JPH1154307A - Manufacture of magnet alloy thin strip and resin binding bonded magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a magnet alloy thin strip with good yield of the magnet alloy thin strip obtained and lower dispersion of magnetic characteristics in the same lot of the alloy thin strip, by holding the average speed of flow of molten metal within suitable limits in spraying alloy molten metal on a metallic roll. SOLUTION: A magnet alloy thin strip 26 is obtained by spraying R-TM-B based alloy molten metal 23 (where R is a rare-earth element primarily including Nd and Pr, and TM is a transition metal) on a rotating metallic roll 27 at the average speed of flow 0.2 to 5 m/s (preferably 0.5 to 3.0 m/s) to rapidly solidify the alloy molten metal 23. Next, the alloy thin strip 26 obtained or after heat treating is powdered, and the obtained powder and resin are mixed and them molded. As a result, the magnet alloy thin strip can be manufactured with good yield of the magnet alloy thin strip obtained and lower dispersion of magnetic characteristics in the same lot of the alloy thin strip.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a permanent magnet material, and more particularly to a method for producing a rare earth permanent magnet material by a molten metal quenching method.

[0002]

2. Description of the Related Art A method for producing a magnet alloy ribbon by injecting a molten alloy of a rare-earth magnet material onto a single metal roll and rapidly solidifying the molten alloy is described in Japanese Patent Publication No. 3-52528, page 4-7. From line 30 to page 5, line 9, column 42, a sample of the alloy ingot was placed in a quartz tube and melted, and then the molten metal was passed through a circular hole orifice provided at the bottom of the quartz tube to give a very large heat capacity to the molten metal. It is described that an alloy thin ribbon is obtained by spraying a metal disk having the alloy ribbon. However, it has not been examined how the flow velocity of the molten metal at the time of molten metal injection affects the magnetic properties of the obtained alloy ribbon.

[0003]

The above-mentioned conventional method for producing a magnet alloy ribbon has the following problems.

[0004] 1) Depending on various conditions at the time of injection of the molten metal, the dimensional variation of the magnetic alloy ribbon is large, and the magnetic characteristics are accordingly varied.

[0005] 2) The yield (yield) of the magnet alloy ribbon to be produced is degraded with respect to the input weight (the weight of the raw material or the master alloy) depending on various conditions during the injection of the molten metal.

[0006] 3) In the case where there is variation in lots in the magnet alloy ribbon, satisfactory magnet characteristics cannot be obtained even if a bonded magnet is produced using the alloy ribbon as a powder.

The present invention solves the above-mentioned problems of the prior art, and obtains a magnetic alloy ribbon obtained by setting the average molten metal flow velocity when the molten alloy is injected onto a metal roll in an appropriate range. It is a first object of the present invention to provide a method for producing a magnet alloy ribbon having a good yield of the alloy and less variation in the magnetic properties of the alloy ribbon in the same lot.

It is a second object of the present invention to provide a method for manufacturing a resin-bonded bonded magnet having excellent magnetic properties, in which the powder produced from the magnetic alloy ribbon thus obtained is bonded to a resin.

[0009]

In order to achieve the above object, a method for producing a magnetic alloy ribbon according to the present invention comprises the steps of:
A magnet alloy ribbon formed by spraying a B-based alloy (R is a rare earth element mainly composed of Nd and Pr, and TM is a transition metal) onto a rotating metal roll to rapidly solidify the molten alloy. Wherein the average molten metal flow velocity during the injection of the molten alloy is 0.2 to 5 m / s.

The method for producing a magnetic alloy ribbon according to the present invention is characterized in that a molten metal of an R-TM-B (R is a rare earth element mainly composed of Nd and Pr, TM is a transition metal) is prepared by rotating a metal alloy. In a method for producing a magnet alloy ribbon, wherein the molten alloy is rapidly cooled and solidified by injecting the molten alloy onto a roll to be melted, wherein the average molten metal flow velocity at the time of injecting the molten alloy is 0.5 to 3 m / s. .

