JPH0669010A - Manufacture method of r-t-m-n based bonded magnet - Google Patents

Abstract

PURPOSE:To devise a manufacturing method for a R-T-M-N based bonded magnet having ThMn12 type crystal structure substituting for an Nd-Ti-Fe nitride base magnet easily producing the particles having super-fine crystal structure gaining coersive force exceeding 3kOe easily processed later. CONSTITUTION:Nd-N-Fe based powder in specific composition (where M: contains at least one out of Cr, V, Mo or a part thereof can be substituted with Ti not exceeding 50%) are formed into a mixture in atomic order by mechanical alloying step and then further heated for diffusion at 600-850 deg.C to produce particles of a specific mean crystalline particle diameter in the main phase of RT12x-Mx (where x=1-2) having TyMn12 type crystal structure to be nitrified in N2 gas atmosphere meeting specific requirements for making the produced Nd-M-Fe based powder coupled with resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an R-T-M-N-based bonded magnet which has a low rare earth concentration and can be used in various motors and actuators, is low in cost, and has high corrosion resistance. The required metal powder or alloy powder mixed and mixed with the composition is mechanically alloyed in a specific atmosphere, and R having a ThMn ₁₂ type crystal structure is subjected to diffusion treatment.
T _{12- ■} M _■ (where α = 1 to 2) as the main phase is an aggregate powder with a fine crystal structure, which is further nitrided and is bonded with a resin to have a high coercive force R-T-M -It is related with the manufacturing method of a N type bond magnet.

[0002]

2. Description of the Related Art Resin-bonded magnets are used in various fields for reasons such as good dimensional accuracy, cost reduction advantage of integral molding with multiple members, and good yield in thin-wall molded products. There is a -Fe-B type powder. N
As the d-Fe-B based permanent magnet powder, a magnet powder having an ultrafine structure obtained by a superquenching method or the like has been used. The Nd-Fe-B system permanent magnet powder has a low Curie point (Tc) of around 300 ° C and a large temperature coefficient of Br and iHc, and thus has a problem that the temperature coefficient of magnet characteristics is large. Bring up Tc
However, the temperature coefficient α of Br is limited to about −0.08% / deg at most.

Recently, the R ₂ Fe ₁₇ compound has occluded N ₂ to increase Tc nearly twice as much as an absolute temperature, resulting in Nd-
160 ° C higher than Tc of Fe-B system, and further Sm ₂
It has been reported that the Fe ₁₇ nitride can provide an anisotropic magnetic field exceeding the anisotropy of R ₂ Fe ₁₄ B.

[0004]

Since the Sm ₂ Fe ₁₇ nitride contains a large amount of Sm, which is a small amount of resources, there is a problem that it becomes relatively expensive, and a permanent magnet powder containing abundant resources of other elements is used. It has been demanded.

Nd-Ti-Fe nitride based magnets have also been proposed, but Nd-Ti-Fe nitride based magnets are magnetized by containing about 18 wt% of Nd, which is a low melting point zinc-bonded magnet. Although it can be used for production, a sufficient coercive force was not obtained as a resin-bonded magnet. This is because in the zinc-bonded magnet, the crystal grain size of the main phase having the ThMn ₁₂ type crystal structure is much larger than the critical diameter of single domain particles, and is several μm. That is, when a zinc-bonded magnet is pulverized as a powder for a bonded magnet, the crystal grain size is not sufficiently smaller than the grain size of the granules, so that a large dependence of the magnetic properties on the powder grain size appears, and when the grain size becomes smaller, the intrinsic coercive force becomes smaller. There is a problem that iHc is extremely deteriorated.

The present invention is an R-T-M- having a ThMn ₁₂ type crystal structure which replaces the Nd-Ti-Fe nitride based magnet.
The purpose is to provide bonded magnets of N-based composition, and
An object of the present invention is to provide a method for producing an R-T-M-N bond magnet in which a coercive force of 3 kOe or more can be obtained, a powder having an ultrafine crystal structure can be easily obtained, and the powder can be easily handled thereafter.

