
Applying a magnetic field of 0 kOe to magnetize the contained permanent magnet,
The magnetostrictive alloy rod was a self-biased magnetic field type magnetostrictive material.

With respect to this magnetostrictive alloy rod, the applied magnetic field was changed within a range of ± 300 Oe by a facing magnetic pole type electromagnet at room temperature, and the magnetostriction characteristics were evaluated using a strain gauge.
The result is shown in FIG. As is clear from FIG. 1, this magnetostrictive material is almost linear in the applied magnetic field range of -300 Oe to +300 Oe, including near the zero magnetic field (there is a self-biased magnetic field), and has an applied magnetic field response of about 120 to 130 ppm / kOe. And the magnetostriction in this applied magnetic field range is about -400 ppm to +400 ppm, which is a large value close to about 800 ppm in total. Therefore, the magnetostrictive alloy rod according to the present embodiment has excellent magnetostrictive characteristics and has good response to the applied magnetic field over the entire range of the applied magnetic field, so that there is no need to newly provide a bias magnetic field using a permanent magnet or the like.

Further, for 10 magnetostrictive alloy rods manufactured from the magnetostrictive material of the present embodiment by the above-described method, 10 kO
_eWhen the magnetostriction (λ _10kOe ) in the applied magnetic field was measured,
The dispersion was small at 1200 ± 20 ppm, and a good value was obtained as an absolute value.

Further, since the magnetostrictive alloy rod obtained in this embodiment has high dimensional accuracy in a desired shape, it is not necessary to perform post-processing. When the mechanical strength was measured by a three-point bending test, a good value of 17 kg / mm ² was obtained.

<Example 2-15> First, ingots of the respective alloys having the compositions shown in Table 1 below were produced in the same manner as in Example 1, and then the ingots of the respective alloys obtained by melting the respective alloy ingots were prepared. The mixed molten metal has a diameter of 3 in an Ar atmosphere.
Ultra-quenching was performed by a single roll method using a Cu roll having a thickness of 00 mm and a roll speed of 25 m / sec to obtain a magnetostrictive alloy powder having an average particle diameter of 100 μm.

Then, this giant magnetostrictive alloy powder was integrated with a permanent magnet powder having the type and mixing ratio shown in Table 1 by hot pressing in the same manner as in Example 1 to form a rod of a magnetostrictive material. After applying a self-biased magnetic field of 30 kOe by the same method, the magnetostriction was measured in a magnetic field of ± 0.3 kOe. The results are shown in Table 1.

[0040]

[Table 1]

As is clear from Table 1, the magnetostrictive materials of the present embodiment all have a symmetric magnetostriction centered on a zero magnetic field in the magnetic field range of ± 0.3 kOe (the absolute value is the same and the positive and negative signs are opposite). Has a substantially linear applied magnetic field response,
The absolute amount of magnetostriction is also large. Therefore, it was confirmed that the magnetostrictive materials of Examples 2 to 15 also had good magnetostrictive characteristics.

[0042]

As described above, the magnetostrictive material of the present invention has a self-biased magnetic field, and exhibits excellent magnetostriction characteristics in both the amount of magnetostriction and the response of the applied magnetic field. Since the magnetostrictive material of the present invention does not require an external bias magnetic field, the device structure can be simplified.

[Brief description of the drawings]

FIG. 1 is a diagram showing magnetostriction characteristics of a rod made of a magnetostrictive material according to one embodiment of the present invention.

FIG. 2 is a diagram showing magnetostriction characteristics of a conventional magnetostrictive material.

FIG. 3 is a schematic sectional view of a conventional magnetic-mechanical displacement conversion device.

[Explanation of symbols]

 1 Magnetostrictive alloy piece 2 Electromagnet 3 Permanent magnet

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masashi Sabashi 1 Koga Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Research Institute, Inc. (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 33 / 02 C22C 38/00 303

Claims (1)

(57) [Claims] 1. A magnetostrictive material wherein a mixed powder of a magnetostrictive alloy powder and a permanent magnet powder is integrated.