JP4310738B2 - Soft magnetic alloys and magnetic parts - Google Patents

Description

  The present invention is applicable to various transformers, various reactors, choke coils for active filters, smooth choke coils, common mode choke coils, electromagnetic shields and other noise countermeasure components, laser power supplies, accelerator pulse power magnetic components, motors, generators, etc. The present invention relates to a soft magnetic alloy including nanoscale fine crystal grains excellent in mass productivity and a magnetic component using the same.

  High saturation used for various transformers, various reactors, choke coils for active filters, smooth choke coils, noise suppression parts such as common mode choke coils and electromagnetic shields, laser power supplies, pulse power magnetic parts for accelerators, motors, generators, etc. Known magnetic alloys exhibiting low magnetic core loss at magnetic flux density include silicon steel, amorphous alloys, FeCuNbSiB-based, FeZrB-based, FeNbB-based Fe-based nanocrystalline alloy materials, and the like. A silicon steel sheet is inexpensive and has a high magnetic flux density, but has a problem of high magnetic core loss for high frequency applications. The Fe-based amorphous alloy has a problem that its magnetostriction is large and its characteristics are deteriorated by stress, and there is a problem that noise is high in applications where currents in an audible frequency band are superimposed. On the other hand, the Co-based amorphous alloy has a problem that the saturation magnetic flux density is as low as 1 T or less in a practical material and is thermally unstable. For this reason, when used for high power applications, there are problems that the parts become large and that the magnetic core loss increases due to aging.

Fe-based nanocrystalline alloys exhibit excellent soft magnetic properties, and are therefore used in magnetic cores such as common mode choke coils, high frequency transformers, and pulse transformers. Typical composition systems are Fe-Cu- (Nb, Ti, Zr, Hf, Mo, W, and the like described in Patent Document 1 (Japanese Patent Publication No. 4-4393) and Patent Document 2 (Japanese Patent Laid-Open No. 1-242755). Ta) -Si-B based alloys and Fe-Cu- (Nb, Ti, Zr, Hf, Mo, W, Ta) -B based alloys are known. These Fe-based nanocrystalline alloys are usually produced by rapidly cooling from a liquid phase or a gas phase to form an amorphous alloy and then microcrystallizing it by heat treatment. As a method of quenching from the liquid phase, a single roll method, a twin roll method, a centrifugal quench method, a spinning in spinning solution, an atomizing method, a cavitation method, and the like are known. Further, as a method of quenching from the gas phase, a sputtering method, a vapor deposition method, an ion plating method and the like are known. Fe-based nanocrystalline alloy is a microcrystallized amorphous alloy produced by these methods, has almost no thermal instability as found in amorphous alloys, and is as high as Fe-based amorphous alloys. It is known to exhibit excellent soft magnetic characteristics at a saturation magnetic flux density and low magnetostriction. Furthermore, nanocrystalline alloys are known to have little change over time and excellent temperature characteristics.
It has also been studied to add Co to these Fe-based nanocrystalline alloys.

Japanese Patent Publication No. 4-4393 JP-A-1-242755

However, nanocrystalline FeCuNbSiB-based alloys and nanocrystalline FeNbB alloys have problems such as high Nb, easy reaction with nozzles and melting crucibles when producing amorphous alloys, and material embrittlement. When manufacturing a large amount of material, there are problems in that the crucible life, the nozzle life and the alloy tend to become brittle. In addition, FeZrB-based alloys and FeHfB-based alloys containing Zr and Hf are difficult to manufacture in the atmosphere and have a problem that the nozzle life is short and the productivity is poor.
For these reasons, there has been a strong demand for the appearance of a material having a high saturation magnetic flux density, a low magnetic core loss, and easier manufacturing.

