JP4529198B2 - Iron-based permanent magnet containing a small amount of rare earth metal and method for producing the same - Google Patents

Description

【００５８】
【表２】

表１において、例えば「Ｒ」と表示している欄の「Ｎｄ_2.8」は希土類元素としてＮｄを２．８原子％添加したことを示しており、「Ｎｄ₁＋Ｐｒ_0.5」は希土類元素としてＮｄを１原子％、Ｐｒを０．５原子％添加したことを示している。
【００５９】
表２からわかるように、実施例Ｎｏ．１〜Ｎｏ．１０はいずれも残留磁束密度Ｂ_rが１．３Ｔ以上、角形比Ｊ_r／Ｊ_sが０．８以上、固有保磁力Ｈ_cjが２５ｋＡ／ｍ以上の特性を示した。
【００６０】
各実施例の構成相をＣｕＫαの特性Ｘ線によって分析したところ、Ｆｅ₃Ｂ相、Ｎｄ₂Ｆｅ₁₄Ｂ相が混在する多相組織であった。なお、Ｓｉ、ＧａおよびＣｕ等はこれらの各相でＦｅの一部と置換される。
【００６１】
熱処理後の結晶相の結晶粒径を透過型電子顕微鏡（ＴＥＭ）によって分析したところ、平均結晶粒径は何れの試料についても３０ｎｍ以下であった。
【００６２】
以上、本発明を永久磁石について説明してきたが、希土類元素の含有量を低めにするか、Ｓｉを添加するなどして保磁力を１〜５０ｋＡ／ｍの範囲に調整すれば、本発明の永久磁石を半硬質磁性材料としても用いることもできる。その場合は、高い角形比および残留磁束密度を活かして、本発明の永久磁石を優れたヒステリシス材として各種のカップリング装置などに好適に利用することができる。
【００６３】
【発明の効果】
本発明によれば、希土類元素の含有量が少ないため、高い残留磁束密度を持ちながら、耐食性や耐酸化性に優れた永久磁石を提供できる。また、高価な希土類元素の含有量が少ないため、製造コストを低く抑えることも可能である。
【図面の簡単な説明】
【図１】本発明の実施例について、Ｘ線回折パターンを示すグラフである。
【図２】本発明による永久磁石の製造方法に好適に用いられるメルトスピニング装置の構成図である。
【符号の説明】
１ 溶解室
２ 急冷室
３ 溶解炉
４ 貯湯容器
５ 出湯ノズル
６ ロート
７ 回転冷却ロール
１ａ、２ａ、８ａ ガス排気口
２０ 原料[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a permanent magnet exhibiting a high residual magnetic flux density optimum for various motors, speakers, meters, focus convergence rings, and the like, and a method for manufacturing the same.
[0002]
[Prior art]
In the field of high residual magnetic flux density is required, mainly, alnico magnet remanence B _r has a magnetic characteristic of the intrinsic coercive force H _cj is 30~1600kA / m or more 1T, the remanence B _r 0. Nd of Sm-Co sintered magnets intrinsic coercive force H _cj above 8T has a magnetic characteristic of more than 450kA / m, and the remanence B _r is the intrinsic coercive force H _cj above 1T with magnetic properties of 950 kA / m _2. Description of the Related Art Nd—Fe—B sintered magnets whose main phase is a compound of ₂ Fe ₁₄ B type crystal structure are widely used.
However, alnico magnets and Sm—Co sintered magnets have a problem that the supply amount and price from the country of origin of these main raw materials Co are unstable. Further, Sm—Co sintered magnets and Nd—Fe—B sintered magnets also have a problem that rare earth elements (Sm and Nd) are expensive.
[0003]
In order to avoid such problems, research and development of magnetic materials having a relatively low concentration of rare earth elements has been promoted. As a result, for example, a magnetic material having a composition of Nd _3.8 Fe _77.2 B ₁₉ (atomic%) and having an Fe ₃ B type compound as a main phase has been proposed (R. Coehoorn et al., J. de Phys. C8, 1988, pp669-670). This magnetic material is obtained by crystallizing, by heat treatment, an amorphous alloy obtained by rapidly solidifying a molten raw material alloy by a liquid quenching method. As a result of the heat treatment, the amorphous alloy has a fine metal structure in which an Fe ₃ B phase showing soft magnetism and an Nd ₂ Fe ₁₄ B phase showing hard magnetism are mixed. The magnetic material has a metastable structure exerts the intrinsic coercive force H _cj of remanence B _r and 160~240kA / m of about 1T.