Further, the method for producing a resin-bonded bonded magnet according to the present invention is characterized in that a molten metal of R-TM-B type (R is a rare earth element mainly composed of Nd and Pr, and TM is a transition metal) The average molten metal flow rate is set to 0.2 to 5 m / s
A magnet alloy ribbon is obtained by spraying and rapidly solidifying to obtain a magnetic alloy ribbon, and the obtained alloy ribbon is directly or heat-treated, then pulverized into powder, and the obtained powder and resin are mixed. It is characterized by being obtained by post-molding.

Further, the method for producing a resin-bonded bonded magnet of the present invention comprises the steps of: preparing an R-TM-B-based (R is a rare earth element mainly composed of Nd or Pr, TM is a transition metal) alloy metal melt; A magnet alloy ribbon is obtained by injecting the molten metal at an average melt flow rate of 0.5 to 3 m / s on the roll to be solidified by rapid cooling and solidifying, and the obtained alloy ribbon is directly or heat treated and then pulverized. A powder obtained by mixing the obtained powder and a resin and then molding.

[0013]

Embodiments of the present invention will be described below.

1) Outline of manufacturing method (magnet alloy ribbon, resin-bonded bonded magnet) FIG. 1 is a schematic diagram of a method of manufacturing a magnet alloy ribbon using a single roll. Roughly, a raw material or a mother alloy loaded in a nozzle in an appropriate atmosphere is induction-melted by energizing a high-frequency heating coil wound around the nozzle to form a molten alloy. Thereafter, the molten alloy is injected through an orifice (opening) provided at the bottom of the nozzle onto a high-speed rotating metal single roll installed immediately below the nozzle. Since the heat capacity of the metal roll is very large with respect to the injected molten metal, the molten metal is placed on the roll at 10 ⁴ to 10 ⁶ K / s.
The alloy is rapidly solidified at a cooling rate of the order and is extended in the roll rotation direction to form an alloy ribbon. The individual items will be described in more detail below.

First, each of the raw material metals weighed so as to have a desired composition (R-Fe-B system or R-Co system, R-TM system) may be charged into the nozzle, or a high-frequency melting furnace may be used in advance. For example, a sample cut out from a mother alloy ingot having a desired composition produced by the above method may be used. As a material of the nozzle, quartz is most preferable, but other ceramic materials such as alumina and magnesia having high heat resistance may be used. The orifice (opening) is preferably a circular hole or a slit. However, in the case of a slit shape, the longitudinal direction of the slit is preferably in a direction as close as possible to the roll rotation direction (the width direction of the obtained alloy ribbon).

The material of the metal roll is preferably a copper alloy, an iron alloy, a chromium alloy, molybdenum, or the like in order to obtain a sufficient thermal conductivity. An alloy layer may be provided. For example, hard chrome plating may be applied. If the surface roughness of the roll surface is too rough, the wettability between the molten alloy and the roll is reduced. Therefore, it is necessary to finish the surface of the roll with a polishing paper or the like to a sufficiently smooth surface in advance. Specifically, it is desirable to maintain an average surface roughness of 1/3 or less of the thickness of the alloy ribbon to be manufactured. The rolls may be water-cooled to increase the cooling capacity.

After the settings such as sample loading and roll polishing are completed, the inside of the chamber is first evacuated to 10 ^-2 torr or less by a vacuum pump, and then the chamber is filled with an inert gas until the desired pressure is reached. I do. Ar, He, or the like may be used as the inert gas.

After a desired atmosphere is established, the coil is energized to obtain a molten metal. However, as shown in FIG. 1, it is not necessary to take a method of directly heating the sample by putting it in the nozzle.
Specifically, the molten alloy which is obtained by putting the raw material in a crucible separately provided and melted may be transferred to a nozzle and then injected. The heating method is not limited to induction heating, and a method of providing a heating element such as a carbon heater around the nozzle may be used.

