JPH0260105A - Rare-earth permanent magnet - Google Patents

Abstract

PURPOSE:To obtain the title rare-earth permanent magnet having stabilized magnetic characteristics by a method wherein the decrease in coercive force of the permanent magnet is prevented by having the carbide contained in a magnetic alloy deposited in the alloy as the prescribed element of carbide. CONSTITUTION:The title rare-earth permanent magnet consists of the sintered magnet alloy mainly composed of the fundamental composition of R (containing at least a kind selected from the rare-earth element containing Y) of 25 to 35wt.%, B of 0.5 to 2.0wt.%, M<1> (containing at least a kind selected from Fe, Co, Al, Ni, Mn, Si and Ga) of 60 to 70wt.%, M<2> (containing at least a kind selected from Cr, Mo, Nb, Ta, Ti, V, W and Zr) or 0.1 to 10wt.%, and carbon of 0.01 to 1.0wt.%, which will be mixed from raw material metal, a molding improving material, powder improving material and the like, is contained in the above-mentioned magnet alloy. Said carbon is deposited in the alloy by forming the M<2> and a carbide. The carbon prevents the formation of a carbide with the R having R-rich phase in an R-Fe-B magnet, and as a result, the lowering of coercive force is eliminated, and a rare-earth permanent magnet, having stabilized magnetic characteristics, can be manufactured.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention involves precipitating C, an impurity element that causes a decrease in the coercive force Hc of an R-Fe-B rare earth permanent magnet, as a carbide in the magnet. This invention relates to a rare earth permanent magnet that prevents a decrease in coercive force.

(Prior Art) R-Fe-B rare earth permanent magnets, which are manufactured by powder metallurgy including the steps of crushing, forming in a magnetic field, and sintering, have excellent magnetic properties and are attracting attention as high-performance magnets. The coercive force Hc of this magnet sometimes deteriorates, and it has been revealed that the cause of this is that carbon forms carbides with R in the R-rich phase. Therefore, as a method to prevent Hc deterioration, it is possible to remove this carbon from the magnet composition or convert it into a compound that does not affect the magnetic properties.
Part of B in phase Ia B is replaced with carbon, or
Methods such as creating an alloy composition in which R corresponding to an R-rich phase in which carbon substantially decreases by forming R in an R-rich phase and carbides have been adopted, but these methods are not always satisfactory. It wasn't.

(Problems to be Solved by the Invention) The technical problems to be solved by the present invention are as described above.
Carbon, which is a cause of deterioration of the coercive force of Fe-B rare earth permanent magnets, should not remain in the magnet composition, or it should be converted into a compound that does not affect the magnetic properties. This impurity carbon is thermally decomposed during sintering because it acts as an impurity in the raw metal, and also because the forming improver used to improve formability and the powder stabilizer used to prevent oxidation of powder are organic substances. Although they are mixed in as products, using high-purity materials with less impurity carbon as the raw material metal increases costs, and since the use of the latter organic substances is unavoidable, there is a disadvantage that they are unavoidably mixed.

(Means for Solving the Problems) In order to solve the above problems, the present inventors investigated various causes and solutions for the decrease in coercive force due to carbon, and found that R-Fe-B rare earth permanent magnets were the cause. When carbon is mixed into the ferromagnetic phase, even if part of the B in the R*Fe+4B phase is replaced with carbon, there is almost no effect on the magnetic properties.
It was found that in magnet alloys made by conventional methods, most of the carbon forms carbides with R in the R-rich phases other than the R2Fed4B phase, resulting in a substantial decrease in the R-rich phase and a low coercive force. . In addition, this magnet is a liquid-phase sintered magnet in which the R-rich phase becomes a liquid phase during sintering and sintering progresses, so a sufficient amount of R17-rich phase is required for sintering.
It has been found that when R in the rich phase forms a carbide, this carbide does not become a liquid phase during sintering, so the R-rich phase is substantially reduced, resulting in a decrease in Hc. The amount of carbon that affects Hc is 0.01% by weight or more, and Hc
To prevent a decrease in carbon content, reduce the amount of carbon mixed in during the manufacturing process to zero.
．． It is conceivable to control the amount of R to less than 0.01% by weight, or to create an alloy composition in which R, which corresponds to an R-rich phase that is substantially reduced by carbon, is increased in advance. However, as mentioned above, it is extremely difficult to suppress the amount of carbon mixed into the magnet to 0.01% by weight in terms of mass production. Furthermore, if the alloy composition is made to have an increased amount of R, there is a drawback that the saturation magnetization decreases by the increased amount.