In order to solve the above-mentioned problems, the present inventors have intensively studied and expressed by the general formula: (Fe _1-a Co _a ) _100-y-b-c Mo _y B _b C _c (atomic%). In the formula, a, y, b, and c satisfy 0.2 ≦ a ≦ 0.9 , 5 ≦ y ≦ 15, 2 ≦ b ≦ 15, 2 ≦ c ≦ 15, and 7 ≦ y + b + c ≦ 30, respectively. A soft magnetic alloy having a satisfactory composition and having a part or all of a structure made of body-centered cubic crystal grains having a grain size of 50 nm or less exhibits a high saturation magnetic flux density and a low core loss characteristic. And the present invention has been conceived.

The soft magnetic alloy of the present invention is obtained by quenching a molten metal having the above composition by a super rapid quenching method such as a single roll method, once producing an amorphous alloy, processing it, raising the temperature to a temperature higher than the crystallization temperature, and performing a heat treatment. It is produced by forming microcrystals having an average particle size of 50 nm or less. Although it is desirable that the amorphous alloy before the heat treatment does not contain a crystalline phase, it may contain a crystalline phase in part. Amorphous alloy production by a rapid quenching method such as a single roll method is performed in the atmosphere, Ar, He, or under reduced pressure. Moreover, it may manufacture in the atmosphere containing nitrogen gas, carbon monoxide, or a carbon dioxide gas. The heat treatment is usually performed in an inert gas such as argon gas, nitrogen gas, helium, or in vacuum. In some cases, it may be performed in the atmosphere. Magnetization loop with high or low squareness ratio when induced magnetic anisotropy is applied by applying a magnetic field strong enough to saturate the alloy for at least part of the heat treatment period In particular, when the magnetization loop has a low squareness ratio, the core loss can be further reduced. Although depending on the shape of the alloy magnetic core, in general, a magnetic field of 8 kAm ⁻¹ or more is applied when applied in the width direction of the ribbon (in the case of a wound core, the height direction of the magnetic core). As the magnetic field to be applied, any of direct current, alternating current, and a repetitive pulse magnetic field may be used. A magnetic field is usually applied for 20 minutes or more in a temperature range of 200 ° C. or higher, and when the temperature is raised, kept at a constant temperature and during cooling, the magnetic core loss can be reduced and the squareness ratio can be reduced, and a more preferable result can be obtained. . When the squareness ratio B _r B _s ^-1 is adjusted to 25% or less, a particularly low magnetic core loss is obtained, and a favorable result is obtained in application. Here, B _s is the saturation magnetic flux density.

Usually, the heat treatment is desirably performed in an inert gas atmosphere having a dew point of −30 ° C. or lower. When the heat treatment is performed in an inert gas atmosphere having a dew point of −60 ° C. or lower, a more favorable result can be obtained with less variation. The highest temperature reached during the heat treatment is equal to or higher than the crystallization temperature, and is usually in the range of 350 ° C to 650 ° C. In the case of the heat treatment pattern held at a constant temperature, the holding time at the constant temperature is usually 24 hours or less, preferably 4 hours or less from the viewpoint of mass productivity. The average heating rate during the heat treatment is preferably from 0.1 ° C / min to 200 ° C / min, more preferably from 0.1 ° C / min to 100 ° C / min, and the average cooling rate is preferably 0.1 ° C / min. To 3000 ° C./min, more preferably 0.1 ° C./min to 100 ° C./min. In this range, an alloy having a particularly low magnetic core loss can be obtained. The heat treatment is not limited to a single step, and a multi-step heat treatment or a plurality of heat treatments can be performed. Furthermore, the alloy can be heated and heat-treated by applying a direct current, an alternating current or a pulsed current to the alloy. Moreover, it can also heat-process under stress and can produce anisotropy.
In addition, the soft magnetic alloy of the present invention has a feature that it is less likely to be embrittled when it is made amorphous than an FeCuNbSiB alloy which is a typical nanocrystalline alloy. For this reason, it is suitable for manufacturing a thick plate material or a wide material. Furthermore, since the crucible life at the time of melting and the nozzle life at the time of producing an amorphous alloy are longer than those of an FeCuNbSiB alloy or the like, it is excellent in mass productivity.