[0004]
[Problems to be solved by the invention]
However, the magnetic material has a problem that the saturation magnetization is low and a uniform fine metal structure cannot be obtained stably. If the fine metal structure is non-uniform, the exchange interaction between particles becomes weak, and the squareness ratio of the demagnetization curve becomes small. For this reason, the magnetic material cannot exhibit a residual magnetic flux density that exceeds the residual magnetic flux density of the Alnico magnet or the Nd—Fe—B sintered magnet.
[0005]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a permanent magnet exhibiting a high saturation magnetic flux density while reducing the content of expensive rare earth elements as compared with the prior art and a method for producing the same. There is to do.
[0006]
[Means for Solving the Problems]
The permanent magnet according to the present invention comprises Fe _100-xy B _x R _y (Fe is iron, B is boron, R is Y, La, Ce, Pr, Nd, and Sm, at least one rare earth selected from the group consisting of Element), wherein x and y in the composition formula have a relationship of 15 atomic% ≦ x ≦ 30 atomic% and 0.1 atomic% ≦ y ≦ 3 atomic%. It is satisfactory, and includes, as a constituent phase, iron, an alloy of iron and boron, and a compound having an R ₂ Fe ₁₄ B type crystal structure, and an average crystal grain size of each constituent phase is 100 nm or less.
[0007]
The average crystal grain size is preferably 50 nm or less.
[0008]
In a preferred embodiment, the residual magnetic flux density B _r is 1.3 T or more, the intrinsic coercive force H _cj is 20 kA / m or more, and the squareness ratio (J _r / J _s ), which is the ratio of the residual magnetization J _r to the saturation magnetization J _s . 0.8 or more.
[0009]
The method of manufacturing a permanent magnet according to the present invention includes Fe _100-xy B _x R _y (Fe is iron, B is boron, R is Y, La, Ce, Pr, Nd, and Sm. An alloy in which x and y in the composition formula satisfy a relationship of 15 atomic% ≦ x ≦ 30 atomic% and 0.1 atomic% ≦ y ≦ 3 atomic%. A molten metal quenching method in a reduced-pressure atmosphere by a melt quenching method to form a rapidly solidified alloy containing an amorphous phase, and heating the rapidly solidified alloy And a heat treatment step of forming a crystal structure including an alloy of iron and boron and a compound having an R ₂ Fe ₁₄ B type crystal structure as a constituent phase, and further setting an average crystal grain size of each constituent phase to 100 nm or less.
[0010]
In a preferred embodiment, in the heat treatment step, the heating temperature is set to 400 ° C. or higher and 700 ° C. or lower, and the heating time is set to 30 seconds or longer.
[0011]
Another method of manufacturing a permanent magnet according to the present invention is selected from the group consisting of Fe _100-xy B _x R _y (Fe is iron, B is boron, R is Y, La, Ce, Pr, Nd, and Sm). At least one rare earth element), wherein x and y satisfy the relationship of 15 atomic% ≦ x ≦ 30 atomic% and 0.1 atomic% ≦ y ≦ 3 atomic% Forming a molten alloy, and quenching the molten alloy by a melt quenching method in a reduced-pressure atmosphere to form a compound having an iron, iron-boron alloy, and R ₂ Fe ₁₄ B type crystal structure as a constituent phase And a rapid cooling step of forming an alloy having an average crystal grain size of each constituent phase of 100 nm or less.
[0012]
The absolute pressure of the reduced-pressure atmosphere is preferably 50 kPa or less.
[0013]
As the melt quenching method, it is preferable to use any one of a rotating roll method, a gas atomizing method, and a liquid quenching method combining a rotating roll method and a gas atomizing method.
[0014]
When the rotating roll method is used as the melt quenching method, it is preferable to adjust the surface speed of the rotating roll to 2 m / sec or more and 10 m / sec or less.
[0015]
The method for manufacturing an alloy for permanent magnets according to the present invention is selected from the group consisting of Fe _100-xy B _x R _y (Fe is iron, B is boron, R is Y, La, Ce, Pr, Nd, and Sm). At least one rare earth element), wherein x and y satisfy the relationship of 15 atomic% ≦ x ≦ 30 atomic% and 0.1 atomic% ≦ y ≦ 3 atomic% And a rapid cooling step in which the molten alloy is rapidly cooled by a melt quenching method in a reduced pressure atmosphere to form a rapidly solidified alloy containing an amorphous phase.
[0016]
The absolute pressure of the reduced-pressure atmosphere is preferably 50 kPa or less.