The molten alloy thus obtained is injected through the bottom orifice. When injecting, a method of injecting (dropping) the molten metal by using gravity can be considered. However, as shown in FIG. 1, an inert gas is applied to a space above the molten metal in the nozzle at an appropriate pressure (Pi). Is preferred.
Specifically, an inert gas discharge device is provided via an electromagnetic valve connected to the upper part of the nozzle, and the pressurized gas in the discharge device is discharged by opening and closing the electromagnetic valve in accordance with the injection timing. The molten alloy is injected. The substantial injection pressure Pi of the molten metal is a pressure difference between the pressure of the inert gas in the discharge device and the atmospheric pressure in the chamber.

The injected alloy melt is rapidly cooled on a roll and solidified to form a magnetic alloy ribbon. Since the thickness of the alloy ribbon generally decreases with the peripheral speed of the roll, the cooling rate conversely increases with the peripheral speed. For this reason, in order to obtain a desired metal structure, it is necessary to set the roll peripheral speed to an appropriate value. For example, in order to obtain good magnetic properties in an as-spun (no heat treatment) state, a roll of several tens nm order is required. The peripheral speed is set so as to obtain a crystal structure. On the other hand, a method of realizing good magnetic characteristics by performing heat treatment after partially or entirely having an amorphous structure may be adopted. In this case, as-spun
As a roll peripheral speed higher than the roll peripheral speed at which the optimum characteristics can be obtained, a part or all of the rolls have an amorphous structure, and then are subjected to heat treatment to be crystallized so that magnet characteristics can be obtained. The heat treatment temperature varies depending on the alloy composition, but is preferably in the range from just above the crystallization temperature to 900 ° C. At temperatures lower than the crystallization temperature, crystallization cannot be achieved. At temperatures exceeding 900 ° C., crystal grains become remarkably coarse, and satisfactory magnetic properties cannot be obtained.

The magnet powder to be provided to the bonded magnet is obtained by pulverizing the above-described magnet alloy ribbon. The particle size of the powder at the time of pulverization may be set to an average particle size of 100 μm or less in consideration of moldability as a bonded magnet.

The powder thus obtained is mixed with either a thermosetting resin such as an epoxy resin or a thermoplastic resin such as a nylon resin, and then molded to obtain a bonded magnet.
Examples of the molding method include compression molding, injection molding, and extrusion molding. Further, if necessary, a small amount of a lubricant, an antioxidant and the like may be added together with the resin.

2) Average molten metal flow velocity The average molten metal flow velocity when the molten alloy is injected onto the roll through the orifice has a great influence on the magnetic properties of the magnetic alloy ribbon.

The average molten metal flow velocity (v) defined in the present invention was calculated as follows.

First, a high-speed video camera captures and records the vicinity of the nozzle tip and the vicinity of the paddle (melt pool) during molten metal injection as schematically shown in FIG. 2, and the time from the start to the end of molten metal injection. Is calculated as the injection time (t). The volume of the injected alloy melt is measured, for example, as follows. First, before the injection, the total weight of the nozzle and the master alloy sample (or raw metal) is measured in advance, and after the production of the alloy ribbon by the injection of the molten metal is completed, the nozzle and the residue remaining in the nozzle are removed. Is measured, and the difference between the two measured values is defined as the weight (W) of the injected molten metal. Furthermore, if the density of the molten metal is known, the injected volume can be known. Although it is difficult to know the density of the molten metal itself, it is considered that the density of the manufactured magnetic alloy ribbon is not so different from the density of the molten metal, so the magnetic alloy ribbon was measured by the Archimedes method in ethyl alcohol. The density value (ρ) was taken as an alternative value. From the density (ρ) and the weight (W) of the molten metal thus obtained, the volume of the injected molten metal was calculated as W / ρ. The value obtained by dividing this volume by the aforementioned unit time (t) is the volume flow rate,
The volume flow rate per unit area obtained by dividing this by the cross-sectional area of the melt flow at the time of injection is the melt flow rate. Although it is difficult to actually determine the cross-sectional area of the molten metal flow at the time of injection, observation of a high-speed video camera shows that the molten metal flow forms a substantially uniform flow during injection, and the orifice at the bottom of the nozzle Since the fuel was injected substantially in conformity with the shape, the sectional area (A) of the orifice was used as the sectional area of the molten metal flow.

