JPH039174B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an alloy for permanent magnets containing Cu, Fe, and Ge as main components and a method for producing the alloy powder for bonded magnets. [Prior art and its problems] Typical conventional permanent magnet materials include alnico, hard ferrite, and rare earth magnets.
The demand for alnico magnets containing 20 to 30 wt.% cobalt has been gradually decreasing due to the instability of the cobalt raw material situation in recent years, and cheap hard ferrite, whose main component is iron oxide, is the mainstream magnet material. It has come to occupy a large part of the country. On the other hand, since rare earth magnets have much higher magnetic properties than other magnets, they have come to be used mainly in small, high-value-added magnetic circuits. However, rare earth magnets are very expensive because they use alloying elements such as Sm, Nd, and Gd, which are not often contained in rare earth ores, and there is also the problem that they are very easy to oxidize when made into alloy powder for magnets. . In other words, at present, no technology has been established to easily and inexpensively separate the various rare earth elements in rare earth ores, and rare earth element powders have particularly strong oxidizing properties. Since there is no established technology for producing oxidation-resistant powder using rare earth powder as a raw material, there has been a problem in stably supplying rare earth magnets as bonding magnets. [Object of the Invention] The object of the present invention is to provide a new bonded permanent magnet that can replace the rare earth magnets described above. In particular, it is an object of the present invention to obtain a magnet alloy powder that can avoid the problem of oxidation of the powder when obtaining a bonding magnet and has excellent magnetic properties such as coercive force. [Structure of the Invention] The present invention comprises Cu of 20 to 85 wt.% and Cu of 2 to 45 wt.%.
A novel magnetic alloy consisting of Fe, 2 to 30 wt.% Ge, and unavoidable impurities is provided. The present invention also includes 20-85 wt.% Cu, 2-45 wt.
% Fe, 2-30wt.% Ge, and further 0.33-15wt.
% of Cr or 0.1 to 3.0 wt. % of Mn, with the remainder being unavoidable impurities. The alloy of the present invention can reach a maximum energy product (BH) max of 5 MGOe and a coercive force of 4 KOe in a preferred composition range, and provides a new high-grade permanent magnet that can replace conventional rare earth magnets. In particular, the alloy of the present invention is suitable for manufacturing bonded magnets in which the powder is dispersed in a medium such as a resin, and the oxidation problem that occurs with rare earth magnet powders can be substantially avoided. This alloy has a main phase of 15μm to 70μm depending on casting.
It is possible to obtain a cast alloy consisting of an alloy phase consisting of a tetragonal phase. In addition, an aggregate powder suitable for bonded magnets can be produced from the powder of this alloy through appropriate molding and crushing steps and heat treatment steps. The alloy of the present invention has a ternary system of Cu-Fe-Ge as its basic component system, but Cr and Mn can also be added to this basic ternary system. In this case, for Cr
It is preferable to add Mn in an amount of 0.33 to 15 wt.%, and Mn in an amount of 0.1 to 3.0 wt.%. [Detailed description of the invention] Cu, Fe, and Ge have good magnetic properties as permanent magnets.
To find for a magnet whose main alloy component is,
Coercive force (Hc) and maximum energy product (BH) max
It is necessary to find an alloy component ratio that can achieve the highest value. In order to increase the coercive force (Hc), it is necessary that the residual magnetism of the magnet is not weakened by demagnetizing force, and to achieve this, it is necessary to make it difficult for the magnetic direction of the many magnetic domains to change. . In other words, it is only necessary to find a basic alloy component ratio that allows the movement of the domain wall to occur due to disorder of the atomic arrangement. Also, the maximum energy product (BH) max
In order to improve the magnetic anisotropy, it is sufficient to increase the magnetic anisotropy, and for this purpose, it is necessary to develop a manufacturing technique that does not cause a decrease in coercive force. Fe is an elastomagnetic element that enhances the magnetic properties of the alloy, which is ensured by four spin-parallel electrons in a 3D irregular orbit, and the crystal structure is a body-centered cubic crystal. Cu is a diamagnetic element with a face-centered cubic crystal structure, and its magnetic susceptibility (x) is -7.6×10 ^-7 emu.
Forms a continuous solid solution with Fe. Ge is a cubic diamagnetic element with a diamond structure, and its magnetic susceptibility (x) is -0.122×
10 ^-6 emu. Ge means Fe, FeGe ₂ , Fe ₃ Ge,
Forms compounds such as FeGe. Also, what is Cu?