[0017]
According to another aspect of the present invention, there is provided a method for producing a permanent magnet, comprising: heating an alloy for permanent magnets according to the present invention as described above to form an iron, an alloy of iron and boron, and a compound having an R ₂ Fe ₁₄ B type crystal structure. And forming an alloy having an average crystal grain size of each constituent phase of 100 nm or less.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
The present inventor has found that a microcrystal of a compound having an R ₂ Fe ₁₄ B type crystal structure can be uniformly formed by quenching an iron-based alloy melt containing a small amount of rare earth element R in a reduced pressure atmosphere. I came up with the idea. Conventionally, for example, when Nd is used as the rare earth element, it has been considered that an amount of Nd exceeding 3 atomic% is indispensable for forming a crystal of the Nd ₂ Fe ₁₄ B phase.
[0019]
The present invention relates to an iron-based permanent magnet represented by a composition formula of Fe _100-xy B _x R _y . Here, Fe is iron, B is boron, R is at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, and Sm. X and y in the composition formula satisfy the relationship of 15 atomic% ≦ x ≦ 30 atomic% and 0.1 atomic% ≦ y ≦ 3 atomic%.
[0020]
In the permanent magnet according to the present invention, a molten alloy having the above composition is rapidly cooled in a reduced pressure atmosphere by a melt-quenching method to form a rapidly solidified alloy containing an amorphous phase, and then the rapidly solidified alloy is heated. Thus, microcrystals (iron, an alloy of iron and boron, a compound having an R ₂ Fe ₁₄ B type crystal structure) having an average crystal grain size of 100 nm or less can be formed in the constituent phase. Instead of doing this, the molten alloy having the above composition is cooled under a reduced pressure atmosphere by a melt quenching method to form an alloy containing microcrystals having an average crystal grain size of 100 nm or less in the constituent phase. Can also be manufactured. In addition, the preferable average crystal grain diameter of each constituent phase is 50 nm or less.
[0021]
Whether the alloy obtained by the melt quenching method is in an amorphous state or a crystalline state can be controlled by adjusting the cooling rate. However, in any case, it is important to quench the molten material alloy in a reduced pressure atmosphere. By performing rapid cooling in a reduced pressure atmosphere, even though the amount of rare earth metal is small, uniform formation of microcrystals (average particle size of 100 nm or less) of the compound having an R ₂ Fe ₁₄ B type crystal structure Is possible for the first time, and as a result, a permanent magnet having excellent magnetic properties is produced.
[0022]
On the other hand, when the molten alloy having the above composition is cooled under an atmospheric pressure, the cooling rate of the molten metal becomes non-uniform, so that α-Fe crystals are likely to be generated, and the R ₂ Fe ₁₄ B type crystal structure is obtained. It becomes impossible to produce | generate the compound which has. In addition, the non-uniform cooling rate leads to the generation of a non-uniform phase, which causes a problem that the crystal grains become coarse when heat treatment for crystallization is performed.
[0023]
In the present invention, a soft magnetic alloy structure phase composed of iron, an alloy of iron and boron, and a hard magnetic compound phase having an R ₂ Fe ₁₄ B type crystal structure are mixed, and the average crystal grain size of each constituent phase is Since it is small, exchange coupling is strengthened. As a result, the squareness ratio of the demagnetization curve is isotropic as shown in the Stoner-Wohlfarth model (ECStoner and EP Wohlfarth, Philons. Trans. R. Soc. London, Ser. A 240, 599 (1948)). becomes larger than the squareness ratio of a demagnetization curve of the magnet _{(J r / J s = 0.5} ), can indicate a 0.8 or more. This fact, so that the residual magnetic flux density B _r excellent magnetic characteristics intrinsic coercive force H _cj is more than 20 kA / m or more 1.3T is exerted.
[0024]
In the present invention, when the average grain size of the microcrystals constituting the crystal phase exceeds 100 nm, the squareness ratio (J _r / J _s ) is less than 0.8, so the average grain size of the microcrystals exceeds 100 nm. It is necessary not to. The average particle size of the microcrystals is preferably 50 nm or less. On the other hand, the smaller the average grain size of the microcrystals, the better. However, it is industrially difficult to form a crystal phase having an average crystal grain size of 1 nm or less with good reproducibility.
[Reason for composition limitation]
When the content of boron (B) is less than 15 atomic%, an amorphous structure cannot be obtained even when the molten alloy is quenched by the liquid quenching method, and the intrinsic coercive force H _cj is only less than 20 kA / m even when heat treatment is performed. . In addition, significantly reduced the squareness ratio of a demagnetization curve exceeds 30 atomic%, the residual magnetic flux density B _r is below 1.3 T. Therefore, the boron composition ratio x needs to satisfy 15 atomic% ≦ x ≦ 30 atomic%, and preferably satisfies 15 atomic% ≦ x ≦ 23 atomic%.
