JPH0576521B2 - - Google Patents

Description

[Detailed description of the invention]

Field of Application The present invention relates to a method for producing Fe-BR permanent magnet material, in which at least one part of the surface of a sintered permanent magnet is
The present invention relates to a method for manufacturing Fe-BR permanent magnet material that prevents deterioration of magnetic properties due to black scale remaining on the main surface or grinding of the magnet surface, and further improves the corrosion resistance of the magnet material. BACKGROUND ART Current representative permanent magnet materials are alnico, hard ferrite and rare earth cobalt magnets. This rare earth cobalt magnet has extremely excellent magnetic properties and is used for a variety of purposes, but the main components, Sm and Co, are both scarce and expensive, so they will not be used for a long time. , it is difficult to stably supply it in large quantities. Therefore, there has been a strong desire for a permanent magnet material that has excellent magnetic properties, is inexpensive, and is composed of constituent elements that are abundant in resources and can be stably supplied in the future. The applicant has previously proposed a new high-performance permanent magnet that does not contain expensive Sm or Co.
proposed a permanent magnet (at least one rare earth element containing Y) (Japanese Patent Application Laid-Open No. 59-46008,
No. 59-64733, JP-A-59-89401, JP-A-59-
No. 132104). This permanent magnet is made of Nd or Pr as R.
Using light rare earths, which are rich in resources, mainly
B, 25MGOe or more with Fe as the main component, at the highest
It is an excellent permanent magnet that exhibits an extremely high energy product reaching over 45MGOe. Recently, with the improvement in performance and miniaturization of magnetic circuits,
Fe-BR-based permanent magnet materials have been attracting more and more attention. To manufacture permanent magnet materials for such uses,
In order to remove irregularities and distortions on the surface of a sintered magnet that has been shaped and sintered, to remove a surface oxidation layer, and to incorporate it into a magnetic circuit, it is necessary to cut the entire surface or the required surface of the magnet body. For processing, we use external blade cutting machines, internal blade cutting machines, surface grinding machines,
Centerless grinders, wrapping machines, etc. are used. However, when Fe-BR-based permanent magnet material is ground using the above-mentioned device, the Fe-BR-based permanent magnet material is extremely easily oxidized in the air as a main component, and immediately produces stable oxides. Since it contains rare earth elements and iron, it generates heat and an oxide layer is formed due to contact with the atmosphere and the machined surface, resulting in a problem of deterioration of magnetic properties. In addition, when a permanent magnet made of an Fe-BR-based magnetically anisotropic sintered body is incorporated into a magnetic circuit, oxides generated on the magnet surface may cause a decrease in the output of the magnetic circuit and variations between the magnetic circuits. There was also the problem of contamination of peripheral equipment due to shedding of surface oxides. Therefore, in order to improve the corrosion resistance of the above-mentioned Fe-BR-based permanent magnet, the applicant first developed a permanent magnet whose surface was coated with a corrosion-resistant metal plating layer by electroless plating or electrolytic plating. (Special application 1982-
162350) and a permanent magnet whose surface was coated with a corrosion-resistant resin layer by spraying or dipping (Japanese Patent Application No. 171907/1982). However, in the former plating method, since the permanent magnet body is a porous sintered body, acidic or alkaline solutions remain in the holes during plating pretreatment, and there is a risk of rusting over time. In addition, since the chemical resistance of the magnet body is poor, the magnet surface is corroded during plating, resulting in poor adhesion and corrosion resistance. Furthermore, since resin coating using the latter spray method is directional, it takes a lot of steps and effort to apply a uniform resin coating to the entire surface of the object to be treated, especially on irregularly shaped magnets with complex shapes. It is difficult to apply a thick coating, and the dipping method results in uneven resin coating thickness, resulting in poor product dimensional accuracy. Purpose of the invention The present invention improves the deterioration of magnetic properties caused by cutting of a sintered magnet body in a new permanent magnet material whose main components are rare earth elements, boron, and iron. The object of the present invention is to provide a method for producing a permanent magnet material on which a corrosion-resistant thin film layer with excellent adhesion and corrosion resistance is deposited without using or contacting the material. Structure and Effects of the Invention This invention provides R (R is at least one of Nd, Pr, Dy, Ho, Tb, or furthermore, La, Ce, Sm, Gd,