[0007]

According to the present invention, the heat treatment for crystallizing the ThMn ₁₂ type crystal structure after mechanical alloying can be performed at about 700 ° C., and as a result, the crystallized crystal grain size is equivalent to the single magnetic domain grain size. As a result of various investigations on the composition which can be expected to exhibit the coercive force for the purpose of stabilizing elements of the ThMn ₁₂ type crystal structure other than Ti, Cr, V
And Mo have been found to be particularly effective, and N of a specific composition
A mixture of d-M-Fe-based powder (M: at least one of Cr, V, Mo can be substituted or a part thereof can be replaced with 80% or less of Ti) by mechanical alloying in the order of several tens of Å. After making, further 600-850
By heat diffusion treatment at ℃, it is possible to obtain a powder having a specific average crystal grain size with a main phase of RT _12-x M _x (where x = 1 to 2) having a ThMn ₁₂ type crystal structure. By nitriding in N ₂ gas under specific conditions,
It has been found that a required R-T-M-N based alloy powder having a coercive force of 3 kOe or more can be produced, the handling of the powder thereafter becomes easy, and a bond magnet can be produced by binding with a resin. completed.

That is, the present invention provides R 7-18 at
% (R: at least one rare earth element and 80% or more of one or two Pr or Nd), T 54 to
83 at% (T: Fe or a part of Fe is replaced by 50% or less of Co), M 7 to 16 at% (M: Cr,
At least one of V and Mo is added, or a part of it is replaced by 80% or less of Ti), and the above-mentioned required metal powder or alloy powder is mixed and mixed, and then in a vacuum or Ar gas. RT having a ThMn ₁₂ type crystal structure is obtained by mechanical alloying in a heat diffusion treatment at 600 to 850 ° C. for 10 minutes to 12 hours.
_A powder having an average grain size of 0.5 μm to 500 μm having a fine crystal structure of 12 μx M _x (where x = 1 to 2) as a main phase and having an average crystal grain size of 0.05 μm to 0.5 μm was obtained. 420 to 650 in 0.5 to 50 atm N2 gas
Perform nitriding treatment by holding at ℃ for 10 minutes to 12 hours, and
7-18 at%, T 54-83 at%, M 7-16
A method for producing an R-T-M-N based bonded magnet, characterized in that permanent magnet powder containing at% and N3-12 at% is bonded with a resin.

Reasons for limiting powder composition In the present invention, the rare earth element R is Y, La, Ce or P.
r, Nd, Sm, Gd, Tb, Dy, Ho, Er, T
m and Lu are included, and at least one of them may be contained in one or two kinds of Pr or Nd in an amount of 80% or more of R, and all of R may be Pr or Nd or Pr and Nd. . It is 1 of Pr or Nd that 50% or more of R is one or two of Pr or Nd.
This is because if 50% or less of two kinds or less, sufficient magnetic anisotropy cannot be obtained, and use of Pr or Nd has an effect of reducing raw material cost as compared with Sm.

Since R tends to adhere to the inner wall of the mill, the surface of the ball, etc. during mechanical alloying, or to decrease due to oxidation, etc., it becomes excessive when compared with the amount of R in the stoichiometric composition of the ThMn ₁₂ type compound during compounding. There is a need to. Therefore, if R is less than 7 at%, the coercive force decreases due to the precipitation of α-Fe, and if it exceeds 18 at%, the non-magnetic phase or the soft magnetic phase precipitates and the residual magnetic flux density deteriorates.
At%

The iron group element T contains at least one of Fe and Co, and it is important that Fe is contained in an amount of 50% or more of T. That is, when Fe in T is less than 50%, sufficient magnetization cannot be obtained, which is not preferable. It is particularly preferable to add Co to less than 50% of T because the Curie temperature rises.
When T is less than 54 at%, a compound having a low coercive force is precipitated to reduce the coercive force and the residual magnetic flux density, and when T is more than 83 at%, the coercive force and the squareness are deteriorated due to α-Fe precipitation.
4 to 83 at%.

