KR20010055808A - Fabrication method of Fe-Cr-Co permanent magnet - Google Patents

Abstract

PURPOSE: A method for manufacturing an Fe-Cr-Co permanent magnet is provided to achieve an inexpensive and simple manufacturing process and realize a sintered Fe-Cr-Co permanent magnet which has excellent crushability and plasticity, a high sintered density and temperature, and superior magnetic characteristic. CONSTITUTION: Fe, Cr, Co are prepared as principle components for an Fe-Cr-Co permanent magnet. Fe, Cr, Co are manufactured, respectively, as crystallite powder after being quenched by using a quenching technology. The quenched powder is grinded as fine powder. The fine powder is mixed with a binder and sintered for 0.5 to 4 hours at temperature ranging from 1100 to 1350°C. An external field of 1-5KOe is loaded at a temperature ranging from 600 to 700°C and the sintered body is thermally processed for 0.5 to 4 hours during the magnetic field. After being maintained for 1 to 10 hours at a temperature of 550-620°C, the body is cooled down to 480°C at a speed of 1-20°C/hr., to be seasoning processed, thereby becoming magnetized.

Description

Fabrication method of iron-chromium-cobalt-based permanent magnets {Fabrication method of Fe-Cr-Co permanent magnet}

According to the present invention, a magnetic alloy for Fe-Cr-Co-based permanent magnet is manufactured into crystalline powder using a rapid cooling technique, and then sintered a molded product obtained by pulverizing to an appropriate particle size, followed by heat treatment to sintered Fe having excellent temperature characteristics. The present invention relates to a method for producing a Fe-Cr-Co permanent magnet for economically manufacturing a -Cr-Co permanent magnet.

Fe-Cr-Co alloys, which are magnetic alloys containing Fe, Cr, and Co as a main component, are generally melt casting methods (see Japanese Patent Publications Nos. 59-143020 and 59-143204), or melt-rolling methods (Japan). Patent Publications Nos. 62-106603 and 56-21049.

In addition, a magnet and the like having a small and complicated shape may be manufactured by powder metallurgy. When manufacturing a sintered Fe-Cr-Co magnet by the powder metallurgy method, the raw material powder is weighed to a predetermined composition and then mixed, molded, sintered and heat treated.

(1) A single metal powder of each element constituting the magnet, that is, a powder of a predetermined amount such as Fe, Cr, Co, Si, Ti, etc. is mixed;

(2) mixing a predetermined amount of powdered Fe-Cr, Fe-Ti, and Fe-Si alloy powders in which alloys of the elements constituting the magnet with Fe in advance are powdered;

Or a magnetic alloy powder obtained by spraying a molten alloy of an alloy containing a predetermined magnetic component together with the powder of the above (1) and (2).

However, there are the following drawbacks when producing sintered Fe-Cr-Co magnets using these raw powders. That is, when the powder of (1) is used, moldability and sinterability are reduced by oxidation of Ti, Si, etc., and there is a disadvantage that the powder price is expensive. When the powder of (2) is used, the oxidation is relaxed compared to (1) in which the metal powder is present alone, but since it is extremely hard, there is a problem that the plastic deformation resistance is increased and moldability is lowered. In addition, when the powder of (3) is used, a sintered body having a uniform composition is obtained as compared with the use of the powders (1) and (2). However, it is easy to oxidize by water or gas spraying of the molten metal and is extremely hard. There is a problem that is lowered.

In addition, in order to sufficiently advance the Fe-Cr-Co alloying using the raw material powder, it must be sintered at a high temperature for a long time, and the particle size of the raw material powder itself should be as small as possible, preferably 200 mesh (74 μm) or less. However, when the powder is manufactured in such fine powder, the moldability is not sufficient and the price is expensive, and the sintered body obtained by sintering the molded body lacking the moldability of the powder does not have a dense structure and the magnetic properties of the magnet are also deteriorated. There is this.

The present invention has been invented through a long research and experiment to solve the problems of the prior art as described above, by producing a Fe-Cr-Co-based alloy powder of the desired composition by using a quick cooling technology by one step directly Fabrication of Fe-Cr-Co permanent magnets, which manufactures sintered Fe-Cr-Co permanent magnets with good crushability and formability, high sintering density, and excellent temperature and magnetic properties in a simple and inexpensive process. The purpose is to provide a method.

