JP2643329B2 - Rare earth-cobalt sintered magnet with excellent magnetic properties and mechanical strength - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a combination of one or two or more rare earth elements containing Y, which is excellent not only in magnetic properties but also in mechanical strength (hereinafter, referred to as "Y"). , R) and a sintered magnet containing cobalt as a main component.

[Conventional technology]

Generally, it is known that there is an R ₂ Co ₁₇ sintered magnet as an R-Co based sintered magnet having high magnetic properties.
R ₂ Co ₁₇ sintered magnets are widely used as components of electric and electronic devices.

The component composition of the above R ₂ Co ₁₇ based sintered magnet is as follows: R: 20 to 30%, Fe: 5 to 30%, Cu: 2 to 15%, Ni: 0.05 to 1.5%, Ti, Zr, One or more of Hf, V, Nb, and Ta: 1.0 to 5.5
%, Balance: Co and inevitable impurities.

More recently, C was added to the above R ₂ Co ₁₇ sintered magnet in an amount of 0.005 to 1.0.
There is also provided one in which the coercive force is improved by adding%.

These R ₂ Co _17- based sintered magnets are manufactured as follows.

First, a melted alloy ingot having a predetermined component composition is pulverized into a fine powder, which is pressed into a green compact having magnetic anisotropy by pressing in a magnetic field, and then heated to a temperature at which a liquid phase is generated in the green compact. Sintering is performed in the region, and then heat treatment of a solution treatment and an aging treatment is performed.

[Problems to be solved by the invention]

However, when the above-described C-containing R ₂ Co _17- based sintered magnet is manufactured by the above-described conventional manufacturing method, at the beginning of the sintering process, the above-mentioned C mainly reacts with the IVa and Va group metals among the alloy components. However, the carbides are poorly wettable with the metal melt, so that they are agglomerated and coarsened during the liquid phase sintering process. Inhibits high density. Therefore, the crystal grains of the C-containing R ₂ Co ₁₇ based sintered magnet matrix also grow remarkably.

As described above, when the solution treatment is performed to homogenize the composition of the dense and dense sintered body in which the crystal grains are remarkably grown, the grain boundary components are located inside the crystal grains because the crystal grains are large and the grain boundary density is small. The time required for diffusion, that is, the solution heat-up time becomes longer.

If the solution treatment is carried out for a long time (for example, 8 hours or more), even if the sintered body has coarse crystal grains, the composition can be solution-solutioned, but the production efficiency is of course reduced. That is, oxidation and evaporation of a rare earth element having a high affinity for oxygen and a high vapor pressure are caused, and the magnetic properties are rather deteriorated.

In addition, the low density and coarse crystal grains of the magnet sintered body embrittle the magnet, lowering the workability, causing chipping or cracking of the final product, and further lowering the residual magnetic flux density. There has also been a problem that the maximum energy product is reduced.

[Means for solving the problem]

The present inventors have conducted research to solve such problems. As a result, when N is further added to the C-containing R ₂ Co ₁₇ based sintered magnet, (1) Reacts with IVa and Va group metals to form unitary carbonitrides or multiple compound carbonitrides depending on the number of components of these metals. R ₂ Co ₁₇ based sintering with high density and high residual magnet density without hindering the liquid phase sintering of magnet compacts due to better wettability with the liquid phase compared to carbide formed by A carbonitride is obtained, and the carbonitride with good wettability is kept fine without agglomeration and coarsening in the sintering step.

(2) Since the fine carbonitrides pin the crystal grain boundaries of the magnet matrix and suppress the growth of crystal grains, the solution process is performed by decreasing the diffusion process of the component elements and increasing the contribution of the grain boundary diffusion. In this case, the homogenization of the composition can be performed efficiently and completely in a short time, and a magnet having improved squareness can be obtained because the pinning force on the domain wall is more uniform.

(3) Since the crystal grains of the magnet matrix are fine, remarkable improvement in toughness is also observed in terms of mechanical properties.

That's the finding.

The present invention has been made on the basis of the above findings, and is as follows: R: 20 to 30%, Fe: 5 to 30%, Cu: 2 to 15%, Ni: 0.05 to 1.5%, Ti, Zr , Hf, V, Nb, Ta, one or two or more: 1.0 to 5.5
%, And further contains C: 0.008 to 0.5%, N: 0.002 to 0.2%, and the balance: has a composition of Co and unavoidable impurities (more than weight%), and more preferably, C ≧ The present invention is characterized by a rare earth-cobalt based sintered magnet excellent in magnetic properties and mechanical strength having a relationship of N.