That is, the average molten metal flow velocity (v) of the present invention is calculated by the following equation.

[0027]

(Equation 1)

Next, the reasons for limitation of the present invention will be described.

As shown in FIG. 2, the injected molten alloy forms a paddle (pool of molten metal) 25 immediately above the roll.
When the average molten metal flow rate is within the range of the present invention, the shape of the paddle 25 during injection is very stable, the alloy ribbon is almost continuously produced, and a long ribbon with little thickness variation is produced. You. On the other hand, FIG. 3 is a similar schematic diagram when the average molten metal flow velocity is larger than 5 m / s. As shown in the figure, the shape of the paddle 35 is unstable, and the paddle 35 is in a state of jumping from the roll 37. not only that,
It was also confirmed that a part of the molten metal was rebounded by the roll 37 as it was and scattered as drop-shaped particles 38 or irregular-shaped particles 39 as shown in FIG. As a result of this situation, the average molten metal flow velocity (v) is 5 m /
If it is larger than s, the yield of the magnet alloy ribbon excluding the above-mentioned drop-shaped or irregular-shaped particles is significantly reduced, and the production cost is increased. Further, the drop-shaped particles 38 or the irregular shaped particles 3 shown in FIG.
No. 9 hardly cools by heat conduction of the metal roll 37 at the time of solidification and is mainly cooled by heat transfer of the atmosphere gas, so that the solidification speed is extremely low. Therefore, the crystal grain size forming the internal microstructure is several μm to several tens μm.
It contains many m-level crystal grains, and satisfactory magnetic properties cannot be obtained. Therefore, if the bonded magnet is manufactured in a state where the drop-shaped or irregular-shaped particles are mixed, the magnetic properties are deteriorated.

On the other hand, when the average molten metal flow velocity is less than 0.2 m / s, the time required for injection becomes longer and the process becomes longer, resulting in higher cost. In addition, the temperature of the molten metal is significantly reduced by cooling by the blowing inert gas flow.
As a result, the supercooling degree of the alloy melt is significantly different between the ribbon formed at the early stage of the injection and the ribbon formed at the end of the injection, resulting in a large difference in the microstructure, and hence a variation in the magnetic properties. Furthermore, during the injection, the molten metal near the orifice solidifies,
In some cases, it becomes impossible to perform further injection. For the above reasons, it is desirable that the average molten metal flow velocity (V) be 0.2 to 5 m / s.

More preferably, the average molten metal flow velocity (V) is desirably 0.5 to 3 m / s. Within such a range, it is possible to obtain a magnet alloy ribbon having a better yield and less variation in magnetic properties.

Parameters for controlling the average molten metal flow velocity (V) include the following.

Molten injection pressure (Pi) Orifice area (A) Molten temperature and viscosity at the time of injection The most influential parameter among the above is the injection pressure (Pi) of the molten metal, and the average molten metal increases with the injection pressure. The flow rate also increases. The temperature and viscosity of the molten alloy also vary depending on the alloy composition.

Hereinafter, the present invention will be described more specifically with reference to examples.

(Example 1) Nd, F having a purity of 99.9% or more
e, each metal of Co and Fe-B alloy are weighed respectively,
In a high frequency induction melting furnace, Nd _11.5 Fe _bal. B ₆ N
b ₁ a composition was obtained mother alloy ingot shape of a round bar with a diameter of 10φ of (Composition A).