Fe-Cr-Co-based permanent magnet production method of the present invention for achieving the above object, in the method for producing a Fe-Cr-Co-based permanent magnet containing Fe, Cr, Co as a main component, Fe- Cr-Co-based alloys are prepared into crystalline quenching powder using rapid cooling technology, the quenching powder is pulverized into fine powder, the binder is mixed and sintered at a temperature range of 1100 to 1350 ° C for 0.5 to 4 hours. Thereafter, the sintered body was heat-treated in a magnetic field for 0.5 to 4 hours while loading an external magnetic field of 1 to 5 KOe in a temperature range of 600 to 700 ° C, and maintained at a temperature of 550 to 620 ° C for 1 to 10 hours, then up to 480 ° C. It is characterized by carrying out aging heat treatment while cooling at a rate of -20 ° C / hr to magnetize.

The present invention is also characterized in that, in the above production method, the quenching powder production process is performed at a cooling rotor speed of 6 to 50 m / sec to produce a fine crystalline quenching powder of 1 to 50 µm. .

Hereinafter, the present invention will be described in detail.

In the present invention, first, the Fe-Cr-Co-based alloy in the molten state is cooled at a wheel speed of a rapid cooler of 6 to 50 m / sec by using an ejection type melt rotation method as described in Korean Patent No. 48371. In this way, a microcrystalline (1-50 µm) rapid cooling powder is obtained. At this time, when the speed of the rotating body of the rapid cooler is 6 m / sec or less, the force for discharging the alloy in the molten state is weak to obtain powder, and the rotating body may be 50 m / sec or more. It is preferable to set the speed to 6-50 m / sec. At this time, the particle form of the powder has a flake shape.

The quenched powder has a particle size of 250 mesh or less through a pulverization process in an organic solvent such as hexane, acetone, alcohol, or an inert atmosphere such as argon gas or air. Prepared as a powder.

When the fine powder is prepared by pulverization after rapid cooling as described above, moldability and sinterability are hardly deteriorated by oxidation of additive elements such as Ti or Si, which are easy to oxidize, and thus the molding density and sintering density are improved, and the structure after sintering is improved. It is very uniform, which is beneficial for improving magnetic properties.

The quenched powder pulverized as described above is mixed with a binder such as wax. At this time, the binder is 0.5 to 3wt% mixed, dissolved in an organic solvent such as alcohol or acetone and mixed in a liquid state is preferable because it is uniformly applied to the quench powder. If the amount of the binder is 0.5wt% or less, it is difficult to expect a sufficient effect as a binder. If the amount of the binder is 3wt% or more, the amount is too large, so that molding is difficult and it is difficult to completely remove the binder later in the sintering process.

As described above, it is preferable to prepare a molded body by filling a powder mixed with a binder into a mold and compression molding at a pressure of 1 to 10 ton / cm 2, because the molding pressure is low at a molding pressure of 1 ton / cm 2 or less to maintain strength. This is because the mold pressure is high at 10 ton / cm 2 or more, and the mold is severely damaged.

The molded article obtained as described above is subjected to sintering under vacuum or argon or hydrogen atmosphere to densify. At this time, the sintering conditions are preferably carried out for 0.5 to 4 hours in the temperature range of 1100 ~ 1350 ℃. In this case, the sintering temperature is lower than 1100 ° C., so that the magnetic properties are lowered because the sintering temperature is not low enough. It is preferable to set it as.

Next, the sintered compact is maintained for 0.5 to 4 hours in an external magnetic field of 1 to 5 KOe in a temperature range of 600 to 700 ° C. to perform heat treatment in the magnetic field. The reason of the heat treatment in the magnetic field is to increase the amount of precipitates of Fe-Co-based composition (the precipitates show ferromagneticity) that precipitate during the heat treatment, and to give an alignment effect to grow with the orientation during precipitation. When the magnetic field treatment is 0.5 hours or less, the precipitation of the precipitate is incomplete, and the magnetic properties are lowered. When the magnetic field treatment is 4 hours or longer, the size of the precipitate becomes coarse. desirable.

The aging treatment is carried out at a temperature range of 550 to 650 ° C. for 1 to 2 hours and then cooled to 480 ° C. at a rate of 1 to 20 ° C./hr. If the temperature of the aging treatment is 550 ° C. or less, the effect is not sufficient. If the temperature is 650 ° C. or higher, the precipitate grows and the magnetic field treatment effect is reduced, so the aging treatment temperature is preferably limited to 550 to 650 ° C.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Cr, Co, Si, Ti, Fe ingots are weighed in a 26wt% Cr-12% Co-0.45% Si-0.45% Ti-bal.Fe composition and melted completely with a plasma arc in an argon (Ar) gas atmosphere. After that, a quench powder having a flake shape was produced by an extracting melt rotor, and the cooling speed at this time, that is, the rotation speed of the cooling rotor was changed to 8.51 to 3.32 m / sec.

