JP2005045090A - METHOD FOR MANUFACTURING FeCrCo PERMANENT MAGNET USING ELECTRIC DISCHARGE PLASMA SINTERING PROCESS - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an FeCrCo permanent magnet constituted of a sintered body with high magnetic characteristics, wherein relative density is high as the percentage ranging from 95 to 99.9%, the shortest side is 2mm or more long and the degree of freedom of shape is high in a low temperature ranging from 800 to 1300°C and in a short time ranging from 1min to 60min by a powder metallurgy method by using an electric discharge plasma sintering method using powder for a FeCrCo magnet whose average powder particle diameters range from 1.0 to 500μm. <P>SOLUTION: This FeCrCo permanent magnet sintered body is manufactured by a powder metallurgy method using an electric discharge plasma sintering method, and has its relative density rate ranging from 95 to 99.9% and such high magnetic characteristics that Br=1.2 to 1.4T, (BH)max=33.4 to 47.7kJ/m<SP>3</SP>, iHc=39.8 to 51.7kA/m. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an FeCrCo permanent magnet and a method for manufacturing the same, and more particularly to an FeCrCo permanent magnet sintered body using a discharge plasma sintering method and a method for manufacturing the same.

  The FeCrCo magnet is a low density sintered body having a relative density ratio of 65 to 75% even in a sintering process at a high temperature of 1300 to 1500 ° C. because each of the basic constituent elements FeCrCo is very difficult to sinter. However, there are problems such as deterioration of properties when adding additive elements such as B for the purpose of improving sinterability, and it is very difficult to manufacture an FeCrCo permanent magnet using a powder metallurgy method. It is manufactured by rolling an FeCrCo cast body manufactured by higher frequency melting to a thickness of a predetermined dimension, and hot-rolling or cold-punching the rolled body with a die-cutting press.

  For this reason, the thickness that can be punched by cold punching is limited to 2 mm, so that a product having the shortest side length of 2 mm or more cannot be manufactured.

Actually, in Patent Document 1, an additive element such as B is added to increase the density, but the composition without the additive element has a relative density ratio of 85% even if external heating sintering is performed at 1300 ° C. On the other hand, in a composition with a high density by adding an additive element such as B, on the contrary, (BH) max = 33.6 to 37.6 kJ / m ³ and slight addition of the additive element slightly improves the magnetic characteristics. However, there is a drawback in that the level of application is still limited in consideration of practicality in a wide range.

In the prior art, the sinterability between FeCrCo, which is the main constituent element in the powder for FeCrCo permanent magnet, is very poor, and the relative density ratio of the sintered body is 80% even at a high temperature sintering temperature of 1300 to 1500 ° C. Since the density is extremely low, the density of the FeCrCo magnet powder is increased by sintering the powder, and the FeCrCo permanent magnet composed of the hardly sinterable elements is manufactured by powder metallurgy. Because it is impossible, the FeCrCo casting manufactured by the high vacuum high frequency melting furnace is repeatedly rolled to a thickness of 2 mm or less, which is the thickness that can be punched by pressing, and the resulting FeCrCo magnet plate material is pressed. In order to make a FeCrCo permanent magnet product by punching in, there is a shape restriction that the shape freedom in the thickness direction is 2 mm or less Tsu shortcomings there was.
JP 57-130404 A

  Therefore, the technical problem of the present invention is that a powder for an FeCrCo magnet having an average powder particle size of 1.0 to 500 μm is used at a low temperature of 800 to 1300 ° C. by a powder metallurgy method and 1 min to 1 min. FeCrCo permanent magnet made of a sintered body having a high magnetic property and a high density with a relative density of 95 to 99.9% and a shortest side length of 2 mm or more and a high degree of freedom in a short time of 60 min and its manufacture And to provide a method.

  According to the present invention, the average powder particle size is 1.0 to 500 μm by at least one of the atomized powder preparation method using water or gas, the airflow dry pulverization method using a jet mill, and the wet pulverization method. A method for producing an FeCrCo permanent magnet is characterized in that a sintered compact having a high density is obtained by powder metallurgy using a discharge plasma sintering method. can get.

  Further, according to the present invention, in the method of manufacturing the FeCrCo permanent magnet, a discharge plasma sintering method by energizing a large current causes a plasma discharge heating, a Joule heat heating effect, and a pressure compression effect during sintering to 800 to 1300 ° C. A high-density FeCrCo permanent magnet having a relative density ratio of 95 to 99.9% is obtained at a low temperature.

  Further, according to the present invention, in any one of the above methods for producing a FeCrCo permanent magnet, in a short time of 1 min to 60 min due to discharge plasma heating by high current energization, Joule heat heating effect and pressure compression effect during sintering. A method for producing a FeCrCo permanent magnet is obtained, which is characterized by obtaining a sintered body of high density FeCrCo permanent magnet having a relative density ratio of 95 to 99.9%.

