JPS62122108A - Manufacture of sintered rare earth magnet - Google Patents

Abstract

PURPOSE:To obtain excellent magnetic characteristics, particularly, high coercive force (Hc) and the maximum energy product by roasting a molded shape and applying vacuum deaeration treatment to the molded shape at a specific temperature before it is transferred to a sintering process in an inert-gas atmosphere. CONSTITUTION:Molded shaped containing rare earth metals can be manufactured according to the manufacture of all molded shaped which have been adopted in the manufacture of sintered rare earth magnets, and the molded shapes being manufactured are arranged on shelves in a furnace, and roasted for normally 30-300min at a temperature of 100-500 deg.C in a hydrogen gas current at normally approximately 1atm. The molded shapes are roasted, and vacuum deaeration treatment is executed to the molded shapes. The treatment is conducted by evacuating hydrogen gas used during roasting and holding furnace pressure of 10-120min at normally 0.001-30mmHg, and the temperature of 100-700 deg.C is preferable as an ambient temperature applied at that time, and a temperature on roasting is kept normally as it is. The molded shapes from which organic matter and carbon are removed are sintered through holding for normally 30-60min on a compound such as SmCo5 Sm2Co17 at a sintering temperature in an inert-gas atmosphere.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides excellent magnetic properties, particularly low coercive force (Hc).
) and the maximum energy product ((BH)max), the method relates to a method of tearing a sintered rare earth magnet with stable quality.

[Conventional technology]

Conventionally, sintered rare earth magnets such as SmCo B type and Sm2Co1□ type have been produced by melting raw metals in a predetermined proportion by arc melting or high frequency melting, and then casting, or by melting rare earth metal oxides into other materials. An ingot having a predetermined composition is obtained by reduction in the coexistence of metal powder, which is then coarsely crushed with a roll crusher in a protected atmosphere, and then crushed with toluene using a ball mill, a motion mill, and an attritor. Alternatively, a fine alloy powder obtained by pulverizing in an inert solvent such as xylene and drying is used as a raw material powder, and then a lubricant or binder such as stearic acid, stearamide, oleic acid, paraffin, etc. is added to this raw material powder. is added and molded in a mold to which a magnetic field is applied, and this molded body is first
After roasting in vacuum or under a hydrogen or argon atmosphere at a temperature of about 10°C to remove the organic matter derived from the inert solvent, lubricant and binder, the molded body is roasted in the same furnace. For example, the Sm
When manufacturing CoB type or Sm2Co1□ type magnets, it is generally heated to a predetermined temperature within the range of 1000 to 1250°C for 30 to 30°C.
It is manufactured by sintering under conditions of holding for 60 minutes.

[Problem that the invention seeks to solve]

In such a method for manufacturing a sintered rare earth magnet, the removal of the organic matter is not sufficient even through the roasting, and some of the organic matter remaining in the compact is removed during the roasting process and during the subsequent sintering. Some of the carbon decomposed and produced during the process remains in the sintered magnet, reducing its magnetism, especially its coercive force and maximum energy, and the amount of this remaining carbon depends on the size and size of the compact. There is a problem in that the quality of the product varies depending on various factors such as the location of the compact placed in the sintering furnace, and as a result, the quality of the product varies.

[Findings based on research] In order to solve these problems, the inventors of the present invention have conducted various studies and found that when a molded body is roasted at 100 to 500°C in a hydrogen stream, the organic matter in it is Most of the carbon is removed and some carbon remains in the compact, which is then subjected to a sintering process in an inert gas atmosphere such as argon for 10 minutes.
When vacuum degassing is performed at a temperature between 0 and 700°C, the amount of carbon remaining in the sintered body is significantly reduced, resulting in a marked improvement in its magnetism. It has been found that this can be achieved relatively uniformly, regardless of the location of the molded body in the furnace.

[Means for solving problems]

This invention was invented based on the above knowledge, and aims to provide a method for manufacturing a sintered rare earth magnet having excellent magnetic properties, particularly high i magnetic force and maximum energy product, and containing a rare earth metal. In a method for manufacturing a sintered rare earth magnet by roasting and sintering a molded body, the molded body is roasted at a temperature between 100 and 500°C in a hydrogen stream, and then 100° C. It is characterized in that it is subjected to a vacuum degassing treatment at a temperature between 700° C. and 700° C., and then the molded body is sintered in an inert gas atmosphere.

[Specific configuration of the invention]

Next, a specific configuration of the present invention will be explained.

(1) Molded body containing rare earth metal Shaped body containing rare earth metal can be manufactured according to any molded body manufacturing method that has been conventionally adopted in manufacturing sintered rare earth magnets. Rare earth metals, Co j Fe, N
Predetermined components are melted by melting raw metals such as i, zr, etc. in vacuum or in an inert gas atmosphere by arc melting or high frequency melting, or by reducing rare earth metal oxides under other metal powders. An ingot having a composition of It is manufactured by adding stearic acid or paraffin, etc., which acts as a lubricant or binder, to the powder, kneading it, and press-molding it in a mold at a pressure of 1 to 2 tons/- while applying a magnetic field. .

(2) Roasting process The molded bodies produced as described above are arranged on a shelf in a furnace and roasted at 100 to 500 m
Roasting is normally carried out for 30 to 300 minutes at a temperature between 100°C and 100°C, but if the roasting temperature is less than 100°C, the removal of organic matter will not be achieved satisfactorily, while if it exceeds 500°C, the compact will The roasting temperature was set in the range of 100 to 500°C because cracks would occur in the roasting process.

(3) Vacuum degassing treatment The vacuum degassing treatment applied to the compact after the roasting is an effective treatment for further reducing the amount of organic matter and carbon remaining in the compact. , the hydrogen gas used during roasting is evacuated and the pressure inside the furnace is usually 0.001 to 3.
0 ttmHg for 10 to 120 minutes, and the ambient temperature applied at this time is usually conveniently maintained at the same temperature as during roasting.