Next, the reason for limiting the component composition of the R ₂ Co ₁₇ sintered magnet in the present invention as described above will be described.

(1) When the R component and the R component are less than 20%, the coercive force decreases, and when the R component exceeds 30%, the residual magnetic flux density decreases. Therefore, the content is set to 20 to 30%.

(2) The Fe component and the Fe component have an effect of improving the residual magnetic flux density, but if the content is less than 5%, the desired effect cannot be obtained.
%, The coercive force decreases, so the content is set to 5 to 30%.

(3) The Cu component and the Cu component have the effect of improving the coercive force, but if the content is less than 2%, the desired high coercive force cannot be secured. The content was determined to be 2 to 15% because the density was lowered.

(4) Ni component and Ni component have the effect of improving the squareness of the magnet and increasing the maximum energy product. However, if the content is less than 0.05, the desired effect cannot be obtained, while the content exceeds 1.5%. Since the coercive force will decrease when it is contained, its content is set to 0.
It was set at 05-1.5%.

(5) One or more of Ti, Zr, Hf, V, Ta, and Nb. These components have an effect of forming carbonitrides and suppressing crystal grain growth, but the content is less than 1.0%. In this case, the amount of carbonitride deposited is insufficient and the desired result cannot be obtained.
%, The amount of carbonitride precipitates excessively and lowers the residual magnetic flux density.
5.5%.

(6) The C component and the C component form carbonitrides and have an effect of suppressing grain growth, but if the content is less than 0.008%, the amount of carbonitrides precipitated is insufficient, and the desired effect is obtained. On the other hand, if the content exceeds 0.5%, the precipitation amount of carbonitride becomes excessive and the residual magnetic flux density decreases, so that the content is 0.00%.
It was determined to be 8 to 0.5%. C is an organic solvent used to prevent the oxidation of the powder in the step of pulverizing the alloy ingot by a ball mill, a vibration mill, an attritor mill, or the like, or various kinds of additives added to improve the press formability of the fine powder. The C content is added to the product in the form of an agent (lubricant, binder), and the C content can be adjusted within the above range by, for example, adding C powder to the magnet powder.

(7) N component, N component forms carbonitrides, has an effect of improving sinterability and suppressing crystal grain growth, but its content is 0.002%
If the content is less than 0.5%, the desired effect cannot be obtained.On the other hand, if the content exceeds 0.5%, the amount of carbonitride precipitated becomes excessive and the residual magnetic flux density decreases.
002-0.2%.

(8) C ≧ N, with respect to the relationship between the amount of C and the amount of N, if the amount of N exceeds the amount of C, some free N that does not react with the Group IVa, Va metal is generated, and this free N solidifies in the matrix. To reduce the crystal magnetic anisotropy and thereby reduce the coercive force of the magnet,
The amount was determined to be ≧ N amount.

N may be added as a nitride of a component element, but can also be added to the magnet by adding N ₂ gas to the sintering atmosphere, and appropriately selecting the volume fraction of N ₂ gas in the atmosphere. By doing so, the N content of the magnet can be adjusted within the above range.

〔Example〕

Next, the present invention will be specifically described based on embodiments.

(1) Examples 1 to 9 and Comparative Examples 1 to 5, Sm: 25.3%, Fe: 15.0%, Cu: 8.0%, Ni: 1.4%, Zr: 2.3 in an Ar atmosphere using a high-frequency melting furnace. %, Hf: 0.2%, balance: An alloy having a composition (the above, weight%) consisting of Co and inevitable impurities was cast into an ingot.

The ingot was pulverized in a stamp mill in an Ar gas atmosphere, and further pulverized in a diflon using a vibration mill to obtain an alloy powder having an average particle size of about 4 μm.

To this alloy powder, stearic acid was added as a lubricant in an amount of 0.05% for the purpose of improving press formability, and in order to further change the C content of the magnet, Examples 1 to 9 in Table 1 and Comparative Examples 1 to 5 and The amount of C powder shown in Conventional Example 1 was added to obtain a raw material powder.

The thus obtained raw material powders having different C contents are
While being oriented in a magnetic field of 12 KOe, it was compressed at a pressure of 1.5 ton / cm ^{2 in} a direction perpendicular to the orientation direction to produce a green compact having a length of 10 mm, a width of 10 mm and a height of 10 mm.