Further, according to the present invention, the FeCrCo permanent magnet sintered body has a relative density ratio of 95 to 99.9%, Br = 1.2 to 1.4T, and (BH) max = 33.4 to 47.47. A FeCrCo permanent magnet sintered body having high magnetic properties of 7 kJ / m ³ and iHc = 39.8 to 51.7 kA / m can be obtained.

  Furthermore, according to the present invention, in the FeCrCo permanent magnet sintered body, the FeCrCo permanent magnet sintered body characterized in that the length of the shortest side is 2 mm to 500 mm.

As described above, according to the present invention, in the method for producing a FeCrCo permanent magnet,
An average powder particle size = 1.0 to 500 μm of FeCrCo raw material powder by a powder metallurgy method using a discharge plasma sintering method at a low temperature of 800 to 1300 ° C. in a short time of 1 to 60 minutes and a sintering density of 7. 22-7.58 g / cm ³ , high density with a relative density ratio of 95-99.9%, Br = 1.2-1.4T (12.0-14.0 kG), (BH) max = 33.4- Excellent magnetic properties of 47.7 kJ / m ³ (4.2 to 6.0 MGOe), iHc = 39.8 to 51.7 kA / m (500 to 650 Oe) and the shortest side length of 2 mm to 500 mm It has become possible to provide permanent magnet products characterized by having a degree of freedom in shape.

  First, the present invention will be described in more detail.

  FIG. 1 is a diagram showing a schematic configuration of an apparatus for carrying out the discharge plasma sintering method of the present invention. FIG. 2 is a flowchart showing a manufacturing process of a sintered product using a discharge plasma sintering method using the apparatus of FIG.

  Referring to FIG. 1, this apparatus 10 is manufactured by Sumitomo Coal Industry Co., Ltd., and includes an upper punch 1, a lower punch 2, and a sintering die 3 disposed around the opposing portion. The powder 4 to be sintered is filled in the space formed by the upper punch 1, the lower punch 2, and the sintering die 3. One end of each of the upper punch electrode 5 and the lower punch electrode 6 is provided at each end of the upper punch 1 and the lower punch 2 opposite to the opposing ends, and is accommodated in the water-cooled vacuum chamber 7. The other ends of the upper punch electrode 5 and the lower punch electrode 6 are drawn out from the upper and lower ends of the chamber and project outside. A special pressurizing mechanism 16 is connected to the other end of each of the upper punch electrode 5 and the lower punch electrode 6, and a special sintering power source 15 is connected thereto. The sintering power supply 15 and the pressurizing mechanism 16 are connected to a measuring system 18 including a position measuring mechanism 18a, an atmosphere control mechanism 18b such as vacuum or Ar, a water cooling mechanism 18d, and a temperature measuring device 18e, respectively, via a control device. ing.

  In spark plasma sintering using such an apparatus, pulsed electric energy is directly applied between green compacts, and the energy of the discharge plasma generated instantaneously by spark discharge is thermally diffused and activated. This is a method that enables chemical sintering.

  In the present invention, as described above, by using the discharge plasma sintering method, the FeCrCo permanent magnet sintered body having high magnetic properties and low temperature, short time, high density and high degree of freedom by powder metallurgy. It is a manufacturing method of the FeCrCo permanent magnet product which can be manufactured. In addition, by using the discharge plasma sintering method for the FeCrCo permanent magnet raw material powder having an average powder particle size of 1.0 to 500 μm, the powder composite method is low in temperature, short time, high density, and high in the degree of freedom of shape. This is a method for producing an FeCrCo permanent magnet product capable of producing an FeCrCo permanent magnet sintered body having magnetic properties.

That is, in the present invention, an FeCrCo permanent magnet is manufactured by a discharge plasma sintering method using an FeCrCo raw material having an average powder particle size of 1.0 to 500 μm, so that a low temperature of 800 to 1300 ° C. and a short of 1 min to 60 min. In time, the sintered density is 7.22 to 7.58 g / cm ³ (× 10 ³ kg / m ³ ), the relative density ratio is 95 to 99.9%, and the shortest side length is 2 to 500 mm. An FeCrCo permanent magnet sintered body having an extremely high degree of shape freedom is obtained.