[0025]
When the content of the rare earth element R is less than 0.1 atomic%, a compound phase having an R ₂ Fe ₁₄ B type crystal structure cannot be precipitated, and only an intrinsic coercive force H _{cj of} less than 20 kA / m can be obtained. On the other hand, if it exceeds 3 atomic%, a uniform fine crystal structure cannot be obtained when crystallized, resulting in a decrease in squareness ratio and a residual magnetic flux density B _s of 1.3 T or more cannot be obtained. For this reason, the composition ratio y of the rare earth element R needs to satisfy 0.1 atomic% ≦ y ≦ 3 atomic%, and preferably satisfies 0.5 atomic% ≦ y ≦ 3 atomic%. The reason why the heavy rare earth metal heavier than Gd in the periodic table is excluded as the rare earth element used is that the magnetic moment of the heavy rare earth element and the magnetic moment of Fe and Co are antiparallel, and the magnetizations cancel each other. This is because a high magnetic flux density cannot be obtained.
[0026]
The raw material is composed of elements M (Al, Si, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb. At least one element selected from the group) may be added. The addition of the element M brings about effects such as an improvement in the squareness ratio J _r / J _s and an expansion of the operating temperature range in which optimum magnetic characteristics can be exhibited. If the content of the element M is less than 0.05 atomic%, such an effect is not sufficiently exhibited, and if it exceeds 7 atomic%, the magnetization starts to decrease. For this reason, the composition ratio z of the additive element M needs to satisfy 0.05 atomic% ≦ z ≦ 7 atomic%, and preferably satisfies 0.2 atomic% ≦ z ≦ 5 atomic%.
[0027]
Further, cobalt (Co) may be added to the raw material. Co exhibits the effect of improving the squareness ratio by being replaced with a part of Fe. For this reason, it is preferable to add Co when particularly increasing the squareness ratio. However, the Co substitution amount is less than 0.1% of Fe, the effects are not sufficiently exhibited, and it is impossible to obtain a residual magnetic flux density B _r of more than 1.3T more than 50%. Therefore, the Co substitution amount m needs to be 0.001 ≦ m ≦ 0.5, and is preferably 0.005 ≦ m ≦ 0.1.
[0028]
In addition, Fe occupies the residual content of the above elements.
[0029]
Next, an embodiment of a method for manufacturing a permanent magnet according to the present invention will be described.
[0030]
First, a raw material represented by the above composition formula is prepared, and this raw material is heated and melted to prepare a molten alloy. The molten alloy is rapidly cooled by a melt quenching method to form a rapidly solidified alloy containing an amorphous phase. As the melt quenching method, it is preferable to use any one of a rotating roll method, a gas atomizing method, and a method in which a rotating roll method and a gas atomizing method are combined.
[0031]
In this embodiment, a raw material alloy is manufactured using the melt spinning apparatus shown in FIG. In order to prevent the oxidation of the raw material alloy containing rare earth elements that are easily oxidized, the alloy manufacturing process is executed in an inert gas atmosphere. As the inert gas, a rare gas such as helium or argon is preferably used. Note that it is not preferable to use nitrogen as an inert gas because nitrogen easily reacts with rare earth elements.
[0032]
The apparatus shown in FIG. 2 includes a raw material alloy melting chamber 1 and a quenching chamber 2 that can maintain a vacuum or an inert gas atmosphere and adjust the pressure.
[0033]
The melting chamber 1 is a melting furnace 3 that melts the raw material 20 blended so as to have a desired magnet alloy composition at a high temperature, a hot water storage container 4 having a hot water discharge nozzle 5 at the bottom, and a mixture while suppressing entry of air. And a blended raw material supply device 8 for supplying the raw material into the melting furnace 3. The hot water storage container 4 has a heating device (not shown) that stores the molten alloy 21 of the raw material alloy and can maintain the temperature of the hot water at a predetermined level.
[0034]
The quenching chamber 2 includes a rotary cooling roll 7 for rapidly cooling and solidifying the molten metal 21 discharged from the hot water nozzle 5.
[0035]
In this apparatus, the atmosphere in the melting chamber 1 and the quenching chamber 2 and the pressure thereof are controlled within a predetermined range. Therefore, atmospheric gas supply ports 1b, 2b, and 8b and gas exhaust ports 1a, 2a, and 8a are provided at appropriate locations in the apparatus. In particular, the gas exhaust port 2a is connected to a pump in order to control the absolute pressure in the quenching chamber 2 within the range of vacuum to 50 kPa.
