GB1559100A

GB1559100A - Sintered magnetic materials

Info

Publication number: GB1559100A
Application number: GB2915976A
Authority: GB
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 1975-10-09
Filing date: 1976-07-13
Publication date: 1980-01-16
Also published as: NL7600389A; JPS5246500A; JPS5755281B2; DE2604026A1; DE2604026B2; NL183685C; CH618538A5; DE2604026C3; NL183685B

Description

(54) SINTERED MAGNETIC MATERIALS (71) We, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD., a Japanese body corporate, of 1006 Kadoma, Osaka, Japan, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement:- The present invention is concerned with sintered magnetic materials, and the production thereof.

According to the present invention, there is provided a sintered magnetic material having a composition which (ignoring impurities and incidental ingredients) is expressed by the formula Sm(Co,~x~yFexCuy)z, in which x is 0.01 to 0.15, y is 0.05 to 0.15, and z is 7.8 to 8.2, and having an average grain size of less than 10 microns and the material having an intrinsic coercive force of at least 1000 oersteds.

The present invention also comprises a method of making a sintered magnetic material having a composition which (ignoring impurities and incidental ingredients) is expressed by the formula Sm(Co1~xFexCuy)z, in which x is 0.01 to 0.15, y is 0.05 to 0.15, and z is 7.8 to 8.2, which comprises sintering a powdered alloy comprising Sm, Co, Fe and Cu in suitable proportions, the sintering conditions being such that the sintered material has an intrinsic coercive force of at least 1000 oersteds and an average grain size of less than 10 microns.

The method according to the invention preferably comprises making an alloy comprising Sm, Co, Fe and Cu in suitable proportions, the alloy also containing 0.1 to 2V by weight of Zn, reducing the alloy to a fine powder compacting and sintering, the sintering being controlled such that the sintered material has an intrinsic coercive force of at least 1000 oersteds and an average grain size of less than 10 microns.

The addition of zinc to the alloy, as mentioned above, promotes sintering and causes better shrinkage during sintering. No significant quantity of zinc remains in the resulting sintered material, since virtually all the zinc evaporates during sintering.

In the following description, reference will be made to the accompanying drawings, in which: Figure 1 is a graph showing the intrinsic coercive force (,Hc) of a number of sintered specimens of approximate composition Sm(Co0.85Fe0.05Cu0.10)z, as a function of z when sintered at 12400C; Figure 2 is a graph showing the intrinsic coercive force, the average grain size and the relative density of a number of sintered specimens having the approximate composition Sm(Co085Fe005Cu0.10)8, as a function of the sintering time at a sintering temperature of 1230"C: and Figure 3 is a graph showing the intrinsic coercive force for a specimen having the approximate composition Sm(Co08sFeOOscuo1)8o as a function of the sintering temperature with a sintering time of 30 minutes.

In order that the invention may be more fully understood, the following examples are given by way of illustration: Example 1 Alloys were prepared by melting the constituent metals specified below, the metals being used in such proportions as to provide a nominal composition of Sm(CoO,8sFeo 05CuO ,o)8.o The as cast alloys were crushed into coarse grains and then pulverized into fine powders having an average particle size of about 3 microns by jet milling. The powders were pressed in a magnetic field of 15KOe and further compacted into green bodies by isostatic pressing at about 3 tons/cm2. The thus compacted bodies were sintered at a pressure of 5xl0-5 mm Hg for 25 or 30 minutes at various temperatures between 1125 and 1260"C.

Chemical analysis of the resultant sintered bodies showed that almost all the Zn present in the as cast alloys had evaporated off during sintering. The addition of a small amount of Zn has an effect of promoting sintering and thus causing a better shrinkage of the specimens, although the final sintered products do not contain any significant amount of Zn.

Typical chemical analyses are given below: Content (wit.%) Specimen No. Sm Co Fe Cu Zn Total z3 as cast 24.4 62.1 3.9 8.1 1.1 99.6 Z6 as cast 24.0 62.5 3.9 8.2 1.1 99.7 sintered 24.2 63.1 3.8 8.2 < 0.1 99.4 Z12 as cast 23.5 62.6 4.0 8.0 1.1 99.2 For example, sintered specimen Z6 can be expressed by the formula Sm(CoO.843Feo.os3cuo.1o1zno.oo1)7 92 if impurities not analyzed are ignored. However, chemical analysis to determine the absolute value of the Sm content is subject to an error of up to 0.5 /". The relative amount of Sm with respect to the rest of the composition of these alloys was determined from the intensity of the characteristic x-ray of Sm by means of Xray fluorescent analysis. The relative amount of Sm is most accurately determined in this way and it is preferred to refer to the relative amount of Sm because the absolute value of the Sm content cannot be very accurately determined as mentioned above. The results were as shown below.

Relative amounts of Sm Specimen No. (Arbitrary Unit) Z3 1.1746 Z4 1.1751 Z5 1.1643 Z6 1.1527 Z8 1.1561 Z9 1.1379 Z10 1.1472 Z12 1.1179 Z13 1.1443 Z14 1.1230 The best values of coercive force in the resultant sintered bodies were obtained by sintering at about 1240"C. Figure 1 shows the variation of coercive force with z value for these sintered bodies.