In the present invention, the Co amount ratio a needs to satisfy 0.2 ≦ a ≦ 0.9. If a is less than 0.2, it causes an increase in magnetic core loss, which is not preferable. A more preferable range of the Co amount ratio a is 0.2 ≦ a ≦ 0.6. Within this range, the core loss is low, the saturation magnetic flux density is high, and more preferable results are obtained. A particularly preferable range of the Co amount ratio a is 0.3 ≦ a ≦ 0.5. In this range, since the magnetic core loss is particularly low and the saturation magnetic flux density is high, more preferable results can be obtained.
Mo has the effect of refining the crystal grain size and the crystallization temperature, and has the effect of facilitating the formation of amorphous during quenching, and the Mo amount y needs to be 2 atomic% or more and 15 atomic% or less. . If the Mo amount y is less than 5 atomic%, the crystal grains become coarse, which is not preferable. If it exceeds 15 atomic%, the saturation magnetic flux density is significantly increased, which is not preferable. A more preferable amount of Mo is 5 atom% or more and 12 atom% or less. A particularly low core loss is obtained in this range.
The B content b needs to be 2 atomic% or more and 15 atomic% or less. This is not preferable if the amount of B is less than 2 atomic%, and it is not preferable because it is difficult to make the structure fine and sufficient soft magnetic properties cannot be obtained. If the amount of B exceeds 15 atomic%, the magnetic flux density is remarkably lowered. Because. In particular, the B amount b is desirably 4 atomic% or more and 12 atomic% or less. A particularly low core loss is obtained in this range.
The C amount c needs to be 2 atomic% or more and 15 atomic% or less. This is not preferable if the amount of C is less than 2 atomic%, and it is not preferable because the structure is difficult to be refined and sufficient soft magnetic characteristics cannot be obtained. If the amount of C exceeds 15 atomic%, the magnetic flux density is significantly reduced and the soft magnetic characteristics are not preferable. This is because it is not preferable.
The sum y + b + c of Mo, B and C needs to be 10 atom% or more and 30 atom% or less. If it is less than 10 atomic%, since it is difficult to make it amorphous by the ultra-quenching method, non-uniform crystals are likely to be formed, and there is a problem that sufficient soft magnetic properties cannot be obtained even if the crystal grains are subjected to heat treatment. If it exceeds 30 atomic%, the magnetic flux density is significantly reduced, which is not preferable.

In the present invention, substituting 2 atomic percent or less of the total amount of Fe and Co with at least one element selected from Cu and Au can further reduce the magnetic core loss and obtain a preferable result. This is not preferable because it becomes brittle.
Further, a part of Mo is Ni, Cr, Mn, V, Nb, Ta, Ti, Zr, Hf, W, Sn, Zn, In, Ag, Sc, white metal element, Mg, Ca, Sr, Y, rare earth Substitution with at least one element selected from the elements N, O and S can be expected to improve corrosion resistance, expand the heat treatment temperature range, and refine the structure.
When a part of C is replaced with at least one element selected from Si, Ge, Ga, Al, Be and P, magnetostriction can be adjusted and high frequency characteristics can be improved.

  In the present invention, when at least part or all of the remainder other than the body-centered cubic structure crystal grains is in an amorphous phase, high resistivity and fine crystal grains can be realized, and magnetic core loss at high frequencies is reduced. More favorable results are obtained. The average crystal grain size of the body-centered cubic crystal grains needs to be 50 nm or less. This is because if the average grain size of the body-centered cubic crystal grains exceeds 50 nm, the soft magnetic characteristics are significantly deteriorated.