Create cubic crystal compounds such as Cu ₃ Ge. _FeGe2 ,
Fe ₃ Ge, FeGe, and Cu ₃ Ge all have a cubic crystal structure and do not exhibit high magnetic properties, but Cu−Fe−
In the Ge system, the crystal phase changes, Cu20~85wt.%, Fe2~
At 45wt.% and Ge2 to 30wt.%, it becomes a tetragonal phase and exhibits high magnetic properties. In other words, Cu20~85wt.%, Fe2~45wt.%,
High magnetic properties can be obtained when Ge is mixed in a limited amount from 2 to 30 wt.%. Cu is an essential element in the magnet alloy of the present invention, and if Cu is less than 20 wt.%, high coercive force (Hc) cannot be obtained. On the other hand, if Cu exceeds 85 wt.%, the residual magnetic flux density (Br) decreases, making it impossible to obtain an excellent permanent magnet. Therefore, it is necessary to contain Cu in the range of 20wt.% to 85wt.%. Fe is an essential element in the magnet alloy of the present invention, and if Fe is less than 2wt.%, the residual magnetic flux density (Br) decreases. On the other hand, if Fe exceeds 45 wt.%, high coercive force (Hc) cannot be obtained. Therefore, Fe is 2wt.
The content should be between % and 45wt.%. Ge is an essential element in the magnet alloy of the present invention. If Ge is less than 2wt.%, it becomes a cubic phase and high coercive force (Hc) cannot be obtained, and if Ge exceeds 30wt.%, residual magnetic flux density (Br ) decreases, making it impossible to obtain an excellent permanent magnet. Therefore, Ge is 2wt.%
Contain in the range of ~30wt.%. In addition, at least one of Cr, Mn, Co, and Ni
By adding more than one species in an amount of 0.2 to 15 wt.%, more specifically, Cr in an amount of 0.33 to 15 wt.% and Mn in an amount of 0.1 to 3.0 wt.%,
It is possible to improve coercive force, etc., improve manufacturability, lower price, and improve oxidation resistance of Cu-Fe-Ge bonded magnets. However, if Cr or Mn is added in excess of the above-mentioned range, the residual magnetic flux density (Br) will decrease due to the addition to improve the coercive force, so there is naturally a limit to the amount of these elements added. If the upper limit value of each element is the above-mentioned value, the residual magnetic flux density can be made equal to or higher than the residual magnetic flux density of a conventional hard ferrite magnet, and it becomes possible to increase the coercive force of the bonded magnet. In addition, when two or more of these elements are contained, the total maximum content is less than or equal to the content of the one with the maximum value among the added elements, thereby increasing the coercive force of the bonded magnet. It becomes possible. The alloy of the present invention is Cu20~ as a casting alloy.
85wt.%, Fe2 to 45wt.%, Ge2 to 30wt.% and possibly additional 0.33 to 15wt.% Cr or 0.1
Contains one or more types of Mn of ~3.0wt.%, and the main phase is 15μ
It is composed of an alloy phase consisting of a tetragonal phase of m ~ 70 μm, and the maximum energy product (BH) max is 1 ~ 70 μm.
A casting alloy for magnets having a coercivity of 4MGOe (4KOe) is provided. The alloy of the present invention is particularly useful for bonded magnets. According to the present invention, as alloy powder for bonded magnets, 50% fine powder with a particle size of 20 μm or less is aggregated.
Aggregate powders of ~500 μm can be obtained. The method for manufacturing this bonded magnet will be explained below. The aggregate powder for bonded magnets of the alloy of the present invention has a particle size of
It must be composed of fine powder of 20 μm or less.
If it exceeds 20 μm, magnetic domains tend to occur within the crystal grains of individual fine powders, and magnetization reversal occurs, making it impossible to obtain a high coercive force. Further, if the particle size is less than 0.5 μm, the specific surface area increases and it is easily oxidized, making handling somewhat difficult, so a fine powder of 0.5 μm to 20 μm is preferable. The fine powder with this particle size is pressure-molded and then crushed.
