JP4506965B2 - R-T-M-B rare earth permanent magnet and method for producing the same - Google Patents

Description

  The present invention relates to an RTMB rare earth permanent magnet having corrosion resistance, low dust generation and environmental compatibility, and a method for producing the same.

  Rare earth-based sintered magnets have been widely used in many fields because of their excellent magnetic properties and economy, but in recent years, optical pickups have been used as a means of improving energy efficiency in order to realize environmentally friendly technologies. Demand for driving and energy-saving motors is increasing. However, since rare earth metal materials such as Nd are generally easily oxidized in a very short period of time in humid air, the disadvantages are the magnetic property degradation and contamination caused by dropping of the magnet material. Exists as.

  Therefore, in general use, as a protective film on the surface of the magnet, a metal film as disclosed in JP-A-60-54406 (Patent Document 1), JP-A-9-63833 (Patent) Inorganic coatings as described in Document 2), organic coatings as described in JP-A-9-180922 (Patent Document 3), and magnet surfaces are ion-plated as disclosed in JP-A-7-74043 (Patent Document 4). A method of dry-coating with a metal vapor deposition film such as aluminum using a tinting has been proposed.

  Among these, when more advanced low dust generation and corrosion resistance are required, metal coatings are generally prescribed among the above, but the fine holes that reach the magnet base generated in these coatings are the cause of dust generation and corrosion. Therefore, attempts have been made to seal these micropores by giving a physical impulse such as shot blasting to the metal film or top-coating with a chromium oxide film.

  For magnets that are not chamfered at the corners or that are prone to cracking or chipping, use a barrel plating method in which a magnet is placed in a drum-shaped container called a barrel and plated. In this rack plating method, the portion where the magnet is sandwiched between the racks (the rack is attached to a frame called a rack, dipped in the plating tank together with the rack, and plated). (Hereinafter referred to as contact), the phenomenon of not being plated occurs, and the contact mark causes dust generation and corrosion as well as the previous fine hole. Therefore, it can be top-coated with a chromium oxide film or the contact mark can be epoxy resin. Attempts have been made to seal with protection by changing the contact position during plating.

  However, the sealing by the physical impact mentioned above does not block the micro holes in the shape of a cylindrical magnet that is hard to receive external impact, such as a coating on the inside of the cylinder, and small magnets or thin magnets with a magnet size of several millimeters or less In such cases, it is difficult to fix the magnet and the impact is difficult to be transmitted. Therefore, the fine holes are not sealed, and the magnet itself is broken or cracked due to insufficient mechanical strength of the magnet. ing.

  The top coat with chromium oxide coating is difficult to handle because of the chemical properties of chromium oxide, and it is difficult to handle all waste generated during processing together with the treatment liquid that forms the coating. Due to the recent increase in environmental awareness as represented by lead-free soldering in the production of component boards, there is an urgent need for alternative technologies, such as the need to reduce or eliminate the use of chromium oxide.

Sealing the contact traces with epoxy resin has problems in production such that the sealing portion is raised and the dimensional accuracy is deteriorated and complicated sealing work is required separately.
In the method of changing the contact position in the middle of plating, plating does not deposit well on the contact mark and the contact mark may not be sufficiently filled, and it is sufficient measures such as requiring a top coat with chromium oxide as a post treatment. It may not be possible.
JP-A-60-54406 JP-A-9-63833 JP-A-9-180922 Japanese Patent Laid-Open No. 7-74043

  The present invention has been made in view of the above circumstances, and provides an RTMB rare earth permanent magnet having excellent corrosion resistance, low dust generation, environmental compatibility, and adhesiveness, and a method for producing the same. With the goal.