At least one of Er, Eu, Tm, Yb, Lu, Y
(consisting of seeds) 10 atomic% ~ 30 atomic%, B2 atomic% ~
Hard powder with a Mohs hardness of 5 or more is injected together with pressurized gas onto the surface of a sintered permanent magnet body whose main components are 28 at% and 65 at% to 80 at% of Fe and whose main phase is tetragonal. This is a method for producing a permanent magnet material, characterized in that after removing the surface layer, an Al thin film layer is deposited on the surface of the magnet body. To describe it, the present invention provides the following features:
Hard powder with desired properties is injected together with pressurized gas to remove surface layers such as black crust, oxidation layer, and strained layer from the sintered magnet, and then an Al thin film layer is applied to the cleaned magnet surface. This is intended to improve the deterioration of magnetic properties caused by oxidation and cutting, as well as to improve the adhesion between the material and the surface thin film layer, as well as the corrosion resistance of the material. In addition, the permanent magnet material of the present invention has a compound having a tetragonal crystal structure with an average crystal grain size in the range of 1 to 80 μm as the main phase, and a nonmagnetic phase (oxide (excluding phases). The manufacturing method of this invention uses resource-rich light rare earths such as Nd and Pr as R, and B,
25MGOe or more with Fe as the main component, at the highest
It is an excellent permanent magnet that exhibits an extremely high energy product exceeding 45MGOe, high residual magnetic flux density, and high coercive force.Al Fe-BR with a thin film stably adhered to the surface
permanent magnet materials can be obtained at low cost. In this invention, hard powders having a Mohs hardness of 5 or more include Al ₂ O ₃ based, silicon carbide based, ZrO ₂ based,
There are boron carbide-based powders, garnet-based powders, etc., and Al ₂ O _3- based powders with high hardness are preferred. If the Mohs hardness of the hard powder is less than 5, the grinding force is too small and the grinding process takes a long time, which is not preferable. In this invention, the average grain size of the hard powder is 20μ
m to 350 μm is preferable; if it is less than 20 μm, the grinding force is too small and it takes a long time to grind;
If it exceeds m, the surface roughness of the sintered magnet surface will become too rough and the amount of grinding will become non-uniform, which is not preferable. The injection conditions for hard powder are a pressure of 1.0Kg/cm ²
If the grinding process is less than
If it exceeds 6.0Kg/cm ² , the amount of grinding on ^the magnet surface will become uneven ^, and there is a concern that the surface roughness will deteriorate. preferable. Furthermore, if the injection time is less than 0.5 minutes, the amount of grinding will be small and uneven, and if it exceeds 60 minutes, the amount of grinding on the magnet surface will increase and the surface roughness will worsen. A preferred injection time is . In addition, air or an inert gas such as Ar or _N2 gas can be used as the pressurized fluid for injecting the hard powder, but in order to prevent oxidation of the magnet body, an inert gas is preferable. If used, it is desirable to use dehumidified air. In this invention, in order to deposit an Al layer on the cleaned surface of the sintered magnet from which the oxidized surface phase has been removed,
Thin film forming methods such as vacuum evaporation, sputtering, and ion plating can be selected and used as appropriate. In addition, the thickness of the thin film layer is determined by taking into account peeling of the thin film layer, reduction in mechanical strength, and ensuring corrosion resistance.
A thickness of 30 μm or less is preferred, most preferably 5 μm.