The present invention is a magnet that solves the above-mentioned disadvantages, and relates to a rare earth permanent magnet having a composition in which impurity carbon is precipitated in an R-rich phase as a compound that does not affect magnetic properties. , R (R is at least one kind of rare earth elements including Y) is 25 to 35% (weight %, the same applies hereinafter), and B is 0.5%.
~2.0%, M' (Fe, Co, A1.Ni, Mn
, St, and Ga) containing Fe)
is 60-70%, M2 (Cr, Mo, Nb, Ta, Ti
, V, W, Zr) is 0.1
-10.0% and 0.01 to 1.0% carbon, and the rare earth permanent magnet is characterized in that the carbon forms a carbide with M2.

The present invention will be explained in detail below.

The present invention provides an R-Fe-B rare earth permanent magnet (R is at least one rare earth element including Y),
As a result of various studies aimed at suppressing the decrease in HC due to carbon inevitably mixed in from raw metals, forming improvers, powder stabilizers, etc., we found that the carbon contained in the R-Fe-B magnet alloy was replaced with Cr, We have discovered that the decrease in Hc can be suppressed by precipitating it in a magnet alloy as a carbide with one or more elements (M2) of Mo, Nb, Ta, Ti, V, W, and Zr. The invention has been achieved.

That is, the basic composition of the present R-Fe-B rare earth permanent magnet is as follows: R (R is at least one kind of rare earth elements including Y) is 25 to 35% (weight %, the same applies hereinafter), B
is 0.5 to 2.0%, M' (Fe, C.

, A1. At least one of Ni, Mn, Si, and Ga) containing Fe is 60 to 70%, M'' (Cr
, MO1-b, Ta, Ti, ■, W, Zr) is a sintered magnet alloy whose main component is 0.1-1000%, and contains raw material metals as impurities during the manufacturing process. It contains 0.01-1.0% carbon that is unavoidably mixed in from molding improvers, powder stabilizers, etc., but this carbon forms carbides with M2 and precipitates in the alloy. ing. The effect of precipitation in this alloy is to prevent carbon from forming carbides with R in the R-rich phase in the R-Fe-B magnet. That is, when R in the R-rich phase forms a carbide, this carbide does not become a liquid phase during sintering, so that the substantial R-rich phase decreases. As a result, the R switch phase required for sintering becomes insufficient, and Ha decreases. However, since M3 is an element that forms carbides more easily than Ml, if it is precipitated in the alloy as a carbide with the carbon-based M3 contained in the magnet alloy, the R-rich phase will not be substantially reduced and carbon will be mixed in. The decrease in Hc caused by this can be suppressed. In addition, since carbides with M2 mainly precipitate in the R-rich phase and do not precipitate when RaFeI<B, the amount of mM added that causes less decrease in saturation magnetization is sufficient to form carbides. That is, 0.1 to 10.0% is required, but if this amount is exceeded, M2 becomes R2Feha B
Since it becomes included in the phase and the saturation magnetization decreases, it is necessary to keep it within this range. R is 25% or less and B
When R is less than 0.5%, sufficient coercive force cannot be obtained, and when R exceeds 35% or B exceeds 2%, saturation magnetization decreases significantly and good magnetic properties cannot be obtained. No, R is La, Ce%Pr, Nd%Sm
%Eu, Gd, Tb, Dy, Ho, Er, T
one or more rare earth elements such as m, Yb, Lu and Y, in particular light rare earth elements such as Pr and Nd and their combination with Tb.
, toy is preferably combined with heavy rare earth elements.

Ml mainly consists of Fe, Co, AI, Ni, Mn, Si,
At least one type of Ga is selected from these and combined for the purpose of improving the reversible temperature coefficient of the magnet and increasing the coercive force.

The carbon content of the raw material metal is 0.2% or less for R metal and 0.1% or less for ferroboron, and the carbon content from the raw material metal is
Mainly, carbon material is generated from these metals, and as a result, the carbon material mixed into the magnet alloy is 0. The content is approximately 0.1% to 0.1%. Molding improvers, which are a source of impurity carbon, are mainly made of paraffins or long-chain fatty acids such as stearic acid, palmitic acid, and oleic acid, and are added during compression and pressure molding of fine magnetic alloy powder. It is added to improve fluidity into the mold and ease of release after molding. Also,
The powder stabilizer is polyoxyethylene alkyl ether,
These include polyoxyethylene fatty acid ester, polyoxyethylene alkyl allyl ether, etc., and are used by coating the powder surface to prevent chemically active magnetic alloy powder from generating heat and igniting. These additives are added in amounts of about 0.0% to the magnet alloy powder. O is added in an amount of 1 to 0.5%, and the amount of carbon corresponds to approximately 0,008 to 0.4%. Furthermore, when the magnet powder is obtained by wet grinding, there is contamination of about 0°O1 to 0.1% carbon from the solvent. In addition, carbides are mainly formed when carbon from the raw metal is formed during casting, and carbon from forming improvers and powder stabilizers is mainly formed during sintering. The present invention will be described below with reference to specific examples, but the present invention is not limited to these examples.
represents the total percentage by weight.

