JPS63216308A - Alloy powder for permanent magnet - Google Patents

Abstract

PURPOSE:To offer low-cost and high-performance alloy powder for a magnet, composed of a rare-earth element, iron and boron, which can be used both for sintering and for resin bonding by a method wherein the alloy powder which has been finely pulverized by a gas atomizing method are classified and they are then annealed while their heat-treatment condition is changed according to the range of their particle size. CONSTITUTION:Alloy powder for a permanent magnet by this invention are composed of 8-30 atomic % of R (R contains at least more than one rare-earth element including Y), 2-28 atomic % of B, less than 50 atomic % of Co and less than 15 atomic % of Mo; their remaining part is composed of Fe. Because the alloy powder is produced by using a gas atomizing method, their particle sizes are distributed widely. The powder of a big particle size whose particles are constituted by a crystal phase and where an amorphous phase is hardly detected are annealed at a high temperature and for long hours such as at 1000 deg.C and for 24 hours so that their coercive force can be increased. The powder of a small particle size which contains the amorphous phase are annealed at a low temperature and for short hours such as at 700 deg.C and for 10 minutes so that their high coercive force can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an alloy powder for permanent magnets based on a rare earth-iron-poron compound.

[Conventional technology]

Conventionally, alloy powders used in the production of rare earth-iron-boron magnets include crushed alloy ingots for sintering as shown in Japanese Patent Application Laid-Open No. 1987-54242. 64759, obtained by pulverizing a ribbon obtained by melt spinning. Powders obtained by a gas atomization method as disclosed in Japanese Patent Application Laid-Open No. 60-17905 were known. It was also known that powders such as those mentioned above were subjected to uniform heat treatment in order to improve their magnetic performance.

[Problem that the invention seeks to solve]

However, as mentioned above, the following prior art rare earth metals - iron -
Boron alloy powder for magnets has the following drawbacks. First, the powder obtained by crushing 1 alloy ingot is effective for use in sintered magnets, but the coercive force in powder form is
Since it is about Os, it cannot be used as resin pond ω Ishikawa powder. In addition, when using the melt spinning method, a powder that is effective for both sintered magnets and resin pound magnets can be obtained, but this powder is essentially isotropic and its gross energy product is 10 MGOg It is difficult to say that the advantages of rare earth-iron-bond magnets are fully utilized, and an extra step of pulverization is required compared to the atomization method. Although the powder is produced by the atomization method, when this powder is simply heat-treated, the performance obtained as a resin pound magnet is worse than that obtained by the melt spinning method, with (BH) maw = 5 MGOg culmability, and it has high properties. For oxidation, a pulverization step is required, which poses problems such as high cost and risk of oxidation.

The magnet alloy according to the present invention solves these problems, and its purpose is to create a rare earth alloy that is low cost, has high performance, and can be used for both sintering and resin ponds. The purpose of the present invention is to provide an alloy powder for iron-poron magnets.

[Means for solving problems]

The alloy powder for permanent magnets of the present invention has R (R#: at least one kind of rare earth element including tY) 8 to 30 atoms -B
(Boron) 2~28N To, Cjo (:l
/<Ruto) 50 atoms or less, Cjr (chromium) or Mo (molybdenum) 15 atoms or less, and the remainder is '
It is characterized by melting an alloy consisting of FPe (iron) and other impurities unavoidable in manufacturing, classifying the alloy powder into fine particles using a gas atomization method, and annealing the alloy powder by changing heat treatment conditions depending on the particle size range. do.

The reasons for limiting the composition of the alloy powder for magnets according to the present invention will be explained below. Rare earth elements include Y and Lα.

Oe, Pr, Nd, 13m, Ru,
Gd, Tb, Dy, Ho, Er
, Tmxb, and LuhZ candidates, and one or more of these may be used in combination. The highest magnetic performance is obtained with yd, pr, and therefore in practical terms Nd, Pr, Nd-P? -Alloy, Nd-Pr
-Oe alloy is used. The main phase of the R-Fe-B magnet is RPeB. Therefore, if R is less than 8 atoms, no flakes or the above-mentioned compounds are formed, and a cubic crystal structure having the same structure as α iron is formed, making it impossible to obtain Fe with high magnetic properties. On the other hand, R is 3
When the number of atoms exceeds 0, the non-magnetic Rτich phase increases and the magnetic properties are significantly deteriorated.

BkeR2Fgl is an essential element for forming the B phase, and if it is less than two atoms, a rhombohedral R-Fs groove structure is formed, so a high coercive force cannot be expected. If the number of atoms exceeds 7t28 atoms, the non-ferrous phase of B rich will increase and the residual magnetic flux density will drop significantly, so it is desirable that it is lower than that. The warm properties of the magnet are also improved. Basically ij Co
#'iR,F'g,, replacing the 7g site of B phase -(
However, as the amount added increases, a lav e s phase called R(Fg co) is formed, resulting in a decrease in coercive force. For this purpose, it is appropriate to add up to Viso atoms ts.