X-ray diffraction analysis was performed on the quench powder prepared as described above, and the results are shown in Table 1 below. As can be seen in Table 1 all appeared crystalline tissue.

Magnetic Alloy Composition Rapid cooling body speed (m / sec) Quench Base Organization Quenching powder 26% Cr-12% Co-0.45% Si-0.45% Ti-bal.Fe 8.50 Crystalline One Invention 26% Cr-12% Co-0.45% Si-0.45% Ti-bal.Fe 16.36 Crystalline 2 26% Cr-12% Co-0.45% Si-0.45% Ti-bal.Fe 24.60 Crystalline 3 26% Cr-12% Co-0.45% Si-0.45% Ti-bal.Fe 32.72 Crystalline 4

The quenched powder prepared as described above was pulverized in an alcohol solvent using an attritor, and then classified using a sieve specified in ASTM E11 of 400 mesh to obtain a particle size of 38 micrometers or less. A powder was obtained.

The powder thus pulverized was molded at a vertical pressure of 8 ton / cm 2, and these molded bodies were sintered at 1350 ° C. for 1 hour in a vacuum atmosphere.

After sintering the sintered body at 1250 ° C for 10 minutes, heat treatment was performed for 1 hour in a magnetic field of 4.5 KOe at a temperature range of 600 to 700 ° C for 1 hour, and then maintained at 620 ° C for 1 hour, followed by 5 ° C / hr up to 480 ° C. After cooling at a rate, permanent magnet specimens were obtained.

The density and magnetic properties of the permanent magnet specimens prepared as described above were measured, and the results were compared with those of the permanent alloy manufactured by the casting and rolling methods of the magnet alloy of Table 1 below. Shown in

Specimen No. Rapid cooling body speed (m / sec) Self-characteristics Remarks Residual magnetic flux density (Br) (G) Coercive force (Hc) (Oe) Maximum magnetic energy product (BH) max (MGOe) Conventional a - 13,000 600 5.50 Conventional casting method b - 12,000 550 4.50 Conventional rolling method Invention One 8.51 13,200 618 5.71 Quenching powder 2 16.61 13,150 612 5.62 Quenching powder 3 24.60 13,050 605 5.58 Quenching powder 4 32.72 12,800 582 5.34 Quenching powder

As shown in Table 2, the sintered permanent magnet [invention material (1-4)] prepared in accordance with the present invention is superior in magnetic properties to that of the permanent magnets [conventional material a] produced by the conventional casting method or more. It can be seen that the magnetic properties are significantly improved compared to the permanent magnets [conventional material b] manufactured by the conventional rolling method.

As described in detail above, when the Fe-Cr-Co-based permanent magnet manufacturing method of the present invention is used, Fe-Cr-Co-based alloy powder of the desired composition is prepared by using a quick cooling technique by one step directly As a result, a sintered Fe-Cr-Co permanent magnet having good crushability and moldability, high sintered density, and excellent temperature and magnetic properties can be manufactured in a simple and inexpensive process.

Claims (2)

In the method for manufacturing a Fe-Cr-Co-based permanent magnet containing Fe, Cr, Co as a main component, Fe-Cr-Co-based alloy is prepared as a fine crystalline quenching powder using a rapid cooling technology, After pulverizing the quenching powder into fine powder, mixed with a binder and sintered at a temperature range of 1100 to 1350 ° C. for 0.5 to 4 hours, The sintered body was heat-treated in a magnetic field for 0.5 to 4 hours while loading an external magnetic field of 1 to 5 KOe in a temperature range of 600 to 700 ° C, A method of producing a Fe-Cr-Co permanent magnet characterized in that it is subjected to aging heat treatment while maintaining the temperature at a temperature of 550 to 620 ° C. for 1 to 10 hours and cooling to 480 ° C. at a rate of 1 to 20 ° C./hr. . The method of claim 1, wherein the quenching powder manufacturing process using the rapid cooling technique is cooled to a cooling rotor speed of 6 to 50m / sec to produce a fine crystalline quenching powder of 1 to 50㎛ Method for producing a Fe-Cr-Co permanent magnet.