Furthermore, by performing heat treatment at 600℃ to 800℃ and then crushing, the surroundings of individual crystal grains are
An aggregate powder covered with a Cu-rich phase is obtained. The particle size of this aggregate powder is preferably about 50 μm to 500 μm. If a magnetic field is applied in a certain direction during pressure molding of this aggregated powder, an alloy powder for magnetically anisotropic magnets can be obtained. Alloy powder can be obtained. The reason why the heating temperature in the heat treatment is set to 600°C to 800°C is to obtain a powder that has a high coercive force and is suitable as a raw material powder for bonded magnets. This is to obtain a eutectic with the compound. This eutectic reaction occurs at around 850°C, but heating above 600°C is required to obtain a coercive force (Hc) of 1 KOe or more. However, if the temperature exceeds 800°C, sintering progresses and subsequent crushing becomes difficult, grain growth occurs and the coercive force decreases. Note that the heat treatment time at this time is appropriately selected depending on the composition, particle size, etc. After this heat treatment, it is preferable to crush the powder into powders of 50 μm to 500 μm. By setting the thickness to 50 μm or more, progress of oxidation during heat treatment can be avoided as much as possible, and handling can be facilitated. However, if the alloy powder for bonded magnets has a particle size exceeding 500 μm, the moldability will be poor and a high filling rate will not be obtained. Therefore, the particle size of the aggregate powder is preferably 50 μm to 500 μm. Thus, according to the invention, 20-85 wt.%
of Cu, 2-45 wt.% Fe, 2-30 wt.% Ge, and in some cases 0.33-15 wt.% Cr or 0.1
A magnetic alloy containing ~3.0wt.% of one or more types of Mn, with the remainder consisting of unavoidable impurities, is cast, and this casting is crushed to obtain a grain size of 20 μm in which the main phase is a tetragonal phase.
A fine powder of 600 m or less is produced, the fine powder is pressure-molded in a magnetic field or in a non-magnetic field, and then crushed.
A method for producing an alloy powder for bonded magnets is provided, which comprises heating at a temperature of .degree. C. to 800.degree. C. and then crushing the powder to an aggregate particle size of 50 .mu.m to 500 .mu.m. By appropriately selecting the type and amount of the binder to be mixed, molded, and solidified with the aggregated powder produced by this method, it is possible to produce a bonded magnet with a desired shape and desired use. . The amount of binder is desirably 30% or less in terms of volume composition in order to express the magnetic properties of the permanent magnet material. The alloy powder of the present invention can be molded without sintering, impregnated with a resin binder and solidified to form a bonded magnet, or the alloy powder can be mixed with an alloy powder binder and molded, and after sintering, this can be heat-treated to create a bonded magnet. You can also get Further, as a molding method, in addition to normal press molding, injection molding, extrusion molding, and isostatic pressing can be employed. The resin used as the binder can be thermosetting or thermoplastic, but thermally stable resins are preferable, such as polyamide, polyimide, phenolic resin, fluororesin, silicone resin, and epoxy. Resin, methyl methacrylate monomer, nylon resin, etc. can be selected as appropriate. In addition, when using something other than synthetic resin as a binder, there are solder alloys such as Al, Sn, and Pb, and in the case of alloys, they are used in powder form. The alloy magnet according to this invention and the bonded magnet using the alloy powder have a maximum energy product (BH)
max is 3 MGOe or more, and in the most preferred composition range (BH) max is 5 MGOe or more. The characteristics of the alloy of the present invention will be explained below using typical examples. Example 1 As a starting material, copper with a purity of 99.99%, purity 99.9
% electrolytic iron and Ge with a purity of 99.999%, these were high-frequency melted in an Ar atmosphere and left to cool in a crucible to produce Cu: 59.2wt.%, Fe:
An ingot with a dendrite structure containing tetragonal crystals as the main phase was obtained with a composition of 36.8 wt.% and Ge: 4.0 wt.%. The composition (weight%) is Cu: 56.7at.%, Fe:
40.0at.%, Ge: 3.3at.%. The obtained ingot is crushed by a crusher for 35
The mixture was coarsely ground to a mesh size or smaller, and then finely ground using a ball mill to obtain a fine powder with an average particle size of 5 μm. This fine powder was charged into a mold, oriented in a magnetic field and pressed at a pressure of 1.5 t·cm ^-2 , and then crushed in a stamp mill to give a particle size of 50 μm to 500 μm. The obtained powder was heated at 750°C for 2 hours in Ar, and then aged in Ar at 600°C for 2 hours, and then crushed. The powder obtained by crushing after this heat treatment was agglomerated powder with a particle size of 50 to 500 μm, which was agglomerated fine powder with an average particle size of 5 μm, and had a coercive force (Hc) of 1.5 KOe. The aggregated powder with the above properties was charged into a mold, oriented in a magnetic field of 5KOe, and molded at a pressure of 2.0t cm ^-2 , then hydrostatically pressed into a mold with a length of 15 mm x width of 10 mm x thickness.