Figure 2 shows intrinsic coercive force, average grain size and density of the sintered specimens obtained as a function of the sintering time at a sintering temperature of 12300C and demonstrates that as the sintering time increases beyond about 30 minutes, the coercive force deteriorates.

Example 2 The Z12 and Z4 powders of Example 1 were mixed in the appropriate ratio so as to provide the Z6 composition. The mixed powders were subjected to the same process as described in Example 1; the resultant sintered bodies exhibited a coercive force between 5000 and 8000 Oe which was essentially the same as the optimum value of the coercive force in Example 1.

Example 3 Specimens Z17 to Z28 with a nominal composition of approximately Sm(CoO,8sFeo 05CuO ,o)8 o were prepared by the same method as that of Example 1. The relative amount of Sm in the specimens obtained. (determined in the same way as in Example 1). the sintering temperature, the sintering time and the coercive force, are given below.

Relative amount Sintering Sintering Specimen of Sm temperature time iHc No. (Arbitrary Unit) ( C) (min.) (Oe) Z17 1.1216 1190 30 1900 Z18 1.1567 1140 30 14000 Z19 1.1724 1140 30 13800 Z20 1.1372 1140 30 2400 Z21 1.1822 1140 30 600 Z22 1.1563 1140 25 14300 Z23 1.1349 1140 25 10600 Z24 1.1292 1140 25 14100 Z25 1.1185 1135 25 12000 Z26 1.1363 1140 25 2200 Z27 1.1344 1119 25 > 15000 Z28 1.1314 1125 25 13600 Figure 3 shows the intrinsic coercive force as a function of the sintering temperature for specimen Z19 with a sintering time of 30 minutes.

Figure 3 demonstrates that if the sintering temperature is too high (above about 1214"C in the case of specimen Zl9) the intrinsic coercive force is below 1000 oersteds.

In the above Examples, specimens Z3, Z4, Z5 and Z21 were not according to the invention, z being too low in Z3, Z4 and Z21, and the coercive force being insufficient in Z5.

WHAT WE CLAIM IS: 1. A sintered magnetic material having a composition which (ignoring impurities and incidental ingredients) is expressed by the formula Sm(Co,~x~yFexCuy)z, In which x is 0.01 to 0.15, y is 0.05 to 0.15, and z is 7.8 to 8.2, and having an average grain size of less than 10 microns and the material having an intrinsic coercive force of at least 1000 oersteds.

2. A method of making a sintered magnetic material having a composition which (ignoring impurities and incidental ingredients) is expressed by the formula Sm(Co,~xFexCuy)z, in which x is 0.01 to 0.15, y is 0.05 to 0.15, and z is 7.8 to 8.2, which comprises sintering a powdered alloy comprising Sm, Co, Fe and Cu in suitable proportions, the sintering conditions being such that the sintered material has an intrinsic coercive force of at least 1000 oersteds and an average grain size of less than 10 microns.

3. A method according to claim 2, which comprises making said alloy comprising Sm, Co, Fe and Cu, the alloy also containing 0.1 to 2% by weight of Zn, reducing the alloy to a fine powder, compacting the powder, and carrying out said sintering.

4. A method according to claim 1, substantially as herein described in any of Examples 1 to 3.

5. A sintered magnetic material, when obtained by a method according to any of claims 2 to 4.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Example 3 Specimens Z17 to Z28 with a nominal composition of approximately Sm(CoO,8sFeo 05CuO ,o)8 o were prepared by the same method as that of Example 1. The relative amount of Sm in the specimens obtained. (determined in the same way as in Example 1). the sintering temperature, the sintering time and the coercive force, are given below. Relative amount Sintering Sintering Specimen of Sm temperature time iHc No. (Arbitrary Unit) ( C) (min.) (Oe) Z17 1.1216 1190 30 1900 Z18 1.1567 1140 30 14000 Z19 1.1724 1140 30 13800 Z20 1.1372 1140 30 2400 Z21 1.1822 1140 30 600 Z22 1.1563 1140 25 14300 Z23 1.1349 1140 25 10600 Z24 1.1292 1140 25 14100 Z25 1.1185 1135 25 12000 Z26 1.1363 1140 25 2200 Z27 1.1344 1119 25 > 15000 Z28 1.1314 1125 25 13600 Figure 3 shows the intrinsic coercive force as a function of the sintering temperature for specimen Z19 with a sintering time of 30 minutes. Figure 3 demonstrates that if the sintering temperature is too high (above about 1214"C in the case of specimen Zl9) the intrinsic coercive force is below 1000 oersteds. In the above Examples, specimens Z3, Z4, Z5 and Z21 were not according to the invention, z being too low in Z3, Z4 and Z21, and the coercive force being insufficient in Z5. WHAT WE CLAIM IS:

1. A sintered magnetic material having a composition which (ignoring impurities and incidental ingredients) is expressed by the formula Sm(Co,~x~yFexCuy)z, In which x is 0.01 to 0.15, y is 0.05 to 0.15, and z is 7.8 to 8.2, and having an average grain size of less than 10 microns and the material having an intrinsic coercive force of at least 1000 oersteds.