  As a result of intensive studies to achieve the above object, the present inventor has found that in an R-T-MB-based rare earth permanent magnet having a metal plating film on the substrate, the fineness penetrating to the substrate existing in the metal plating film. In order to obtain a magnet in which a phosphorus compound containing a metal that is electrochemically equivalent or noble than the magnet base is deposited or deposited on the bottom part (magnet base part) and the vicinity (metal coating part) of the hole, and these magnets are obtained. In addition, an RTMB-B rare earth permanent magnet having a metal plating film on the substrate is immersed in an aqueous solution of a specific acid and / or base that contains an electrochemically equivalent or noble metal to the magnet substrate. As a result, the present inventors have found that the manufacturing method to be effective is effective.

That is, the present invention is based on R-T-M-B (R is at least one of rare earth elements including Y and Sc, T is Fe or Fe and Co, M is Ti, Nb, Al, V, Mn, Sn. , Ca, Mg, Pb, Sb, Zn, Si, Zr, Cr, Ni, Cu, Ga, Mo, W, Ta, and the content of each is 5% by mass ≦ R ≦ 40 mass%, 50 mass% ≦ T ≦ 90 mass%, 0 mass% ≦ M ≦ 8 mass%, 0.2 mass% ≦ B ≦ 8 mass%)) Further, after forming a metal film made of at least one selected from Fe, Co, Ni, Sn, and Cu in a single layer or multiple layers using a plating method, the magnet is at least selected from Fe, Co, Ni, Sn, and Cu. A metal, sodium dihydrogen phosphate, dihydrogen phosphate Um, sodium phosphate dibasic, and at least one compound selected from dipotassium hydrogen phosphate, sulfuric acid, nitric acid, acetic acid, oxalic acid, citric acid, peak b phosphate, sodium sulfate, potassium sulfate, sodium nitrate, potassium nitrate, sodium acetate, potassium, potassium oxalate, sodium oxalate, sodium citrate, potassium citrate, sodium pin b phosphate, was immersed in an aqueous solution containing at least one compound selected from potassium pyrophosphate, metal formed on the surface of the rare earth sintered magnet R- characterized in that at least one metal selected from Fe, Co, Ni, Sn, Cu and a phosphorus compound containing the metal are deposited on the surface of the magnet corresponding to the bottom of the fine hole reaching the magnet surface of the film. A method for producing a TMB-based rare earth permanent magnet is provided. The present invention also provides Fe, Co, Ni, Sn, Cu on the magnet surface corresponding to the bottom of the fine hole reaching the magnet surface of the metal film formed by the method and formed on the surface of the rare earth sintered magnet. An R-T-MB-based rare earth permanent magnet in which at least one kind of metal selected from the above and a phosphorus compound containing the metal is deposited is provided.

  The R-T-M-B rare earth permanent magnet and the manufacturing method thereof according to the present invention impart high corrosion resistance, low dust generation, environmental compatibility, and good adhesion to the rare earth permanent magnet, further expanding the application range. It is useful as a spreader.

  In the rare earth sintered permanent magnet represented by RTMB used in the present invention, R is a rare earth element including Y and Sc, specifically, Y, Sc, La, Ce, Pr, Nd. , Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. At least one rare earth element selected from the group consisting of Nd is preferably used. The content is 5% by mass or more and 40% by mass or less, preferably 10% by mass or more and 35% by mass or less. T is Fe or Fe and Co, and the content thereof is 50% by mass or more and 90% by mass or less, and preferably 55% by mass or more and 80% by mass or less. M is at least one element selected from Ti, Nb, Al, V, Mn, Sn, Ca, Mg, Pb, Sb, Zn, Si, Zr, Cr, Ni, Cu, Ga, Mo, W, and Ta. The content is 8% by mass or less, preferably 5% by mass or less. B is contained in an amount of 0.2 to 8% by mass, preferably 0.5 to 5% by mass. In addition, C, N, O, H, P, S, etc., which are industrially inevitable impurity elements at present, are also included.