M, that is, at least one of Cr, V, and Mo is contained, or a part of the content is 50% or less of Ti.
RFe _12-x M having a ThMn ₁₂ type structure
It is an essential element for forming the _x compound, and if it is less than 7 at% (x is less than 1), the R ₂ Fe ₁₇ phase and α-Fe are not precipitated to obtain the desired compound, and more than 16 at% (x Is more than 2.0), the magnetization is remarkably reduced, so the content is set to 7 to 16 at%. Ti is one of the stabilizing elements of the ThMn ₁₂ type structure, and can be used as a part of M. However, when Ti exceeds 50% of M, the stable temperature range of the ThMn ₁₂ type structure becomes 850 ° C. or higher. Therefore, Ti is set to 80% or less of M because the fine crystal structure of No.

When N is less than 3 at%, sufficient uniaxial anisotropy cannot be obtained, and when it exceeds 12 at%, ThMn1
The type 2 structure becomes unstable, and the parent phase is the R ₂ Fe ₁₇ phase or α-F.
Since it is not preferable because it decomposes into e, it is set to 3 to 12 at%.

Reasons for Limiting Manufacturing Conditions In the present invention, the mechanical alloying method involves mixing and adjusting a pure metal powder or an alloy powder mixed in a required composition, and then storing a finely pulverized medium such as steel balls in a vacuum or Ar gas. The alloy is mechanically alloyed by the fine pulverizer. As a device used for mechanical alloying, a ball mill, a vibration mill, a planetary ball mill, an attritor, etc. can be used if the inside of the container can be replaced with an inert gas,
Since the operating conditions differ depending on the performance, etc., it must be selected appropriately.

After mechanical alloying, diffraction lines other than the peaks of α-Fe and the element M (Cr, V, Mo) are powder X.
It usually does not appear in the line diffraction pattern, and it is preferable to perform the mechanical alloying treatment until the state is reached. Diffusion treatment condition after mechanical alloying is 6
The reason for limiting the temperature to 00 to 850 ° C. for 10 minutes to 12 hours is as follows. If the diffusion treatment temperature is lower than 600 ° C., the diffusion rate of the constituent elements is slow, and therefore, from the composition obtained by mixing the constituent elements obtained after mechanical alloying in a microscopic order, an RFe _12-x M _x compound having a ThMn ₁₂ type structure is obtained. It is not preferable because the rate of precipitation of iron is extremely slow and the reaction takes a long time. If it exceeds 850 ° C, ThMn ₁₂ R
The Fe _12-x M _x compound is rapidly produced, but it becomes coarse crystals and the coercive force is lowered, which is not preferable. Spreading processing time is 1
If it is less than 0 minutes, it will be difficult to make the entire powder into a uniform structure, and if it exceeds 12 hours, the coercive force will decrease due to the growth of coarse grains and the powder will be oxidized during the heat treatment, resulting in a decrease in magnetic properties and a processing cost. It is not preferable because it rises sharply. A more preferable diffusion processing time is 30 to 60 minutes.

The average crystal grain size of the powder after the diffusion treatment is 0.0
The reason for limiting the thickness to 5 μm to 0.5 μm is that it is practically difficult to generate crystals with a thickness of less than 0.05 μm, and even if crystals with a size of less than 0.05 μm are obtained, there is no advantage in terms of properties,
This is because if it exceeds μm, it becomes larger than the critical diameter of the single domain particle, and the coercive force of the powder decreases, which is not preferable as the powder for permanent magnet.

In the present invention, the average particle size of the fine powder having a fine crystal structure is limited to 0.5 to 500 μm. When the average particle size is less than 0.5 μm, there is a risk of magnetic deterioration due to oxidation of the powder, and when it exceeds 500 μm. This is because nitriding requires a long time and is not preferable.

The N ₂ pressure during the nitriding treatment is 0.5 to 50 at.
The reason for limiting to m is that the nitriding reaction rate is slow when the pressure is less than 0.5 atm and the reaction proceeds rapidly when the pressure is increased.
If it exceeds 50 atm, the processing equipment becomes too large, which is not preferable in terms of industrial production cost. The reason for limiting the temperature during nitriding treatment to 420 to 650 ° C is 420 ° C.
If it is less than 650 ° C, nitriding does not proceed, and if it exceeds 650 ° C, α-Fe
And RN are generated and the RTM compound (RT _12-x M _x ) is decomposed, resulting in deterioration of magnet characteristics. Also,
If the holding time during the nitriding treatment is less than 10 minutes, sufficient nitriding does not proceed, and if it exceeds 12 hours, decomposition occurs and deterioration of magnet characteristics is caused, so that the holding time is set to 10 minutes to 12 hours.