[0036]
The melting furnace 3 can be tilted, and the molten metal 21 is appropriately poured into the hot water storage container 4 through the funnel 6. The molten metal 21 is heated in the hot water storage container 4 by a heating device (not shown).
[0037]
The hot water discharge nozzle 5 of the hot water storage container 4 is disposed in the partition wall between the melting chamber 1 and the quenching chamber 2 and causes the molten metal 21 in the hot water storage container 4 to flow down to the surface of the cooling roll 7 positioned below. The orifice diameter of the hot water nozzle 5 is, for example, 0.5 to 2.0 mm. When the viscosity of the molten metal 21 is large, the molten metal 21 is less likely to flow through the hot water nozzle 5, but in this embodiment, the quenching chamber 2 is held at a lower pressure than the melting chamber 1. During this time, a pressure difference is formed, and the molten metal 21 is smoothly discharged.
[0038]
The surface of the cooling roll 7 is covered with, for example, a chromium plating layer, and the diameter of the cooling roll 7 is, for example, 300 to 500 mm. The water cooling capacity of the water cooling device provided in the cooling roll 7 is calculated and adjusted according to the solidification latent heat per unit time and the amount of hot water.
[0039]
According to the apparatus shown in FIG. 2, for example, a total of 20 kg of the raw material alloy can be rapidly solidified in 15 to 30 minutes. The alloy thus formed is an alloy ribbon (alloy ribbon) 22 having a thickness of 70 μm to 150 μm and a width of 1.5 mm to 6 mm.
[0040]
Next, a raw material alloy manufacturing method performed using the apparatus of FIG. 2 will be described.
[0041]
First, the general formula is Fe _100-xy B _x R _y (Fe is iron, B is boron, R is Y, La, Ce, Pr, Nd, and at least one selected from the group consisting of Sm and Sm) A molten metal 21 of an alloy represented by a rare earth element (15 atomic% ≦ x ≦ 30 atomic%, 0.1 atomic% ≦ y ≦ 3 atomic%) is produced and stored in the hot water storage container 4 of the melting chamber 1.
[0042]
Next, the molten metal 21 is discharged from the hot water nozzle 5 onto the water-cooled roll 7 in a reduced pressure Ar atmosphere, rapidly cooled by contact with the water-cooled roll 7, and solidified. As the rapid solidification method, it is necessary to use a method capable of controlling the cooling rate with high accuracy. In this embodiment, a rotating roll method, which is one of the melt quenching methods, is used.
[0043]
In this embodiment, when the molten metal 21 is cooled and solidified, the cooling rate is set to 10 ² to 10 ⁷ ° C / second. At this cooling rate, the temperature of the alloy is lowered to a temperature lower by ΔT1. Since the temperature of the molten alloy 21 before the rapid cooling is close to the melting point Tm (for example, 1200 to 1300 ° C.), the temperature of the alloy decreases from Tm to (Tm−ΔT1) on the cooling roll 7. According to the experiments by the present inventors, ΔT1 is preferably in the range of 700 to 1100 ° C. from the viewpoint of improving the final magnet characteristics.
[0044]
The time for which the molten alloy 21 is cooled by the cooling roll 7 corresponds to the time from the contact of the alloy with the outer peripheral surface of the rotating cooling roll 7 until it leaves, and in the case of this embodiment, 0.05 to 50 mm. Seconds. Meanwhile, the temperature of the alloy further decreases by ΔT2 and solidifies. Thereafter, the solidified alloy leaves the cooling roll 7 and flies in an inert atmosphere. While the alloy is in the form of a ribbon, the temperature is lowered to (Tm−ΔT1−ΔT2) as a result of the heat deprived from the atmospheric gas. ΔT2 varies depending on the size of the apparatus and the pressure of the atmospheric gas, but is about 100 ° C. or higher.
[0045]
Note that the atmosphere in the quenching chamber 2 is in a reduced pressure state. The atmosphere is preferably composed of an inert gas having an absolute pressure of 50 kPa or less. The rapid solidification may be performed in a vacuum atmosphere having a pressure of 0.1 kPa or less. In addition, when the pressure of atmospheric gas exceeds 50 kPa, since the influence of atmospheric gas being caught between a rotary roll and a molten alloy becomes remarkable, since a possibility that a uniform structure | tissue cannot be obtained becomes strong, it is unpreferable.
