JPH04263403A - Anisotropic permanent magnet and manufacture thereof - Google Patents

Abstract

PURPOSE:To enhance the magnetic efficiency of an R-Fe-B anisotropic magnet, and to facilitate its manufacture. CONSTITUTION:The title permanent magnet is composed of a rare-earth element of 10 to 21 atomic %, boron of 3 to 15 atomic %, and the remaining part consisting of an iron group element and inevitable impurities. When the iron- group element is 100 atomic %, its X-atomic % is replaced with cobalt, and Y-atomic % is replaced with nickel. X is 30 atomic % or smaller, and Y is 1.5 atomic % or smaller, the alloy of raw material, having (X+10Y) of 11 atomic % or more, is formed into spherical powder by a gas atomizing method in which inert gas is used, and a molded article is formed by plastically processing the powder at 550 to 800 deg.C.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth-iron-boron (R--Fe--B) permanent magnet having anisotropic magnetic properties and a method for manufacturing the same.

0002

BACKGROUND OF THE INVENTION Anisotropic permanent magnets are known that use an alloy containing 10 to 21 atomic percent of rare earth elements, 3 to 15 atomic percent of boron, and the balance being iron and unavoidable impurities. Here, one or both of Nd and Pr is generally used as the rare earth element, and the effects of both elements on the magnetic properties of the product are almost the same. There are two methods for imparting anisotropy to this alloy:

[0003] The first manufacturing method involves casting an alloy ingot with a predetermined composition, pulverizing it into fine powder of 3 to 10 μm, orienting the powder in a magnetic field, shaping it, and then molding it in an inert gas atmosphere. Sinter treatment.

[0004] The second manufacturing method involves melting an alloy of a predetermined composition, rapidly solidifying it by melt spinning to obtain flakes, forming the flakes by hot pressing, and further processing by hot upsetting. Apply pressure to orient the axis of easy magnetization in the direction of application.

[0005] In the magnets manufactured by these methods,
For the purpose of improving the magnetic performance, attempts have been made to replace part of R with Dy or part of Fe with Co.

[0006]

[Problem to be solved by the invention] Although the addition of Co was found to be effective in raising the Curie point of the magnet and reducing the demagnetization rate at high temperatures, the magnetic properties, especially the maximum magnetic energy product, were hardly improved. . Addition of Dy can improve magnetic properties, but Dy is extremely effective and poses a practical problem. Therefore, this invention provides R-Fe-B
The aim is to improve the magnetic properties of the anomalous permanent magnet system, especially the maximum magnetic energy product.

[0007]

[Means for Solving the Problems] The basic composition of the raw material alloy used in this invention is 10 to 21 atomic percent of well-known rare earth elements, 3 to 15 atomic percent of boron, and the balance is iron group elements and unavoidable impurities. As a rare earth element, N
Use one or both of d and Pr. As a feature of this invention, the iron element in the alloy is composed of X atomic % of cobalt, Y atomic % of nickel, and the balance iron, and these X and Y are as follows: 0≦X≦30 0≦Y≦1 .5 This value satisfies X+10Y≧11.

[0008] In this invention, in order to impart irregularity to the product, the above raw material alloy is melted, it is made into a spherical powder by a gas atomization method using an inert gas, and this powder is heated at a temperature of 550°C to 800°C. By plastic working, it is molded into a predetermined shape and at the same time gives irregularity.

As the above-mentioned inert gas, argon, neon, helium, or a mixture thereof is used. The size of the spherical powder used for plastic processing is such that if it is extremely small, it will oxidize during handling, and if it is too large, it will interfere with plastic processing.
It is desirable that the thickness is 0 μm or less. Furthermore, during plastic processing, in order to prevent oxidation during heating and processing, it is desirable to vacuum seal the powder in a metal container capable of plastic processing, and heat and process the entire container.

[0010] Examples of the plastic working include forward extrusion processing,
Appropriate methods such as backward extrusion, ring extrusion, rolling, and warm upsetting can be employed, and the direction in which anisotropy is produced is determined by the direction of strain produced at that time. In order to obtain remarkable anisotropy, it is desirable that the processing ratio (cross-sectional area before processing/cross-sectional area after processing) be 4.6 or more.

[0011] During plastic working, if the working speed is too high, the strain rate of the material will increase and cause damage, so it is necessary to suppress the strain rate to 0.3 or less. The strain rate Ve is calculated as follows, regardless of the processing mode. Strain E=lnK Strain rate Ve=E/T (sec -1) Here, k is the machining ratio, and T is the residence time from when a certain part of the material enters the machining area to when it leaves the machining area. .

0012

[Function] In the above-mentioned two conventional manufacturing methods, even if a part of the iron in the raw material alloy was replaced with one or both of cobalt and nickel, no noticeable improvement in magnetic properties could be obtained. However, in the present invention, a gas atomization method using an inert gas is used to powderize the raw material alloy, and the powder is vacuum-sealed in a container and heated and plastic-processed. Alternatively, the effect of partially substituting iron with nickel was noticeable, and the magnetic properties, especially the maximum magnetic energy product, could be greatly improved. The biggest reason for this is thought to be that oxidation of the raw material powder was suppressed from the time of powdering the raw material alloy to the completion of plastic working.