Or and Ni are elements that have a great effect on improving magnetic force, and their effects are observed when added up to about 30 atoms. However, increasing the amount of Cr or Mo added means decreasing the proportion of Fg, which greatly reduces the residual magnetic flux density If, so it is appropriate to add the amount up to 15 atoms.

Since the alloy powder for permanent magnets of the present invention is produced using a gas atomization method, the powder has a wide particle size distribution. The cooling rate hζ differs depending on the particle size, and therefore the fine structure of the powder is also complicated. As shown in Japanese Patent Application No. 61-29501 filed by the inventors of the present invention, with this alloy composition, a high coercive force can be obtained by heat treatment even in the casting method. Therefore, for powders with a large particle size where each particle is composed of a crystalline phase and almost no amorphous phase is observed, annealing is performed at a high temperature for a long time such as 1000℃ for 24 hours to improve the coercivity. Increase power. In addition, for small particle size powders that contain an amorphous phase, a high coercive force can be obtained by annealing at a low temperature of 700° C. for 10 minutes for a short time. In this case, care must be taken to ensure that the amorphous phase is not completely crystallized, as this is the key to achieving a high coercive force.

In addition, as mentioned above, it is heat-treated according to particle size and has a high coercive force.
The alloy powder is now mixed and used as alloy powder for resin-bonded magnets./l''-1 Due to the problem of magnet formability, the maximum particle size is required to vary by about 200 μm. Therefore, the particle size a is a condition for gas atomization.
: It is desirable that the thickness be up to about 20 μm. Since the alloy powder for sintered magnets is required to have a small particle size h1, the atomization conditions are also adjusted to produce powder with a small particle size.

〔Example〕

Hereinafter, the present invention will be described in detail based on examples.

(Example 1.) First, an alloy with a desired composition was high-frequency melted in a KR atmosphere, and supersonic gas atomization was performed using gauze gas.
A spherical powder of 0 μm or less was produced. This powder was classified into two types, 40 μm or more and 40 μm or less, using an air classifier.
For powders larger than 0 μm, heat treatment at 1000°C for 24 hours.
70'C for powders with a diameter of 40μm or less
Annealing treatment for 10 minutes was carried out in a heated chamber, and the mixture was mixed again.
Mixed with 2.5 wt epoxy resin, 15 KOe m
After molding in-situ, it was fired at 150°C to form a single resin bond, and its magnetic performance was measured.

Table 1 shows the compositions of various alloy powders for extrusion prepared by the above steps. At this time, Fe and CO with a purity of 999% or higher, af- and MO-based ferro alloys (61,6
%C! r and 61.7% MO), Vi7 zo as B
Holotho alloy (16,321B, o, 15% p,
l, a, 68% 5iO112%O1 balance Fg),
The rare earth metal used is one with a purity of 95% (impurities are mainly other rare earth metals).

Table 2 shows the magnetic performance when the composition powder shown in Table 1 was made into a resin pound by the method described above. The effect of orientation was different from that of amorphous powder, and clearly high magnetic performance was obtained.

Table 1 Table 2 (Sample 431.32 is sample /1622 and shoulder 27 respectively)
powder with the composition of 1000'CX24 without distinguishing the particle size.
(Example 2.) Of the compositions listed in Table 1, 42.10.24.26
Each type of powder was coarsely ground to under 80 mesh using a stamp mill, and then ground in a ball mill for 4 hours to obtain a fake fine powder with an average particle size of 4 μm. This fine powder was oriented in a magnetic field and molded at a pressure of 2tΔ1 at 1,1100°C x 2
Sintering was performed for 4 hours, followed by aging treatment at 700° C. for 1 hour. The magnetic performance of the sintered magnets thus obtained is shown in Table 3.

Table 3 [Effects of the Invention] - As described above, according to the present invention, it is possible to improve the magnetic properties of the gas atomized powder by applying heat treatment according to the grain deformation of the powder, especially for resin-bonded magnets. The use of this powder has the effect that its magnetic performance is clearly increased compared to conventional simple heat treatment or amorphous powder. Furthermore, when used in sintered magnets, its magnetic performance is sufficiently high, and it is industrially useful as a powder for canstone alloys, which can be used for both resin ponds and sintering processes at low cost.

that's all

Claims (1)

[Claims] (1) B (R is at least one kind of rare earth element including Y) 8 to 30 atom%, B (boron) 2 to 28 atom%, C
o (cobalt) 50 at % or less, Cr (chromium) or Mo (molybdenum) 15 at % or less, and the balance is Fe (
A permanent product characterized by melting an alloy consisting of iron) and other impurities that are unavoidable during manufacturing, classifying the alloy powder into fine particles using a gas atomization method, and annealing the alloy powder by changing heat treatment conditions depending on the particle size range. Alloy powder for magnets.