JP2015122391A - MANUFACTURING METHOD OF SmFeN MAGNET AND SmFeN MAGNET - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a SmFeN magnet capable of sufficiently exerting magnetic properties even under a high temperature environment, requiring no power supply facility, capable of reducing facility cost, and to provide a SmFeN magnet.SOLUTION: The manufacturing method of a SmFeN magnet includes: applying a nitriding treatment to a SmFe powder to convert it to a SmFeN magnetic powder; and, when sintering it to produce a SmFeN magnet, either after the nitriding treatment process or during the sintering treatment process, applying a heat treatment at 350 to 550°C for 5 to 60 hours to precipitate αFe and sinter it.

Description

  The present invention relates to a method for producing an SmFeN-based magnet and an SmFeN-based magnet, and more particularly to a method for producing an SmFeN-based magnet having excellent heat resistance.

  SmFeN magnets have better corrosion resistance than NdFeB magnets. However, when sintered at 900 ° C. or higher, which is the conventional sintering temperature, the main phase is decomposed and the magnet characteristics are lost. Therefore, conventionally, bonded magnets using resin or the like as a binder are the mainstream. However, the bond magnet has a problem that it cannot be used in a high temperature atmosphere of 200 ° C. or higher because it contains a resin. Thus, for example, in Patent Document 1, current is passed between upper and lower punches that define a cavity during sintering, and sintering is instantaneously advanced by Joule heat due to contact resistance between magnetic powder particles, thereby reducing the thermal load. Thus, a method for realizing an SmFeN-based sintered magnet has been proposed.

JP-A-2005-171264

  However, in the above conventional method, there is a problem that it is necessary to attach a power supply facility to the sintering facility, and the structure capable of exhibiting magnetic properties is lost because the surface of the magnetic powder is partially heated. there were.

  Therefore, the present invention solves such a problem, a method for producing an SmFeN-based magnet and an SmFeN that can reduce power supply equipment, reduce equipment costs, and can sufficiently exhibit magnetic properties even in a high-temperature atmosphere. It aims at providing a system magnet.

  In order to achieve the above object, in the manufacturing method of the SmFeN-based magnet of the first invention, the nitriding treatment is performed when the SmFe powder is nitrided to obtain the SmFeN magnetic powder, and this is sintered to produce the SmFeN-based magnet. It is characterized by being obtained by performing heat treatment at 350 to 550 ° C. for 5 to 60 hours after the step or in the sintering treatment step to precipitate and sinter αFe.

  In the SmFeN magnet of the second invention, αFe deposited on the surface of the parent phase of SmFeN magnetic powder is sintered by diffusion bonding with the parent phase of other SmFeN magnetic powder or αFe deposited on the surface of the parent phase. .

  According to the present invention, αFe is precipitated on the surface of the parent phase of the SmFeN magnetic powder through a sufficiently low temperature nitriding process or a sufficiently low temperature sintering process, and other SmFeN magnetic powder A sintered state can be generated by diffusion bonding with the parent phase or αFe precipitated on the surface of the parent phase. Therefore, SmFeN magnetic powder can be sintered without attaching power supply equipment to the sintering equipment as in the prior art, and the equipment cost can be greatly reduced. Moreover, since the magnet characteristics of the SmFeN magnetic powder can be sintered at a sufficiently low temperature, such a sintered magnet does not use a resin material unlike the bonded magnet, so that it does not impair the magnetic characteristics. Use at a high temperature of 500 ° C. is possible and corrosion resistance is maintained.

  As described above, according to the present invention, it is possible to realize an SmFeN-based magnet that does not require power supply equipment, can reduce equipment costs, and can sufficiently exhibit magnetic characteristics even in a high-temperature atmosphere.

It is a figure which shows the SEM image of the roll surface of a SmFe ribbon. It is a figure which shows the reflected electron beam image by the side of the roll surface of a SmFe ribbon.

  The embodiment described below is merely an example, and various design improvements made by those skilled in the art without departing from the gist of the present invention are also included in the scope of the present invention.

(First embodiment)
In this embodiment, as shown in FIG. 1, a molten SmFe is dropped onto a quenching roll, and a SmFe ribbon is produced by a quenching method. Note that a reduction diffusion method or the like may be used instead of the rapid cooling method.

  Subsequently, after heat-treating the SmFe ribbon (powder) at 500 to 900 ° C. in an argon atmosphere, the SmFeN ribbon is subjected to nitriding treatment by heating at 300 to 600 ° C. in an atmosphere of nitrogen gas alone or a mixed gas of ammonia and hydrogen. (Magnetic powder). In this embodiment, after nitriding, heat treatment is performed at 350 to 550 ° C. for 5 to 60 hours in a nitrogen gas atmosphere. By such treatment, αFe can be deposited on the roll surface of the ribbon after the nitriding treatment.

  The heat treatment after the nitriding treatment in this embodiment may use an argon gas other than the nitrogen gas or may be performed in a vacuum state. Here, at 350 ° C. or lower, αFe is not efficiently precipitated, whereas when it is set at 550 ° C. or higher, the SmFeN ribbon is chemically decomposed and the magnetic properties are deteriorated. In addition, αFe does not precipitate reliably within 5 hours or less. On the other hand, if the heat treatment is performed for 60 hours or more, the productivity is deteriorated. In particular, from the viewpoint of productivity, the upper limit of the more preferable range of the heat treatment is 30 hours.