These green compacts were placed in an N ₂ gas-containing Ar gas atmosphere shown in Examples 1 to 9 and Comparative Examples 1 to 5 in Table 1 at a temperature of 121.
Sintering was carried out at 0 ° C. for 1 hour. For comparison, sintering was performed in a pure Ar gas atmosphere under the same conditions as above, and Table 1 shows the results as Conventional Example 1.

Examples 1 to 9 and Comparative Example 1 obtained by sintering under the above conditions
To 5 and Conventional Example 1 were subjected to a solution treatment in a pure Ar gas atmosphere at a temperature of 1180 ° C. for 2 hours and then quenched by Ar gas spraying, followed by pure Ar gas. After heating in an atmosphere at a temperature of 800 ° C. for 2 hours, aging treatment was performed in which cooling was performed continuously at a cooling rate of 30 ° C./hour to a temperature of 400 ° C.

C and N contained in the magnet thus manufactured
Was analyzed, and the density, flexural strength and magnetic properties of the manufactured magnet were measured. The results are shown in Table 1.

The squareness ratio in the magnetic properties is a value indicated by the ratio of the knee magnetic field H _K (the strength of the reverse magnetic field at which the magnetization strength becomes 90% of the residual magnetic flux density) to the coercive force iHc in the demagnetization curve. is there.

(2) Examples 10 to 18 and Comparative Examples 6 to 10, Sm: 17.9%, Ce: 7.6%, Fe: 20.0%, Cu: 6.0%, Ni: An alloy having a composition of 0.5%, Ti: 1.9%, V: 0.3%, and balance: Co and unavoidable impurities (above, by weight) was melted and cast into an ingot.

The ingot was pulverized in a stamp mill in an Ar gas atmosphere, and further pulverized in a diflon using a vibration mill to obtain an alloy powder having an average particle size of about 4 μm.

To this alloy powder, 0.05% of stearic acid was added as a lubricant for the purpose of improving the press formability, and further, in order to change the C content of the magnet, the C powder was used in Example 10 shown in Table 2.
To 18, Comparative Examples 6 to 10 and Conventional Example 2 to obtain raw material powders.

The raw material powder thus obtained was compressed under the same conditions as in Example 1 to produce green compacts having a length of 10 mm, a width of 10 mm, and a height of 10 mm. The sintering was carried out in an atmosphere of Ar gas having a different N ₂ gas content and a pure Ar gas atmosphere shown in Examples 10 to 18, Comparative Examples 6 to 10 and Conventional Example 2 at a temperature of 1185 ° C. for 1 hour. went.

These sintered bodies were placed in a pure Ar gas atmosphere at a temperature of 1120 ° C., 2
After performing the solution treatment under the condition of holding time, quenching is performed by spraying Ar gas, and then in an Ar gas atmosphere, at a temperature of 830.
After heating at a temperature of 2 ° C. for 2 hours, an aging treatment was carried out to continuously cool to 400 ° C. at a cooling rate of 30 ° C./hour.

C and N contained in the magnet thus manufactured
And analyze the density, flexural strength, The residual magnetic flux density, coercive force, maximum energy product and squareness ratio were measured, and the results are shown in Table 1.

From the results shown in Tables 1 and 2, the mechanical properties and magnetic properties of the examples of the present invention are superior to those of the comparative examples and the conventional examples. Therefore, C: 0.008 to 0.5% by weight. , N: 0.002 to 0.2%, and it is necessary to simultaneously contain the following. Examples 1 to 7 are more excellent in mechanical and magnetic properties than Examples 8 to 9 in Table 1. Further, since Examples 10 to 16 are similarly superior to Examples 17 to 18 in Table 1, it can be seen that more excellent results can be obtained if the relationship of C ≧ N is satisfied.

〔The invention's effect〕

By further adding an appropriate amount of N to a conventionally known C-containing R ₂ Co ₁₇ -based magnet, a more excellent R ₂ Co ₁₇ -based magnet can be provided, and an industrially superior effect can be obtained.

Claims (2)

(57) [Claims] 1. A rare earth element containing one or more kinds of rare earth elements containing Y: 20 to 30%, Fe: 5 to 30%, Cu: 2 to 15%, Ni: 0.05 to 1.5%, Ti: , Zr, Hf, V, Nb, Ta, one or two or more: 1.0 to 5.5
And C: 0.008 to 0.5%, N: 0.002 to 0.2%, and the balance: Co and unavoidable impurities (the above, by weight%). Rare earth-cobalt sintered magnet with excellent mechanical strength. 2. The rare earth-cobalt sintered magnet according to claim 1, wherein C and N have a relationship of C ≧ N.