[0046]
The cooling roll 7 is preferably formed from Cu, Fe, or an alloy containing Cu or Fe. If the cooling roll is made of a material other than Cu or Fe, the releasability of the quenched alloy from the cooling roll is deteriorated, which may cause the quenched alloy to be wound around the roll.
[0047]
The surface roughness of the cooling roll is preferably centerline average roughness Ra ≦ 0.8 μm, maximum Rmax ≦ 3.2 μm, and ten-point average roughness Rz ≦ 3.2 μm. A rough surface of the cooling roll is not preferable because the quenched alloy tends to stick to the roll.
[0048]
In order to obtain the crystalline phase alloy directly by the melt quenching method, the roll surface peripheral speed of the cooling roll may be set to 2 to 10 m / sec. Thereby, an alloy structure showing hard magnetic properties is obtained. If the roll surface peripheral speed is less than 2 m / sec, the average crystal grain size becomes too large, and the desired magnetic properties cannot be obtained, which is not preferable. On the other hand, when the roll surface peripheral speed exceeds 10 m / sec, the quenched alloy becomes an amorphous phase and cannot be crystallized without heat treatment.
[0049]
When the ultra-quenching process is performed so that the amorphous phase exists, a heat treatment is performed on the rapidly solidified alloy, thereby generating microcrystals having an average crystal grain size of 100 nm or less. This heat treatment is preferably performed at a temperature of 400 ° C. to 700 ° C., more preferably 500 ° C. to 700 ° C. for 30 seconds or more. When the heat treatment temperature exceeds 700 ° C., grain growth is remarkable and magnetic properties deteriorate. On the contrary, when the heat treatment temperature is less than 400 ° C., the R ₂ Fe ₁₄ B phase does not precipitate, so that a high coercive force cannot be obtained.
[0050]
If heat treatment is performed under the above conditions, microcrystals (iron, an alloy of iron and boron, and a compound having an R ₂ Fe ₁₄ B type crystal structure) may be formed so that the average crystal grain size is 100 nm or less. it can. Although the preferable heat treatment time varies depending on the heat treatment temperature, for example, when heat treatment is performed at 600 ° C., it is preferable to perform heating for about 30 seconds to 30 minutes. If the heat treatment time is less than 30 seconds, crystallization may not be completed.
[0051]
According to the manufacturing method described herein, while showing remanence B _r is 1.3T or more as high intrinsic coercive force H _cj is not less 20 kA / m or more, yet squareness ratio J _r / J _s is 0 .8 or more permanent magnets can be manufactured with good reproducibility.
(Example)
Examples of permanent magnets according to the present invention will be described below.
[0052]
Example No. 1-No. About each of 10, Fe, B, Si, Ga, Cu, Nd, Pr, La, and Ce having a purity of 99.5% or more were weighed so that the total amount was 30 grams and put into a quartz crucible. Each Example No. 1-No. The composition of 10 was as shown in Table 1. Since the quartz crucible has an orifice having a diameter of 0.8 mm at the bottom, the raw material is melted in the quartz crucible and then melted into an alloy melt and dropped downward from the orifice. The raw material was dissolved using a high-frequency heating method in an argon atmosphere with a pressure of 1.33 kPa. In this example, the melting temperature was set to 1300 ° C.
[0053]
By pressurizing the molten metal surface at 26.7 kPa, the molten metal was jetted onto the outer peripheral surface of the copper roll located 0.7 mm below the orifice. The roll rotates at high speed while the inside is cooled so that the temperature of the outer peripheral surface is maintained at about room temperature. For this reason, the molten alloy dripped from the orifice comes into contact with the circumferential surface of the roll and is taken away in the circumferential speed direction while taking heat away. Since the molten alloy is continuously dripped onto the roll peripheral surface through the orifice, the alloy solidified by rapid cooling has a ribbon (width: 1 to 2 mm, thickness: 10 to 20 μm) extending in a thin strip shape. Will have.
[0054]
In the case of the rotating roll method (single roll method) employed in the present embodiment, the cooling rate is defined by the roll peripheral speed and the molten metal flow rate per unit time. The flow-down amount depends on the orifice diameter (cross-sectional area) and the molten metal pressure. In the example, the orifice has a diameter of 0.8 mm, the molten metal injection pressure is 26.7 Pa, and the flow-down rate is about 0.6 kg / min. . In this embodiment, the roll peripheral speed Vs was set to 40 m / sec. In order to produce a quenched alloy for the permanent magnet of the present invention, the cooling rate when quenching the molten alloy is an important parameter. In order to obtain a rapidly solidified alloy containing an amorphous phase, the cooling rate is preferably 10 ³ ° C / second or more. In order to achieve a cooling rate in this range, the roll peripheral speed is set to 7 m / second or more. It is preferable.