  Next, the SmFeN ribbon is sent to a sintering apparatus. The sintering temperature in the sintering apparatus can be made sufficiently lower than in the prior art, and in the present embodiment, it can be set to 350 to 550 ° C., a sufficiently low temperature at which the magnet characteristics are not lost. The sintering time is about 1 hour, and hot pressing is performed in an argon or nitrogen atmosphere or in a vacuum at a pressure of 400 kgf / cm 2 or more. As described above, sintering at such a low temperature is possible because αFe precipitated on the surface of the parent phase of the ribbon precipitates on the parent phase of the other ribbon or the surface of the parent phase. This is because the sintered state appears by diffusion bonding with αFe.

(Example)
The SmFe ribbon obtained by the rapid cooling method is heat-treated at 500 to 900 ° C. in an argon atmosphere, and then subjected to nitriding treatment at 300 to 600 ° C. in a mixed gas atmosphere of ammonia and hydrogen, and then at 460 ° C. and 5 in an argon atmosphere. Precipitation of αFe was performed by heat treatment over time. This is shown in FIGS. FIG. 1 is an SEM image of the roll surface of the SmFe ribbon, and precipitation of αFe is observed. FIG. 2 is a reflected electron beam image on the roll surface side of the SmFe ribbon, in which αFe is deposited in the surface region of the parent phase sandwiched by arrows. The SmFeN ribbon having an average particle diameter of 100 μm obtained by this treatment was put into a known 50 × 50 graphite mold, heated to 460 ° C., and hot-pressed at 400 kgf / cm 2 for 1 hour to sinter. In this process, αFe precipitated on the surface of the parent phase of each ribbon was diffusion-bonded to the parent phase of other ribbons or αFe deposited on the surface of the parent phase to be in a sintered state.

  A 7 × 7 × 5 (mm) rectangular parallelepiped was cut out from the obtained sintered molded product having a length and width of 50 mm and a thickness of 14 mm as a sample and magnetized by applying a 45 KOe magnetic field. Magnetic properties of the obtained low-temperature sintered magnet, that is, residual magnetic flux density (Br), coercive force (iHc), and maximum energy product ((BH) max) were measured with a BH curve tracer. The results are shown in Table 1. Further, as a comparative example, Table 1 similarly shows the results when a sample having the same shape is manufactured with a bonded magnet (manufactured by Daido Electronics: model number SP-14). According to this, the sintered magnet manufactured according to the present example exhibits excellent magnetic properties equivalent to or better than those of conventional bonded magnets.

(Second Embodiment)
In the first embodiment, αFe is deposited after nitriding, but αFe may be deposited in the sintering process. In this case, the SmFe ribbon is manufactured by the rapid cooling method in the same manner as in the first embodiment, and then the SmFe ribbon is heat treated at 500 to 900 ° C. in an argon atmosphere, and then nitrogen gas alone or a mixture of ammonia and hydrogen is used. Nitriding treatment is performed by heating at 300 to 600 ° C. in a gas atmosphere to obtain a SmFeN ribbon. Subsequently, the SmFeN ribbon is sent to a known sintering apparatus.

  And it is hot at a pressure of 400 kgf / cm2 or higher while heating in an argon or nitrogen atmosphere or in a vacuum for 5 to 60 hours at a temperature of 350 to 550 ° C., which is sufficiently low compared with the prior art in a sintering apparatus. Press. In such a sintering process, αFe is precipitated on the surface of the parent phase of each ribbon, and at the same time, αFe precipitated on each ribbon is mixed with αFe deposited on the parent phase of the other ribbon or on the surface of the parent phase. The sintered state is revealed by diffusion bonding. The reason why the temperature range and time range of the heat treatment are set as described above in the main sintering step is the same as in the first embodiment.

(Example)
The SmFe ribbon obtained by the rapid cooling method was heat-treated at 500 to 900 ° C. in an argon atmosphere, and then nitridated at 300 to 600 ° C. in a mixed gas atmosphere of ammonia and hydrogen. The SmFeN ribbon having an average particle diameter of 100 μm obtained by this treatment was put into a known 50 × 50 graphite mold, heated to 460 ° C., and hot-pressed at 400 kgf / cm 2 for 10 hours for sintering. That is, in the process of low-temperature long-time heating and pressurization, αFe is precipitated on the surface of each thin ribbon, and αFe precipitated on each thin ribbon is precipitated on the parent phase of other magnetic powder or the surface of the parent phase. Diffusion bonding with αFe resulted in a sintered state.

  A 7 × 7 × 5 (mm) rectangular parallelepiped was cut out from the obtained sintered molded product having a length and width of 50 mm and a thickness of 14 mm as a sample and magnetized by applying a 45 KOe magnetic field. Magnetic properties of the obtained low-temperature sintered magnet, that is, residual magnetic flux density (Br), coercive force (iHc), and maximum energy product ((BH) max) were measured with a BH curve tracer. The results are shown in Table 2. Further, as a comparative example, the results when a sample having the same shape is manufactured with a bonded magnet (manufactured by Daido Electronics: model number SP-14) are also shown in Table 2. According to this, the sintered magnet manufactured according to the present example exhibits excellent magnetic properties equivalent to or better than those of conventional bonded magnets.

Claims (2)

When the SmFeN magnetic powder is produced by nitriding the SmFe powder and manufacturing the SmFeN magnet by sintering, the heat treatment is performed at 350 to 550 ° C. for 5 to 60 hours after the nitriding process or in the sintering process. The method for producing an SmFeN-based magnet is characterized in that αFe is deposited and sintered by performing the step. An SmFeN magnet in which αFe deposited on the surface of the parent phase of SmFeN magnetic powder is sintered by diffusion bonding with another parent phase of SmFeN magnetic powder or αFe deposited on the surface of the parent phase.