The magnet is manufactured using a generally known manufacturing method in which an alloy is prepared from raw materials, and then pulverized to obtain a powder, which is molded into a desired shape and sintered. For example, the following method is mentioned. Pure crucible metals refined from rare earth oxides and fluorides, rare earth alloys, pure iron, ferroboron, pure metals and alloys of each additive element are used as raw materials, and these are filled in crucibles made of heat-resistant oxides and vacuumed Alternatively, after heating and dissolving in an inert gas, for example, Ar atmosphere using high frequency, it is poured into a mold and cooled, or poured onto a rotating cooling roll and rapidly cooled to produce a raw material alloy.
In this raw material alloy, in addition to the R ₂ Fe ₁₄ B phase (R is at least one kind of rare earth elements including Y and Sc (the above), the same shall apply hereinafter), α-Fe phase, R rich phase, B rich phase, etc. remain. If necessary, solution treatment is performed at a temperature of 700 to 1,200 ° C. in a vacuum or an inert gas atmosphere.

The raw material alloy is measured by using a device such as a jaw crusher, brown mill, jet mill, etc., or by occluding and releasing hydrogen gas into roughly crushed grains, for example, using a laser diffraction particle size distribution analyzer. In this case, the average particle size is pulverized to 20 μm or less.
Next, the obtained powder is molded into a desired shape by press molding in a magnetic field, and subsequently sintered at a temperature of 900 to 1,200 ° C. in a vacuum or an inert gas atmosphere.
If necessary, the sintered magnet may be cut into an arbitrary shape or heat-treated.

  The magnet obtained by sintering removes the oil and fat adhering to the surface during the manufacturing process with a basic aqueous solution, and then removes the passive layer such as oxide existing on the surface with an acidic aqueous solution. The surface is coated with a metal film using a known method such as electric Ni plating used, electric Cu plating using a pyrophosphoric acid bath, or other electroless plating. The plating may be performed by a rack method or a barrel method.

  The coating may be a single layer of Fe, Co, Ni, Sn, Cu or an alloy thereof, or a plurality of layers to improve the function of the coating. In the present invention, the coating layer thickness for obtaining the corrosion resistance and the low dust generation property should be about 1 to 40 μm, preferably 3 μm or more and 25 μm or less. If it is less than 1 μm, although depending on the coating processing technique, the substrate cannot be sufficiently covered in many cases, and the function as a film cannot be exhibited. In addition, if it exceeds 40 μm, the number of micropores reaching the substrate existing in the metal film is greatly reduced, and the significance of carrying out the present invention is diminished, and the volume of the magnet occupying the same volume is reduced. In the case of high-performance magnets, the finally obtained magnetic properties are deteriorated, causing problems in use.

In the present invention, the magnet coated with the metal thus obtained is made of at least one metal selected from Fe, Co, Ni, Sn, Cu, sodium dihydrogen phosphate, potassium dihydrogen phosphate, hydrogen phosphate. disodium, and at least one selected from dipotassium hydrogen phosphate, sulfuric acid, nitric acid, acetic acid, oxalic acid, citric acid, peak b phosphate, sodium sulfate, potassium sulfate, sodium nitrate, potassium nitrate, sodium acetate, potassium acetate, sodium oxalate, oxalate potassium, sodium citrate, potassium citrate, sodium pin b phosphate, immersed at any temperature and time in an aqueous solution (treatment liquid) containing at least one selected from potassium pyrophosphate.

  The concentration of the metal and other components contained in the treatment liquid may be determined in accordance with the treatment temperature and time. When the pH of the treatment liquid, which is one of the conditions under which the present invention is expressed, is an index, the treatment temperature The pH of the solution may be adjusted to 0.3 to 6.5 or 8.0 to 12.5. In addition, pH adjustment may be performed by increasing / decreasing the density | concentration of a component, and potassium hydroxide, sodium hydroxide, etc. may be used.

In this case, the temperature and time may be selected as long as the effect to be obtained between 15 and 60 ° C. is obtained, but considering productivity, it is preferably between 1 and 5 minutes between 25 and 40 ° C. .
At this time, a surfactant using a salt of a higher fatty acid or the like may be added to the treatment liquid in order to ensure sufficient penetration of the treatment liquid into the micropores.