[0055]
CuKα characteristic X-ray analysis was performed on the quenched alloy ribbon thus obtained. As a result, Example No. 1 and no. 2 is a coexisting structure of Fe ₃ B and Nd ₂ Fe ₁₄ B. 3-No. 10 was confirmed to be amorphous. In FIG. 1 and no. 3 shows the X-ray diffraction pattern.
[0056]
Example No. 3-No. Ten amorphous alloy ribbons were subjected to heat treatment at a temperature shown in Table 1 for 10 minutes in an argon atmosphere to perform crystallization. After this heat treatment, samples having a width of 1 to 2 mm, a thickness of 10 to 20 μm, and a length of 3 to 5 mm were prepared from the ribbons cooled to room temperature, and the magnetic properties of each sample were measured by VSM. Table 2 shows the measurement results. In Table 2, Example No. 1 and no. The measurement results for 2 are also shown.
[0057]
[Table 1]

[0058]
[Table 2]

In Table 1, for example, “Nd _2.8 ” in the column labeled “R” indicates that 2.8 atomic% of Nd was added as a rare earth element, and “Nd ₁ + Pr _0.5 ” represents Nd as a rare earth element. It shows that 1 atomic% and Pr are added by 0.5 atomic%.
[0059]
As can be seen from Table 2, Example No. 1-No. 10 are both remanence B _r is more than 1.3 T, the squareness ratio J _r / J _s is 0.8 or more, an intrinsic coercive force H _cj showed more characteristics 25 kA / m.
[0060]
When the constituent phases of each example were analyzed by CuKα characteristic X-rays, it was a multiphase structure in which Fe ₃ B phase and Nd ₂ Fe ₁₄ B phase were mixed. Si, Ga, Cu, and the like are substituted with part of Fe in each of these phases.
[0061]
When the crystal grain size of the crystal phase after the heat treatment was analyzed by a transmission electron microscope (TEM), the average crystal grain size was 30 nm or less for any sample.
[0062]
As described above, the present invention has been described with respect to the permanent magnet. If the coercive force is adjusted to the range of 1 to 50 kA / m by lowering the rare earth element content or adding Si, the permanent magnet of the present invention will be described. A magnet can also be used as a semi-hard magnetic material. In that case, the permanent magnet of the present invention can be suitably used as an excellent hysteresis material for various coupling devices by utilizing the high squareness ratio and residual magnetic flux density.
[0063]
【The invention's effect】
According to the present invention, since the rare earth element content is small, it is possible to provide a permanent magnet having high corrosion resistance and oxidation resistance while having a high residual magnetic flux density. In addition, since the content of expensive rare earth elements is small, it is possible to keep the manufacturing cost low.
[Brief description of the drawings]
FIG. 1 is a graph showing an X-ray diffraction pattern for an example of the present invention.
FIG. 2 is a configuration diagram of a melt spinning apparatus preferably used in the method for producing a permanent magnet according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Melting chamber 2 Quenching chamber 3 Melting furnace 4 Hot water storage container 5 Hot water discharge nozzle 6 Funnel 7 Rotary cooling rolls 1a, 2a, 8a Gas exhaust port 20 Raw material

Claims (10)

Fe _100-xy B _x R _y (Fe is iron, B is boron, R is at least one rare earth element selected from the group consisting of Y, Ce, Pr, Nd, and Sm) A permanent magnet,
X and y in the composition formula are
Satisfying the relationship of 15 atomic% ≦ x ≦ 30 atomic%, and 0.1 atomic% ≦ y ≦ 3 atomic%, and as a constituent phase, iron, an alloy of iron and boron, and R ₂ Fe ₁₄ B type crystal structure An average crystal grain size of each constituent phase is more than 1 nm and not more than 100 nm,
The residual magnetic flux density B _r is 1.3 T or more, the intrinsic coercive force H _cj is 20 kA / m or more, and the squareness ratio (J _r / J _s ) which is the ratio of the residual magnetization J _r to the saturation magnetization J _s is 0.8 or more. A permanent magnet characterized by being. Fe _100-xy B _x R _y (Fe is iron, B is boron, R is at least one rare earth element selected from the group consisting of Y, Ce, Pr, Nd, and Sm), Forming a molten alloy in which x and y in the composition formula satisfy a relationship of 15 atomic% ≦ x ≦ 30 atomic% and 0.1 atomic% ≦ y ≦ 3 atomic%;
Under a reduced pressure atmosphere, the alloy melt is rapidly cooled by a melt quenching method to form a rapidly solidified alloy containing an amorphous phase; and
