JPS58135605A - Manufacture of permanent magnet - Google Patents

Abstract

PURPOSE:To allow a permanent magnet to maintain such properties as those characteristic of a material demonstrating high performance without a decrease of Br due to substitution by boron by a method wherein, during the process of manufacturing the permanent magnet made of a rare earth cobalt intermetallic compound, sintering is carried out in the atmosphere of hydrogen to remove boron. CONSTITUTION:An alloy R(Co1-xBx)A is employed, where R is formed of one kind of rare earth element or a combination of more than one thereof as the main element of Sm, with 3.5<=A<=8.5, 0.001<=x<=0.3. An alloy composed of Sm(Co0.96B0.04)4.6 is subjected to arc fusion, after being roughly crushed in an iron mortar to prepare pulverized fine powder by means of a jet mill with a particle size of 4mum(F.S.S.S.). The crused fine powder obtained is subjected to transverse magnetization within a magnetic field of 10kOe for forming purposes and the formed body is subjected to two-stage sintering of 1,100 deg.CX1hr+1,140 deg.C X2hrs in a hydrogen current. In addition, after the body is held while being heated at 1,100 deg.CX0.5hr, it is gradually cooled to 830 deg.C at a cooling speed of 2 deg.C/min and then rapidly cooled within silicon oil.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an intermetallic compound consisting of a rare earth element and t'0@B. Rare earths, mainly RCo5; Baltic magnets have high magnetic anisotropy and relatively large saturation magnetization, so they are made into permanent magnets.
22MGOg at SwaCoq.

(Srxαy PrrLs) 26MG HiI with Co5
A sintered magnet with a (BE)nag of At present, Cb substitution type R2 (along with 'a17) is being used in many applications as a representative material for rare earth cobalt magnets. Problems such as the occurrence of phenomena that are likely to occur have arisen.

In order to solve these problems, replacing KCo with B was considered. Although the occurrence of cracks and the galling phenomenon were solved by improving the mechanical properties by B substitution, B1 by B substitution
There was a large decrease in the properties of the material, and the properties as a high-performance material could not be maintained.

The present invention was designed to prevent the reduction of By by B substitution. That is, by using a hydrogen atmosphere during sintering, it was possible to remove B and avoid a decrease in fir. The improvement in the mechanical properties of the powder due to B substitution is mainly exhibited during compaction in a magnetic field.

In other words, the B-substituted powder improves the pressure transmission rate and alleviates the galling phenomenon with the mold, resulting in a crack-free molded product.

The deboronization is usually carried out in a hydrogen atmosphere at a temperature range of 1080-1180 t). In the case of alloys containing B, the sintering temperature tends to decrease, but since it is related to the pulverized particle size, it becomes possible to sinter powder with a relatively large pulverized particle size. B removal is carried out during the process of densification, but the so-called open p
It is most efficient to remove B in the presence of ort. Therefore, two-stage sintering can also be adopted. In other words, in the first stage of sintering, the density is reduced to 75 to 85 of the theoretical density while removing B.
16! In the second stage of sintering, the theoretical density is 97~
Get 98 yen. Also, since this tax B uses hydrogen, it is necessary to create an escape route for B. Therefore, consideration must be given to the arrangement of the sintered body in the furnace, the flow of hydrogen gas, etc. in order to optimize the removal of B.

The sintered magnet obtained by the present invention has B in the sintering process.
This is because diffusion becomes active due to the behavior of

It becomes very homogeneous. Therefore, the material is highly thermally stable and weather resistant.

The sintered magnet according to the present invention is generally produced by melting into an ingot, coarsely crushing the ingot, or finely crushing the ingot.

It is manufactured by compression molding in a magnetic field, sintering with removal of B, and heat treatment. For melting, At or Ar is introduced, then B is introduced, and finally rare earth elements, which are easily oxidized and have a high vapor pressure, are introduced. Although it is cast in a molten metal +t-y-i case, it is sometimes cast into a water-cooled ingot because it is necessary to produce a homogeneous ingot without segregation. Alternatively, the ingots may be divided into a large number of comparatively small quantities and cast.

Coarse pulverization is performed as a pretreatment for fine pulverization using a crusher, a brown mill, an iron mortar, or the like. Both are -52
The grain size is about the same as that of a meshi. Fine grinding is done by jet
Mills, vibratory mills, and ball mills are used, all of which require a non-oxidizing atmosphere. N2 gas for jet mills, acetone for vibration mills and ball mills.