  When the treatment liquid prepared in this way soaks into the micropores, a local battery is formed between the magnet base, the metal film, and the treatment liquid, and a part of the magnet base that becomes electrochemically base is started. Preferentially dissolves relatively quickly. When the melting of the magnet substrate starts, the metal in the treatment liquid deposits on the electrochemically noble part.

  This electrochemically noble part is on the metal film where the metal film is in contact with the magnet substrate, but other than that when the voltage is forcibly applied from the outside, dissolution occurs. Since it becomes the part which is not melt | dissolving near the part which exists, the metal in a process liquid deposits there. In addition, since a metal that is electrochemically more noble than the magnet substrate in the treatment liquid is deposited on the magnet substrate in sequence, it plays a role of a protective film against the treatment solution. To minimize remarkable corrosion deterioration due to preferential erosion of the magnet substrate that has occurred in the fine pores when an R-T-M-B rare earth permanent magnet having a magnetic field is immersed in an aqueous solution of acid or base it can.

Further, at this time, a phosphorous compound is generated by the reaction of at least one of sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate with the metal in the treatment liquid, and is deposited in the fine pores. The hole is sealed.
After the treatment, rinse with ion exchange water or pure water and then dry.

  The micropore described in the present invention is an opening observed on the surface of the metal covering the magnet, and the size is expressed as a diameter of a perfect circle having an area equivalent to the opening. This refers to the following or the traces of the rack contacts present on the metal coating produced by the rack plating method.

  By the above method, the metal formed on the substrate in the RTMB-based rare earth permanent magnet having a metal film made of at least one selected from Fe, Co, Ni, Sn, and Cu on the substrate. It is possible to obtain a rare earth permanent magnet in which fine holes reaching the substrate existing in the coating are sealed with a metal composed of at least one selected from Fe, Co, Ni, Sn and Cu and a phosphorus compound containing these metals.

  Examples of the present invention and comparative examples will be specifically described below, but the present invention is not limited thereto.

[Examples 1-4, Comparative Examples 1-4]
A raw material alloy of Nd 32% by mass, Co 7% by mass, Fe 59.8% by mass, and B1.2% by mass was produced from the required raw materials under an Ar atmosphere by high-frequency heating and melting, coarsely pulverized with a jaw crusher, and then a nitrogen atmosphere Then, it was pulverized using a jet mill to obtain a fine powder having an average particle size of 3.5 μm. Subsequently, the obtained powder was filled in a mold, molded by applying a pressure of 1.0 ton / cm ² while applying a magnetic field of 10 kOe, sintered in vacuum at 1,100 ° C. for 2 hours, and 550 ° C. Then, heat treatment was performed for 1 hour. After the obtained magnet was processed into two types of 10 × 20 × 2 mm and 5 × 5 × 2 mm, the fats and oils were removed using a commercially available basic degreasing aqueous solution, and the passive layer was formed using a nitric acid aqueous solution. After the removal, electric Ni plating was performed by a barrel plating method using a Watt bath, and a Ni film having a film thickness of 6 μm was coated to obtain a magnet for evaluation. The obtained magnet was immersed in a treatment solution shown in each of the following examples at 25 ° C. for 2 minutes, rinsed with ion-exchanged water, and then dried in a forced circulation dryer at 80 ° C. for 10 minutes.
Example 1: Fe 0.005 mol / L, pyrophosphoric acid 0.01 mol / L, dihydrogen phosphate sodium
Lilium 0.1 mol / L
Example 2: Ni 0.01 mol / L, pyrophosphoric acid 0.02 mol / L, potassium pyrophosphate
0.05 mol / L, sodium dihydrogen phosphate 0.1 mol / L
Comparative Example 1: Untreated Comparative Example 2: Commercial Chromate Treatment Agent