Approximately 15 per lot from this ingot
g sample was cut out, and an alloy ribbon was produced using an apparatus as shown in FIG. Each cut sample is placed in a quartz tube provided with a circular orifice of 0.6 mmφ at the bottom,
After the sample was melted by energizing the heating coil in an Ar atmosphere, 2000 rpm (peripheral speed: 20.9 m /
The molten alloy was sprayed on a 200 mm diameter copper roll rotating in s) by spraying Ar gas to obtain an alloy ribbon. In producing the magnet alloy ribbon, a total of 7 lots of alloy ribbons were obtained by changing the injection pressure (Pi) of Ar gas.

Each lot was shot and recorded with a high-speed video camera at 400 frames per second from the viewing window provided in the chamber, and the injection time (t) of the molten alloy was measured.

Further, the weight and density of the injected molten metal were calculated by the method described in the above embodiment. All had a density of 7.60 Mg / m ³ . From these measured values, the average molten metal flow rate (v) was calculated for each sample from Equation 1 above. Further, for each lot, the thickness is 50 μm with respect to the weight of the ingot sample put in.
The yield was determined by taking the ratio of the weights of the following manufactured alloy ribbons. Further, at least 10 or more thin samples of about 20 mg were collected from each lot, and each sample was measured by a vibrating sample magnetometer (VSM) at a maximum applied magnetic field of 1.44 MA / m. The standard deviation of the measured value of the maximum energy product of each sample of the same lot was calculated to evaluate the characteristic variation within the lot.

Table 1 shows the injection pressure (P
i), the evaluation results of the average molten metal flow velocity (v) and the yield, and the evaluation results of the magnetic property variation are shown. The evaluation of the yield was shown in the table as ◎ for 90% or more, ○ for 75 to 90%, and X for less than 75%. In addition, the evaluation of the magnetic property variation within the lot was performed when the standard deviation was 1 MGOe or less.
GOe was evaluated as ○ and 2MGOe was evaluated as ×.

[0040]

[Table 1]

When the average flow velocity of the molten metal was less than 0.2 m / s, the orifice was clogged with the molten metal, and the molten metal was not injected from the middle, and solidified with a part remaining in the quartz tube. Therefore, the yield is deteriorated as shown in the table. When the average molten metal flow rate is larger than 5 m / s, the weight of the drop-shaped particles and the irregular-shaped particles increases, so that the thickness is 50 μm.
The yields of the following alloy ribbons were low. When the average molten metal flow rate is in the range of 0.5 to 3 m / s, a very high yield can be obtained.

Further, with respect to the magnetic properties, by setting the average molten metal flow rate within the range of the present invention, it is possible to obtain a magnet alloy ribbon with less variation within a lot.

Each of the above-mentioned A1, A3, A6, and A10 was pulverized to obtain a magnet powder, and the obtained powder was 1.8.
After mixing with a wt% epoxy resin, the mixture was compression molded at a pressure of 6 ton / cm ² to obtain a bond magnet of 10φ × 7t. The magnetic properties of the resulting bonded magnet were measured by a direct current magnetic flux meter at a maximum applied magnetic field of 2 MA / m. Table 2 shows the obtained magnetic properties.

[0044]

[Table 2]

As is clear from the table, according to the present invention, a resin-bonded bonded magnet having excellent magnetic properties can be obtained.

(Example 2) Ingots having the respective compositions shown in Table 3 were prepared in the same manner as in Example 1, samples were cut out from each ingot, the roll rotation speed was set to 4000 rpm, the injection pressure, the orifice shape and the like were changed. Several alloy ribbons were made.

[0047]

[Table 3]

The average molten metal flow velocity (v) at the time of injection and the yield of the alloy ribbon were evaluated in the same manner as in Example 1 for each ribbon.

When the obtained alloy ribbon was examined by X-ray diffraction, it was confirmed that all of the diffraction peaks were broad and the structure was partially amorphous. These ribbons were subjected to a heat treatment at a heat treatment temperature not lower than the crystallization temperature of each ribbon for 10 minutes, and then pulverized by a raikai machine to obtain powder. The obtained powder was mixed with 1.8 wt% of an epoxy resin and then compression-molded at a pressure of 6 ton / cm ² to obtain a bonded magnet of 10φ × 7t.
The magnetic properties of the resulting bonded magnet were measured by a direct current magnetic flux meter at a maximum applied magnetic field of 2 MA / m.