Organic solvents such as toluene and alcohol are used. When an organic solvent is used, drying is carried out under vacuum at a temperature of 50 μm in a heatable vacuum box. The optimum fine particle size varies depending on the composition, but is generally 3 to 7 μm (F, S, S, S). Compression molding in a magnetic field is carried out at a magnetic field strength of 10-20 KC7g and a molding pressure of 2-10t09/ai. There are two types of compression molding: vertical magnetic field and horizontal magnetic field, and the choice is made depending on the shape of the product and the required magnetic properties. Horizontal magnetic field forming provides a better degree of orientation than vertical magnetic field, and generally provides higher magnetic properties. Sintering can be performed in a 4r and B# air stream, in a vacuum, or in a hydrogen stream, but in order to remove B, it is necessary to carry out the sintering in a hydrogen stream. The sintering temperature varies depending on the composition and the pulverized particle size, but a temperature of 1000 to 1180 is used. The method of flowing the hydrogen stream for removing B differs depending on the structure of the furnace, but care must be taken to ensure that B easily rides on the hydrogen stream and is discharged to the outside pressure of the furnace. The deboronized and densified sintered body is heat treated, but generally a slow cooling and quenching type in an Ar@ flow is used. For example, 1080υxO0
5^r, after heating and holding, slowly cool at a cooling rate of 0.5"! t7/vain, and after reaching 800-900 V, immediately cool it to 20-400 V, and cool it in Jr. air flow at a cooling rate of 8-n. It is rapidly cooled in oil.

The alloy used in the present invention is R(Co1-:xBx)A. Here, R is 1 of a rare earth element centered on Sn+.
species or a combination of two or more species, 5.5≦A≦8.5
, 0.001≦X≦0.5. If A is 35 or less.

Because the rare earth element content becomes too large, the saturation magnetization decreases sharply, and when it is 8.5 or more, a - ('6 occurs as dendrites and reduces the crystal magnetic anisotropy. When X is 0.001 or less If the mechanical properties of the material are not sufficiently improved by B substitution, and if it is 0.5 or more, the residual amount of B is high (
This results in a large decrease in saturation magnetization, making it undesirable as a permanent magnet material. Note that a part of Co is II, (,'u, Ni,
Ti, Zr, Bf, Nlr, Ta.

The effects of the present invention can also be obtained by substitution with elements such as Ml-Cα.

The present invention will be explained below with reference to Examples.

<Example 1> An alloy of 5ra (CO(196BAOa)4.6) was arc melted.

After coarsely pulverizing in an iron mortar, finely pulverized powder was prepared by pulverizing with a jet mill. The grinding particle size is 4 μm (p, s, s, s
). The obtained finely pulverized powder was subjected to transverse magnetic field molding in a magnetic field of 10 KOg. , this molded body was heated at 1100°C in a hydrogen stream.
Sintering was performed in two stages: 1 hr + 1140 t x 2 hrz. Further, after heating and holding at Kt + oo°C x 0.5ArI.

It was slowly cooled down to 850V at a cooling rate of 2/ratn and quenched in silicone oil. The obtained magnetic properties are shown in Table 1. For comparison.

The case of sintering in +15clX2Ar# lr is also shown.

Table 1 also shows the B content values for sintering in hydrogen and Ar.
It can be seen that the amount of B in the case of sintering in hydrogen is z=o, oos, and that B is sufficiently removed.

Example 2> (Prt12Snaαa) CCO11L98BQB
2) The alloy 4.7 was treated in the same manner as in Example 1 to obtain finely pulverized powder. The obtained pulverized powder was molded in a vertical magnetic field into 20”
A toroidal-shaped powder compact of 10"
Two-stage sintering of 150t×2Ar# was performed. 1 more
100υ×α5hr, 2t/ra*n after heating and holding
The sample was slowly cooled to 950 υ at a cooling rate of 1, and then rapidly cooled in silicone oil.

The obtained magnetic properties are 9500G to Br "EC" 8700 (h IEc P-1950001 (BH) am -215lQO.

The density was B-5097cc. Although the amount of residual B was z=o, oo2, no cracks were observed. For comparison (Prα2S course u
) Coa and y were also treated in the same way, but could not be molded due to peeling phenomenon◎ <Example 3>((,"1155ma5)(t'0l-ZBac
)4.5&: 0, 0.001.

0.02, 0.04, 0.1, a2, rJ
, 5, and 0.4 were treated in the same manner as in Example 1 to produce finely pulverized powder. The obtained pulverized powder was subjected to transverse magnetic field molding. These molded bodies were sintered between 900 and 00t7. B removal treatment was carried out at 800° C. x 2 hrz in a hydrogen stream before sintering, and after heating and holding at 1000 υ x 1 hr, the material was cooled down to 800 V at a slow cooling rate of 2 V/sin and quenched in silicone oil. FIG. 1 shows the obtained magnetic properties and the amount of residual B. It can be seen that when the amount of B is up to 0.5, no deterioration of magnetic properties is observed and a good sintered body can be obtained.

[Brief explanation of drawings]

Claims (1)

[Claims] R(Co1-zBx)A (where R is one or a combination of two or more rare earth elements centered on the S shoulder. 55≦A≦8.5, 0.001≦X ≦0.5) In the process of manufacturing a rare earth cobalt intermetallic compound permanent magnet having a composition of A method for producing a permanent magnet that is homogeneous and has good thermal stability.