The layer thickness is from m to 25 μm. Reason for limiting the components of the permanent magnet material Rare earth element R used in the permanent magnet material of this invention
accounts for 10 to 30 atom% of the composition, but Nd,
At least one of Pr, Dy, Ho, To, or additionally Lu, Ce, Sm, Gd, Er, Eu, Tm,
Those containing at least one of Yb, La, and Y are preferred. Further, although it is usually sufficient to use one type of R, in practice, a mixture of two or more types (mitsumetal, dididium, etc.) can be used for reasons such as convenience of availability. Note that R does not need to be a rare earth element, and may contain impurities that are unavoidable in production within an industrially available range. R is an essential element in the new above-mentioned permanent magnet material, and if it is less than 10 atomic %, the crystal structure becomes cubic, which is the same structure as α-iron, so high magnetic properties, especially high coercive force, can be obtained. If the R-rich content exceeds 30 atom %, the non-magnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent properties cannot be obtained. Therefore, the rare earth element is in the range of 10 atomic % to 30 atomic %. B is a permanent magnet material according to the present invention,
It is an essential element, and if it is less than 2 atomic %, the rhombohedral structure becomes the main phase and high coercive force (iHc) cannot be obtained, and if it exceeds 28 atomic %, the B-rich nonmagnetic phase increases and the residual magnetic flux is Because the density (Br) decreases,
An excellent permanent magnet cannot be obtained. Therefore, B is
The content should be in the range of 2 atomic % to 28 atomic %. Fe is an essential element in the new above-mentioned permanent magnet.If it is less than 65 at%, the residual magnetic flux density (Br) decreases, and if it exceeds 80 at%, high coercive force cannot be obtained. atomic% ~ 80 atomic%
Contains. Further, in the permanent magnet material according to the present invention,
Replacing a portion of Fe with Co can improve the temperature characteristics of the obtained magnet without impairing its magnetic properties, but if the Co substitution amount exceeds 20% of Fe, the magnetic properties is undesirable because it causes deterioration. Co substitution amount is 5 atomic% or more in total amount of Fe and Co
In the case of 15 atomic %, (Br) increases compared to the case without substitution, which is preferable for obtaining a high magnetic flux density. Further, the permanent magnet material according to the present invention has R,
In addition to B and Fe, the presence of unavoidable impurities in industrial production can be tolerated, but a part of B can be replaced by 4.0 atom% or less of C, 3.5 atom% or less of P, 2.5 atom% or less of S, 3.5
By substituting at least one type of Cu in a total amount of 40 atomic % or less, it is possible to improve the manufacturability of permanent magnets and reduce the cost. In addition, at least one of the following additive elements has a coercive force for the R-B-Fe permanent magnet,
Improving the squareness of the demagnetization curve or improving manufacturability,
It can be added because it is effective in reducing costs. However, addition to improve coercive force causes a decrease in residual magnetic flux density (Br), so it is desirable to add in a range that is equal to or higher than the residual magnetic flux density of conventional hard ferrite magnets. Al less than 9.5 atom%, Ti less than 4.5 atom%, V less than 9.5 atom%, Cr less than 8.5 atom%, Mn less than 8.0 atom%, Bi less than 5.0 atom%, Mb less than 9.5 atom%, 9.5 Ta less than 9.5 atom%, Mo less than 9.5 atom%, W less than 9.5 atom%, Sb less than 2.5 atom%, Ge less than 7 atom%, Sn less than 3.5 atom%, Zr less than 5.5 atom%, 9.0 atom % or less Ni, 9.0 atomic % or less Si, 1.1 atomic % or less Zn, 5.5 atomic % or less Hf.However, if two or more types are contained, the maximum content is By including the additive element having the maximum value at atomic % or less, it is possible to increase the coercive force of the permanent magnet. It is essential that the main crystalline phase be tetragonal in order to produce a sintered permanent magnet with superior magnetic properties than a fine and uniform alloy powder. Further, the permanent magnet of the present invention can be press-molded in a magnetic field to obtain a magnetically anisotropic magnet, and can be press-molded in a non-magnetic field to obtain a magnetically isotropic magnet. The permanent magnet material according to this invention has a coercive force iHc≧
1KOe, residual magnetic flux density Br>4kG, and the maximum energy product (BH) max is (BH)max≧10MGOe in the most preferable composition range, and the maximum value reaches 25MGOe or more. In addition, when the main component of R in the permanent magnet material of this invention is 50% or more of light rare earth metals mainly consisting of Nd and Pr, R12 atomic% to 20 atomic%, B4 atomic% to 24 atomic%, Fe74 When the main component is (BH) max35MGOe or more, it shows excellent magnetic properties, especially light rare earth metals such as Nd
In this case, the maximum value reaches 45MGOe or more. Examples Example 1 As starting materials, electrolytic iron with a purity of 99.9%, ferroboron alloy, and Nd with a purity of 99.7% or more are used. After mixing these, they are high-frequency melted, and then cast in a water-cooled copper mold to produce a product of 16.0Nd7.0B77. An ingot with a composition of 0Fe was obtained. Thereafter, this ingot was coarsely ground using a stamp mill, and then finely ground using a ball mill to obtain a fine powder with an average particle size of 2.8 μm. This fine powder was inserted into a mold, oriented in a magnetic field of 15 kOe, and molded at a pressure of 1.2 t/cm ² in a direction parallel to the magnetic field. The obtained molded body was sintered at 1100°C for 1 hour in an Ar atmosphere to obtain a size of 25 mm in length x 40 mm in width x thickness.