A molded body with a size of 10 mm was produced. Then the molded body
A bonded magnet was obtained by impregnating a methyl methacrylate monomer in a vacuum of 10 ^-3 Torr and heat curing at 100° C. for 1 hour. The magnetic properties of this bonded magnet and the magnetic properties of the cast alloy magnet described above were measured. The results are shown in Table 1. Example 2 Cu: 59.2wt.%, Fe: 36.8wt.% in Example 1.
%, Ge: instead of the composition of 4.0wt.%, Cu:
83.2wt.%, Fe: 2.7wt.%, Ge: 13.8wt.%,
Example 1 was repeated except that a cast alloy magnet with a composition of Mn: 0.3 wt.% was produced. This composition (weight%) is Cu: 84.3 at.%, Fe: 3.1 at.%, Ge:
This corresponds to 12.3at.% and Mn: 0.3at.%. The measurement results of the magnetic properties of this cast alloy and bonded magnet are also listed in Table 1.

[Table] Example 3 As a starting material, copper with a purity of 99.99%, purity 99.7
% electrolytic iron (contains about 0.3% impurities such as nickel, cobalt, manganese, etc.), 99.99% pure germanium, and 99.99% pure chromium as raw materials, which are high-frequency melted in an Ar atmosphere and then water-cooled steel. Cast in a mold, Cu: 32.3wt.%, Fe:
An ingot with a dendrite structure containing tetragonal crystals as the main phase was obtained with a composition of 42.6 wt.%, Ge: 18.5 wt.%, and Cr: 6.6 wt.%. This composition (weight%) is Cu: 30.8at.%,
Corresponds to a composition of Fe: 46.1 at.%, Ge: 15.4 at.%, and Cr: 7.7 at.%. The obtained ingot was coarsely ground to 35 mesh or less using a crusher, and then finely ground using a ball mill to obtain a fine powder with an average particle size of 5 μm. This fine powder was charged into a mold, oriented in a magnetic field of 8 KOe and pressurized with a pressure of 1.5 t·cm ^-2 , and then crushed in a stamp mill to give a particle size of 50 μm to 500 μm. The obtained powder was heated at 750°C for 2 hours in an Ar atmosphere, and then aged in Ar at 600°C for 2 hours, and then crushed to obtain aggregated powder of 50 μm to 500 μm. Ta. The above aggregated powder was coated with methyl methacrylate monomer in a vacuum of 10 ^-3 Torr, taken out from the container, charged into a mold, and oriented in a magnetic field of 8 KOe at 2.0 t.cm ^-2 A bonded magnet was obtained by heating and pressurizing and molding at 100°C. The dimensions of the molded object are the length
It is 15mm x width 10mm x thickness 10mm. The magnetic properties of the above cast alloy magnet, aggregate powder of 50 μm to 500 μm, and bonded magnet were measured, and the second
Obtained the results in the table. Example 4 Cu: 32.3wt.%, Fe: 42.6wt.% in Example 3.
%, Ge: 18.5wt.%, Cr: 6.6wt.%, Cu: 83.2wt.%, Fe: 2.7wt.%, Ge:
Example 3 was repeated except that a cast alloy magnet with a composition of 13.8 wt.%, Mn: 0.3 wt.% was produced. The composition (weight%) is Cu: 84.3at.%, Fe: 3.1at.%.
%, Ge: 12.3at.%, Mn: 0.3at.%. The measurement results of the magnetic properties of the cast alloy, aggregated powder, and bonded magnet are also listed in Table 2.

【table】

Claims (1)

[Claims] 1 20-85 wt.% Cu, 2-45 wt.% Fe, 2-
Magnetic alloy consisting of 30wt.% Ge and unavoidable impurities. 2 20~85wt.% Cu, 2~45wt.% Fe, 2~
Contains 30wt.% Ge, and further contains 0.33-15wt.%
A magnetic alloy containing one or more of Cr or 0.1 to 3.0 wt.% Mn, with the remainder consisting of unavoidable impurities. 3 20~85wt.% Cu, 2~45wt.% Fe, 2~
Contains 30wt.% Ge, and in some cases
0.33~15wt.% Cr or 0.1~3.0wt.% Mn 1
A magnetic alloy containing at least 10% of the species and the remainder consisting of unavoidable impurities is cast, and this casting is pulverized to produce a fine powder with a grain size of 20 μm or less whose main phase is a tetragonal phase, and the fine powder is placed in a magnetic field. Alternatively, a method for producing an alloy powder for bonded magnets, which comprises pressure forming in a non-magnetic field, crushing, further heating at 600°C to 800°C, and then crushing to an aggregate particle size of 50 μm to 500 μm.