The Fe-BR bond magnet according to the present invention relates to anisotropic and isotropic magnets, and is well known in the following compression molding, injection molding, extrusion molding, rolling molding, resin impregnation method and the like. Any of the above manufacturing methods may be used.
In the case of compression molding, a thermosetting resin, a coupling agent, a lubricant, etc. are added to the magnetic powder and kneaded, followed by heating after compression molding,
It is obtained by curing a resin. In the case of injection molding, extrusion molding, and rolling molding, it is obtained by adding and kneading a magnetic powder with a thermoplastic resin, a coupling agent, a lubricant, etc., and then molding by injection molding, extrusion molding, or rolling molding. . In the resin impregnation method, the magnetic powder is compression-molded, heat-treated as required, impregnated with a thermosetting resin, and heated to cure the resin. In addition, the magnetic powder is obtained by compression molding, heat treatment if necessary, and then impregnated with a thermoplastic resin.

In the present invention, the filling rate of the magnetic powder in the bonded magnet depends on the manufacturing method, but is 70-9.
It is 9.5 wt% and the balance 0.5 to 30 wt% is resin or the like. In the case of compression molding, the filling rate of magnetic powder is 9
5-99.5 wt%, 90-95w in case of injection molding method
t%, and in the case of the resin impregnation method, 96 to 99.5 wt% is preferable. In the present invention, the synthetic resin used as the binder may be either thermosetting or thermoplastic, but a thermally stable resin is preferable, for example, polyamide, polyimide, polyester, phenol resin, fluororesin, silicon resin, epoxy resin. Etc. are appropriately selected.

[0021]

According to the present invention, since at least one of Cr, V and Mo is contained as a stabilizing element of the ThMn ₁₂ type crystal structure or a part thereof is replaced by Ti, the ThMn ₁₂ type crystal structure is mechanically alloyed after mechanical alloying. The heat treatment for crystallization can be performed at about 700 ° C., and as a result, the crystal grain size of the crystal is equal to the single domain grain size, and the coercive force is exhibited. Further, the present invention is, after the prepared mixture in atomic order the R-T-M-N based alloy powder of a specific composition in mechanical alloying by heating diffusion treatment further 600 to 850 ° C., ThMn ₁₂ Having a crystal structure
It is possible to obtain a powder having a specific average crystal grain size of _{12- ■} M _■ (where α = 1 to 2) as a main phase, and subjecting this to nitriding treatment in N ₂ gas under specific conditions to give 3 kOe or more. The required R-T-M-N based alloy powder having a coercive force of 1 can be produced, the subsequent handling of the powder becomes easy, and the R-T-M-N based alloy powder can be easily bonded by binding it with a resin. A bonded magnet can be manufactured.

[0022]

【Example】

Examples Nd powder having a particle size of 250 μm or less, Fe powder having a particle size of 150 μm or less, Co powder, Mo powder, and C as raw metal powders
After mixing r powder, Ti powder and V powder into the composition shown in Table 1,
36g of this blended raw material is 128mm in diameter x 132m in length
It is inserted into a ball mill of m size, and further, a stainless steel ball having a diameter of 9.8 mm is charged as a finely pulverizing medium. After replacing the inside of the ball mill with Ar gas, the rotation speed is 95 rpm and the rotation time is 100 hours. Mechanically alloyed. As a result of mechanical alloying, Example No. 1 to
The raw material of No. 11 was a fine powder having an average particle size of 1.5 μm. This powder was found to have an amorphous phase and crystalline α- by X-ray diffraction.
It was a mixture phase of Fe and M (M: Cr, V, Mo).

Next, heat treatment is performed in Ar gas under the diffusion treatment conditions shown in Table 1, and RT _12-x M _x (where x = 1 to 2) having a ThMn ₁₂ type crystal structure is used as a main phase. A powder was obtained. The average crystal grain size and the average grain size of the powder are respectively 0.
It was 1 μm and 1.5 μm. As a result of SEM observation, the particle size distribution of the powder was large, and each powder appeared to be agglomerated with fine particles.