The soft magnetic alloy of the present invention is formed by coating the surface of the alloy ribbon with a powder or a film of SiO ₂ , MgO, Al ₂ O ₃ or the like as necessary, forming a surface treatment by chemical conversion treatment, and forming an insulating layer. More preferable results can be obtained by performing a process such as forming an oxide insulating layer on the surface and performing interlayer insulation. This is because, in particular, the effect of eddy currents at high frequencies across the layers is reduced, and the magnetic core loss at high frequencies is improved. This effect is particularly remarkable when used in a magnetic core having a good surface state and a wide ribbon. Furthermore, impregnation and coating can be performed as necessary when producing a magnetic core from the alloy of the present invention.
The soft magnetic alloy of the present invention exhibits the best performance for high frequency applications, but can also be used for applications of sensors and low frequency magnetic components. In particular, it can exhibit excellent characteristics in applications where magnetic saturation is a problem. The alloy of the present invention, which is heat-treated while applying a magnetic field in a direction substantially perpendicular to the direction of magnetization when in use, has a lower core loss than a conventional ribbon material having a high saturation magnetic flux density. The alloy of the present invention can obtain excellent characteristics even in a thin film or powder.
The soft magnetic alloy of the present invention is less likely to be magnetically saturated even when a large magnetic field is applied, and is suitable for use in power electronics having a relatively large capacity.

Crystal grains having an average grain size of 50 nm or less are formed on at least part or all of the soft magnetic alloy of the present invention. The crystal grains preferably have a ratio of 30% or more of the structure, more preferably 50% or more, and particularly preferably 60% or more. A particularly desirable average crystal grain size is 5 nm to 30 nm, and a particularly low magnetic core loss is obtained in this range.
The crystal grains formed in the above-described soft magnetic alloy of the present invention have a body-centered cubic (bcc) crystal phase mainly composed of FeCo, and dissolve Si, B, Al, Ge, C, Mo, etc. May be. Further, a regular lattice may be included. The balance other than the crystalline phase is mainly an amorphous phase, but an alloy consisting essentially of the crystalline phase is also included in the present invention. In the case of an alloy containing Cu or Au, there may be a face-centered cubic phase (fcc phase) partially containing Cu or Au.
When the compound phase is not present in the soft magnetic alloy of the present invention, the magnetic core loss is lower, but the compound phase may be partially included.

  According to the present invention, various types of reactors for large currents, choke coils for active filters, smooth choke coils, various transformers, noise shielding parts such as electromagnetic shield materials, laser power supplies, pulse power magnetic parts for accelerators, motors, generators Soft magnetic magnetic alloy containing nanoscale fine crystal grains with high saturation magnetic flux density, low magnetic core loss, and easier manufacturing during manufacturing, and high-performance magnetic parts using the same can be realized The effect is remarkable.

  The present invention will be described below with reference to examples, but the present invention is not limited thereto.

A molten alloy of (Fe _0.6 Co _0.4 ) _bal. Mo ₇ B ₉ C ₉ (atomic%) was rapidly cooled by a single roll method to obtain an amorphous alloy ribbon having a width of 5 mm and a thickness of 18 μm. The amorphous alloy ribbon was wound around an outer diameter of 19 mm and an inner diameter of 15 mm to produce a toroidal magnetic core.
The produced magnetic core was inserted into a heat treatment furnace in a nitrogen gas atmosphere, and heat treatment was performed with the heat treatment pattern shown in FIG. During the heat treatment, a magnetic field of 280 kAm ⁻¹ was applied in a direction perpendicular to the magnetic path of the alloy magnetic core (in the width direction of the alloy ribbon), that is, in the height direction of the magnetic core. The alloy after the heat treatment is crystallized, and as a result of electron microscope observation, most of the structure is composed of fine body-centered cubic crystal grains having a grain size of about 10 to 20 nm, and the proportion of crystal grains is estimated to be about 72%. It was lost. The remaining matrix phase was mainly an amorphous phase. FIG. 2 shows an X-ray diffraction pattern. For comparison, an X-ray diffraction pattern after a similar heat treatment is performed on an alloy of Fe _bal. Mo ₅ B ₉ C ₉ (atomic%) that does not contain Co outside of the present invention. In the alloy of the present invention, a crystal peak indicating a FeCo phase having a body-centered cubic structure was observed, and a peak indicating a compound phase was hardly observed. In contrast, the Fe _bal. Mo ₅ B ₉ C ₉ (atomic%) alloy that does not contain Co outside of the present invention has many crystal peaks indicating the presence of a compound phase in addition to the FeCo phase having a body-centered cubic structure. It was.