The magnet produced in the same manner as above was used to remove oils and fats using a commercially available basic degreasing aqueous solution, and after removing the passive layer using an aqueous nitric acid solution, electroplating Ni was carried out using a watt bath and rack plating. An evaluation magnet was prepared by coating with a 6 μm thick Ni film. The obtained magnet was immersed in a treatment solution shown in each of the following examples at 25 ° C. for 2 minutes, rinsed with ion-exchanged water, and then dried in a forced circulation dryer at 80 ° C. for 10 minutes.
Example 3: Fe 0.005 mol / L, citric acid 0.1 mol / L, dihydrogen hydrogen phosphate
Um 0.1 mol / L
Example 4: Ni 0.01 mol / L, pyrophosphoric acid 0.05 mol / L, dihydrogen phosphate sodium
Um 0.1 mol / L
Comparative Example 3: Untreated Comparative Example 4: Commercial Chromate Treatment Agent

  Of the samples obtained above, those having a size of 10 × 20 × 2 mm were subjected to a pressure cooker test (PCT) at 120 ° C. and 2 atm for 48 hours, 72 hours and 96 hours, and a 5 mass% sodium chloride aqueous solution. After immersing at 35 ° C. for 48 hours, 72 hours and 96 hours, washing with water, drying, and immediately observing the occurrence of rust, plating film swelling and peeling at 2.5 to 20 times using a stereomicroscope And for the dimension of 5 × 5 × 2 mm, the degree of magnetic property deterioration showing the change in magnetic flux density and coercivity in Permeance 1 measured by VSM as a percentage around 120 ° C. × 24 hours, The results were evaluated for each, such as the shear adhesive strength when a magnet that had passed one month after treatment was bonded to an iron plate with acrylic and epoxy adhesives and the magnet was compression sheared at a linear speed of 10 mm / min. The results are shown in Table 1.

[Examples 5-8, Comparative Examples 5-8]
A raw material alloy of Nd 32% by mass, Co 7% by mass, Fe 59.8% by mass, and B1.2% by mass was produced from the required raw materials under an Ar atmosphere by high-frequency heating and melting, coarsely pulverized with a jaw crusher, and then a nitrogen atmosphere Then, it was pulverized using a jet mill to obtain a fine powder having an average particle size of 3.5 μm. Subsequently, the obtained powder was filled in a mold, molded by applying a pressure of 1.0 ton / cm ² while applying a magnetic field of 10 kOe, sintered in vacuum at 1,100 ° C. for 2 hours, and 550 ° C. Then, a heat treatment was performed for 1 hour to obtain a magnet. After the obtained magnet was processed into two types of 10 × 20 × 2 mm and 5 × 5 × 2 mm, the fats and oils were removed using a commercially available basic degreasing aqueous solution, and the passive layer was formed using a nitric acid aqueous solution. Removed. Next, after applying Cu electroplating by barrel plating using a pyrophosphoric acid bath, applying Ni plating by barrel plating using Watt bath, and coating each with 3 μm, a total of 6 μm Cu / Ni two-layer coating An evaluation magnet was obtained. The obtained magnet was immersed in a treatment solution shown in each of the following examples at 25 ° C. for 2 minutes, rinsed with ion-exchanged water, and then dried in a forced circulation dryer at 80 ° C. for 10 minutes.
Example 5: Fe 0.005 mol / L, acetic acid 0.1 mol / L, sodium dihydrogen phosphate
Um 0.1 mol / L
Example 6: Ni 0.01 mol / L, pyrophosphoric acid 0.01 mol / L, pyrophosphoric acid potassium
0.05 mol / L, potassium dihydrogen phosphate 0.1 mol / L
Comparative Example 5: Untreated Comparative Example 6: Commercial Chromate Treatment Agent

The magnet produced in the same manner as described above was subjected to electric Cu plating by a rack plating method using a pyrophosphoric acid bath after removing fats and oils using a commercially available basic degreasing aqueous solution and removing a passive layer using an aqueous nitric acid solution. Thereafter, electric Ni plating by a rack plating method was performed using a Watt bath, and each was coated with a Cu / Ni bilayer coating of 3 μm, for a total of 6 μm, to obtain an evaluation magnet. The obtained magnet was immersed in a treatment solution shown in each of the following examples at 25 ° C. for 2 minutes, rinsed with ion-exchanged water, and then dried in a forced circulation dryer at 80 ° C. for 10 minutes.
Example 7: Ni 0.01 mol / L, acetic acid 0.02 mol / L, dihydrogen phosphate sodium
Um 0.1 mol / L
Example 8: Cu 0.01 mol / L, pyrophosphoric acid 0.01 mol / L, pyrophosphoric acid potassium
0.05 mol / L
Comparative Example 7: Untreated Comparative Example 8: Commercial Chromate Treatment Agent