The FeCrCo permanent magnet is composed of 20 to 80 atomic% of Fe, which is a main constituent element of the raw material composition for FeCrCo permanent magnet powder, 5 to 40 atomic% of Cr, and 5 to 40 atomic% of Co. In addition, one or more elements of Mo, Ti, and V are simultaneously contained as additive elements in an amount of 0.1 to 10 atomic%, and other elements are o, N, C, Si, Mn, P, S, Cu, A FeCrCo magnet raw material containing one or more elements of Ni at the same time of 0.001 to 10 atomic% at the same time in the atmosphere, in N ₂ gas or in an inert gas, gas atomization method, water atomization method into water, or N ₂ gas or Average powder by air-flow crushing method using jet mill using compressed air or wet ball mill crushing method using alcohol, hexane, toluene, pure water etc. as solvent Diameter to prepare a powder of 1.0～500Myuemu, then using a carbon graphite or WC carbide type or nitride ceramic types, using a discharge plasma sintering ^{furnace, 1 × 10 -1 Torr (=} 13. 3 Pa) or less in vacuum or 0.1 kg / cm ² (98.1 hPa) to 5.0 kg / cm ² (4900 hPa) in an inert gas atmosphere such as Ar, or N ₂ gas atmosphere, 1 A to 50000 A A high-density FeCrCo permanent magnet sintered body was obtained by simultaneous heating by Joule heating by current conduction effect, local heating by plasma discharge, and conduction heating.

That is, it is heated at 0.1 to 500 ° C./min, and at a temperature of 800 to 1300 ° C. × 0.1 to 100 minutes, plasma discharge heating and Joule heating are performed by energizing a large current, and at the same time a molding pressure of 0.1 to 100 kg / After pressure forming at mm ² (about 0.98 to 98 MPa), in the atmosphere or in an inert gas such as Ar of 0.1 kg / cm ² (98.1 hPa) to 5.0 kg / cm ² (4900 hPa) or A FeCrCo permanent magnet sintered body was manufactured by a sintering process in which plasma discharge heating and pressure sintering was performed by energizing a large current cooled in an N ₂ gas atmosphere.

Then, after holding at 900 to 1300 ° C. for 0.1 to 100 minutes in the atmosphere or in an inert gas atmosphere such as Ar of 0.1 kg / cm ² (98.1 hPa) to 5.0 kg / cm ² (4900 hPa), A uniform heat treatment was performed in the air or in an atmosphere of 0.1 kg / cm ² (98.1 hPa) to 5.0 kg / cm ² (4900 hPa) of an inert gas such as Ar, an N 2 gas atmosphere, or water.

Next, an inert gas such as Ar in the atmosphere or 0.1 kg / cm ² (98.1 hPa) to 5.0 kg / cm ² (4900 hPa) with a DC1 or AC external magnetic field of 0.001 to 10 T applied. Alternatively, in a N ₂ gas atmosphere, after holding at 500 to 800 ° C. for 0.1 to 1000 minutes, heat treatment in a magnetic field is performed in which rapid cooling or slow cooling treatment is performed for 0.1 minutes to 100 hours to 25 ° C., which is room temperature. did.

Next, in the atmosphere or in an inert gas or N ₂ gas atmosphere such as Ar of 98.1 hPa (0.1 k / cm ² ) to 5.0 kg / cm 2 (4900 hPa), 500 to 800 ° C. × 0.1 After holding for 100 minutes, a two-phase separation aging treatment was performed in which rapid cooling or slow cooling treatment was performed at room temperature of 25 ° C. for 0.1 minutes to 100 hours to produce a FeCrCo permanent magnet sintered body product.

  In the FeCrCo permanent magnet sintered body thus produced by the discharge plasma sintering method, the sintered body produced by the powder metallurgy method using the external heating sintering method as the first effect is used for the FeCrCo permanent magnet raw material powder used. As the particle size becomes coarser, the tendency to densification decreases and the relative density ratio decreases remarkably, whereas in the plasma sintered body produced by the powder metallurgy method using the discharge plasma sintering method, Since a relative density ratio of 90 to 99.8%, which is a practically no relative problem, is obtained even when the diameter is in the range of 1 μm to 500 μm, discharge plasma sintering is used as a sintering process for FeCrCo permanent magnet powder. The densification effect by using the knot method is confirmed.

  In terms of the average particle diameter of the FeCrCo powder to which the present invention is applied, it is difficult to produce a powder having an average particle diameter of 1.0 μm or less with an FeCrCo permanent magnet composition in practice. Since the ratio tends to decrease, the average particle diameter of the applied FeCrCo permanent magnet raw material powder was set to 1.0 to 500 μm.

  As a second effect, in the sintered body produced by the powder metallurgy method using the external heating sintering method, the relative density ratio is as low as 85% even at a high temperature of 1400 ° C., whereas the discharge plasma sintering method is used. In the spark plasma sintered body manufactured by the above method, a relative density ratio of 95%, which has no practical problem at a low temperature of about 800 ° C., has already been obtained. The effect is confirmed.

  As for the plasma sintering holding temperature in the FeCrCo powder to which the present invention is applied, there is a slight tendency to decrease the relative density ratio at temperatures below 800 ° C., and at 1300 ° C. and above, there is a tendency to deteriorate characteristics due to approaching the melting point of FeCrCo. Since the possibility is very high, the application temperature range in the spark plasma sintering method is a temperature range of 800 ° C. to 1300 ° C., which is a temperature range in which a high relative density ratio is obtained.