A sintered body with a size of 30 mm was obtained. Furthermore, two-stage aging treatment was performed in Ar at 800°C for 1 hour and at 630°C for 1.5 hours. The above permanent magnet was cut into a size of 5 mm in length, 10 mm in width, and 3 mm in thickness using a #200 diamond as a grindstone at a rotation speed of 2400 rpm and a feed rate of 5 mm/min in the atmosphere. Furthermore, this cut sample had an average particle size of 50 μm,
Using Al ₂ O ₃ hard powder with Mohs hardness of 12, pressure 3.0
Grit blasting was performed for 15 minutes with pressurized gas of Kg/cm ² and N ₂ gas to remove the surface layer of the magnet. Next, in a vacuum container with a vacuum degree of 5 × 10 ^-5 Torr,
Place the above sample, supply Ar gas, and
After discharging for 20 minutes at a voltage of 400 V in Ar gas at 10 ^-2 Torr, a 99.99% pure Al plate was used as the coating material and heated.
The evaporated Al was ionized, and these ionized particles were attracted by the electric field and adhered to the test piece constituting the cathode, forming an Al thin film. The thickness of the thin film formed on the surface of the test piece was 20 μm. The above ion plating conditions are
The treatment was at 1.5 kV for 15 minutes. This test piece was subjected to a corrosion resistance test and a thin film adhesion strength test after the corrosion resistance test. In addition, the magnetic properties before and after the corrosion resistance test were measured. The test results and measurement results are shown in Table 1. For comparison, the above test piece was solvent degreased for 3 minutes with trichloride, 60°C with 5% NaOH,
After degreasing with alkaline for 3 minutes, pickling with 2% HCl at room temperature for 10 seconds and reducing the current density in Watts bath.
Electric nickel plating was carried out under the conditions of 4 A/dm ² , bath temperature of 60° C., and 20 minutes to obtain a comparative test piece (comparative example) having a 20 μm thick nickel plating layer on the surface. This test piece was subjected to the same tests and measurements as in Example 1 above, and the results are also shown in Table 1. The corrosion resistance test was performed by evaluating the appearance of the test piece after it was left in an atmosphere of 60° C., 90% humidity, and 90% humidity for 500 hours. Further, the adhesion strength test was evaluated by breaking the above-mentioned test piece after the corrosion resistance test and observing the fracture surface.

[Table] As is clear from Table 1, the method of the present invention improves the deterioration of magnetic properties caused by cutting or cutting, and also provides a permanent magnet with excellent corrosion resistance. Ru.

Claims (1)

[Claims] 1 R (R is at least one of Nd, Pr, Dy, Ho, Tb, or in addition, La, Ce, Sm, Gd,
At least one of Er, Eu, Tm, Yb, Lu, Y
(consisting of seeds) 10 atomic% ~ 30 atomic%, B2 atomic% ~
The main components are 28 at%, Fe65 at% to 80 at%,
On the surface of a sintered permanent magnet whose main phase is tetragonal,
A method for producing a permanent magnet material, characterized in that a hard powder having a Mohs hardness of 5 or more is injected together with pressurized gas to remove the surface layer of the magnet body, and then an Al thin film layer is deposited on the surface of the magnet body.