It is known that Nd and Pr have almost the same effect on the magnetic properties of products. In other words,
Even if part or all of Nd is replaced with Pr, as long as the ratio of the total amount of Nd and Pr in the alloy remains constant, the magnetic properties of the product will hardly change. FIG. 1 shows the range of amounts of cobalt and nickel to replace iron in the raw material alloy. That is, when the relationship between the amount of cobalt X (at %) and the amount of nickel Y (at %) in the total amount of iron, cobalt, and nickel (100 at %) is X+10Y<11, and the amount of cobalt X is 3
If the nickel content Y exceeds 0 atomic % or exceeds 1.5 atomic %, the magnetic properties of the product will not be sufficiently improved.

Furthermore, in the present invention, it is possible to employ a plastic working method with extremely good productivity, such as forward extrusion, making it possible to industrially advantageously produce anisotropic magnets with excellent performance. Ta.

[0015]

EXAMPLES Example 1 Various R-Fe-B alloys shown as Samples 1 to 6 in Table 1 were melted and powdered to a particle size of 298 μm or less by argon gas atomization. Each of these is filled into a mild steel capsule with an outer diameter of 28 mm, a length of 35 mm, and a wall thickness of 1 mm, the inside of which is evacuated and sealed by electron beam welding. This was made into a billet and subjected to forward extrusion processing under the following conditions. Preheating 600℃ x 5 minutes Extrusion temperature
650±5℃ Extrusion ratio 4.0 (diameter 28mm → diameter 14mm)
Strain rate 0.05 per second

Table 1 shows the magnetic properties of the obtained magnet material. Note that Z is the extrusion direction, r is the radial direction, and θ is the direction perpendicular to r.

[Table 1] Examining Table 1, it can be seen that the magnetic properties of Samples 3, 4, and 5 are significantly improved by the addition of Co, but Samples 2 and 6 have significantly improved magnetic properties.
Almost no improvement in magnetic properties was observed by the addition of Co.

Example 2 Various R-Fe-B alloys shown as Samples 7 to 9 in Table 2 were each powdered under the same conditions as in Example 1 and processed into magnet materials under the same conditions. Table 2 shows the magnetic properties of the obtained magnet material.

[Table 2] Examination of Table 2 shows that the magnetic properties of Sample 8 are significantly improved by the addition of Ni, but in Samples 7 and 9, almost no improvement in the magnetic properties by the addition of Ni is observed.

Example 3 Various R-Fe-B alloys shown as Samples 10 to 12 in Table 3 were powdered under the same conditions as in Example 1, and processed into magnet materials under the same conditions. Table 3 shows the magnetic properties of the obtained magnet material.

[Table 3] Examining Table 3, samples 10 and 11 contain Ni and Co.
Although the effect of improving magnetic properties by simultaneous addition of
In sample 12, the magnetic properties are rather reduced.

FIG. 1 shows the distribution of Samples 1 to 12, with the Co content X (atomic %) plotted on the horizontal axis and the Ni content (atomic %) plotted on the vertical axis. Reference numerals 1 to 12 in the figure indicate the sample numbers, and the numbers in parentheses indicate the maximum magnetic energy product (BH) max (MGOe) in the r direction. As is clear from FIG. 1, the range in which the maximum magnetic energy product in the r direction is approximately 13 MGOe or more is the area surrounded by three straight lines where X=30 Y=1.5 X+10Y=11.

[0020]

[Effect of the invention] As is clear from the above examples,
According to the present invention, the magnetic properties of an R-Fe-B magnet alloy can be improved by adding one or both of Co and Ni, and a gas atomization method with good productivity and an appropriate method with good productivity can be used. By employing the plastic working method, irregular magnets with desired shapes can be mass-produced at low cost.

[Brief explanation of the drawing]

FIG. 1 is a distribution diagram showing the range of Co amount and Ni amount in the present invention.

[Explanation of symbols]

1-12 Sample number

Claims (2)

[Claims] Claim 1: 10 to 21 atomic % of rare earth elements, 3 to 15 atomic % of boron, and the balance consisting of iron group elements and unavoidable impurities, and the iron group elements are composed of X atomic % of cobalt and Y An alloy consisting of atomic% nickel and the balance iron, where X and Y are 0≦X≦30 (atomic%) 0≦Y≦1.5 (atomic%) X+10Y≧11 (atomic%) An anisotropic permanent magnet characterized by being a molded product of gas atomized powder using active gas. 2. Rare earth elements are 10 to 21 atomic %, boron is 3 to 15 atomic %, the balance is iron group elements and unavoidable impurities, and the iron group elements are cobalt in X atomic % and Y Melting an alloy in which atomic% is nickel and the balance is iron, and the above X and Y are 0≦X≦30 (atomic%) 0≦Y≦1.5 (atomic%) X+10Y≧11 (atomic%) The powder is made into a spherical powder by a gas atomization method using an inert gas, and this powder is heated at 550°C to 80°C.
A method for producing an anisotropic permanent magnet, characterized in that a molded product having a predetermined shape is obtained by plastic working at a temperature of 0°C.