  As a third effect, in the sintered body produced by the powder metallurgy method using the external heating sintering method, the rising tendency of the relative density ratio with respect to the external heating holding time is very slow, and the relative density ratio is stable. In spite of the fact that the relative density ratio is only 85%, which is not practically usable, although the holding time of 200 minutes or more is required, the plasma produced by the discharge plasma sintering method. In the sintered body, since the relative density ratio is remarkably improved with a holding time of about 1 minute, and a practically sufficient high relative density ratio sintered body is obtained with a holding time of about 40 minutes, discharge plasma sintering is possible. The effect of promoting dense sintering in a short time in the method is confirmed.

  As for the plasma sintering holding time in the FeCrCo powder to which the present invention is applied, it is difficult to control the quantitative temperature at a low temperature due to the properties of the apparatus if it is 1 minute or less. Therefore, the application treatment time in the discharge plasma sintering method was set to 1 to 60 minutes, which can obtain a stable high relative density ratio sintered body.

As a fourth effect, in the sintered body produced by the powder metallurgy method using the external heating sintering method, the values of Br, (BH) max, iHc which are magnetic characteristics are Br due to the influence of the low relative density ratio. ^{= 0.72~0.95T (7.2~9.5kG), (BH} ) max = 11.9~17.5kJ / m 3 (1.5~2.2MGOe), iHc = 27.9~31 .8 kA / m (350 to 400 Oe), on the other hand, Br = 1.2 to 1.4 T (12.0 to 14.0 kG) in the magnetic properties of the plasma sintered body produced by the spark plasma sintering method. ), (BH) max = 33.4-47.7 kJ / m ³ (4.2-6.0 MGOe), iHc = 39.8-51.7 kA / m (500-650 Oe) and high magnetic properties are obtained. Magnetic field in the spark plasma sintering method. The effect of improving the gas characteristics is confirmed.

  As the fifth effect, in an externally heated sintered body produced by a powder metallurgy method using an externally heated sintering method, heating to 1300 ° C. or higher is required even if an additive element such as B is added. The mass production is poor due to a problem on the sintering equipment, and in fact, an FeCrCo permanent magnet made by powder metallurgy using an external heating and sintering furnace has not been produced. In general, an FeCrCo casting manufactured by a high vacuum high frequency melting furnace is used. Forming in the thickness direction because the FeCrCo permanent magnet product is made by punching the resulting FeCrCo magnet plate material with a press to repeat the rolling to a thickness of 2 mm or less, which is the thickness that can be punched by the press. In contrast to the fact that the degree of freedom is limited to 2 mm or less, FeCrC at low temperature and in a short time by using the discharge plasma sintering method. Since the permanent magnet raw material powder can be densified and FeCrCo can be manufactured by powder metallurgy, the length of the shortest side, which is the product thickness, is 2 mm to 500 mm. The effect of becoming higher is confirmed.

  As for the size of the plasma sintered body product in the FeCrCo powder to which the present invention is applied, the shape in which the FeCrCo permanent magnet product with stable characteristics can be manufactured in consideration of the temperature distribution of the current discharge plasma sintering apparatus is Since 500 mm is the limit, the length of the shortest side in a range where improvement in the degree of freedom of shape is expected is set to a range of 2 mm to 500 mm.

As described above, in the method for producing an FeCrCo permanent magnet, an FeCrCo powder having an average powder particle size = 1.0 to 500 μm is formed at a temperature of 800 to 1300 ° C. in a short time of 1 to 60 minutes using the discharge plasma sintering method. Thus, by producing an FeCrCo high-density sintered body by powder metallurgy, the length of the shortest side is 2 to 500 mm and the shape freedom is high, Br = 1.2 to 1.4T (12.0 to 14 0.0KG), (BH) max = 33.4-47.7 kJ / m ³ (4.2-6.0 MGOe), iHc = 39.8-51.7 kA / m (500-650 Oe). An FeCrCo permanent magnet manufacturing method for obtaining an FeCrCo permanent magnet can be provided.

  Now, an embodiment of the present invention will be described.

(First embodiment)
The FeCrCo permanent magnet raw material powder used in the first embodiment of the present invention has a Fe composition of 60 atomic%, a Cr composition of 25 atomic%, and a Co composition, which is a typical composition for producing an FeCrCo magnet. Is composed of 13 atomic% of the main elements, and the additive element contains Ti composition of 0.5 atomic% and V composition of 0.5 atomic% at the same time, and other elements include O, N, C, Si, Mn, A material containing 1.0 atomic% of one or more elements of P, S, Cu, and Ni at the same time was used.