By heating the rapidly solidified alloy, a crystal structure containing iron, an alloy of iron and boron, and a compound having an R ₂ Fe ₁₄ B type crystal structure as a constituent phase is formed, and the average crystal grain size of each constituent phase is determined. A heat treatment step of more than 1 nm and less than 100 nm,
The rapid cooling step
Reducing the temperature of the rapidly solidified alloy to a temperature lower by 700 to 1100 ° C. than the melting point of the alloy by bringing the molten alloy into contact with a rotating cooling roll;
After the rapidly solidified alloy leaves the cooling roll, further cooling the rapidly solidified alloy in the reduced-pressure atmosphere gas, and further reducing the temperature of the rapidly solidified alloy by 100 ° C. or more;
A method for manufacturing a permanent magnet, comprising: 3. The method of manufacturing a permanent magnet according to claim 2, wherein in the heat treatment step, the heating temperature is set to 400 ° C. or more and 700 ° C. or less, and the heating time is set to 30 seconds or more and 30 minutes or less . Fe _100-xy B _x R _y (Fe is iron, B is boron, R is at least one rare earth element selected from the group consisting of Y, Ce, Pr, Nd, and Sm), Forming a molten alloy in which x and y in the composition formula satisfy a relationship of 15 atomic% ≦ x ≦ 30 atomic% and 0.1 atomic% ≦ y ≦ 3 atomic%;
Under a reduced pressure atmosphere, the molten alloy is rapidly cooled by a melt quenching method to form a crystal structure containing iron, an alloy of iron and boron, and a compound having an R ₂ Fe ₁₄ B type crystal structure as a constituent phase. And a quenching step of producing an alloy having an average crystal grain size of more than 1 nm and not more than 100 nm,
The rapid cooling step
Reducing the temperature of the rapidly solidified alloy to a temperature lower by 700 to 1100 ° C. than the melting point of the alloy by bringing the molten alloy into contact with a rotating cooling roll;
After the rapidly solidified alloy leaves the cooling roll, further cooling the rapidly solidified alloy in the reduced-pressure atmosphere gas, and further reducing the temperature of the rapidly solidified alloy by 100 ° C. or more;
A method for manufacturing a permanent magnet, comprising: The method for producing a permanent magnet according to any one of claims 2 to 4, wherein the absolute pressure of the reduced-pressure atmosphere is a vacuum or 50 kPa or less.   6. The permanent magnet according to claim 2, wherein any one of a rotating roll method, a gas atomizing method, and a liquid quenching method combining a rotating roll method and a gas atomizing method is used as the melt quenching method. Manufacturing method.   The method for producing a permanent magnet according to claim 4 or 5, wherein a rotating roll method is used as the melt quenching method, and a surface speed of the rotating roll is set to 2 m / sec or more and 10 m / sec or less. Fe _100-xy B _x R _y (Fe is iron, B is boron, R is at least one rare earth element selected from the group consisting of Y, Ce, Pr, Nd, and Sm), Forming a molten alloy in which x and y in the composition formula satisfy a relationship of 15 atomic% ≦ x ≦ 30 atomic% and 0.1 atomic% ≦ y ≦ 3 atomic%;
A rapid cooling step of rapidly cooling the molten alloy under a reduced pressure atmosphere by a melt quenching method to form a rapidly solidified alloy containing an amorphous phase, and
The rapid cooling step
Reducing the temperature of the rapidly solidified alloy to a temperature lower by 700 to 1100 ° C. than the melting point of the alloy by bringing the molten alloy into contact with a rotating cooling roll;
After the rapidly solidified alloy leaves the cooling roll, further cooling the rapidly solidified alloy in the reduced-pressure atmosphere gas, and further reducing the temperature of the rapidly solidified alloy by 100 ° C. or more;
The manufacturing method of the alloy for permanent magnets containing this. The method for producing an alloy for permanent magnets according to claim 8, wherein the absolute pressure of the reduced-pressure atmosphere is vacuum or 50 kPa or less. A crystal structure comprising iron, an alloy of iron and boron, and a compound having an R ₂ Fe ₁₄ B type crystal structure as a constituent phase by heating the permanent magnet alloy produced by the production method according to claim 8 or 9. And producing an alloy having an average crystal grain size of more than 1 nm and not more than 100 nm in each constituent phase.

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