Then, the DC B-H loop of the alloy magnetic core, 100kHz, was measured core loss _{P cv} at 0.2T. FIG. 3 shows the direct current B-H loop, and Table 1 shows the results obtained. For comparison, Table 1 shows the magnetic properties of the Fe _bal. Mo ₅ B ₉ C ₉ (atomic%) alloy that does not contain Co and is not subjected to the same heat treatment. _{B s} of the present invention the alloy magnetic core is beyond the 1.4 T. On the other hand, P _cv of the alloy of the present invention was 300 kWm ⁻³ , which was significantly lower than P _cv = 12600 kWm ^{−3 of the} Fe _bal. Mo ₅ B ₉ C ₉ (atomic%) alloy containing no Co. The coercive force Hc, as well as the core loss, showed a significantly lower value for the alloy of the present invention.

A molten alloy having a composition represented by the general formula: (Fe _1-a Co _a ) _bal. Mo ₅ B ₉ C ₉ (atomic%) is rapidly cooled by a single roll method to form an amorphous alloy thin film having a width of 5 mm and a thickness of 18 μm. I got a belt. The amorphous alloy ribbon was wound around an outer diameter of 19 mm and an inner diameter of 15 mm to produce a toroidal magnetic core. This alloy magnetic core was heat-treated with the same heat-treatment pattern as in Example 1 and subjected to magnetic measurements. Crystal grains were formed in the structure of the alloy after the heat treatment, but when the Co amount a was 0.1 or more, the average crystal grain size was reduced and crystal grains of 50 nm or less were formed. FIG. 4 shows the Co amount a dependence of the core loss P _cv per unit volume at saturation magnetic flux density B _s , squareness ratio B _r / B _s , 100 kHz, 0.2 T. The saturation magnetic flux density B _s is high at 0.1 ≦ a ≦ 0.6. Particularly high Bs was obtained with 0.2 ≦ a ≦ 0.5. The squareness ratio B _r B ₈₀₀₀ ⁻¹ indicates a low value of Co amount ratio of 0.2 to 40%. P _cv decreases when the Co amount ratio a is 0.1 or more. It can be seen that it is significantly more preferable at 0.2 or more, which is more preferable.

The molten alloy having the composition shown in Table 2 was rapidly cooled by a single roll method to produce an amorphous alloy ribbon having a width of 25 mm and a thickness of 18 μm. The amorphous alloy ribbon was wound around an outer diameter of 19 mm and an inner diameter of 15 mm to produce a toroidal magnetic core. The alloy magnetic core was heat-treated with the heat treatment pattern shown in FIG. The magnetic field application direction during the heat treatment was applied in a direction perpendicular to the magnetic path of the magnetic core (alloy ribbon width direction). In the alloy after the heat treatment, crystal grains composed of an extremely fine bcc phase having a grain size of 50 nm or less were formed. DC B-H loop of the alloy magnetic core after heat treatment, 100kHz, was measured core loss _{P cv} at 0.2T. Table 2 shows the results obtained. Since the alloy of the present invention has a high saturation magnetic flux density and low magnetic core loss, it is suitable for a high frequency choke coil for high power applications, a magnetic core material for transformers, a core material for pulse power, and the like. On the other hand, the nanocrystalline alloy containing Co outside of the present invention has a large magnetic core loss and inferior characteristics in the high frequency region.

An amorphous alloy ribbon having the composition shown in Table 3 having a thickness of 25 μm was produced, and the ratio of the embrittled portion was determined. It cut | disconnected to 200 mm length, torn 20 amorphous alloy ribbons, and calculated | required the ratio of the location broken brittlely, and made it the brittleness rate. The results are shown in Table 3. In addition, an amorphous alloy ribbon having the composition shown in Table 3 was repeatedly produced, and the number of times until immediately before the nozzle could not be used was determined to determine the nozzle life. The results are also shown in Table 3.
The brittleness rate of the amorphous alloy ribbon used in the alloy of the present invention is lower than that of the amorphous alloy used in the conventional nanocrystalline alloy, and it is easy to process into parts and is excellent. In addition, the nozzle life can be extended and the mass productivity is excellent.