Using an FeCrCo magnet raw material having the above composition, a powder having an average particle size of 10, 50, and 100 μm by a water atomization method using water, and an average particle size of 1 by an airflow pulverization method using a jet mill pulverizer using N ₂ gas. A FeCrCo permanent magnet powder having an average particle size of 500 and 1000 μm was produced from the 0.0 μm powder by a disk mill. Thereafter, a carbon graphite mold is used, and a vacuum of 1 × 10 ⁻¹ Torr (13.33 Pa) or less or 0.1 kg / cm ² (98.1 hPa) to 5.0 kg / cm ² using a discharge plasma sintering furnace. (4900 hPa) Ar or other inert gas atmosphere or N ₂ gas atmosphere A high-density FeCrCo permanent magnet by Joule heat heating by a large current energizing effect of 1 A to 50000 A, local heating by plasma discharge, and simultaneous heating by energizing heating A sintered body was obtained.

That is, it is heated at 85 to 150 ° C./min, and at 700 to 1300 ° C. × 1 to 60 minutes, plasma discharge heating and Joule heat heating by energizing a large current are performed, and at the same time, a molding pressure of 4 kg / mm ² (39.2 MPa) After the pressure forming, the FeCrCo permanent magnet sintered body is subjected to a sintering process in which plasma discharge heating and pressure sintering is performed by energizing a large current cooled in an Ar inert gas of 0.1 kg / cm ² (98.1 hPa). Manufactured.

Then, after maintaining in an inert gas atmosphere of 0.2 kg / cm ² (196.2 hPa) at 1200 ° C. for 60 minutes, a leveling heat treatment was performed in which quenching treatment was performed in water.

Next, in a state where an external DC magnetic field of 0.05 T is applied, after holding at 650 ° C. × 90 minutes in an Ar inert gas atmosphere of 0.2 kg / cm ² (196.2 hPa), the room temperature reaches 25 ° C. A heat treatment was performed in a magnetic field that gradually cooled in 12 hours.

Next, after maintaining in an inert gas atmosphere of 0.2 kg / cm ² (196.2 hPa) at 600 ° C. for 80 minutes, a slow cooling treatment is performed to 25 ° C., which is room temperature over 20 hours. The FeCrCo permanent magnet sintered product was manufactured by aging treatment.

  FIG. 2 is a graph showing changes in the average particle diameter and relative density ratio density of the FeCrCo raw material powder in the plasma sintering method and the external heating sintering method of the discharge plasma sintered body manufactured under the above manufacturing conditions. In FIG. 2, the horizontal axis represents the average particle diameter of the FeCrCo permanent magnet powder, the vertical axis represents the relative density ratio of the discharge plasma sintered body produced by the discharge plasma sintering method and the external heating method, and the external heating sintered body. The relationship of relative density ratio is shown.

  As shown by the curve 12 in FIG. 2, in the externally heated sintered body produced by the powder metallurgy method using the externally heated sintering method, the average particle size of the FeCrCo permanent magnet raw material powder used is from 1 μm to 500 μm. As the diameter becomes coarser, the densification tendency deteriorates and the relative density ratio tends to decrease remarkably.

  On the other hand, as shown by the curve 11, in the plasma sintered body produced by the powder metallurgy method using the discharge plasma sintering method, a tendency of decreasing the relative density ratio is observed at 1000 μm, but the average particle size is 1 In the range of 0.0 μm to 500 μm, a stable relative density ratio is obtained, and the value is also 95 to 99.8%, and a relative density ratio at a level that has no practical problem as an FeCrCo permanent magnet product can be obtained. It can be confirmed that

  FIG. 2 also shows the relationship between the average powder particle size and the relative density ratio of the sintered body in the external heating sintering method in which heating is performed by external heating used as a sintering method in general powder metallurgy. ing.

The sintered body produced by the external heating sintering method used at this time was pressure-molded at 5.0 ton / cm ² (490 MPa) with a hydraulic press using the same powder having the same composition as the plasma sintered body, A FeCrCo permanent magnet sintered body was manufactured by an external heating sintering method in which external heating sintering was performed in a resistance heating method sintering furnace.

That is, it was manufactured by a sintering process in which it was heated at 10 ° C./min, rapidly cooled by holding an Ar inert gas of 0.2 kg / cm ² (196.2 hPa) after holding at 1400 ° C. × 120 min.

  Next, a heat treatment in a magnetic field and a two-phase separation heat treatment under the same conditions as those of the discharge plasma sintered body were performed to obtain a FeCrCo permanent magnet product.

(Second Embodiment)
FIG. 3 is a diagram showing the relationship between the sintering holding temperature of the discharge plasma sintered body produced by the discharge plasma sintering manufactured by the manufacturing method of the first embodiment and the sintered density of the discharge plasma sintered body. In FIG. 3, the horizontal axis indicates the plasma sintering holding temperature and the external heating sintering holding temperature, and the vertical axis indicates the value of the sintered compact density of the plasma sintered body produced at each plasma sintering holding temperature and external heating holding temperature. Show.