  Among the samples obtained above, those having dimensions of 10 × 20 × 2 mm were subjected to a pressure cooker test (PCT) at 120 ° C. and 2 atm for 48 hours, 72 hours and 96 hours, and 5% by mass sodium chloride. After immersing in an aqueous solution at 35 ° C. for 48 hours, 72 hours, and 96 hours, washed with water, dried, and immediately observed the occurrence of rust, plating film swelling and peeling at a magnification of 2.5 to 20 times using a stereomicroscope. The result and the degree of magnetic property deterioration that shows the change in percentage of each value of magnetic flux density and coercive force in Permeance 1 measured by VSM at around 120 ° C. × 24 hours as a percentage for a size of 5 × 5 × 2 mm 1 month after the treatment, the magnet was bonded to an iron plate with an acrylic and epoxy adhesive, and the shear adhesive strength when the magnet was compression-sheared at a linear speed of 10 mm / min was evaluated for each. The results are shown in Table 2.

In the examples of the present invention, changes were observed in 96 hours in both the PCT and salt water immersion tests. This is the same corrosion resistance as the conventional chromate treatment (Comparative Examples 2, 4, 6, 8), and better results were obtained than Comparative Examples 1, 3, 5, and 7.
The magnetic properties were not deteriorated by the treatment of the present invention, and the shear adhesive strength was equal to or higher than that of the comparative example.

Claims (3)

R-TMB (R is at least one of rare earth elements including Y and Sc, T is Fe or Fe and Co, M is Ti, Nb, Al, V, Mn, Sn, Ca, Mg, Pb , Sb, Zn, Si, Zr, Cr, Ni, Cu, Ga, Mo, W, Ta, and their contents are 5% by mass ≦ R ≦ 40% by mass, 50%, respectively. Mass% ≦ T ≦ 90 mass%, 0 mass% ≦ M ≦ 8 mass%, 0.2 mass% ≦ B ≦ 8 mass%.) Fe, Co, Ni After forming a metal film made of at least one selected from Sn, Cu in a single layer or multiple layers using a plating method, the magnet is coated with at least one metal selected from Fe, Co, Ni, Sn, Cu and diphosphate. Sodium hydrogen, potassium dihydrogen phosphate, dihydrogen phosphate Thorium, and at least one compound selected from dipotassium hydrogen phosphate, sulfuric acid, nitric acid, acetic acid, oxalic acid, citric acid, peak b phosphate, sodium sulfate, potassium sulfate, sodium nitrate, potassium nitrate, sodium acetate, potassium acetate, potassium oxalate, sodium oxalate, sodium citrate, potassium citrate, sodium pin b phosphate, was immersed in an aqueous solution containing at least one compound selected from potassium pyrophosphate, the magnet surface of the metal film formed on the surface of the rare earth sintered magnet At least one metal selected from Fe, Co, Ni, Sn, Cu and a phosphorus compound containing the metal are deposited on the surface of the magnet corresponding to the bottom of the fine hole reaching A method for producing a B-based rare earth permanent magnet.   The method for producing an R-T-MB-based rare earth permanent magnet according to claim 1, wherein the method is immersed in the aqueous solution according to claim 1, followed by washing with water and drying.   On the magnet surface corresponding to the bottom of the fine hole reaching the magnet surface of the metal film formed on the surface of the rare earth sintered magnet obtained by the manufacturing method according to claim 1 or 2, Fe, Co, Ni, Sn, An RTMB-based rare earth permanent magnet in which at least one metal selected from Cu and a phosphorus compound containing the metal are deposited.