Further, nitriding was performed under the conditions shown in Table 2 in N ₂ gas stream having N ₂ pressure of 1 atm, and then cooled. The composition of the obtained powder alloy is shown in Table 1. Further, 2.0 wt% of epoxy resin was added to the obtained powder alloy, and after resin bonding, the characteristics of the bonded magnet were measured and shown in Table 2.

Comparative Example Using the same raw material powder as in Example, the composition shown in Table 1 was added, and then the same mechanical alloying treatment as in Example was applied, and the obtained powder was held at 300 ° C. for 15 minutes for diffusion. The heat treatment was performed, and the same nitriding treatment as in the example was performed to obtain a magnet powder (Comparative Example No. 12). The composition of the obtained powder is shown in Table 1, and the characteristics are shown in Table 2. Example No. Two
After blending to the same composition as the sample, the same mechanical alloying treatment and diffusion heat treatment as those in the example are applied to obtain 900 ° C., N
₂ and cooled after nitriding treatment pressure of 2 atmospheres, the resulting powder (Comparative Example No.13) the composition of Table 1, the properties of the bonded magnet after the resin binding in the same manner as in Example were measured Table 2 Shown in.

Using the same raw material powder as in the example, Nd1
After mixing so as to have a compounding composition of 4 at%, Fe 79 at%, and Ti 7 at%, the same mechanical alloying treatment as in the example was performed, and further, a diffusion heat treatment in Ar gas was performed at 800 ° C. for 10 hours, which was obtained. As a result of X-ray diffraction of the powder, the obtained powder (Comparative Example No. 14) was NdFe.
It was found to be a mixture of ₇ , NdFe ₇ and TiFe ₂ . Even when the nitriding treatment of holding the powder of Comparative Example at 650 ° C. for 15 minutes was performed, the coercive force of the obtained bond magnetic force was 1 kO.
It was below e.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

According to the present invention, at least one of Cr, V, and Mo is contained as M of the stabilizing element of the ThMn ₁₂ type crystal structure, or a part thereof is replaced by 80% or less of Ti in a specific composition. By using the -M-Fe-based compounded powder, the heat diffusion treatment after mechanical alloying is 600-
The temperature can be set to a relatively low temperature of 850 ° C., and this diffusion treatment facilitates RT having a ThMn ₁₂ type crystal structure.
It is possible to obtain a powder having a specific average crystal grain size of _{12- ■} M _■ (where α = 1 to 2) as a main phase, and subjecting this to nitriding treatment in N ₂ gas under specific conditions to give 3 kOe or more. The required R-T-M-N based alloy powder having the above coercive force can be produced, the subsequent handling of the powder becomes easy, and various forms of R-T-M-N based bonded magnet can be obtained by combining with the resin. Can be easily manufactured.

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Claims (1)

[Claims] 1. R 7-18 at% (R: at least one rare earth element and 80% or more of one or two Pr or Nd), T 54-83 at% (T: Fe
Alternatively, a part of Fe is replaced with 50% or less of Co), M
7 to 16 at% (M: Cr, V, Mo at least 1
The required metal powder or alloy powder is mixed and mixed, and then mechanically alloyed in a vacuum or in Ar gas so that the content of the seed or the composition thereof is replaced by 80% or less of Ti). Further 600-850 ℃, 1
By heat diffusion treatment for 0 minutes to 12 hours, RT _12-x M _x (where x = 1 to 2) having a ThMn ₁₂ type crystal structure as a main phase and an average crystal grain size of 0.05 μm to 0.5 μm A powder having a fine crystal structure and an average particle size of 0.5 μm to 500 μm is obtained, and the powder is subjected to a nitriding treatment in which the powder is kept at 420 to 650 ° C. for 10 minutes to 12 hours in 0.5 to 50 atm of N ₂ gas, and R 7-18 at%, T 54-83 at
%, M 7 to 16 at% and N 3 to 12 at% are obtained, and this is bonded with a resin, and a method for producing an R-T-M-N bond magnet is characterized.