If the ambient temperature during this vacuum degassing is less than 100°C, the organic matter and carbon will not be removed sufficiently;
If the temperature exceeds 0°C, an excessive amount of carbon may remain in the sintered body or cracks may occur in the sintered body, so the temperature was set at 100 to 700°C.

(4) Sintering process The molded body from which organic substances and carbon have been removed by the vacuum degassing treatment described above is heated to a sintering temperature, that is, for example, SmCo5 in an inert gas atmosphere such as argon or helium.
and Sm2Co17, it is usually 1000-1250℃
, and for PrCo 5 it is usually 950-115
Sintering is carried out by raising the temperature to 0° C. and keeping it at that temperature for usually 30 to 60 minutes.

〔Example〕

Next, examples of the present invention will be explained while comparing them with comparative examples.

SmCo alloy powder obtained by grinding in toluene was added with 0% normal paraffin in the presence of toluene.
5% (weight%, same below) and stearic acid 0.1%
After evacuating the air in the furnace with a vacuum pump, hydrogen was introduced into the furnace, and while the hydrogen was flowing, After the atmosphere in the furnace was heated to 400°C at a heating rate of 5°C/min, the molded body was roasted by maintaining this temperature at 400°C for 30 minutes.

Then, while maintaining the temperature inside the furnace at 400°C, the hydrogen gas inside the furnace was evacuated for 30 minutes.
The molded body was subjected to vacuum degassing treatment.

The degree of vacuum during this evacuation was several tens of rmHg for about the first 10 minutes, and 0.01 mHg when the evacuation was completed about 30 minutes after the start of evacuation.

Immediately after the completion of vacuum deaeration, argon gas is introduced into the furnace, the temperature inside the furnace is raised from 400 ° C. to 1130 ° C., and this temperature is maintained at 21 kV f'i'le- to sinter the compact,
Thereafter, the sintered magnet 1 of the present invention was manufactured by cooling it, and its solidity properties are shown in Table 1.

Furthermore, for comparison, among the various conditions adopted in the above manufacturing method, a comparative sintered magnet was prepared under the same conditions as the above manufacturing method, except that one condition was changed to the "manufacturing conditions" in Table 1. Nos. 1 to 7 were manufactured, and their solid-gas properties are also shown in Table 1.

Example 2 Obtained by a method similar to that described in Example 1,
Chemical composition of Sm2Co 17 containing 0.5 parts normal paraffin and 0.1 part stearic acid (Sm:25
Unfortunately, Fe: 15%, Cu: 6%, Ni: 1.
4%, Zr: 3%, remaining diCo (weight ratio composition),
8 m x8,,+x8. A cube-shaped compact having dimensions of fil was charged into an externally heated tubular furnace, and the atmosphere inside the furnace was replaced with hydrogen gas. The molded body was roasted by increasing the temperature to 400° C. and maintaining this temperature for 30 minutes.

Next, the introduction of hydrogen gas was stopped, and the hydrogen was evacuated for 30 minutes while the furnace temperature was maintained at 400° C., thereby subjecting the compact to a vacuum degassing treatment. During this evacuation, the pressure inside the furnace decreased from the initial atmospheric pressure to 30 r for the first few minutes.
The pressure decreased to mHg, but the pressure decreased slowly after that.
0.005mmHgl after 30 minutes: 1. Immediately after the completion of vacuum degassing, the inside of the furnace was changed to an argon atmosphere, the molded body was exposed to 1230° C. for 1 hour to sinter, and then slowly cooled to produce the sintered magnet 2 of the present invention, and further 1. =
For comparison, Comparative Sintered Magnet 8 was also made using the same procedure as above, except that a molded body without any lubricant or binder was roasted in argon at a temperature of 550°C for 1 hour. The magnetic properties are shown in Table 2.

Table 2 [Effects of the Invention] From the results shown in Tables 1 and 2, both sintered magnets 1 and 2 of the present invention have good magnetic properties, especially Hc and (BH).
Comparative sintered magnets 4 and 5 were manufactured with a roasting temperature outside the range of the present invention, but the roasting temperature was outside the range of the present invention, and the roasting atmosphere was different from that of the present invention. Comparative sintered magnets 2 and 6 were used as atmospheres.
Comparative sintered magnets with significantly to significantly low Hc and (BH)max, and which were produced by roasting under conditions outside the scope of this invention, even if they were molded without using a lubricant or binder. Comparative sintered magnets 1 and 8 had slightly lower Hc and (BH)max due to residual toluene used in the pulverization process. It can be seen that in comparison sintered magnet 7, which was vacuum degassed at a temperature exceeding the vacuum degassing temperature of Renmei, the sample was damaged by cracks during the measurement of magnetic properties, and these were completely useless as a magnet.

As is clear from the above-mentioned Etsumei, according to the present invention, the organic matter that remains in the compact or sintered body and reduces the magnetism of the sintered magnet is effectively (-1 and uniformly removed).
The industrially useful effect of manufacturing rare earth sintered magnets with excellent magnetic properties, particularly high coercive force (He) and maximum energy product ((BH)max), and uniform quality with good reproducibility, has been achieved. It will be done.

Claims (1)

[Claims] In a method for producing a sintered rare earth magnet by roasting and sintering a molded body containing a rare earth metal, the molded body is roasted in a hydrogen stream at a temperature between 100 and 500°C, and then The method for manufacturing a sintered rare earth magnet, which comprises subjecting the compact to a vacuum degassing treatment at a temperature between 100 and 700°C, and then sintering the compact in an inert gas atmosphere.