As shown by a curve 22 in FIG. 3, the sintered body density of the externally heated sintered body produced by the externally heated sintering method is almost 1200 ° C. It begins to enter a temperature range of ℃ or higher and shows a tendency of density increase due to remarkable densification, but even at an external heating holding temperature of 1450 ℃, which is a critical temperature range on the high temperature side in a general resistance heating type external heating sintering furnace The sintered density has been improved only to 6.8 g / cm ^3, and only a low-density sintered body that cannot be practically used as an FeCrCo permanent magnet product has been obtained.

On the other hand, as shown by the curve 21, the discharge plasma sintered body manufactured by the discharge plasma sintering method has a density of 7.22 g / cm ³ which is already higher than that of the external heating sintered body even in the low temperature range of 800 ° C. Further, in the temperature range of 900 ° C. or higher, the sintered body density tends to be saturated due to a sufficient densification promoting effect, and the sintered density value is also 7.42 to 7.58 g / cm ^{3, which} is FeCrCo. Since it is a practically sufficient value as a permanent magnet product, the use of the discharge plasma sintering method has no practical problem as a FeCrCo permanent magnet product from a low temperature range of 800 ° C., which is 650 ° C. lower than the external heating sintering method. It can be confirmed that an FeCrCo permanent magnet sintered body having a sintered body density of 7.2 g / cm ³ or more, which is a sintered body density without any other, can be produced.

  FIG. 4 is a view showing the relationship between the discharge plasma sintering holding temperature of the FeCrCo permanent magnet manufactured by the discharge plasma sintering method and the relative density ratio in the discharge plasma sintered body.

  As shown in FIG. 4, as the data of the relative density with respect to the theoretical density, the horizontal axis represents the plasma sintering holding temperature and the external heating sintered holding temperature, the vertical axis represents the relative density ratio in the plasma sintered body, and the external heating sintered body. The relative density ratio in is shown.

  As shown in FIG. 4, in FIG. 4, the sintering density of the discharge plasma sintered body by the discharge plasma sintering and the external heating sintered body sintered by the external heating sintering method relative to FIG. The difference in behavior can be clearly confirmed.

  As shown by a curve 32 in FIG. 4, in the external heating sintering method, a remarkable increase tendency of the sintering density is recognized from around 1200 ° C., but the relative density ratio is 85 even in a high temperature region of 1450 ° C. %, And conversely, if it is attempted to further heat and densify, it will reach a temperature just below the melting point and will not be in the form of a FeCrCo permanent magnet. When sintered by the sintering method, it can be confirmed that it is the limit to obtain a sintered body having a relative density ratio of about 85%. However, when the FeCrCo permanent magnet sintered body is manufactured using the discharge plasma sintering method according to the present invention as a manufacturing method for FeCrCo permanent magnet powder, Joule heating by plasma discharge sintering, plasma discharge heating, and pressure forming treatment during sintering are performed. By applying simultaneously, as shown in curve 31, the relative density ratio already shows a relative density ratio equal to or higher than the relative density ratio at external heating 1450 ° C. = 95% even at a low temperature of 800 ° C., and further heated to 900 ° C. or higher. As a result, the relative density ratio that is sufficiently practical as an FeCrCo permanent magnet product shows a value of 98% or more, so that an FeCrCo permanent magnet product that is sufficiently practical at a temperature as low as 650 ° C. can be obtained compared to the external heating sintering method. By using the discharge plasma sintering method even in the powder metallurgy method using FeCrCo permanent magnet powder, a low temperature of about 800 ° C. Has a high sintered body relative density ratio from, it is confirmed that can be manufactured sufficiently practicable FeCrCo permanent magnet.

(Third embodiment)
FIG. 5 shows the sintering time of the discharge plasma sintered body produced by the discharge plasma sintering produced by the production method of the first embodiment and the externally heated sintered body sintered by the external heating sintering method with respect to the holding time during sintering. It is the figure which showed the relative density ratio change of the consolidation density. In FIG. 5, the horizontal axis represents the plasma discharge sintering time and the external heating sintering holding time, and the vertical axis represents the relative density ratio of the discharge plasma sintered body and the external heating sintered body.

  As shown by the curve 42 in FIG. 5, even in the external heating sintering method, an increase in the sintering density ratio is recognized as the sintering time increases, but the relative density ratio increases from holding time = 60 minutes or more. Although the trend has slowed and the relative density ratio has already shown a saturation tendency at the time of holding for 240 minutes, even at a high temperature of 1400 ° C., the relative density ratio is still 85%, which is only practically unusable. It is not done.

  However, in the spark plasma sintered body shown by the curve 41, the relative density ratio has already been improved to 96.5% by holding for a very short time such as 1 minute, and the relative density ratio tends to be sufficiently saturated at the holding time of 10 minutes. In addition, since the value of 98.3%, which is a relative density ratio that can be sufficiently used in practice, has already been obtained, Joule heating by plasma discharge sintering, plasma discharge heating, and pressure forming during sintering are performed. By applying them simultaneously, it can be confirmed that the densification rapidly progresses and it is possible to produce a high-density FeCrCo permanent magnet sintered body even in a very short processing time of about 1 minute.