The results of the evaluation of the average molten metal flow velocity (v) and the yield of the alloy ribbon for the samples obtained as described above (the evaluation criteria are the same as in Example 1) and the magnetic properties of the bonded magnets are shown in Table 1. 4 is also shown.

[0051]

[Table 4]

As is clear from the table, according to the present invention, a magnet alloy ribbon can be obtained at a high yield in any of the compositions, and a bonded magnet having better magnetic properties can be obtained.

[0053]

According to the first and second aspects of the present invention, a magnet alloy ribbon having a small variation in magnetic properties can be obtained with a high yield by regulating the flow velocity when the molten alloy is injected. The present invention can provide a method for producing an alloy ribbon to be used.

Further, according to the third and fourth aspects of the present invention, the magnetic alloy ribbon thus obtained is used as it is.
Alternatively, a method for producing a resin-bonded bonded magnet having excellent magnetic properties can be provided by mixing powder formed by pulverization after heat treatment with a resin and then molding.

[Brief description of the drawings]

FIG. 1 is a schematic view of a magnet alloy ribbon manufacturing apparatus.

FIG. 2 is a schematic diagram of the vicinity of the molten metal when the molten alloy is injected.

FIG. 3 is a schematic diagram of the vicinity of the injection molten metal when the average molten metal flow velocity exceeds 5 m / s.

[Explanation of symbols]

11, 23, 33 ... molten alloy 12, 21, 31 ... nozzle 13, 22, 32 ... high frequency heating coil 14, 27, 37 ... metal roll 15, 26, 36 ... magnet Alloy ribbon 16 ··· Roll rotation axis 17 ··· Roll rotation direction 24, 34 ··· Molten jet flow 25, 35 ··· Paddle (melt pool) formed in a roll shape 38 ··· Drop-shaped particles 39 ・ ・ ・ Irregular shaped particles

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01F 41/02 H01F 1/08 A

Claims (4)

[Claims] 1. An R-TM-B (R is a rare earth element mainly composed of Nd and Pr, TM is a transition metal) alloy is sprayed onto a rotating metal roll to rapidly cool the alloy melt. A method for producing a magnetic alloy ribbon comprising solidifying, wherein an average molten metal flow velocity at the time of jetting the molten alloy is 0.2 to 5 m / s. 2. An R-TM-B (R is a rare earth element mainly composed of Nd and Pr, TM is a transition metal) alloy is sprayed onto a rotating metal roll to rapidly cool the alloy melt. A method for producing a magnetic alloy ribbon comprising solidifying, wherein an average molten metal flow velocity during injection of the molten alloy is 0.5 to 3 m / s. 3. An R-TM-B (R is a rare earth element mainly composed of Nd and Pr, TM is a transition metal) alloy is melted on a rotating metal roll at an average melt flow rate of 0.2 to 3. 5m /
s to obtain a magnetic alloy ribbon by quenching and solidifying to obtain a magnetic alloy ribbon, and the obtained alloy ribbon as it is or after heat treatment, pulverized to a powder, and the obtained powder and resin A method for producing a resin-bonded bonded magnet, which is obtained by molding after mixing. 4. An R-TM-B type alloy (R is a rare earth element mainly composed of Nd and Pr, and TM is a transition metal) is placed on a rotating metal roll with an average molten metal flow rate of 0.5 to 0.5. 3m /
s to obtain a magnetic alloy ribbon by quenching and solidifying to obtain a magnetic alloy ribbon, and the obtained alloy ribbon as it is or after heat treatment, pulverized to a powder, and the obtained powder and resin A method for producing a resin-bonded bonded magnet, which is obtained by molding after mixing.