A molten alloy of (Fe _0.6 Co _0.4 ) _bal. Cu ₁ Mo ₅ B ₉ C ₉ (atomic%) was rapidly cooled by a single roll method to obtain an amorphous alloy ribbon having a width of 25 mm and a thickness of 18 μm. . The amorphous alloy ribbon was wound to produce a toroidal magnetic core. This alloy magnetic core was heat-treated in a magnetic field while applying a magnetic field in the height direction of the magnetic core (alloy ribbon width direction). The heat treatment was performed in the same pattern as in Example 1, and the magnetic field was applied for the entire period. This alloy was confirmed by transmission electron microscopy and X-ray diffraction to form body-centered cubic crystal grains having a particle diameter of 10 to 20 nm. Also, the DC magnetic properties and 100kHz, was measured core loss _{P cv} at 0.2T. The squareness ratio B _r B _s ⁻¹ was 2%, and P _cv was 310 kWm ⁻³ . Next, a primary winding and a secondary winding were provided on this magnetic core to constitute an inverter transformer. For comparison, an inverter transformer having the same shape was made of silicon steel, and the temperature rise was measured. The temperature rise of the transformer made from the alloy of the present invention is 36 ° C., the temperature rise of the transformer made of silicon steel is 45 ° C., and the magnetic part of the present invention constructed from the alloy of the present invention has lower loss, lower temperature rise, and excellent ing. A smooth choke coil was produced using the same material and evaluated by comparing with a choke coil made of silicon steel. As a result, the temperature increase of 6 ° C. was lower in the choke coil of the present invention.

  According to the present invention, various types of reactors for large currents, choke coils for active filters, smooth choke coils, various transformers, noise shielding parts such as electromagnetic shield materials, laser power supplies, pulse power magnetic parts for accelerators, motors, generators Soft magnetic magnetic alloy containing nanoscale fine crystal grains with high saturation magnetic flux density, low magnetic core loss, and easier manufacturing during manufacturing, and high-performance magnetic parts using the same can be realized The effect is remarkable.

It is the figure which showed an example of the heat processing pattern concerning this invention. It is the figure which showed an example of the X-ray-diffraction pattern of the alloy concerning this invention. It is the figure which showed an example of the direct current | flow BH loop of the alloy concerning this invention. Saturation magnetic flux density _{B s} of the alloy according to the present invention and shows squareness ratio _B r / _{B s,} 100kHz, the Co amount a dependence of the core loss P _cv per unit volume in the 0.2T.

Claims (7)

General formula: (Fe _1-a Co _a ) _100-y-b-c Mo _y B _b C _c (atomic%), where a, y, b, and c are 0.2 ≦ a ≦ 0, respectively. .9 , 5 ≦ y ≦ 15, 2 ≦ b ≦ 15, 2 ≦ c ≦ 15, and 10 ≦ y + b + c ≦ 30, and part or all of the structure has an average particle size of 50 nm or less A soft magnetic alloy comprising crystal grains having a body-centered cubic structure. The soft magnetic alloy according to claim 1, wherein the B content is 4 atomic% or more and 12 atomic% or less. 3. The soft magnetic alloy according to claim 1, wherein at least a part or all of the remainder other than the body-centered cubic crystal grains is an amorphous phase. 4. The soft magnetic alloy according to any one of claims 1 to 3 , wherein 2 atomic percent or less of the total amount of Fe and Co is substituted with at least one element selected from Cu and Au. Part of Mo is Ni, Cr, Mn, V, Nb, Ta, Ti, Zr, Hf, W, Sn, Zn, In, Ag, Sc, white metal element, Mg, Ca, Sr, Y, rare earth element, The soft magnetic alloy according to any one of claims 1 to 4 , wherein the soft magnetic alloy is substituted with at least one element selected from N and O. A part of C Si, Ge, Ga, Al , soft magnetic alloy according to any one of claims 1 to 5, characterized in that substituted with at least one element selected from Be and P. A magnetic component comprising the soft magnetic alloy according to any one of claims 1 to 6 .

Images