(Example 1) As a starting material, electrolytic iron with a purity of 99.9%, 817.5
% and the balance is composed of impurities such as Fe and carbon, Nd metal with a purity of 99.5% or more, AI gold metal Nb metal with a purity of 99.9% or more, Nd:
32.0%, Fe: 65.5%, B: 1.1%, Al:
Nb: 0.4%, Nb: 1.0%, and an ingot was obtained by high frequency melting.

This ingot was coarsely pulverized and then wet-pulverized in N-hexane using a ball mill to obtain a slurry of alloy powder with an average particle size of 3.3 μm. 0.1 part of stearic acid as a molding improver was wet mixed with 100 parts by weight of the alloy powder in this slurry, and then dried to obtain an alloy powder. This alloy powder was oriented in a magnetic field of 15 kOe, and 1. Ot
/cm” and then press molded at 1080℃XI in Ar.
A permanent magnet was produced by sintering under the conditions of 2 hours and then aging at 600°C for 2 hours.

When the structure of this magnet was observed using EPMA, it was found that most of the carbon contained in the alloy formed carbides with Nb and precipitated within the Nd-rich phase. Table 1 shows the magnetic properties and carbon content of the obtained permanent magnet.

(Example 2) As a starting material, electrolytic iron with a purity of 99.9%, 817.5
% and the balance is composed of impurities such as Fe and carbon, Nd metal with a purity of 99.5% or more, AI gold metal Cr metal with a purity of 99.9% or more, Nd:
32.0%, Fe: 65.5%, B: 1.1%, Al:
Cr: 0.4%, Cr: 1.0%, and an ingot was obtained by high frequency melting.

A permanent magnet was produced using this ingot under the same conditions as in Example 1. When the structure of this magnet was observed using EPMA, it was found that
Most of the carbon contained in the alloy formed carbides with Cr and precipitated within the Nd-rich phase. Table 1 shows the magnetic properties and carbon content of the obtained permanent magnet.

(Example 3) As a starting material, electrolytic iron with a purity of 99.9%, 817.5
% and the remainder consists of impurities such as Fe and carbon, Nd metal with a purity of 99.5% or more, AI gold metal Mo metal with a purity of 99.9% or more, Nd:
32.0%, Fe: 65.5%, B: 1.1%, A1:
0.4% and Mo: 1.0%, and an ingot was obtained by high frequency melting.

A permanent magnet was produced using this ingot under the same conditions as in Example 1. When the structure of this magnet was observed using EPMA, it was found that
Most of the carbon contained in the alloy formed carbides with MO and precipitated within the Nd-rich phase. Table 1 shows the magnetic properties and carbon content of the obtained permanent magnet.

(Example 4) As a starting material, electrolytic iron with a purity of 99.9%, 817.5
% and the balance is composed of impurities such as Fe and carbon, Nd metal with a purity of 99.5% or more, AI gold metal and Ti metal with a purity of 99.9% or more, Nd:
32.0%, Fe: 65.5%, B: 1.1%, A]:
Ti: 0.4%, Ti: 1.0%, and an ingot was obtained by high frequency melting.

A permanent magnet was produced using this ingot under the same conditions as in Example 1. When the structure of this magnet was observed by EPMA, it was found that most of the carbon contained in the alloy formed carbides with Ti and precipitated within the Nd-rich phase. Table 1 shows the magnetic properties and carbon content of the obtained permanent magnet.

(Comparative example) As a starting material, electrolytic iron with a purity of 99.9%, B10.5
% and the balance is composed of impurities such as Fe and carbon, Nd metal with a purity of 99.5% or more, AI gold metal with a purity of 99.9% or more, Nd: 32.0% by weight
, Fe2: 66.5%, B: 1.1%, and A1: 0.4%, and an ingot was obtained by high frequency melting. A permanent magnet was produced using this ingot under the same conditions as in Example 1. When the structure of this magnet was observed using EPMA, it was found that most of the carbon contained in the alloy formed carbides with Nd and precipitated within the Nd-rich phase. Table 1 shows the magnetic properties and carbon content of the obtained permanent magnet.

(Effects of the invention) As is clear from Table 1, the present invention can prevent deterioration of magnetic properties due to carbon that is inevitably mixed in during the manufacturing process of R-Fe-B permanent magnets, and rare earths have stable magnetic properties. Permanent magnets can be manufactured and this has industrially beneficial effects.

Claims (1)

[Claims] R (R is at least one rare earth element including Y) is 25 to 35% (% represents weight %, the same applies hereinafter), B is 0.5 to 2.0%, M^1 (Fe , Co, Al
, Ni, Mn, Si, Ga) is 60-70%, M^2 (Cr, Mo, N
b, Ta, Ti, V, W, Zr) is 0.1 to 10.0% and C (carbon) is 0.0%.
A rare earth permanent magnet consisting of 1 to 1.0%, characterized in that C forms a carbide with M^2.