(Fourth embodiment)
FIG. 6 is a diagram showing a residual magnetic flux density Br which is a magnetic characteristic of an FeCrCo permanent magnet manufactured by a powder metallurgy method using a discharge plasma sintering method manufactured by the manufacturing method of the first embodiment. FIG. 6 shows the behavior of the residual magnetic flux density Br, which is the magnetic characteristic of the plasma sintered body with respect to the plasma sintering holding temperature. The horizontal axis represents the plasma sintering temperature, and the vertical axis represents Br in the plasma sintered body. Yes.

  FIG. 6 also shows the residual magnetic flux density Br, which is the magnetic characteristic of the externally heated sintered body produced by the externally heated sintered method at the same time, with the externally heated holding temperature on the horizontal axis and the externally heated sintered body on the vertical axis. Of Br.

  FIG. 7 is a diagram similarly showing the maximum energy product (BH) max. FIG. 7 shows the behavior of the maximum energy product (BH) max, which is the magnetic characteristic of the plasma sintered body with respect to the plasma sintering holding temperature. The horizontal axis represents the plasma sintering temperature, and the vertical axis represents ( BH) max.

  FIG. 7 also shows the maximum energy product (BH) max, which is the magnetic characteristic of the externally heated sintered body manufactured by the externally heated sintering method, with the horizontal axis indicating the external heating holding temperature and the vertical axis indicating the external heating. (BH) max of the sintered body is shown.

  FIG. 8 is a diagram similarly showing the coercive force iHc. FIG. 8 shows the behavior of the coercive force iHc, which is the magnetic characteristic of the plasma sintered body with respect to the plasma sintering holding temperature. The horizontal axis represents the plasma sintering temperature, and the vertical axis represents iHc in the plasma sintered body. .

  FIG. 8 also shows the coercive force iHc, which is the magnetic property of the externally heated sintered body manufactured by the externally heated sintered method at the same time, with the externally heated holding temperature on the horizontal axis and the externally heated sintered body on the vertical axis. iHc is shown.

  As shown by a curve 52 in FIG. 6, with respect to the externally heated sintered body manufactured by the externally heated sintering method, Br = 0.95T (9.5 kG at maximum) due to a decrease in the sintered body density level due to insufficient densification. Only a value that is practically unusable as an FeCrCo permanent magnet material.

  On the other hand, in the spark plasma sintered body produced by the spark plasma sintering method shown by curve 51, Br = 1.2T (12 which is already a practically sufficient characteristic as a FeCrCo permanent magnet product even at a low temperature of 800 ° C. 0.0KG), and further heating to bring the sintering temperature to a temperature range of 950 ° C. to 1300 ° C. Br = 1.3 to 1.4T (13. From 0 to 14.0 kG), it is possible to produce FeCrCo permanent magnet powder by a powder metallurgy method using a discharge plasma sintering method. It is confirmed that the magnet can be manufactured.

As for FIG. 7, the externally heated sintered body manufactured by the externally heated sintering method as in FIG. 6 is at most (BH) due to the decrease in the sintered body density level due to insufficient densification, as shown by the curve 62. Only a value of max = 17.5 kJ / m ³ (2.2 MGOe) is obtained, and only a value practically unusable as an FeCrCo permanent magnet material is obtained. On the other hand, in the spark plasma sintered body manufactured by the spark plasma sintering method, as shown by the curve 61, (BH) max = 33.4 kJ / m ³ (4.2 MGOe) even at a low temperature of 800 ° C. Already practically high maximum energy product, and further heating to make the sintering temperature range from 1100 ° C. to 1300 ° C. (BH) max = 43.0-47.7 kJ / M ³ (5.4 to 6.0 MGOe) is obtained, and a high (BH) max value can be obtained by producing FeCrCo permanent magnet powder by a powder metallurgy method using a discharge plasma sintering method. It is confirmed that an FeCrCo permanent magnet having very excellent magnetic properties can be manufactured.

  As in FIGS. 6 and 7, FIG. 8 also shows the effect of the decrease in the density level of the sintered body due to insufficient densification in the externally heated sintered body manufactured by the externally heated sintering method, as shown by the curve 72. Thus, only a value of iHc = 31.8 kA / m (400 Oe) is obtained at the maximum, whereas in the discharge plasma sintered body manufactured by the discharge plasma sintering method, as shown by the curve 71, 800 ° C. IHc = 39.8 kA / m (500 Oe) at a low temperature of 5 ° C., which shows a higher coercive force value than that of an externally heated sintered body manufactured by an externally heated sintering method, and further in a heated temperature range of 1050 ° C. to 1300 ° C. Shows an extremely high coercive force of iHc = 47.7-51.7 kA / m (600-650 Oe). Therefore, a discharge plasma sintering method is used for FeCrCo permanent magnet powder. By produced by powder metallurgy, that can be produced is FeCrCo permanent magnet very excellent magnetic properties with high values of the coercive force iHc is confirmed.

(Fifth embodiment)
At the same time, the production of FeCrCo permanent magnets by the conventional powder metallurgy method was impossible because FeCrCo, which is the basic constituent element, was not capable of showing remarkable sinterability. It is made into a thin plate by rolling, and then the FeCrCo permanent magnet material is manufactured by hot or cold punching because it is difficult to sinter and at the same time has poor workability such as machinability and grindability. Considering mass productivity at the time, there is a limit to the punching pressure at the time of punching, so the thickness direction dimension when using the FeCrCo permanent magnet as a thin plate material has to be 2 mm or less at the maximum. By applying the FeCrCo permanent magnet manufacturing method by powder metallurgy using FeCrCo permanent magnet powder, there is no need to make a thin plate material and the thickness Not need to be 2mm or less for the dimensions of the countercurrent, it can be confirmed that the length of the substantially shortest side becomes possible very shape high degree of freedom manufacture of FeCrCo permanent magnets than 2mm is.

  As described above, according to the manufacturing method of the FeCrCo permanent magnet according to the present invention, it is possible to manufacture a sintered compact of the FeCrCo permanent magnet sintered and densified by the powder metallurgy method using the discharge plasma sintering method. Can be applied.

It is a figure which shows schematic structure of the apparatus for implementing the discharge plasma sintering method of this invention. It is a figure which shows the relationship between the average powder particle diameter of FeCrCo permanent magnet raw material powder, and the relative density ratio of the plasma sintered compact manufactured by the plasma sintering method and the external heating sintering method, and an external heating sintered body. It is a figure which shows the relationship of the sintered compact density of a plasma sintered compact and an external heating sintering body with respect to plasma sintering retention temperature and external heating sintering retention temperature. It is a figure which shows the relationship of the relative density ratio of a plasma sintered compact and an external heating sintering body with respect to plasma sintering holding temperature and external heating sintering holding temperature. It is a figure which shows the relationship of the relative density ratio of a plasma sintered compact and an external heating sintering body with respect to plasma sintering holding time and external heating sintering holding time. It is a figure which shows the residual magnetic flux density Br which is a magnetic characteristic of a plasma sintered compact and an external heating sintered body with respect to plasma sintering holding temperature and external heating sintering holding temperature. It is a figure which shows the maximum energy product (BH) max which is a magnetic characteristic of a plasma sintered compact and an external heating sintered body with respect to plasma sintering holding temperature and external heating sintering holding temperature. It is a figure which shows the coercive force iHc which is a magnetic characteristic of a plasma sintered compact and an external heating sintered body with respect to plasma sintering holding temperature and external heating sintering holding temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper punch 2 Lower punch 3 Sintering die 4 Powder 5 Upper punch electrode 6 Lower punch electrode 7 Water-cooled vacuum chamber 10 Apparatus 11, 21, 31, 41, 51, 61, 71 The characteristic of the sintered compact by a discharge plasma method Curves 12, 22, 32, 42, 52, 62, 72 Curves showing characteristics of the sintered body by the external heating sintering method 15 Sintering power source 16 Pressurizing mechanism 17 Controller 18 Measuring system 18 a Position measuring mechanism 18 b Atmosphere control Mechanism 18d Water cooling mechanism 18e Temperature measuring device

Claims (5)

  FeCrCo permanent magnet powder having an average powder particle size of 1.0 to 500 μm by at least one of atomizing powder production method using water or gas, air-flow dry pulverization method using a jet mill, and wet pulverization method And producing a sintered compact in which the powder is sintered and densified by a powder metallurgy method using a discharge plasma sintering method.   2. The method of manufacturing a FeCrCo permanent magnet according to claim 1, wherein the discharge plasma sintering method using a large current is applied to a low temperature of 800 to 1300 [deg.] C. by plasma discharge heating, Joule heat heating effect and pressure compression effect during sintering. Thus, a high-density FeCrCo permanent magnet having a relative density ratio of 95 to 99.9% is obtained.   The method for producing a FeCrCo permanent magnet according to claim 1 or 2, wherein the relative density ratio is 95 to 95 minutes in a short time of 1 min to 60 min due to discharge plasma heating by high current energization, Joule heat heating effect and pressure compression effect during sintering. A method for producing a FeCrCo permanent magnet, comprising obtaining a 99.9% sintered body of high-density FeCrCo permanent magnet. The FeCrCo permanent magnet sintered body has a relative density ratio of 95 to 99.9%, Br = 1.2 to 1.4T, (BH) max = 33.4 to 47.7 kJ / m ³ , iHc = 39. FeCrCo permanent magnet sintered body having a high magnetic property of .8 to 51.7 kA / m. 5. The FeCrCo permanent magnet sintered body according to claim 4, wherein the length of the shortest side is 2 mm to 500 mm.

Images